New Feline Virus Threatens Health of Cats

P e rsp e ctive s A Newsletter for Cat Fanciers From The Cornell Feline Health Center Summer 1988 New Feline Virus Threatens Health of Cats Margaret Barr, D.V.M. Feline immunodeficiency virus (FIV), formerly associated disease even when repeated tests for called feline T-lymphotropic lentivirus (FTLV), the virus were negative. Now that a test for is a recently recognized feline virus belonging FIV is available, it is apparent that about 20 to the family Retroviridae. Although FIV is in percent of these FeLV-negative, immunosup- the same family of viruses as feline leukemia pressed cats are infected with the feline lenti virus (FeLV), it is not classified in the oncor virus. navirus subfamily. Instead, the morphology and biochemistry of FIV closely resemble the FIV or FeLV? characteristics of the retroviruses that are associated with non-malignant disease processes. Feline immunodeficiency virus and feline leuke These viruses, the lentiviruses, include the mia virus are similar in certain disease manifes causative agents of progressive pneumonia of tations. However, there are major differences sheep, infectious anemia of horses, arthritis- indicating that FIV is not just a slightly differ encephalitis of goats, and acquired immunodefi ent strain of FeLV. One difference between ciency syndrome (AIDS) of humans. FIV and FeLV is the morphology (shape) of the viral particle. Infected cells can be examined Clinically, the disease caused by FIV may by electron microscopy, a technique which al have been recognized for years. However, the lows visualization of very tiny particles by immunodeficiency-like syndrome with its multi magnifying them tens-of-thousands of times. tude of secondary infections, anemia, and low Viruses can be seen budding from the outer white-blood-cell counts, is indistinguishable surface of the cell into the surrounding envi from the non-neoplastic syndromes associated ronment. Both FIV and FeLV have a char with FeLV infection. Prior to the isolation of acteristic outer envelope, comprised of a por FIV, many cats were diagnosed as having FeLV- tion of the host cell’s membrane and some viral proteins, which is formed around the virus as it exits the cell. However, the internal structure of the FIV particle is elongated or cone- Inside this Issue . shaped while that of FeLV is more circular. New Feline Virus Threatens page 1 The genome (genetic material) of FIV, as Health of Cats with other retroviruses, consists of single stranded ribonucleic acid (RNA). The produc The Mighty Mite page 3 tion of a double-stranded deoxyribonucleic acid (DNA) copy of the viral genome is an essential Honor Roll page 7 step in the replication of this virus within the host cell. This step requires the activity of an Student Receives Summer Fellowship page 8 enzyme, reverse transcriptase, which is carried into the cell as one of the viral proteins. All retroviruses must have their own reverse trans criptase since it is an enzyme which is not generally used by host cells. FIV can be dis Perspectives 2 O n C a t s tinguished from FeLV by a difference in envi count. This decrease in white cells is primarily ronmental conditions necessary for optimal due to a lack of neutrophils, cells which are activity of this enzyme. involved in protecting the cat against bacterial infections. A low red-blood-cell count (ane Also, FIV and FeLV are only distantly re mia) frequently develops. The cause of this lated since they are antigenically different. sometimes precipitous drop in blood cells is Antibodies produced in cats infected with FIV unknown, although it is likely due to a loss of do not recognize FeLV antigens (viral proteins), precursor cells in the bone marrow. and antibodies to FeLV do not bind to FIV particles. Furthermore, FIV is not antigenically Once the white-blood-cell count decreases, cross-reactive with human immunodeficiency the cat’s ability to protect itself against infec virus (HIV), the lentivirus responsible for AIDS tion is compromised. Bacteria, viruses, and in people. fungi, which are common in the cat’s everyday environment and generally are innocuous to a Pathogenesis of FIV Infection healthy cat, can cause severe illness in the immunosuppressed individual. It is these secon Very little is known about the sequence of dary infections which are responsible for most events which occurs following initial infection of the clinical signs associated with FIV. with the virus. The actual method of infection, or mode of transmission, is also unknown. Signs of FIV Infection Transmission through bite wounds is the most likely method of viral spread since free-roaming The clinical signs associated with the disease male cats are most frequently infected. Other are diverse because numerous secondary infec- types of salivary contact, such as the use of contaminated food and water bowls and social grooming practices, may also play a role in transmission. However, casual, nonaggressive contact such as this does not appear to be an Perspectives efficient route of infection. Transmission from A Newsletter for Cat Fanciers an infected queen to her kittens does occur, On Cats From The Cornell Feline Health Center but it is unknown whether this happens in utero (during gestation) or when the newborn The ultimate purpose of the Cornell Feline Health Center is to kittens ingest infected milk. A fairly high improve the health of cats everywhere, by developing methods to prevent or cure feline diseases, and by providing continuing percentage of infected cats are neutered, there education to veterinarians and cat owners. All contributions are fore sexual transmission probably is not a pri tax-deductible. mary method of initiating infection. Director: Fredric W. Scott, D.V.M., Ph.D. Editor: June E. Tuttle Secretaries: Sheryl A. Thomas, Gwen Frost, Following the initial contact of the cat with Karen Havekost FIV, the virus appears to be carried to regional Special Consultant: Leo A. Wuori, D.V.M. lymph nodes, where it may replicate in a sub This publication is made possible, in part, by population of white blood cells known as T- a grant from 9-Lives Cat Foods. We grate fully acknowledge this interest and support lymphocytes. These cells are suspected of being in the furthering of feline health. This the primary target of FIV since laboratory acknowledgement of our gratitude is not an endorsement of any particular company or culture techniques require the use of feline T- product. cells in order to grow the virus. The virus ®1988 by Cornell University on behalf of the then spreads to lymph nodes throughout the Cornell Feline Health Center, College of body, resulting in a general lymphadenopathy Veterinary Medicine, Ithaca, NY 14853. All rights reserved. Permission to reprint se (enlarged, lymph nodes). This stage of the lected portions must be obtained in writing. disease generally goes unnoticed by the cat’s Cornell University is an equal opportunity, owner unless the nodes are greatly enlarged. affirmative action educator and employer. Some time later, perhaps days but possibly weeks to months, the cat may develop a fever accompanied by a drop in the white-blood-cell 3 The Mighty Mite Dwight D. Bowman, B.A., M.S., Ph.D. Although mites are small external parasites, Ear mites are transmitted from cat to cat they can be detrimental to a cat’s health. during contact, and kittens will often become Mites are in the same family (arachnid) as infected from their mother. These mites cause spiders and ticks. Their common characteristics the cat to have intense itching of the ears and include having eight legs as adults and a hard also cause the production of a characteristically external shell (exoskeleton). However, mites dark-brown ear wax. During severe infestations, are considerably smaller and usually can be a cat may tilt its head to one side or shake its identified only by microscopic examination. head. Usually, both ears will be infested. Mites usually remain on the same host through Secondary bacterial infections can also develop out the entire course of their development. in the ear canal. In a multiple cat household, Thus, several generations can easily occur on all of the cats may be infested, and will require the same animal. The mites of this type that treatment. Ear mites can be a persistent prob are of interest to the cat owner include Oto- lem, especially if the cat has access to the dectes cynotis, Notoed res cati, Sarcoptes scabei, outdoors. Cheyletiella blakei and Demodex cati. Larval trombiculid mites, commonly called chiggers, Diagnosis is based on the microscopic exam have feeding habits that are more like those of ination of ear wax. Treatment consists of a tick; they only attach to their host long applying ear mite medications as per the veter enough to feed. inarian’s instructions. Before applying the medication it is usually necessary to remove the Otodectes cynotis (ear mites) excess ear wax and debris from the outer ear canal. The adult mites derive their sustenance from their feline host by piercing the skin of the outer ear canal. The hatching larvae feed on Notoedres cati the ear wax. Ear mites mature within 3 to 5 days and begin reproducing. This is a very small mite that burrows along underneath the superficial layers of the skin, causing a condition called notoedric mange (feline scabies). These mites are most com monly found on the top of the head or the forehead of the infested cat. Usually, the first sign will be a bald patch in one of these two areas caused by constant scratching by the cat. The bald patch may extend down the back of the head or across the bridge of the nose onto the cheeks. Prolonged infestations result in a grayish crust forming over the affected skin.

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