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Coccidioides spp

Coccioides immitis and, more rarely, Paracoccioides brasiliensis have been recorded as causing fungal infections in cats[1].

Cats are infrequently infected with these fungal organism, which belong to the Family Onygenales. Although only a limited number of cases have been described in cats, primarily in the Americas, it appears that the primary route of infection is by inhalation of small airborne conidiospores[2].

Infection by direct inoculation of the organism has also been reported. Dissemination occurs through hematogenous and lymphatic routes. A competent cell-mediated immune response must be present to contain infection. Infection with feline leukemia and feline immunodeficiency viruses does not appear to predispose cats to coccidioidomycosis. Humans are not at risk for the disease from contact with infected cats but may become infected through shared environmental exposure[3].

Clinical signs

In C. immitis infections, nonspecific signs of fever, anorexia, and weight loss are common. Dermatologic abnormalities, such as draining lesions and abscesses, are the most common finding in infected cats. Ocular inflammation, bony lesions, and lower respiratory signs are less frequently reported clinical findings.

P. brasiliensis has been reported as causing neurological signs associated with CNS infections (including intention tremors, nystagmus, mydriasis and severe bilateral facial paralysis) as well as funguria associated with acute interstitial nephritis.

Diagnosis

Clinical signs are nonspecific; however, cats from the endemic area with signs of systemic disease should be suspected of being infected. Cytologic specimens may be sufficient to make a diagnosis. These may be obtained by aspiration of lung parenchyma or lymph nodes, impression smears from draining tracts, or bronchoalveolar lavage. Negative findings do not rule out the disease. The associated inflammatory response is granulomatous. Routine in-office stains sometimes fail to stain the organism. Special stains may be requested from commercial diagnostic laboratories.

As with cytological specimens, special stains may be required to identify the organism in tissue. Grocott-Gomori methanamine silver nitrate and periodic acid-Schiff stains are often useful. The laboratory should be alerted when coccidioidomycosis is a differential diagnosis.

On radiological examination, hilar lymphadenopathy, interstitial lung disease, and pleural disease may be present. Infected bone may have osteoproductive or osteolytic lesions.

Recent studies suggest that serological testing may be more useful than previously thought. Precipitin antibodies and complement-fixing antibodies were found in most cats tested in one study. False negatives may occur. At present, serology is a questionable means of detecting progression of disease and response to therapy. The organism does not typically exfoliate in large numbers, so identification may require a careful microscopic search.

Treatment

Itraconazole is safely dosed at 5 – 10 mg/kg orally twice daily.

Fluconazole appears to be more effective, at doses of 40 mg orally twice daily for long periods of time (3 – 4 years). Urine creatinine must be assessed at regular intervals to monitor toxicity associated both with systemic fungal infections and drug toxicity associated with imidazole drugs[4].

References

  1. ↑ Gonzalez, JF et al (2010) First report on the diagnosis and treatment of encephalic and urinary paracoccidiodomycosis in a cat. JFMS 12:659-662
  2. ↑ Sellon, RK & Legendre, AM (2009) Systemic fungal infections. In: Bonagura, JD & Twedt, DC (Eds). Kirk’s current veterinary therapy. XIV. Saunders Elsevier, St Louis. pp:1265-1267
  3. ↑ Norsworthy, GD (2003) The Feline Patient. 2nd Edition. Lincott Williams & Wilkins
  4. ↑ Wolf, A (1994) Antifungal agents. In: August, JR (Ed) Consultations in feline internal medicine. WB Saunders, Philadelphia

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