Feline Infectious Peritonitis (FIP)
FIP virus is a mutated feline enteric coronavirus, the devastating etiology of multisystemic granulomatous inflammation with necrotizing vasculitis in cats. In stark contrast, the wild type strain of feline enteric coronavirus causes only a mild gastroenteritis. Most cases of FIP develop in multicat households or catteries. FIP can occur in cats of any age but is generally recognized in cats under 5 years old. Anorexia, weight loss, fever, ocular inflammation, ascites, dyspnea, and occasionally icterus may be observed clinically. FIP is the most common cause of icterus in cats under 2 years old.
At necropsy, the abdomen and/or thorax generally contain turbid fluid with fibrin strands. The serosal surfaces of visceral organs, the omentum, and mesentery are covered with variably-sized firm, white nodules. Similar nodules can be found throughout the parenchyma of visceral organs, most commonly within the liver and kidneys.
Laboratory tests:
Histopathology and immunohistochemistry
PCR - liver, kidney, lung, spleen, brain (routine PCR cannot differentiate wild-type enteric coronavirus from the mutated FIP strain)
Feline Leukemia Virus (FeLV) Infection
FeLV is an oncovirus of cats. The principal route of infection is direct contact with contaminated saliva and nasal secretions: this makes sharing of food and water an effective method of virus transmission. Infection is most common in male, outdoor cats between 1 and 6 years of age. Approximately 30% of infected cats become persistently viremic, shed viral particles, and usually die of FeLV-related illnesses within 2 to 3 years. Another 30% of infected cats become transiently viremic, develop antibodies, and recover from the infection in 4 to 6 weeks. The remaining cats retain a latent infection (not actively shedding), but when the host is immunologically suppressed (by infection, stress, or steroid therapy), the latent infection becomes actives, producing viremia, clinical disease, and shedding of viral particles. FeLV infects lymphocytes, monocytes, and hematopoietic progenitor cells in the bone marrow; therefore, secondary infection due to FeLV-induced immunosuppression is common.
At necropsy, approximately 23% of FeLV-infected cats have neoplasms, 96% of which are lymphosarcoma/leukemia. FeLV-related lymphosarcomas are commonly seen in the mediastinum, alimentary tract, spleen, lymph nodes, kidney, and liver. Hemorrhagic necrotizing enteritis resembling that caused by feline panleukopenia (parvovirus) has been reported. FeLV-induced immunosuppression becomes an important predisposing factor to various bacterial and fungal infections.
Laboratory tests:
Histopathology and immunohistochemistry
Immunofluorescent antibody (IFA) test or ELISA - whole blood and serum
False negative results can occur
Feline Immunodeficiency Virus (FIV) Infection
FIV is morphologically similar to, but antigenetically distinct from, HIV in man. Biting among cats is thought to be the primary route of transmission of FIV. Older, male, outdoor cats are most commonly infected. Transplacental and perinatal transmission have been reported. The median ages of healthy, FIV-infected cats and clinically-ill infected cats are 3 years and 10 years, respectively. Co-infection with other viruses such as FeLV, calicivirus, feline herpesvirus, Mycoplasma haemofelis (Haemobartonella felis - feline infectious anemia), or Toxoplasma gondii can occur.
Primary FIV-related clinical syndromes such as diarrhea, glomerulonephritis, nonregenerative anemia, lymphoma, etc, have been reported but FIV infection plays an important role as an immunosuppressive factor, which predisposes animals to other viral, bacterial, and parasitic infections.
Laboratory tests:
Histopathology
ELISA - serum (false negative)
Feline Panleukopenia (Feline Parvoviral Enteritis)
Although the clinical signs are similar to those of canine parvovirus enteritis, including vomiting and bloody diarrhea, feline parvovirus is distinct from canine parvovirus.
Necropsy findings are also similar to those associated with canine parvoviral enteritis. The intestinal wall in cats is thicker than that of food animals or dogs and evidence of luminal changes cannot be seen on external examination. Unless the entire intestine is carefully dissected (the lesion can be segmental with marked distinction between affected and unaffected areas), lesions can be easily missed.
Laboratory tests:
Histopathology and immunohistochemistry
PCR - spleen, small intestine, lymph node
Hypertrophic Cardiomyopathy
The cause of primary, or idiopathic, hypertrophic cardiomyopathy (HCM) is unknown but there is believed to be a genetic basis. There are breed predilections in Maine Coon, Persian, Ragdoll, and American Shorthair cats. Secondary HCM develops as a compensatory response to chronic stress or certain diseases. Hyperthyroidism (bilaterally symmetrical thyroid hyperplasia) is the most common cause of secondary HCM. Affected cats are generally middle-aged male cats (6 years old and older). Cats with mild symptoms are commonly subclinical for years. Symptomatic cats can have symptoms with varying degrees of severity including tachypnea, dyspnea, tachycardia, and signs of thromboembolism. Saddle thrombus is an important sequela, resulting in hind limb paralysis. Sudden death is very common.
At necropsy, the left ventricle and interventricular septum are markedly thickened with a severely narrowed ventricular lumen. Bilaterally symmetrical thyroid hyperplasia and saddle thrombus may be seen.
Laboratory test:
Histopathology
Feline Lower Urinary Tract Disease (FLUTD)
FLUTD is characterized by partial or complete urethral obstruction with clinical signs of pollakiuria, hematuria, and dysuria. Acute death can occur due to hyperkalemia secondary to acute renal failure. FLUTD was previously known as "feline urologic syndrome". Urethral obstruction is often caused by struvite (magnesium ammonium phosphate) urolithiasis and/or struvite-containing mucous plugs. Less commonly, FLUTD occurs due to primary bacterial infection. Affected cats are commonly indoor, obese and between 2 and 6 years of age. The disease is most commonly observed in the winter and spring and there is no apparent sex predilection. Mortality ranges from 6–36%. Chronic renal failure or ascending pyelonephritis is possible long-term outcome of FLUTD. Formation of struvite is related to high magnesium diet, reduced water intake, and high urine pH.
Commonly, at necropsy, a urethral plug may be present. Urethral plugs are a mass of fine, sandy sludge composed of fine struvite crystals admixed with organic debris, which becomes molded to the shape of the urethra. Hemorrhagic cystitis (hematuria) can also occur.
Laboratory test:
Histopathology
Chronic Renal Failure
Chronic renal failure is fairly common in geriatric cats. It is caused by various etiologies including glomerulonephritis, amyloidosis, infarction, pyelonephritis, leptospirosis, urolithiasis, nephrotoxicosis, etc. The clinical presentations can include weight loss, polydipsia-polyuria, poor body condition, and nonregenerative anemia. At necropsy, kidneys are often small, irregularly-shaped, and contain multiple infarcts. Uremia-related lesions similar to those observed in dogs can also be observed.
Laboratory test:
Histopathology