CORNELL FELINE HEALTH CENTER NEWS No. 4 August 1981 Central nervous system disease in the cat Brian A. Summers, B.V.Sc., M.Sc., Ph.D. Fortunately for cats and their owners, disorders of the central nervous system (CNS) in the feline occur only sporadically. The brain and spinal cord are quite unique tissues and their diseases are difficult to treat. Furthermore, the capacity for regeneration and repair in the CNS is limited and consequently many animals (and people) who suffer CNS injury or disease are left permanently incapacitated. Congenital CNS disorders are uncommon in the cat. For example, hydroceph­ alus, which is quite common in certain breeds of dogs, is rarely encountered in the cat. The Manx cat, however, does show a predisposition to spina bifida of the lumbosacral vertebrae and associated changes in the spinal cord (menin- gomyelocoele) may occur. Furthermore, workers at Cornell have associated teratogenic effects with the administration of griseofulvin to pregnant cats. Cyclopia, exencephaly microphthalmia and optic nerve hypoplasia were found. Accordingly, the administration of any drug to the pregnant queen should be with extreme caution. Panleukopenia virus, the cause of infectious feline enteritis, can attack the brain of kittens in utero. Such animals are born with a cerebellar disorder, manifested by dysmetria and tremor once the kittens begin to ambulate. Some animals can compensate reasonably for their defect but, as alluded to above, their brain damage is permanent. Nutritional disease and associated CNS injury are rare but thiamine deficiency may produce an encephalopathy in the cat (and many other species) . Usually this is a result of the destruction of this vitamin by thiaminases of dietary origin (fish). Commercial foods for cats generally provide adequate Bi and this condition is now less commonly encountered. Affected cats may be incoordinated, convulsions may occur, and handling the cat will often induce it to ventroflex the head and neck and roll up into a ball. Early therapy with thiamine may cure this disorder. The most common feline CNS disorders are infectious and involve a spectrum of pathogens. Toxoplasmosis is caused by the protozoan organism Toxoplasma gondii. Occasionally this agent will produce a necrotising encephalomyelitis in the cat. Injury to the CNS is severe and the condition is frequently fatal. Cryptococcosis may affect the feline and produces a disseminated meningo- encephalomyelitis. The organism responsible is a yeast, Cryptococcus neoformans, (Cont. on page 2) Cornell Feline Health Center News page 2 CNS diseases (Cont. from page 1) and again symptoms and pathological cerebellar involvement. Siamese cats changes are severe. are often victims of these disorders but cases in common domestic short A third killer which produces hair cats are seen also. inflammation of the meninges and adjacent brain and spinal cord is the Feline ischaemic encephalopathy is coronavirus of feline infectious a syndrome in the cat somewhat akin to peritonitis. Although predominantly stroke in man. Onset of disease is affecting tissues of the abdominal peracute and is caused by focal cerebral cavity, FIP can involve the nervous ischaemia. Usually seen in mature system with lethal outcome. cats (often in midsummer, curiously enough), it can be expressed by Symptoms for the last three depression, circling, incoordination, conditions mentioned may include or seizures. These acute signs often depression, incoordination, paralysis, resolve in a few days, leaving a seizures, and so on. Interestingly, permanent change which may be behavioral, all three may extend from the CNS to visual, or other. The cause of this the eye, producing a chorioretinitis. disorder is not known. Rabies may produce encephalomyelitis CNS diseases associated with aging in the cat, as in many other animal are occasionally encountered in the species. Fortunately, feline rabies feline. A primary degenerative disorder is documented relatively infrequently. of the spinal cord, myelopathy, has Recently workers in Alabama recorded recently been described in the cat. A the presence of a polioencephalo- similar condition occurs in large myelitis in cats. One or two examples aging dogs such as the German Shepherd. of this emerging disease have been recognized at Cornell also. Finally, tumors occur in the feline CNS and are not uncommon. Meningioma Finally, to complete the spectrum, constitutes the most common primary larvae of the fly Cuterebra will (Cont. on page 4) occasionally gain access to the brain in cats. Apparently these larvae burrow in from the poll region, as signs are referable to cerebellar- medullary injury. The parasite CORNELL FELINE HEALTH CENTER wanders around in the tissue, producing NEWS severe injury. Happily, this bizarre A publication of situation occurs infrequently. Cornell Feline Health Center NYS College of Veterinary Medicine Storage diseases occur in all Cornell University, Ithaca, NY 14853 species and constitute an important group of metabolic disorders. The ©1981 by Cornell Feline Health Center, Ithaca, NY. All rights reserved. Permission to reprint basis of the disorder is an enzyme selected portions must be obtained in writing. deficiency and so the patient stores (in various tissues) metabolites that Director/Fredric W. Scott, D.V.M., Ph.D. cannot be handled by normal catabolic Assistant Director/Leo A. Wuori, D.V.M. Administrative Aide/Edna H. Morusty pathways. Editorial Assistant/Joyce Tumbelston Clinical disease is often a reflection of CNS involvement, as The ultimate purpose of the Cornell Feline Health Center is to improve the health of cats these cells (neurones) are incapable everywhere, by developing methods to prevent of replacement and are soon impaired. or cure feline diseases, and by providing con­ These disorders are inherited and tinuing education to veterinarians and cat symptoms, first seen around one to owners. All contributions are tax-deductible. three months of age, often reflect the Cornell Feline Health Center News page 3 Diagnosis of virus infections in cats Richard C. Weiss, V.M.D., Ph.D. Virus infections constitute the with FeLV are more susceptible to FIP), most important group of infectious and immune status (proper vaccinations, diseases affecting the cat. Viruses adequate intake of colostrum or "first are submicroscopic particles, i.e., milk" after birth, administration of they cannot be observed by the immunosuppressive drugs which may ordinary light microscope, and consist impair resistance to disease, etc.). of proteins and nucleic acids (e.g., Viruses may attack almost any organ DNA or RNA). of the cat and produce a variety of Unlike bacteria and most other clinical syndromes, including respira­ life-forms, viruses require living tory disease (conjunctivitis, rhinitis cells to "stay alive." In fact, out­ or sinusitis, laryngitis, bronchitis, side the living cell, viruses appear and pneumonia); enteric disease (gastro­ crystalline-like, almost mineral in enteritis, dysentery); diseases of the structure. Once these inert particles blood, bone marrow and lymph glands invade cells they acquire the ability (leukemia, lymphosarcoma); disease of to incorporate the essential building the central nervous system (encephalitis, blocks of life, amino acids and meningitis); and generalized or systemic proteins (which are made, free of diseases (e.g., peritonitis). charge, by the cell itself), and may The diagnosis of specific viral reproduce themselves countless times. infections based on clinical symptoms Unfortunately, the cell (or entire alone is frequently difficult, as the organism, if the virus infection is same symptoms of disease may result severe enough) may be destroyed during from the effects of other microbial the process of viral invasion. agents (e.g., bacteria, fungi, myco­ Although cats are frequently plasma, protozoa), parasites, toxins infected by viruses without showing or chemicals, allergies, and cancer. signs of disease, there are several In addition to clinical signs, important viruses of cats that are diagnosis of viral infection may be commonly associated with disease. made by the veterinarian on the basis These include feline panleukopenia of one or more of five methods: virus (distemper, feline enteritis); rabies virus; herpesviruses (feline 1. Viral isolation in tissue rhinotracheitis, pseudorabies); feline culture or eggs. In this method, swabs calicivirus; feline infectious periton­ of infected secretions (oral, nasal, itis virus (FIP); and feline leukemia ocular, rectal) or small pieces of virus (FeLV, feline leukemia). tissue are added to tubes containing living cells. The cells are then grown In general, whether or not an in the laboratory under proper condi­ individual cat will develop disease tions of temperature, carbon dioxide following infection with any of these and acid levels which simulate the viruses depends on many factors, natural body environment. The cells are including age (kittens are frequently examined after several days. If virus very susceptible to viral infections, is present in the samples, the cells particularly when they did not suckle undergo characteristic changes which the queen after birth, and are also are recognized by the virologist. quite vulnerable around weaning time), genetic background, nutritional status, 2. Histopathology. Tissues from environmental stresses, coinfection deceased animals or tissues taken from with other viruses (e.g., cats infected (Cont. on page 4) Cornell Feline Health Center News page