Ocular conditions

Progressive retinal atrophy (PRA)

PRA describes an inherited ophthalmic condition leading ultimately to irreversible blindness. The underlying pathology is of rod and cone photoreceptor dysplasia and/or degeneration. Usually the rod photoreceptors are affected first, leading to night blindness as an early sign. In time, the cone photoreceptors also become involved, so that ultimately total blindness ensues. Two forms of PRA have been described in the Abyssinian breed: autosomal dominant retinal dystrophy (Rdy) and rod-cone degeneration:

Rdy is a rare, early onset, autosomal dominant condition. Mydriasis (dilated pupils) and intermittent nystagmus (rapid sideways movement of the eyes) are apparent from as early as 4 weeks of age. Ophthalmoscopic examination (looking at the retina at the back of the eyes) reveals signs of retinal degeneration from 8-12 weeks of age, and affected cats are usually blind by 1 year of age.

Rod-cone degeneration is the more common type of PRA in this breed. It is recessively inherited, and affected cats begin to show signs of disease at around 1.5 to 2 years of age. Night blindness progresses to total blindness over a period of 2 to 4 years. No genetic tests are yet available for either Rdy or rod-cone degeneration, although the underlying genetic cause for the latter disease has recently been identified (Menotti-Raymond et al 2007).

Narfstrom  K L (1999)  Hereditary and congenital ocular disease in the cat. Journal of Feline Medicine and Surgery 1, 135 – 141
Djajadiningrat-Laanen et al  (2002) Progressive retinal atrophy in Abyssinian and Somali cats in the Netherlands (1981-2001). Tijdschrift voor Diergeneeskunde 127, 508-514
Narfstrom K L et al  (1985) Progressive retinal atrophy in the Abyssinian cat: studies of the DC-recorded electroretinogram and the standing potential of the eye. British Journal of Ophthalmology 69, 618-623
Narfstrom K L(1983) Hereditary progressive retinal atrophy in the Abyssinian cat. Journal of Heredity 74, 273-276
Gould D J & Sargan, D R (2002)  Autosomal dominant retinal dystrophy (Rdy) in Abyssinian cats: exclusion of PDE6G and ROM1 and likely exclusion of Rhodopsin as candidate genes. Animal Genetics 33, 436-440.
Menotti-Raymond M, David VA, Schaffer AA, Stephens R, Wells D, Kumar-Singh, O’Brien SJ, Narfstrom K (2007). Mutation in CEP290 Discovered for cat Model of Human Retinal degeneration. Journal of Heredity 98 (3): 211-220

Musculoskeletal conditions

Myasthenia gravis (r)

The acquired form of myasthenia gravis occurs when auto-antibodies are directed against acetylcholine receptors. Affected cats are reluctant to exercise, and when they do they develop muscular weakness, which may be seen as progressive stiffness, a crouching gait, a weak neck, and muscle tremors. They eventually collapse onto their chest, often with their head to one side of their front paws. They may have a barely audible miaow. Diagnosis is suspected with a positive response to a Tensilon Test (the iv administration of a short-acting cholinesterase inhibitor e.g. edrophonium chloride), or a decremental response to repetitive nerve stimulation, but definitive diagnosis requires anti-acetylcholine receptor antibodies to be detected in the serum and/or anti-receptor antibodies to be seen in muscle biopsies at the neuromuscular junction (send samples to Diane Shelton, D.V.M., Ph.D., Department of Pathology, University of California, San Diego, La Jolla, CA 92093-0612: http://medicine.ucsd.edu/vet_neuromuscular). Treatment usually consists of oral pyridostigmine bromide, plus or minus prednisolone. Since some cats may go into remission it can be useful to monitor the serum anti-acetylcholine receptor antibody titre. Once it has fallen back to zero medication may be discontinued. The prognosis is very variable: severe cases may die from aspiration pneumonia, and while it is not uncommon for acquired cases go into remission, recurrences may occur.

Shelton G D et al (2000) Risk factors for acquired myaesthenia gravis in cats – 105 cases (1986 – 1998). Journal of the American Veterinary medical Association 216, 55 - 57
Shelton G D (2002) Myasthenia gravis and disorders of neuromuscular transmission, Veterinary Clinics of North America - Small Animal Practice 32,189

Patellar luxation and/or hip dysplasia (*) - see general section click here...

Cardiovascular conditions
 

DCM (r)
Abyssinians are often listed as being at an increased risk of dilated cardiomyopathy (DCM).  However, the majority of these reports come from before diets were supplemented with adequate taurine levels, and therefore it remains unclear as to whether the breed have a higher obligate requirement for taurine, a genetic predisposition to DCM, a combination of the two, or simply that feeding habits within this breed once led them to be at a higher risk of DCM.

Fox PR Feline Cardiomyopathies, 2nd Edition, Philadelphia, W.B. Saunders Company, 1999, pp 621-678

Urogenital conditions

Renal amyloidosis – see amyloidosis

Bacterial urinary tract infections - see general section click here...

Endocrine conditions

Congenital hypothyroidism (r)
This condition has been seen and studied in a single research colony of Abyssinian cats. It appeared to be inherited as an autosomal recessive trait. Affected kittens appeared normal at birth, but looked like disproportionate dwarfs by the time they were 6-9 months old: with short limbs, a round body and an enlarged broad head. Affected cats were mentally dull and lethargic. Circulating thyroxin concentrations were low or low-normal, and confirmation relied on TSH or TRH response tests. Treatment involves giving oral l-thyroxin but the response can be variable, with incomplete resolution of clinical signs.

Jones BR, Gruffydd-Jones TJ, Sparkes AH, Lucke VM. (1992) Preliminary Studies on Congenital Hypothyroidism in a Family of Abyssinian Cats. Veterinary Record 131:145-148

Haematological/immunological conditions

Pyruvate kinase deficiency (*)
Pyruvate kinase deficiency is an inherited disease occasionally encountered in Abyssinian and Somali cats, and also reported in the domestic shorthair cat. Pyruvate kinase is an enzyme found within red blood cells which enables them to produce energy to survive. If this enzyme is lacking, the lifespan of the red blood cells is significantly reduced, resulting in a reduction in the number of red blood cells in the circulation (anaemia). The main consequence of the disease is the development of anaemia, however usually this is only intermittently detectable.  Most of the time the anaemia is either only mild, or occurs gradually, enabling the cat to adapt to the anaemia and not show any obvious symptoms. However, a rapid severe life-threatening anaemia can also develop. Although PK deficiency is hereditary, since the anaemia is usually mild and clinical signs may not be obvious, the anaemia may not be noticed until the cat is quite old. The disease is inherited as an autosomal recessive trait. A reliable test is available that can distinguish clear, affected and carrier cats. A recent survey on pyruvate kinase deficiency in Somali cats in the UK identified 47 carrier cats and 8 affected cats in a total of 141 cats that were sampled, giving a mutant allele frequency of 24%

For more information, see the following page of our website: click here...

Ford S et al (1992) Inherited erythroycte pyruvate kinase (PK) deficiency causing haemolytic anaemia in an Abyssinian cat.  Journal of Veterinary Internal Medicine 6, 123
Giger, U., Rajpurohit, Y., Wang, P, Wand, F., Ford, S., Kohn, B., Patterson D.F., Beutler, E., Henthorn, P.S.1997. Molecular basis of erythrocyte pyruvate kinase deficiency in cats. Blood 90:S5b
Giger, U. 2000. Hereditary Erythrocyte Disorders. In Consultations in Feline Internal Medicine. J.R. August, Saunders p 484-489
Giger, U. 2000. Hereditary Erythrocyte Disorders. In Kirk’s Current Veterinary Therapy XIII.  J. Bonagura, Saunders pp 414-419
Harvey, A.M., Holt, P.E., Barr F. J., Rizzo, F. & Tasker S. 2007 Treatment and long term follow up of extrahepatic biliary obstruction with bilirubin cholelithiasis in a Somali cat with pyruvate kinase deficiency. Journal of Feline Medicine and Surgery 9 (5): 242-231
van Geffen, C., Daminet S. & Savary-Bataille K. 2005 Pyruvate kinase (PK) deficiency and extrahepatic bile duct obstruction with bilirubin cholelithiasis in a Somali cat and PK status in 15 related cats. pp596.  Proceedings of the 48th Annual British Small Animal Veterinary Association Congress, Birmingham, UK.
Mansfield, C.S., Clark, P. 2005. Pyruvate kinase deficiency in a Somali cat in Australia. Aust Vet J 83(8): 483-5
Kohn B, Fumi, C, Seng A, Giger U (2005) Anaemia due to erythrocyte pyruvate kinase deficiency and its incidence in Somali and Abyssinian cats in Germany. Kleintierpraxis 50, 305-312
Harvey AM, Helps CR, Seng AS, Giger U, Tasker S (2007) A survey of erythrocyte pyruvate kinase deficiency in Somali cats from the United Kingdom. Proceedings of European College of Veterinary Internal Medicine Congress, Budapest, Hungary

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Amyloidosis
Amyloidosis is a diverse group of diseases that can be seen in many different species of animals. Amyloid is a type of protein, and amyloidosis describes the disease that occurs when this protein is deposited within body organs. Abyssinian cats are predisposed to a form of amlyoidosis, known as familial amyloidosis, which has been demonstrated to be an inherited disease, but the precise mode of inheritance is unknown. In Abyssinians the disease primarily affects the kidneys, however, amyloid deposits are also found in other organs, such as the liver and intestines. The disease has a variable presentation in affected cats, and only those cats who have moderate to severe disease are usually detected. Amyloid deposits have also been found in the kidneys of older Abyssinians who died of other causes and never showed signs of kidney disease, so the disease can also be mild. However, since the disease is inherited, cats with only mild disease can still pass the disease on to their offspring which may themselves develop more severe disease.

Pressler BM, Vaden SL (2003) Managing Renal Amyloidosis in Dogs and Cats Vet Med 98(4):320-332
DiBartola S P, Tarr M J, Benson MD (1986) Tissue Distribution of amyloid deposits in Abyssinian cats with  familial amyloidosis. Journal of Comparative Pathology 96 (4): 387 – 398
DiBartola SP, Hill RL, Fechheimer NS, Powers JD (1986) Pedigree analysis of Abyssinian cats with familial amyloidosis, American Journal of Veterinary Research 47, 2666-2668
DiBartola SP, Benson MD, Dwulet FE, Cornacoff JB (1985) Isolation and characterization of amyloid protein AA in the Abyssinian cat. Laboratory Investigation 52(5): 485-9
Niewold T A et al E (1999) Familial amyloidosis in cats: Siamese and Abyssinian AA proteins differ in primary sequence and pattern of deposition. Amyloid 6:205-209.
Hansen P (1992) Renal Amyloidosis in the Dog and Cat - Pathophysiology, Symptoms, Diagnosis and Treatment, Annales de Medecine Veterinaire 136, 171-178
Gruys E et al (2002) Feline Amyloidosis Kisallat Praxis 3 34 – 40, 42
Tarr M J & diBartola S P (1985) Familial amyloidosis in Abyssinian cats: a possible animal model for familial Mediterranean fever and pathogenesis of secondary amyloidosis. Laboratory Investigation 52, 67A
Boyce JT, DiBartola SP, Chew DJ, Gasper PW (1984) Familial renal amyloidosis in Abyssinian cats. Veterinary Pathology 21(1): 33-8
Chew DJ, DiBartola SP, Boyce JT, Gasper PW (1982) Renal amyloidosis in related Abyssinian cats. Journal of American Veterinary Medical Association 181(2): 139-42
Johnson KH, Sletten K, Werdin RE, Westermark GT, O’Brien TD, Westermark P (1989) Amino acid sequence variations in protein AA of cats with high and low incidences of AA amyloidosis. Comparative Biochem Physiol B 94(4):765-8
DiBartola SP, Reiter JA, Cornacoff JB, Kociba GJ, Benson MD (1989) Serum amyloid A protein concentration measured by radial immunodiffusion in Abyssinian and non-Abyssinian cats. American Journal Of Veterinary Research 50(8): 1414-7
Discussed on Susan Little’s website www.catvet.homestead.com - Selected Inherited Diseases of the Cat

Increased osmotic fragility of erythrocytes
An increase in osmotic fragility of erythrocytes has been documented in a small number of Abyssinian and Somali cats, aged 6 months to 5 years. Some of the cats were closely related suggesting this is likely to be a hereditary disease. The disorder results in a mild to severe intermittent macrocytic haemolytic anaemia, often associated with splenomegaly, hyperglobulinaemia, lymphocytsosis, mild hyperbilirubinaemia and elevated liver enzymes. Definitive diagnosis is based on excluding other causes of haemolytic anaemia together with demonstrating a high erythrocytic osmotic fragility.

Kohn B, Goldschmidt MH, Hihenhaus AE, Giger U (2000) Anaemia, splenomegaly, and increased osmotic fragility of erythrocytes in Abyssinian and Somali cats. Journal of American Veterinary Medical Association 217 (10), 1483-1491

Infectious conditions

Mycobacterium avium-intracellulare complex (MAC) (r)
Disseminated MAC infection (a disease very similar to tuberculosis) has been diagnosed in 10 young Abyssinian cats and one Somali cat (1-5 years of age) from Australia or North America. The clinical course of the infections was prolonged, with cats presenting for weight loss, initially in the face of a good appetite. Additional clinical features included lower respiratory tract signs (difficult breathing and/or coughing) and enlarged peripheral lymph nodes. A marked diffuse interstitial pattern was evident in thoracic radiographs, even in cats without overt respiratory involvement. Hair clipped to perform diagnostic procedures tended to re-grow slowly, if at all. Diagnosis was made by obtaining representative tissue specimens from lymph nodes, liver, or kidney. The best treatment responses were gained by giving long courses (5-14 months) of clarithromycin combined with either clofazimine or rifampicin, and a fluoroquinolone or doxycycline. Certain lines of Abyssinian and Somali cats may suffer from a familial immunodeficiency that predisposes them to infection with slow-growing mycobacteria such as MAC.

Baral RM, Metcalfe SS, Krockenberger MB, Catt MJ, Barrs VR, McWhirter C, Hutson CA, Wigney DI, Martin P, Chen SC, Mitchell DH, Malik R. (2006) Disseminated Mycobacterium avium infection in young cats: overrepresentation of Abyssinian cats. Journal of Feline Medicine and Surgery 8, 23-44
Sieber-Ruckstuhl NS, Sessions JK, Sanchez S, Latimer KS, Greene CE (2007) Long-term cure of disseminated Mycobacterium avium infection in a cat. Vet Rec 160(4): 131-132

Predisposition to FIP - see general section click here...   

Increased risk of deep fungal infections - see general section click here...