I Gatti Norvegesi Bianchi
I gatti possono perdere l’udito anche a causa dell’età, come succede agli umani. In questo caso generalmente si tratta di un processo graduale che è difficile a volte da notare. I timpani diventano meno flessibili e il suono non viene trasmesso in modo efficace. Altri gatti invece nascono parzialmente o completamente sordi per difetto genetico. In molti casi questo difetto genetico è correlato al pigmento ovvero lo si ritrova molto più spesso nei gatti totalmente bianchi.
I gatti completamente bianchi con occhi azzurri , infatti, sono ben conosciuti per essere molto spesso affetti da una sordità ereditaria congenita che può coinvolgere una o entrambe le orecchie.
Gli studi sulle razze hanno definito, quindi, la relazione che c’è tra la sordità e i gatti bianchi con occhi azzurri.
Il gene responsabile è un gene dominante che viene definito W (White – bianco). I primi studi su questo gene risalgono al 1930 e sono stati puoi approfonditi negli anni successivi. Il gene W è un gene che riguarda il pigmento dei gatti ed è un gene dominante sul colore, ma non è collegato all’albinismo. I gatti che portano questo gene non sono sempre di colore bianco solido, ma hanno spesso delle macchie colorate sulla testa che possono scomparire con l’età.
Si vede spesso, infatti, un gattino giovane con una macchietta colorata, generalmente sulla testa, che poi scompare in età adulta. Il colore che si cela sotto il mantello bianco, dominato da W, è rivelato proprio da quella macchietta!
Per questo motivo, i gatti bianchi possono generare cuccioli non bianchi o bicolori.
Questo gene ha una penetrazione completa per i mantelli di colore bianco, difatti tutti gatti che hanno questo gene hanno anche il mantello bianco, ma ha una penetrazione incompleta per quanto riguarda il colore blu degli occhi, correlato alla sordità, anche se sono strettamente collegati.
Non tutti i gatti bianchi però sono sordi e non tutti i gatti con gli occhi blu hanno un difetto di sordità.
La variabile di penetrazione della sordità collegata al colore blu degli occhi può essere causata dall’interazione con altri geni o con fattori ambientali.
Se siamo in presenza della sordità, inoltre, questa può riferirsi ad entrambi gli occhi oppure anche a solo un occhio, quindi può essere bilaterale oppure unilaterale.
Come ci accorgiamo che il gatto è sordo?
Questi gatti generalmente mostrano dei cambiamenti nel comportamento. Ce ne possiamo accorgere dal momento che, pur chiamandoli, non si avvicinano o non si accorgono quando rientriamo a casa.
Se il gatto sordo convive con un altro gatto, generalmente noteremo che tende a fare riferimento proprio a lui per quanto riguarda l’udito. Questo significa che lo troveremo spesso ad osservare l’altro gatto, per comprendere quello che sta succedendo. Se invece si tratta di un unico gatto in casa con il problema della sordità, è molto più facile notare questo difetto. Il gatto ad esempio, potrebbe dormire molto profondamente, potrebbe non notare quando entriamo nella stanza e non rendersi conto di rumori molto forti anche vicini a lui. Se non c’è alcuna reazione ad un battito di mani o ad un rumore molto forte, possiamo davvero sospettare di una possibile sordità.
Gatti bianchi o gatti albini?
Bisogna ben specificare, però, che questi gatti non sono degli albini.
Un vero gatto albino non ha solamente il mantello bianco, ma anche gli occhi si presentano senza pigmento, appaiono difatti rosa. Un gatto albino è molto sensibile alla luce e ha bisogno di protezione solare sulle orecchie per prevenire il cancro alla pelle. Questa prevenzione è comunque necessaria per tutti i gatti di colore bianco.
I gatti bianchi con gli occhi colore blu, arancioni e verdi non sono albini. L’albinismo è una mutazione molto differente che causa l’assenza del colore, non la copertura del colore.
In presenza del gene W, mantello bianco e occhi blu, possiamo avere l’assenza del tappeto lucido (succede anche in alcuni gatti con occhi azzurri con mantello bianco diluito – Siamese) o un tappeto lucido molto sottile, il che significa che la visibilità notturna è molto ridotta. Questa è una ragione in più per non permettere al gatto bianco sordo di uscire!
Alcuni studi hanno dimostrato che se:
◊ Un gatto bianco ha entrambi gli occhi blu ha più probabilità di sviluppare la sordità di 3-5 volte rispetto ad un gatto con gli occhi non blu.
◊ Un gatto bianco con un solo occhio blu ha circa il doppio delle opportunità di essere sordo rispetto ad un gatto con entrambi gli occhi di un altro colore.
◊ Gatti bianchi a pelo lungo hanno tre volte di più la probabilità di essere bilateralmente sordi.
Quali sono i problemi riscontrati?
I gatti sordi emettono dei vocalizzi molto forti proprio perché non sentono esattamente come nell’uomo. A causa dell’estrema utilità dell’udito nella predazione e all’abilità di cacciare, questa può essere ridotta nei gatti completamente sordi o parzialmente sordi. La sordità completa, in ogni caso, non soprime il successo nella caccia. Un gatto sordo risponde ugualmente al suo istinto di predazione.
Ecco perché la vocalizzazione nei gatti completamente sordi è un importante mezzo di comunicazione tra gatti e i gatti sordi possono essere meno bravi a comunicare con i loro simili. I gatti sordi possono entrare in conflitto con altri gatti molto più spesso o non riuscire ad integrarsi bene in un gruppo. Possono trovare più difficoltà quando sono ancora cuccioli e, inoltre, vengono più frequentemente rigettati dalla madre. La loro abilità ridotta di riconoscere dei pericoli è l’handicap più serio soprattutto quando si tratta di gatti che vivono all’esterno. Automobili, cani, macchinari da giardino, sono i pericoli più grandi.
...UN PO' DI GENETICA...
Il gene bianco o gene W, è il responsabile della depigmentazione totale del pelo, che quindi risulta interamente bianco, la pelle del naso e dei polpastrelli è rosa.
Il colore degli occhi può essere coinvolto, ed in tal caso l'occhio è blu o azzurro chiaro e spesso dal lato corrispondente si ha sordità.
Il gene W è epistatico su tutti gli altri geni responsabili della colorazione.
L'allele recessivo, w, non produce depigmentazione. Perciò un gatto bianco può portare informazione genetica per altri colori, ad esempio il nero, senza che questo traspaia nel fenotipo.
Il Gene W è epistatico anche su S, e quindi un gatto interamente bianco può trasmettere informazione genetica anche relativa alle macchie bianche.
THE SNOW CATS
by Paula Swepston ©
This article is 10 years old now, and has been revised from time to time with names of successful white Forest Cats. Nowadays there is no doubt as to their popularity, and the Snow Cat Hall of Fame has grown so large that a thorough update would be impossible. The article is a bit dated because of this, but as it is the best-loved piece I have ever written, I leave it on the site for all Snow Cat fans, and as a bit of Skogkatt history.
White as cherry blossom, white as sea foam, white as whipped cream in a porcelain dish. They're the white cats, of whom Paul Valéry wrote, 'Leur fourrure a l'éclat des glaciers baignés d'aube.' ('Their coats have the dazzle of dawn-bathed glaciers.'*) They're so glamorous, one could almost be excused for presuming a white forest cat the result of 'creative breeding'. I've been informed by well-meaning old bats ('Wouldn't want you to make a mistake, dear') that of course they're not pure; Persian blood must have been mixed in to get the color. This in spite of the fact that their fur quality is nothing like a Persian's, not to mention their head and body shape and long, straight profile. Some people have called them 'salon cats', fit only for sitting around on cushions. ['Booor-ing,' says Fenja over my shoulder.] And one guy told me that white cats, for lack of camouflage, could never survive in the wild. These are the folks who think the only true Skogkatt is a brown tabby. Of course, tiger stripes are a great camouflage in the forest, as are red and tortoise-shell against autumn leaves, and black and blue in a rocky landscape. All these colors were represented among the first forest cats exported from Norway. The whites just took a little longer to reach us.
When Jette Eva Madsen (Felis Jubatus) first showed Flatland's Avedine, in February 1986 in Copenhagen, the purists were shocked. (Maybe jealous?) 'It's an albino,' they said. 'It's a hybrid!' One ugly name after another. But, as Jette says, they couldn't stop looking! And they've been looking ever since. Meanwhile, the beautiful Avedine is European Champion and bears the title Distinguished Merit in honour of her many titled children -- 25 at present count, in a variety of colors. This year's World Show in Geneva looked almost like an 'Avedine family reunion'. There were 4 of her children there, 14 grandchildren, 21 great-grandchildren, and 7 great-great-grandchildren! All this by way of pointing out that she's extraordinary not only for her white fur, but also for a fabulous look that has stamped itself on generation after generation of kittens.
So where do they come from, these white Norwegians? Like all our other beauties, they come out of the woods, the fjords, and the snow. Arvid Engh of the Norsk Skogkattring told Judith Zuurveld there were lots of white semi-longhairs in Rjukan-Telemark, where he grew up in Norway. He said they had always been there -- and he really didn't think they had Persian ancestry. In Jaeren, south of Stavanger on the southwest coast of Norway, there are supposed to be many white Forest Cats running around the countryside. Randi Grotterød (Torvmyra's) tells of an odd-eyed white cat, born in 1942, that lived on her grandparents' farm when she was a little girl; it was a famous hunter and fighter and lived to be 18 years old. Some salon cat! As for the question about camouflage, she has a succinct answer: 'In Norway we have snow almost 6 months a year.' 'Nough said!
I don't know why the white cats didn't arouse as much interest originally as the other colors. Perhaps the breeders preferred working with colors they perceived to be more popular. Avedine was the first white to leave Norway, and that was already 9 years after the FIFé standard had been granted. But as we've seen, the 'snowcats' were there all along. (White is not a 'new' color with Maine Coons either - a white MCO, raised by a Mrs. Pierce, was shown in Madison Square Garden in 1895.)
Flatland's is by no means the only cattery in Norway to include whites in its repertory. One thinks for example of Griselda av Gjernes, imported by Margarete Leleither into Germany in 1986; her lovely granddaughter Graciella av Trollsfjord, among others, continues the white tradition in that country.
Way back in some of our best NFO pedigrees there's an odd-eyed white female named Grynet, born in a litter of four whites before the NFO received breed status in 1977. These cats all lived in the country and chased mice, and Grynet, who stayed with the breeder, was the mother of Charlie av Hanevold, who also had a white sister. From Charlie and the unforgettable Tussi (who died in 1991 at age 14) we get Torvmyra's Eviva Solterona. Among Solterona's offspring are Torvmyra's Orchide, who, through the Naima's Cattery, has so influenced the Swiss NFO's, and Torvmyra's Othilina of Danièle Rocchi’s 'Pendjari' Cattery, of great importance to the breed’s foundation in Belgium and France. Grynet's father was an unnamed white knight with blue 'breakthrough' spots, and her mother was a brown mackerel tabby named Rusken. In 1979 Rusken had another litter of 4 whites. She died a few days after their birth, but the kittens, hand-raised with a baby bottle, all grew to adulthood. Of the four the breeder kept one, and that cat, now 15 years old, is still with her today.
So as we see, they were there all along, hunting, breeding, sleeping by the hearth, and waiting to join their colored brothers and sisters on the show podium. They even put in an appearance in Norse mythology, where they are said by some to be the famous cats who pulled the chariot of the goddess Freyja. In modern times, the first white to be shown was a cat named Nøste. Jette fell in love with her photo in Skogkatten, the Norsk Skogkattring’s newsletter, and jumped at the chance to buy a white kitten from a new litter at Rigmor Syverstad’s 'Flatland's' Cattery. That was Avedine, daughter of Christiana's Rudolph, a brown mackerel tabby, and a lovely white lady named Claire.
Behind Claire's name in our pedigrees one sees only two blank spaces, but the courtship of Claire's parents is one of the great Skogkatt romances. Mama was a black-and-white, one of 5 novice cats belonging to Ms Syverstad about 10 years ago. Papa was a macho white guy, who hung around the woods near the house, but was too shy (or too wary) to come inside. He doesn't have an official name, but to me he's Wotan the White Wanderer.
I've often imagined how it must have been. Some folks might say he was a ne'er-do-well, that he was taking advantage of Claire's mother in order to cadge a free meal. But I prefer to think it was true love. He tried to talk his lady friend into running away to a life under the stars. He hung around night after night, playing his guitar and singing under her window, until finally they let her come out to join him. The honeymoon was passionate but brief. Of course she loved him. But how could she desert her humans? They'd always been so good to her. And how would she take care of her babies when winter came? Why didn't Wotan come in and live with them? He was tempted. And it tickled his heart to think of the little ones coming. But he couldn't picture himself lying around on a sofa and having his picture taken, being combed and bathed, and hauled around for people to ooh! and aah! over, and talk about his ears and tail. Man's got his pride after all, man's gotta hang on to his liberty. And so he went his way, waving his plumy tail, a little heavier of heart, but drying his tears and singing, like Cole Porter's Wildcat Kelly: 'Don't Fence Me In'. Claire's mama was sad, but when the kittens came she knew she'd made the right decision; her humans were happy, and her babies had a home. And little Claire turned out just like her handsome white father. It was only on full-moon nights that Mama allowed herself to think back to the days of her great love story, and ..................
['Paauulaa! You're anthropomooorphizing!'
'Don't be jealous, Fenja. Just because Fisher Blue didn't sing under your window. You got your kittens anyway.'
'You call that romance? Being grabbed by the scruff of the neck ...'
'Careful. This is a family magazine.'
'You misspelled anthropomor ....'
All the same, it's a true story. The white vagabond ate all the food that was put down for him, but could never be lured into the house. In the end, Ms Syverstad took the risk of allowing some of her females outdoors, in hopes of getting a mating, and Claire was the result. Claire herself had only one litter, but through her daughters Flatland's Avedine and Flatland's Alexis she has found her way into Skogkatt legend and some of our classiest pedigrees.
In 1991 white NFO's made their debut in France. Bred by Monica Chopard-von Ritter of Switzerland, they came from the first litters of GIC Isak-Dinesen Felis Jubatus, Best Swiss Semi-longhair Cat, of 1990. (In 1992 his daughter Naima's Zora, belonging to Nelly Brosselard, was Best Swiss Kitten. Their names are Naima's U-Fenja (owned by Paula and Lee Swepston), Naima's U-Farouk (Philippe Kiefer), and Naima's U-Ellis (Sophie Demay-Grolière). All are grandchildren of Flatland's Avedine. Later 2 white cousins joined them: a young female, Skovtur Felis Jubatus, belonging to Nathalie and Sylvie Olivet and Ragnar del Valhalla (I) (Geneviève Cournud).
At the FIFé World Show in Geneva (1994) there were 14 whites among the 121 forest cats registered -- a high percentage considering our 9 color groups. In Germany's 'Top Twenty 1993', the Norwegians were represented by a beautiful white female, EC Ingrid-Sletten Felis Jubatus (owned by Ulrike Wahl). In Denmark, last year's 'Top Ten' adult cats included two white NFO males, EC Harald Rein Felis Jubatus (owners, Minna and Kjeld Krogh), and GIC Norsk Skogkatt Felis Jubatus (Jette Madsen and Martin Kristensen). The latter compounded his honors by being, in the very same year, one of the 'Top Ten' kittens as well! Judith Zuurveld notes that in the Netherlands group 9 has become one of the most popular and successful, and that almost every breeder owns at least one white cat.
They're with us to stay now; one sees them at every show and, more often than not, on the platform for the final nominations and bests as well. From the public one hears cries of delight rather than shock: 'Oh, isn't she beautiful! Do they really come in white too?' Oh yes, they really do. The white forest cats. White as winter moonlight. White as innocence. White as snow.
Paula Swepston © May, 1994
Chatterie de la Maison Forte
NOTES & ACKNOWLEDGEMENTS
*The poem quoted is 'Les chats blancs' by Paul Valéry. The English translation is by David Paul. The drawing of 'Wotan' is by Danish breeder Ann Stougaard©, and is used with her permission and that of the Norsk Skovkattering Danmark.
My thanks to Randi Grotterød ('Torvmyra's', Norway), Jette Eva Madsen ('Felis Jubatus', Denmark), and Judith Zuurveld ('Bergansius', Netherlands) for helping me collect information, and to GIC Naima's U-Fenjawho supervised the typing and printing of this article!
Post Scriptum: A lot of things have happened since this article was written in 1994, one of the nicest being that in Lisbon, April 1995, an odd-eyed white male NFO was chosen World Winner Kitten 1995. His name is Skovhugger Felis Jubatus, and he belongs to Vibeke and Kjeld Jorgensen of Denmark; his father is GIC Norsk Skogkatt Felis Jubatus, mentioned above.
The top-ranking adult NFO in the international Skogkatt of the Year 1996 competition was a white named EC S*Arrow's Amorina, owned by Cecilia Crawford of Sweden. EP/EC T'Annes Sven Jutte, a white neuter male bred and owned by Anne Weijman, was the 'Best Overall' Norwegian in the Netherlands 'Top NFO' list.
Naima's Zora, (now European Champion), was Best Adult Swiss Cat for the year 1994. Skovfyr Felis Jubatus and Naima's U-Fenja are both European Champions now and have retired, leaving show business to the younger generation. Fenja's son EP Jolly Cotton de la Maison Forte has been waving the snowcat banner chez Swepston, as has a daughter, IC Jezebel de la Maison Forte, belonging to Swiss breeder Céline Kuratli. In the Maison Forte breeding program, Fenja's odd-eyed daughter, IC Orchidée Blanche de la Maison Forte has replaced her mother, who remains 'Queen Cat' and an enthusisatic babysitter. In her first year of show business Orchidée was #5 kitten on the French Top 10 list for 1998 - # 4 among the kittens from French catteries, and #5 kitten, Årets Kontinental Skogkatt 1998, Norsk Skogkattring Norway. Jolly Cotton placed #13 among the international neuters in the first Skogkatt of the Year competition (1995), #3 in the Swiss Top Ten of 1996, and # 1 in France in 1997.
At the 1998 FIFé World Show in Poznan, Poland, another descendent of Avedine became World Winner Kitten: Skakmat Felis Jubatus, white, blue-eyed female belonging to Martin Kristensen. Skakmat compounded her honors by winning again in 2000 in Prague; with titles, her long-winded name is now EC WWK98, WWA2000 Skakmat Felis Jubatus.
And so it goes....
Photos of Maison Forte cats: Paula Swepsto
Genetics and the White Cat
by Paula Swepston ©
This article was written in July 1994. A few update comments are incorporated in this presentation.
The genetics of the white cat is a fascinating subject, better explained in all its subtleties by a scientist. However, as lover and breeder of white Norwegian Forest Cats, I'd like to offer a starter course for laymen and discuss, among other things, the problem of possible deafness in white cats of all breeds.
The color white is caused by a dominant epistatic gene symbolized by the letter W (white) which, if inherited by the cat, masks in the phenotype any other color, dominant or recessive, the cat may have in its genetic make-up. The owner may ask in puzzlement, 'Well, what color is my cat really?' When we bought Fenja, Monica Chopard explained to us about the spot of breakthrough pigment usually found on the heads of white kittens; this spot, which disappears as the cat grows older, allows one to determine the animal's underlying genetic color. In Fenja's case the spot was missing, but since her mother is a red it seemed safe to assume that Fenja herself might be tortoiseshell 'underneath', and this was confirmed over the years, as she gave cream and blue cream kittens. At the time, we were novices, and I think one of us ventured to say, 'But maybe she's an all-white cat.' Well, no is the answer. Those do exist, for instance among the Persians and Turkish Angoras, whose breeders marry whites to other whites. There it's possible to have a homozygous (WW) cat, but Fenja is definitely heterozygous (Ww), because only her father is white.
Live and learn. Time went on, I asked a lot of dumb questions, read Roy Robinson, asked more questions, and now it's no longer such a mystery. But not even the scientists agree about everything that goes on under those white exteriors! We've said that the white color is caused by the W gene, but according to a second theory, it could derive from the spotting gene (S) responsible for white paws, noses, and other decorative bits. (To the non-scientific mind this sounds like hoping your freckles will run together so you'll look sun-tanned.) Amanda Thomas, a British Maine Coon breeder researching deafness in white MCO's, believes the W gene to be a mutation of the S, or the S a mutation of the W; in any case they may be related.
As we know, some white cats are born deaf. (This is the chief reason we have not been crossing white x white among Norwegians.) Some breeders, including Ms Thomas, hope to minimize the possibility of deafness by mating their whites with colored cats having little or no white spotting. Judith Zuurveld is skeptical about this because her white male,
EC Acton Bell Felis Jubatus, who probably carries the spotting, has given a relatively low number of deaf kittens (23% as opposed to the 80% quoted by one breeder in an Atout Chat article on Turkish Angoras). Based on her experience she speculates that the S may even protect the offspring against deafness.
[Update 2002: according to the posthumously updated edition of Roy Robinson's 'Genetics for Cat Breeders', it is no longer believed that the white spotting gene bears any relevance to deafness. In an article reproduced elsewhere on the site, Mr, Robinson recommends pairing yellow-eyed hearing whites with large patches of breakthrough color, in order to collect largest possible quantity of protective polygenes. You can read this article by clicking HERE]
It is not a tragedy to have a deaf cat. In fact, as some cats (10-15% of those over 13 years old) lose their hearing with age, it's a good idea for us all to think about living with this disability. We breeders must be especially alert, so we can pick the best homes for deaf kittens and help the new owners protect and communicate with their pets. Even though, as Mr. Robinson says, it is not possible to eliminate deafness, we can hope to lower its incidence in future generations; to this end serious breeders are comparing the results of their matings, and keeping track of them in an organized way.
The initial problem, obviously, is to establish which kittens hear and which don't. Some writers simplify the issue by making it dependent on eye color. One hears over and over again that yellow-eyed cats hear, blue-eyed cats are deaf, and odd-eyed cats hear only out of the yellow-eyed side. But these are generalizations, and are not always true. For one thing, there are also white cats with green eyes, and these never seem to be mentioned at all. Then, as we know, some yellow-eyed cats are deaf, and some blue-eyed cats hear and give hearing kittens in their turn. Of the two odd-eyed kittens we have had here, both are fully hearing on both sides. Still, there may some connection. According to Fran Pennock Shaw in Cat Fancy magazine (USA, Jan.1994), humans who have Waardenburg's Syndrome, a condition involving congenital deafness, usually have a streak of white hair and blue eyes, no matter what their skin color.
Meanwhile, if you're raising a litter of white kittens, you won't want to wait until their eye color has changed before determining how well they hear. In a mixed litter it's easier to decide, because you can compare the whites' progress with that of their colored litter mates. With an all-white family it's more difficult. You can use all sorts of noisy tricks to check reactions: rattling keys, crinkling paper, blowing police whistles. Try to stand where the kittens can't see you when you want to surprise them. (Whether or not you succeed in establishing the kittens' hearing capacities, you'll probably convince their mother to move them all to a dark corner of the cellar!) Another trick that seems to work is hissing at them; the ones who hear will probably hiss right back. But do it away from Mama, and don't exaggerate -- they shouldn't regard you as the enemy! My favorite test is the Dies irae from Verdi's Requiem. Written to wake the dead, this music, turned on full-blast, is ideal for scaring baby kittens across the room! (Afterwards, switch to Mozart!) While they are tiny, by the way, you will only make yourself nervous by studying every little twitch of their ears. By the time our last litter was 3 1/2 weeks old I'd decided they were all either deaf or mentally retarded, when my cleaning lady came downstairs one day and said, 'Sorry, Madame, I can't do your bedroom. Your little kittens are scared of the vacuum cleaner.' She couldn't understand why I was so delighted! When they're a little older, you'll start to notice which ones respond to the sound of the refrigerator door, whether they react when you break a glass.
'Hearing' Through the Paws
‘It is interesting to observe deaf cats compensate through having to rely on other senses of sight and smell and even develop improved sensitivity to vibration via the feet. This is perhaps a crude form of replacement hearing because airborne sounds will be muted as they pass into the ground, but the cat, even if deaf, may be highly sensitive to vibrations....
As we have seen, the whole body of the cat is sensitive to vibration to some degree, but it is thought that the cat's paws are especially competent in this respect. This may help explain why cats are reported to be able to predict the imminence of certain types of earthquakes.'
from Claws and Purrs, Peter Neville©
Sidgwick & Jackson Ltd, London
ISBN 0283 06123 5
But it isn't always easy to tell, even with adult cats. This is complicated by the fact that, according to Ms Shaw, 'the majority of hearing-impaired cats are deaf only in one ear....The cats compensate so well for the partial loss that owners and veterinarians may not suspect anything.' Show judges wear their fingers out trying to get a reaction to little snapping sounds, but a calm, experienced cat of any color may be too bored or disdainful to respond. On the other hand a deaf animal may react to the movement of air beside its ear or may catch sight of the moving fingers. If a deaf cat is living in a household with more than one animal, you may not realize at first that the reason he's coming to dinner is not because you called but because he sees everybody else rushing into the kitchen.
In fact it's not a good idea for deaf cats to live alone. They tend to be sweet and dependent, purring and following their friends around, and need the companionship of humans and other animals. Judith points out that they are ideal for families with big dogs, because they aren't frightened by barking! They're not afraid of hair-dryers either, which can be a blessing as bath time approaches.
These cats respond well to visual cues, and the owner of a deaf pet should work out a system of signals for communication. I've tried it for fun with my hearing cats. They learn very quickly that a 'come here' hand gesture and finger to the lips means a special food treat away from the other cats. Establishing eye contact is important before going on to anything else. Since a deaf cat can't hear you coming it's best, to avoid surprising him, to let him see you before you pick him up or stroke him. Same thing if a reprimand is in order. Make eye contact, then put your hand in front of the cat's face and shake your finger 'no'. Some people turn the light switch on and off rapidly to signal, or stomp their feet -- don't forget, the deaf can still feel vibrations. In some cases a shot of water from a plant sprayer can be useful.
Above all it's important to protect a deaf pet. He can't hear a car coming, and this means you should never let him wander around the neighbourhood. (I feel the same way about my hearing cats, but the added danger here is obvious.) And he can't hear the hisses and growls other animals give as warnings, so, especially until a new cat has settled in with the other family pets, it's a good idea to keep an eye open on his behalf. (Similarly, if one kitten is consistently more aggressive at play than his littermates, it could be because he doesn't hear their protesting squeals.)
No breeder of pure white cats is exempt from the possibility of deaf kittens. We shouldn't be embarrassed about it, but work to keep track of our matings and repeat the ones that produce the lowest incidence of deaf offspring -- the same thing applies to other genetic faults that arise from time to time. Above all, we shouldn't hesitate to talk about the problem with other breeders or with clients. My experience has been that clients are not necessarily put off by the idea of deafness. Frank explanation opens the way to a situation of mutual trust, and prepares the new owners for what they may encounter. Many people want a white kitten whether it's deaf or not. Recently I lost a sale, because a lady absolutely wanted a blue-eyed white -- she didn't mind if it were deaf, but it had to have blue eyes and mine were all yellow-eyed.
A few adjustments may be necessary on the owner's part, but the reward can be an especially loving relationship, and a beautiful companion.
P.S. Since 1995 the use of deaf white cats for breeding and showing is no longer allowed in FIFé. No point going into the pros and cons of this decision now; it was passed, perhaps too hastily, in the hope that the incidence of deaf kittens could be reduced, and FIFé breeders must honor the new rule. All the same, I hope this article may be useful, especially to debutant breeders who may be dealing with their first litter of whites, and that it may help demonstrate that a hearing problem does not handicap a cat for life as a cherished pet.
The following is taken from article written by a French Turkish Angora breeder named Virginia Baehrel for a newsletter called P.A.C.I.O.N.S. I feel that her theories about the red gene protecting against deafness merit consideration. It interests me especially because Fenja - who as indicated above is white with blue cream underneath - has had a 100% batting average: seven white kittens in four litters, with three different fathers, have all been hearing. This is a very modest sample, but is perhaps indicative. I would be very happy to hear of other breeders' experiences!
Whiteness, Deafness, and Genetics
by Virginia Baehrel ©
In Holland, the USA, and France we have noticed that the red gene goes a long way towards cancelling the 'deaf' specificity. The more we blend red into a kitten's pedigree, the more chance the white kitten will be born hearing perfectly. Results: in Holland, certain breeders of US [Turkish Angora] lines (Capaqua, Azima's) as well as some of us [in France], are trying to work with white on the basis of red.
Results: I have never again had any deaf kittens, except one, in spite of two homozygote mothers (not deaf) and white fathers. Why?
Simply because it seems that the cells at the origin of the nerve structures of hearing and the cells which produce melanocytes, which produce pigments such as eumelanine (black and derivatives) and phaeomelanine (red) are linked closely. The W gene appears to be an inhibitor of eumelanine but not of phaeomelanine.
White homozygotes which do not carry colours never transmit colours, but they nevertheless bear genetic traces of these cells. This is why they sometimes have different or green eyes. Without these traces they would be born albinos with red eyes. Since the W gene inhibits the majority of eumelanines, these homozygotes with black ancestors, or which carry black, are born deaf. The blue of their eyes is, in addition, very light. White homozygotes with red grandparents are systematically born not deaf. The more we concentrate the red polygene in the ancestors, the more we concentrate phaeomelanine (in polygenes), and the more the intensity of the eye colour is important.
All crosses possible. The results:
- kittens which are not deaf
- blue eyes
- an almost total absence of deafness....
P.S. A deaf cat does not suffer at all. Of 25 kittens born between 1989 and 1994, I only had one deaf kitten. He was just as lively and healthy as his brothers. He was not rejected and he had his place in the hierarchy of the group. He was extremely alert and even more affectionate than any other 'normal' Turkish Angora.
the Beginning of this article
EXTRACT from an article in the September-October issue of the French magazine FeliMag, entitled De la naissance à trois mois: les étapes de son autonomie, ('From birth to three months: steps towards autonomy') illustrating some facets of normal development in this area. (Our translation)
Even though the auditory canals of newborns are closed, these kittens perceive sounds from the third or fourth day. As early as the day after they are born, a loud or sudden noise will provoke a jump or at least a contraction of the eyelids. An electroencephalogram shows activity in the part of the brain involved in hearing from 2 or 3 days. The hearing canal begins to open at between 6 and 14 days (9 days on average) but is only complete at 17 days. At the same time, the sense of hearing is refined and becomes completely functional at around 4 to 6 weeks. The animal begins to follow sounds (the mother's call, or the sound of your voice) during the second week of life but this orientation mechanism does not function perfectly until around the age of one month. As of the age of 3 weeks, the kitten distinguishes familiar and reassuring sounds from unusual and disturbing noises which provoke a reaction of fear or intimidation.
For further reading, try the following site of British Maine Coon breeder David Brinicombe. You may not agree with everything he says in his study of deafness and the white gene. I myself know too many hearing blue-eyed white cats to be happy with his theory that only yellow-eyed subjects should be used for breeding, and of course the idea of crossing in Foreign Whites to get blue eyes from the albino gene is absolutely unacceptable to anyone interested in keeping a breed like the Forest Cat pure and true to type. However, he has a lot of interesting things to say. Have a look for yourselves! http://dialspace.dial.pipex.com/brini/whtdeaf/whtdoc.htm
Jette Eva Madsen certainly needs little introduction to Forest Cat breeders around the world. Well-known FIFé judge and breeder of Norwegians, (including 5 World Winners, 2 of them white), she is an excellent source of wisdom on the subject of white Forest Cats: http://www.skovkat.dk/jetteweb/deaf.htm
This article was written for The Skogkatt, newsletter of the Norwegian Forest Cat Fanciers' Association, USA.
White Forest Cats: 1998 Update
Dear American Wegie-lovers,
I am writing to try and give you an idea of the status of white Forest Cats over here in Europe. I know that several American breeders have imported whites for their catteries, but it seems that not everyone is certain of how the color is regarded here.
In 1994-95 there was a big brouhaha in Hessen, Germany, over white cats in general, and this led to all the problems we have had since. It was started by a pet owner who had gotten a deaf white kitten from a breeder who neglected to inform the new owner of the kitten's problem. This became a cause célèbre in Germany, and got all the animal rights folks out in force. Among other things, it became popular in Germany to say that raising white cats of any breed was tantamount to 'cruelty to animals'.
FIFé intervened rapidly with an injunction against breeding and showing of deaf cats, their haste justified by a wish to stave off a movement in the European Community to pass an international law forbidding all breeding of white cats.
The FIFé rule stipulates that deaf whites may not be used for reproduction, or presented in shows, not even in the neuter category. This rule was passed at the 1995 FIFé General Assembly. A veterinary certificate testifying to a cat's hearing abilities is required for breeding and/or showing a white. In countries where audiometric testing is possible, this more exact examination is required. (The only country I know of that offers general availability of the audiometric exam is Germany. In Switzerland one has to go to Bern, and in France the vets seem to find it altogether a foreign idea.)
The FIFé rule was not taken up by the independent associations; and at least in France one does see deaf cats being presented in independent shows.
In spite of the problems, the breeding of white cats still flourishes in Europe, especially among the Persians, and of course the Turkish Angoras. It is true that there was some backlash against Norwegians and other whites in SOME contries, but this is evening itself out as time goes on.
In Denmark and Holland, the popularity of whites seems never to have changed much. In Switzerland, according to what I observed at the time, the price of white kittens, even deaf ones sold as pets, DOUBLED in many cases, because they became rare.
In France, there were never so many breeders of white NFO's compared to the more traditional colors, but the popularity of white cats in general does not seem to have suffered with the pet-buying public. There is a long tradition in this country of beautiful white Persians, but I have sold white Norwegians to folks who, having lost an aged Persian, did not care for the more extreme look of Persians being raised today. They still wanted a white cat, though, so they turned to the Forest Cat to get big, longhaired, and white, but without the squashed-in nose. (A fashion, by the way, that does nothing at all to favor the cat's respiratory health, but which is allowed quite happily by pedigree-giving associations. I once heard a famous French Persian breeder, judging a Persian kitten, say to the skeptical audience, 'You may think this is ugly, but he is SUPPOSED to look this way. A good Persian should have NO NOSE AT ALL!' Right, and a healthy cat is SUPPOSED to have tears running down his face his whole life, and asthma attacks to boot! Let's be honest - there are other things besides deafness that can afflict feline quality of life, and many of these are not only tolerated, but even encouraged by the cat fancy!)
I'm a bit surprised that there is still doubt about the popularity of white Forest Cats over here - especially in light of the publicity given the new white World Winner, WW K98 Skakmat Felis Jubatus, owned by Martin Kristensen of Denmark! [update: Beautiful Skakmat is, in fact, the only Forest Cat to be a double World Winner; she won again, as an adult, in 2000.]There was also a white neuter nominated at the Poznan World Show: EC/EP T'Anne's Sven Jutte, bred and owned by Anne Weijman of the Netherlands. Sven has received so many honors I can't even count them, both before and after he was neutered; most recently he was declared Best All-round Forest Cat of 1997 in Holland, and he was # 1 neuter in the 1997 Skogkatt of the Year competition. Other whites featured in that list are GIC Bergansius Nehalennia, Narviks Vulcan Tuvok, and EP/EC S*Wonder's Tarquin. So much for the idea that white Forest Cats are no longer shown in Europe!
In France we had two whites on the Top Ten list for 1997. My own EP Jolly Cotton de la Maison Forte was #1 neuter, and since his photo appeared in one of the French magazines, I have received a gratifying number of requests for white kittens. It is true that most people who start out looking for a Forest Cat pet tend to want a tabby, because that is what they have seen most often at shows and in the press. But when we get calls from people who just want to come see what a Forest Cat looks like, it is usually our 2 white boys who get the most attention.
Don't know if this will be helpful or not - but I think that NFCFA members interested in importing whites may rest assured that the European breeders offering these kittens are not just trying to palm off something unwanted over here; in Europe the fashion for whites is picking up again. Other colors - notably the famous fawns and cinnamons - have been questioned by some European breeders, but from the beginning, white cats have always been a part of the Forest Cat spectrum.
Deafness is a possibility for every breed that features white cats - that is, almost every breed on the face of the earth! So what's new? We are better aware of the problem now, and it does not make white cats less beautiful or desired. White cats are a natural part of the feline community. Breeders did not create the color, and whites have survived, Lo! these many centuries, in fields, forests, and even city streets, without help from mankind.
Those of us who love and breed whites are responsible for surveying the deafness problem, but the argument remains the same: they were always there, always loved, and no amount of constraint placed on breeders is going to eliminate the white street cat! It is our duty is to assure that our white thoroughbreds develop in the healthiest way possible. We must continue to exchange unpredjudiced information, keep trying out various theories as to which matings produce fewer deaf kittens, and propose only the best, hearing subjects for reproduction.
The idea that white cats are defective in other ways, specifically because of their color, is without foundation in any serious forum that I have seen. Recently I have been receiving electronic echoes (well, you know, nothing is private online!) suggesting that the white gene is a sort of 'death gene'! In addition to the possibility of deafness, white cats are supposed to suffer from blindness as well. They are all supposed to have diarrhea, and the females are reckoned to be poor-risk mothers, having small litters and a high incidence of uterine and kitten death. White cats are supposed to lead shorter lives than others, dying at about two years of age.
Well, sounds like 'witch hunt' to me, classic rumor fabrication, based on nothing but hysteria! I have not seen specific cattery names mentioned in this connection, and would respectfully suggest that it is not necessarily the white gene which is at fault in these cases, but the line. The diarrhea may be due to nothing more sinister than poor diet or sanitary conditions; the other problems may occur in cats of any color. In my own cattery, we had reproductive problems with a silver female, and with her mother and grandmother, both black and white; all three are sterilized now. None of these cats' pedigrees has anything at all in common with my 'white line' - which is extremely healthy in every respect, and in which the females have normal-sized litters (4, 5, up to 7 kittens) born easily with no defects.
This whole issue brings to mind Jette Eva Madsen's caution (see her web site address, below) that breeders must never give in to the temptation to use a poorly-typed Forest Cat or one with heart problems, tail fault, or any other undesirable traits, just because it happens to be a hearing white!
Well, there is so much research still to be done, and we may never really be able to pin down exactly how to eliminate the problem. But of course we keep trying.
In closing, I send greetings to all of you 'over there'. One of the hardest things for me about being an American living abroad is not being able to meet you personally, visit the American shows, and see your beautiful Forest Cats up close. The magazine is a big homesickness remedy though, and I read every issue with pleasure. Keep up the good work!
19 October 1998
Further down on this page:
Mr. Robinson's 1995 magazine article on white cats and deafness
Merci de me contacter si vous désirez avoir cette article
en traduction française; je peux vous l'envoyer par e-mail.
Genetics of Colour Variation and Breeds
from 'Genetics for Cat Breeders' by Roy Robinson
The completely white animal with orange, blue or odd eyes (one eye orange, the other blue), is due to the dominant gene W. The short-haired breed is L-W and the long-haired is llW-. The gene is fully dominant, hence the presence of one gene is sufficient to create a solid white animal. The majority of whites are in fact heterozygotes (Ww), mainly it seems because of a propensity of breeders to cross the white to a black or blue, either to improve eye colour (in the case of the orange-eyed variety), coat quality or body type. There is no disadvantage in this; indeed in skilled hands, the results can be beneficial. The deep orange eye, so desired for the orange-eyed variety, will only be achieved or maintained by breeding from the better animals in this respect.
The blue or odd-eyed white is engendered by one of the expressions of the W gene. In addition to producing the white coat, the gene also produces blue eyes. It does not do this in all animals (otherwise the orange-eyed variety would not exist) but in a fair proportion of cats. The completely blue-eyed for appears more frequently than the odd-eyed, as a rule. If a breeder prefers the blue-eyed variety, only matings between blue-eyed animals should be made. This is the only method by which the chances of breeding blue-eyed kittens can be maximized. However, the occurrence of either orange- or blue-eyed kittens is such a chancy business that the breeder has little control over the breeding at will of any particular eye colour The mating of orange-eyed animals together can produce blue-eyed kittens and vice versa. The occurrence of the odd-eyed cat is even more a chance event and there is little prospect of these ever being bred to order.
The deafness associated with the blue-eyed variety is an expression of the W gene. Not all blue-eyed white cats are deaf nor do all orange-eyed white animals have normal hearing. The proportion of deaf animals is fairly low, but too high for any complacency in the opinion of many people. In a protected environment, deafness is not a major hazard although deaf queens can be indifferent mothers because they cannot respond to the piping of kittens. Most people object to the presence of deafness on ethical or aesthetic grounds because it distracts from the wholesomeness of the cat. The only practical method of counteracting the deafness is not to breed from detectable deaf individuals. The deafness will probably never be totally eradicated but attempts can be made to keep the incidence at a low level.
It is possible to create a true breeding strain of blue-eyed white cats by combining the cs [* i.e. Siamese] and W genes. The genotype cscsWW will be blue eyed due to cs and white due to W. This animal has indeed been produced in the lithely built Foreign White [* now known in FIFé as white Siamese: SIA w 67] It is unfortunate that deafness may be a recurring problem. Much will depend in this connection upon the effectiveness of keeping the incidence at a low level.
The completely white coat should not be taken at its face value of an apparent absence of all other coat colour genes. This false idea occasionally finds expression in the belief that the mating of a white cat with a coloured will produce offspring of the same colour as that of the coloured parent. A few matings will soon show that the belief is untrue. In general, white cats may carry a variety of genes masked by the whiteness and unexpected results will occur. Sometimes close study of the parentage of a white cat can give a good idea of the genes which may be carried by the animal and the results which may be expected from various matings.
Source: Genetics for Cat Breeders, Third Edition, by Roy Robinson, F.I. Biol.; ©Pergamon Press, 1991; ISBN 0-08-037506-5
The notes marked by asterisk (*) in the text are mine.
I have put this material up because I think it is important for breeders working with white cats to read what Mr. Robinson had to say. He is, after all, our basic source for information on cat genetics. I do wish he were still with us, as I would love to be able to write to him about various things. For instance, I have to say that I have seen white female cats who were the most devoted mothers even though they were deaf. And, as I have noted elsewhere, I have known deaf cats that gave hearing kittens and hearing whites that gave deaf kittens. But he probably saw this too.
I wonder what he would have made of the present legal situation in Germany. I can't help but feel he would have regarded the current attitude as antagonistic to scientific thought and to the advancement of feline technology.
3 June 2001
White Cats and Deafness
by Roy Robinson
The completely white cat, especially the Long-haired, is rightly regarded as one of the most beautiful of breeds. The eye colour may be orange or blue, or even one eye orange and the other blue on occasion (the Odd-eyed). These cats are healthy and fertile except for one problem, there is a propensity for impaired hearing.
The genetics of the white cat is simple enough. The colour is produced by a dominant gene W which is responsible for several features. These are:
1) white coat
2) blue iris to the eyes, and
The white coat is invariably manifested but the blue irises and deafness are produced in only a proportion of cats but always in association with the white coat.
The Dominant White Syndrome
When a variety of effects are consistently produced, these are termed a syndrome. It is not unusual for one feature of a syndrome to be regularly expressed while the others are less so. This is the case for the dominant white syndrome. This is conventionally interpreted as variable expression of the syndrome. Simply put, the mildly-affected cat would have a white coat but normal eye colour and normal hearing, while the extreme expression would be a white coat with two blue eyes and deaf in both ears.
The white coat is produced by an absence of melanin pigment granules in the hair. Consequently, the hairs are translucent and appear white to human vision. The blue iris colour is due to a partial deficiency of the pigment granules. The defective hearing is due to a progressive degeneration of vital hearing organs of the inner ear.
When a gene produces a consistent syndrome of effects, this implies a common cause, rooted in the early stages of embryonic development. The present syndrome of pigment granule deficiency in the hair and eye, coupled with anomalies of the inner ear, has been described for several species of mammals (cat, dog and mouse) and has been extensively studied. This research indicates the origin of the syndrome can be traced back to an important feature of the embryo, namely the neural crest.
At a certain stage of development, a folding arises in the embryo to create the neural tube which has a very active region known as the neural crest. Active because, as development proceeds, the region supplies cells which are distended to become constituents of a great variety of tissues, organs and the nervous system (Hall 1988).
Abnormal Functioning of the Neural Crest
Included among these cells and of immediate relevance are specialised cells termed melanoblasts which, after arising from the specific sites in the neural crest, migrate between the dermal layers of the skin to take up positions at the base of the hair follicles where they are known as melanocytes. The function of the melanocytes is to synthesise and feed melanin granules into the growing hair. This is how the hairs are coloured.
Normally, the melanoblasts are able to reach all parts of the body so that the skin receives a full complement of melanocytes and the coat is completely coloured. However, this is not invariably the case and the migration may fail to reach some areas of the skin. Consequently, these areas are devoid of melanocytes and the hairs are colourless because they lack melanin granules. When the loss is partial, so that some areas of the skin have melanocytes and other areas do not, the bi-coloured or piebald pattern is produced, i.e. coloured cats with grades of white areas. A total absence of melanocytes results in a completely white coat.
How cats hear
All sounds consist of vibrations, and reach the ear as pressure waves in the air. The pitch of a sound depends on the frequency of the waves - the number of vibrations per second - and its loudness on their amplitude, or size. In order to be heard, the vibrations must trigger nerve signals to the cat's brain that differentiate between sounds of various frequencies and amplitudes. The part of the ear that does this, the cochlea, is deep within the bones of the skull; apart from the section concerned with balance, the rest of the ear - including the visible ear flap, or pinna - collects and transmits the vibrations to the cochlea.
Cone-shaped and equipped with more than a dozen muscles that enable it to be moved through 180 degrees and 'pricked' towards the source of a sound, the pinna collects the slightest sound vibrations. It funnels them down the auditory canal to the ear-drum. The latter's vibrations are transmitted to the cochlea by three tiny bones callled the ear ossicles. These strengthen the vibrations, but an arrangement of small muscles attached to them can dampen down vibrations caused by loud noises, thus helping to prevent ear damage.
The struture of the feline cochlea enables it to respond to sounds as high as 65 kHz (65 kilohertz or 65,000 cycles/second) and possibly higher. This is at least 1½ octaves above the limit of human hearing, which is about 20 kHz, and even exceeds the better-known ability of the dog to hear high-pitched sounds. Human and feline hearing are not very different at low frequencies, the cat's lower limit being about 30Hz (30 hertz, or 30 cycles/second), but the cat's greater sensitivity to high notes is shown by its greater responsiveness to high-pitched human voices and to the squeaks of kittens and mice.
Some white cats ... have degenerative changes of one or both cochleas that cause deafness from the age of about five days. Cats also tend to be deaf in old age as the ear ossicles become less mobile and nerves in the inner ear degenerate. Ear infections can also affect hearing. Deaf cats probably compensate by a sharpening of vision and smell, and becoming extra-sensitive to vibrations (possibly 'hearing' through their feet).
The Book of the Cat by Michael Wright and Sally Walters
© 1980, New Leaf Books, Ltd., ISBN 0 330 26153 3
(out of print - unfortunately!)
The eye may be normally or near normally pigmented even when the coat is completely white. The reason appears to be that the eye tissues do not rely exclusively on the above migration but receive melanocytes by a more direct route, as in the case of the retina cells layer. However, the eye does not always escape and, when it is involved, the iris is blue indicating a general deficiency of pigmentation of the eye. One or both eyes may be affected. In particular, the tapetum lucudum, which is responsible for the characteristic 'eye shine' of cats' eyes, may be partially or completely missing (Bergsma and Brown 1971, Thibos et al, 1980).
Similarly, the organs of the inner ear may be sufficiently well formed for hearing to be normal or near normal. In affected cats, the degeneration is progressive and involves both cochlea and saccule structures. The delicate hair cells of the organ of Corti disintegrate and the sacculecollapses. The former are essential for reception of sound waves and sending impulses to the brain. The result of the degeneration is deafness. The anomaly may affect one or both ears, hence the animal is described as either unilateral or bilateral deaf (Bosher and Hallpike 1965, Mair and Elverland 1977, Elverland and Mair 1980).
The white coat could be regarded as the primary effect of the W gene because it is regularly expressed. However, this is another way of saying that the prime cause is a failure of the melanoblast migration. This implies the sites in the neural crest from which the melanoblasts originate are either deficient or malfunctioning. It is likely that these are not the only cells to be affected. The normal migration of those responsible for normal development of the eye and organs of the inner ear may be disrupted. It has been proposed that these could be either the melanoblasts or melanocytes (Steel and Barkway 1989).
In other words, the action of the gene W is not to induce a white coat. This happens to be incidental. The prime function of the gene is an anomaly of the normal functioning of the neural crest. The exact nature of the anomaly is unknown but the consequences cannot be other than profound because of the importance of cells from the neural crest in embryonic development.
White kittens may have a small spot or patch of coloured fur on the head which disappears with maturity. Observations have revealed that cats with a patch are less likely to be deaf than those without (Table 1). The implication is that the presence of a patch is an indication that these cats received more functional melanocytes (even if few in number) compared with their fellows - that is, they were less severely affected.
The situation is quite different if the incidence of deafness is examined in conjunction with blue eyes.
The association between blue eye colour and deafness is well documented and is shown by Table 2. Cats with blue eyes are more prone to deafness than those with orange eyes. Furthermore, cats with two blue eyes are more likely to be deaf than cats with one blue eye (Table 3). The data is meagre but there is evidence that in doubly unilateral affected individuals, blue eye colour and deafness will occur on the same side of the head.
The implication of the above observations is the obverse of that for patch and deafness. It is apparent that those cats with two blue eyes are more severely affected than those with one. The former cats could have received fewer functional embryonic neural crest cells than the latter. That is, the extent of the underlying neural crest anomaly may vary and this accounts for the variation of expression of the syndrome.
The data is insufficient to establish statistically that kittens with a patch are less likely to have blue eyes (Table 4) although the trend is in this direction. In view of the results described in previous paragraphs such an association would be anticipated and could be confirmed by additional data.
Many blue-eyed white cats, whether partially or completely deaf, lack a tapetum. Insufficient data is available to indicate the proportion of these animals but it would seem to be high. Absence would suggest a severely affected eye, hence it is assumed that it represents an increase in the severity of the anomaly.
Selective Breeding Difficult
The conclusion to be drawn from the analysis is that deafness in white cats is an aspect of a syndrome of effects of the dominant gene W and is inherent in all cats with the gene. Selective breeding against the incidence of deafness is likely to be difficult if not ineffective but if such a policy is to be adopted it would mean taking advantage of any inherited variation in the severity of the neural crest anomaly. That is by a selection of polygenes which could ameliorate the condition. In order to achieve this, it is necessary to have an idea of the variation of the degree of severity of the syndrome. From the data to hand, it is possible to illustrate the variation in the terms of increasing severity in the manner of Table 5.
This will mean that only matings between orange-eyed white cats of sound hearing be allowed. Those with spots or patches as kittens should be especially favoured. Blue-eyed as well as deaf cats (in both cases, unilateral as well as bilateral) would have to be removed from breeding. Mating between white and coloured cats should not be permitted because the genetic status of the latter as regards the postulated polygenes which could ameliorate the severity of the neural crest anomaly cannot be detected.
The objection to breeding cats with the W gene centres on the deafness and this appears to be mainly aesthetic. Deaf cats do not appear to be truly disadvantaged. It is possible that they could have a greater likelihood of being involved in road accidents. The lack of tapetum could mean that the vision is impaired in dim illumination compared with that of a normal cat. A deaf cat kept in a caring environment would be expected to live a normal life.
All breeds of cat which have the W gene will have a propensity to produce deaf individuals. This includes both the Shorthaired and Long-haired breeds, as well as Foreign White, Manx and Rex.
To investigate the problem of deafness in white cats it will be desirable to collect data on the incidence. Simple collection to ascertain whether a cat is deaf or is not deaf could reveal differences between breeds in the incidence. It would be interesting and probably significant if such differences could be adequately established.
However, concentration on one feature is not sufficient: if new information is to be discovered. Especially, an endeavour should be made to collect data on the probable close association between absence of tapetum and deafness. From a genetic viewpoint, to gain greater insight on the pattern of incidence of deafness and other features, data should be collected on complete litters from parents of known status. Each kitten should be as fully classified as possible.
It should be mentioned that the blue eyes of the Birman, Colourpoint and Siamese breeds are produced by a completely different genetic mechanism which is not associated with deafness. This includes the blue-eyed albinos which are bred on the Continent. The eyes of the Siamese are deficient in pigmentation but a tapetum is present.
Bergsma, DR, and Brown, KS (1971) White fur, blue eyes and deafness in the domestic cat J Hered. 62:171-185.
Bosher, SK, and Hallpike, DS (1965) Observations on the histological features, development and pathogenesis of the inner degeneration of the deaf white cat. Proc Roy Soc B 162:14 7-162
Elverland, HH, and Mair, IWS. (1980) Hereditary Deafness in the cat. Acta Otolaryngol 90:360-369
Hall, BK (1988) The Neural Crest Oxford University Press
Main, IS, and Elver land HH. (1977) Hereditary deafness in the cat. Arch WTO Rhino Laryngol 217:199-217
Steel, KP, and Parkway, C. (1989) Another role for melanocytes: their importance for normal stria vascularise development in the mammalian inner ear. Development 107.-453-463
Thebes, LN, Leveque WR, Marsden P. (1980) Ocular pigmentation in white and Siamese cats. Invest Ophthalmol Vis Sci 19:475-486
TABLE 1: Dissociation between patch and deafness.
Chi square = 9.71 for 1 degree of freedom, highly significant.
TABLE 2: Association between blue iris and deafness.
Orange irisBlue iris
Chi square = 17.85 for 1 degree of freedom, highly significant.
TABLE 3: Association between number of blue irises and deafness.
Orange iris1 blue iris2 blue irises
Chi square = 55.00 for 2 degrees of freedom, highly significant.
TABLE 4: Lack of association between patch and eye colour.
Chi square = 1.78 for 1 degree of freedom, not significant.
The figures for Table 1 to 4 are a distillation of data presented by Bergsma and Brown (1971).
TABLE 5: A depiction of increasinq severity of various affected eye colours and deafness of white cats.
Eye colourKitten patchDeafnessTapetum
This article appeared in the August 18, 1995 issue of the publication Cats, U.K.