Unit 8

Feline Health Management

In considering feline health management, we will once again look at health concerns as they relate to Host, Environmental and Agent factors.

Host-Related Health Concerns

Genetically related concerns – A number of health problems have been identified as genetically linked in the cat. The best known are perhaps the male tortoiseshell cat, which is almost always sterile, and the mixed breed white cat with blue eyes, which is often deaf. Some genetic disorders are identified in certain breeds with greater frequency than normal. Examples are:

    • Progressive retinal atrophy – identified in Persian, Siamese and Abyssinian breeds
    • Taillessness – a trait that characterizes the Manx cat and often results in fecal and urinary incontinence

A number of inherited errors of metabolism also exist, not only in cats but other species of animals. In these disorders, there is a deficiency of one of the enzymes of the metabolic pathways with a build-up of intermediate products of metabolism which often result in neuromuscular problems in the affected animals.

Metabolic disease – fatty liver is a concern in cats as well as ruminant species. As with cattle, it often results when obese animals stop eating for a variety of reasons. Unless force-fed, the cat will quickly succumb to this problem. This can become a problem with sick animals, as well as those whose routine is upset by changes in human and/or animal companions, boarding, etc.  As a consequence, attention to body condition and prevention of obesity in cats is an important management tool for health maintenance.

Environment-Related Health Concerns

Nutrition associated imbalances, excesses and deficiencies – cats are true carnivores and consequently have dietary requirements that cannot be met on a strict vegetarian diet. However, feeding a strictly meat diet can also be very detrimental to cats. A diet consisting of large amounts of red meat will cause an imbalance of the Ca:P ratio (too much P) and cause a nutritional secondary hyperparathyroidism and osteoperosis. A diet containing excessive amounts of liver can lead to hypervitaminosis A, with neck and forelimb stiffness and ankylosis of the associated joints. Vitamin E and thiamine deficiency can be caused by feeding too much fish to cats.

Feline Urologic Syndrome (FUS) – This is a multi-factorial syndrome that results in formation of crystals and stones in the urinary bladder and urethra of the cat. This can result in blockage of urine and cause uremia and death if not treated. The crystals and stones that are usually formed are composed of struvite (MgNH4PO3). Conditions that are cold and damp, resulting in cats not going outdoors, social stresses or other conditions that result in the cat not drinking or urinating frequently can predispose to this condition. Feeding a diet that results in production of an acid urine and decreasing the amount of Mg in the diet will diminish the risk of this problem. Unfortunately, when the urine becomes very acid and Mg concentrations are too low, calcium oxalate crystals may be formed and lead to calcium oxalate urolythiasis in a small percentage of cats.  Because there is a very fine balance in desired levels of nutrients and levels that can cause health problems, feeding of high quality, well-balanced commercial cat foods is recommended .

Toxicities – Cats have a slow rate of drug biotransformation, or inability to metabolise some drugs and as a consequence, are very susceptible to toxicity. Aspirin and acetaminophen are two commonly administered drugs that can easily kill cats. One acetaminophen tablet (325 mg) is toxic and 2 tablets can kill a cat; 1 aspirin (5 grain) administered daily for 12 days to a cat can result in toxicity. Ingestion of ethylene glycol will also result in signs of toxicity within 30-60 minutes and can result in death if treatment is not administered within hours.

Agent-Related Health Concerns

Immune-associated diseases

Feline Immunodeficiency Virus (FIV)

    • Retrovirus of the lentivirus subfamily
    • Tissue tropism for the T-lymphocyte (used as a model for the study of Human Immunodeficiency Virus-HIV, the causative agent of AIDS). These viruses are species-specific, so FIV cannot infect people and HIV cannot infect cats.
  • Regulatory genes of FIV contain enhancer sequences that respond to activation signals in activated T-lymphocytes. These are thought to play a major role in the latency and pathogenesis of the disease.
    • Shed in saliva, urine and body fluids
    • Outdoor, free-roaming male cats are at greatest risk for contracting the disease
  • Primarily horizontal transmission (fighting, biting, grooming), not venereal, intrauterine or through nursing
    • As with HIV, FIV has 5 phases of infection
    1. Acute stage -- enlarged lymph nodes, fever, depression, diarrhea
    2. Asymptomatic carrier -- may last months to years
    3. Persistant generalized lymphadenopathy
    4. AIDS related complex -- cat may experience weight loss, chronic diarrhea, oral, respiratory and skin infections
    5. AIDS (acquired immune deficiency) -- many opportunistic infections, emaciation, lymphoid depletion and many other disorders of body systems
    • Diagnosis is by detection of antibodies in blood
  • False-positives due to maternal antibody in kittens up to 4 months of age, nonspecific reactions associated with other feline vaccines, ask for confirmatory test if positive
    • As with HIV, there are no cures or vaccines to prevent the disease. The best way to deal with it in multicat households or catteries is to test and isolate or remove positive animals.

 Feline Leukemia Virus (FeLV)

  • Retrovirus; most common cause of serious illness and death in domestic cats
  • Primarily horizontal transmission; shed in blood, saliva, urine, feces and tears

    In utero infection of as many as 20% of kittens born to infected dams

  • Two clinical stages of FeLV infection
  1. Initial stage (primary infection) lasts 2-6 weeks and corresponds to appearance of virus in blood, saliva, urine and feces for the first time
  • Cats will either make a true recovery and completely clear the virus from their body (60%) or;
  • Will make a false recovery and become persistently viremic for life; these cats will suffer from FeLV related diseases during the secondary stage of the infection, months to years later
  • Outcome depends on cat age, dose of agent, virulence of strain, degree of stress and immune status of the cat.

2.  Secondary stage lasts 1-12 months and results in death of cat due to immunodeficiencies, immune-related disorders or cancer (lymphoma, lymphocytic leukemia or myeloproliferative diseases).

  • There is no cure for the persistently infected cat, however, minimizing stress can delay the onset of the secondary stage.
  • Prevention and control based on routine testing and elimination of carrier cats; cleaning and disinfection of environment before reintroducing new animals
  • Vaccination of FeLV negative cats that are at high risk for contracting infection
  • vaccination does not cause a positive test since the test is measuring viral antigen and not antibodies to the virus
  • there is concern regarding vaccination of cats in general due to a low percentage developing tumors at the vaccination site

 

Feline Infectious Peritonitis (FIP)
  • Caused by infection by a coronavirus (FCoV) similar to an enteric coronavirus that causes a mild intestinal disease
  • Primarily fecal-oral transmission, shared litter boxes; survives in environment up to 6 weeks at room temperature; problem in multi-cat households
  • Vertical transmission is rare; maternal antibodies are protective until 5-6 weeks of age, but kitten immune system not mature enough to respond to exposure until approximately 12 weeks of age – hence a 6-7 week window of opportunity for infection.  Recent research suggests a genetic predisposition to this disease in some lines of cats.
  • Target cell for infection is the macrophage
  • Requires an effective cell-mediated immune response for the cat to recover; if not, persistent virus may cause an exaggerated and nonprotective humoral response that actually results in the disease due to the damaging effects of   immune complexes in the blood vessels
  • Disease is characterized by fluid build-up in the abdomen and/or thorax from blood vessel damage; damage to kidneys, liver, eye, or nervous system by immune complexes
  • Control and Prevention
  • Complicated due to lack of a good, specific test; problems with false positive tests
  • Isolate all cats with signs of FIP (controversy over whether cats actually "catch" the disease from other ill cats)
  • Remove all cats with FIV, FeLV
  • Multicat household that is FCoV negative -- only add seronegative cats and isolate them for 3 weeks to assure that they remain seronegative
  • Multicat household that is seropositive for FCoV
  • Test all queens prior to parturition
  • Isolate into a cleaned, disinfected (1:32 bleach:water) kitten room 1-2 weeks prior to parturition
  • Remove kittens from seropositive queens at 5-6 weeks and keep kittens isolated from all FCoV positive cats
  • Vaccinate all seronegative cats prior to introducing into a household where FCoV is enzootic (no consensus on efficacy and safety of vaccine)

 Feline Respiratory Diseases

  • Two viruses, feline herpesvirus (FHV) also known as feline rhinotracheitis virus, and feline calicivirus (FCV) cause most upper respiratory disease in cats.
  • Sneezing and nasal and ocular discharge are typically observed. Calicivirus can also cause ulcers of the mouth and tongue.
  • Both viruses are usually transmitted directly from cat-to-cat, however herpesvirus can survive for a day and calicivirus for up to a week in the environment, so indirect transmission can also occur. Cats that have recovered from the disease may continue to shed virus for varying amounts of time, and shedding may be interspersed by periods of latency.
  • Vaccination is successful at controlling the disease, but does not prevent shedding of virus in carrier cats. Cats may exhibit mild respiratory disease or acute lameness approximately 1 week post-vaccination. Vaccination failure may be due to persistent maternal antibodies in kittens, or to concurrent infection with FIV, FeLV or overwhelming exposure to the agent(s).

 

Zoonotic Diseases Carried by Cats

Toxoplasmosis – Cats serve both as a definitive and intermediate host for Toxoplasma gondii, the causative agent for toxoplasmosis.

  • Felines are infected with T. gondii by ingesting tissue cysts of the organism from an infected intermediate host (usually mice, but sheep, goats, pigs, chickens, etc. can also serve as an intermediate host if they ingest sporulated oocysts).
  • Felines are the only species in which the sexual phase of the life cycle of T. gondii is completed with the formation of oocysts in the epithelium of the intestine that are passed in the feces. Oocysts must sporulate to become infective; this can occur within 24 hours at room temperature. Sporulated oocysts can survive in the environment for several years and are resistant to disinfectants.
  • If pregnant animals or people ingest sporulated oocysts they can transmit the infection to the fetus and cause abortion,  stillbirth or birth of diseased offspring. People and animals with functional immune systems that become infected will usually have only mild, flu-like symptoms or no apparent illness and will develop protective immunity to further infection.

Cat Scratch Disease -- This is a disease of man caused by a gram negative bacillus (Bartonella henselae) that can be carried in cats as well as dogs, squirrels, goats, etc. It is most commonly spread to people by bites or scratches from cats, hence the name cat scratch disease. It results in local lymph node enlargement, fever, headache and muscle and joint pain.

Dermatophytosis (Ringworm) – This disease is not caused by a worm, but rather by a fungus that infects hair shafts and follicles. It results in hair loss and circular, raised, reddened areas on the skin. The disease is spread to people through direct contact with other infected people, cats, or other animals. Animals appear to build an immunity to the organisms as they mature, since it is most common in the young animal (kittens, calves, lambs). A vaccine has recently been introduced for use in cats, however most veterinarians reserve its use for households with endemic disease.

 

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