Infectious diseases can often be insidious in their clinical presentation. Case studies will be used to highlight some interesting
infectious diseases that can affect the feline patient.
Lungworm infection
Causative agent: Aelurostrongylus abstrusus
Transmission: Predation of paratenic hosts (mice, voles and possibly birds) that ingest infected snails or slugs (intermediate
hosts); Cats are the principle hosts.
Geographic distribution: Worldwide
Pathogenesis: Cats are the principle hosts of this worm. Adult worms live in the bronchioles. Larvae are deposited in the
bronchioles and coughed up, swallowed and shed in the feces. Snails and slugs are the intermediate hosts.
Risk factors: Outdoor cats with exposure to snails and slugs and paratenic hosts
Clinical findings: Related to inflammatory reactions to the parasites. "Asthma"- like signs – coughing, wheezing, overt respiratory
distress. Thoracic radiographs may show diffuse interstitial nodules; peribronchial and alveolar patterns may also be present.
Diagnosis: Detection of larvae in airway washes or lung aspirates or Baermann fecal
Treatment: Fenbendazole 25-50 mg/kg PO q 24 hours for 10-14 days; Ivermectin 400 ug/kg SQ; bronchodilators and glucocorticoids
may be needed to address the inflammation.
Public health considerations: None.
Things to remember: A treatable cause of "asthma"
Mycoplasma polyarthritis
Causative agent: Mycoplasma spp. (M. gatae, M. felis)
Transmission: Cat to cat - suspect initial respiratory, conjunctival or urogenital infection with systemic spread.
Geographic distribution: Worldwide
Risk factors: Large cat population (cattery), exposure to other cats, immunosuppression, stress
Clinical findings: Fever, hyperesthesia, difficulty walking, joint effusion, joint pain.
Diagnosis: Identification of the organism by culture or PCR in joint fluid; suppurative joint effusion
Treatment: Doxycycline 5 mg/kg PO q 12h; Prednisolone may also be needed due to the polyarthritis (2.5 – 5 mg/ cat every 12-24h).
Must treat for an extended period of time.
Public health considerations: Not considered to be a major public health risk.
Things to remember: The organisms may become intracellular, resulting in chronic persistent infection. These organisms may
also stimulate chronic immune-mediated disease.
Toxoplasma gondii -neurologic involvement
Causative agent: Toxoplasma gondii, an obligate intracellular coccidian protozoan parasite
Transmission: Infection acquired by ingestion of infective oocysts or tissue cysts.
Geographic distribution: Worldwide; higher seroprevalence in warm, moist, or tropical climates.
Risk factors: Immunosuppression from infections such as FeLV, FIV, or FIP; Glucocorticoid therapy or antitumor chemotherapy;
post renal transplantation; ingestion of raw meat; outdoor cats hunting prey (birds, rodents).
Clinical findings: Anorexia, lethargy, fever, weight loss, vomiting, diarrhea, respiratory difficulties, icterus, abdominal
effusion, ocular inflammation, blindness, anisocoria, seizures, behavioral changes, incoordination, circling, twitching, tremors,
ataxia, paresis, paralysis, muscle pain/weakness, tetraparesis. Clinical signs may be sudden or slow in onset.
Diagnosis: Serology – IgM, IgG titers on serum and CSF; CSF analysis – high leukocyte count (mononuclear cells and neutrophils),
elevated protein; organism detection rare.
Treatment: Clindamycin 25-50 mg/kg PO or IM divided q. 12h; Trimethoprim-sulfonamide 15 mg/kg PO q 12h; long-term antibiotic
administration may be required.
Public health considerations: Immunocompromised people and pregnant women should avoid contact with raw meat and litter boxes.
Things to remember: Oocysts need at least 24 hours to become infective, so risk of exposure/infection is minimized if litter
boxes are cleaned daily.
