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Pulmonary Response in Cats with Cytauxzoon felis

Clinician's Brief (Capsule)


|August 2016

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Cytauxzoon felis is a protozoal parasite that infects the blood of domestic and wild cats in various regions of the United States. Infected ticks can transmit the parasite to cats while feeding; the parasite then replicates in the cat and spreads throughout the body. Infected cats may be subclinically affected, but clinical signs can include anorexia, depression, lethargy, dehydration, pyrexia, dyspnea, icterus, dark urine, pallor, anemic heart murmur, and increased capillary refill time. Hematology may reveal a normocytic, normochromic, nonregenerative anemia with pancytopenia or moderate neutrophilia. 

This study examined the local pulmonary immune response in cats naturally infected with C felis. Immunohistochemistry was performed postmortem on the lung tissue of 19 cats. The pro-inflammatory mediators and cytokines characterized were tumor necrosis factor-α, interleukin (IL)-1β, IL-6, inducible nitric oxide synthase, and major histocompatibility complex (MHC) II. When compared with uninfected healthy cat lungs, lungs from infected cats showed an increased expression in all these molecules. The authors also found MHC II expressed in the endothelium of infected cats. The authors concluded that C felis infection can cause a significant local pro-inflammatory immune response in the lungs, which adds to the pathogenesis of C felis infection and contributes to morbidity and mortality. This finding may guide the advancement of cytauxzoonosis treatment.


The disease process associated with C felis infection results in significant morbidity and mortality. A better understanding of disease pathology is of practical use in the clinical setting. In addition to parasite-specific drugs, knowledge of the pulmonary pathology assists in treatment during disease progression. This study provided options for a targeted approach to therapy for the inflammatory responses noted in pulmonary tissue. Targeting specific pro-inflammatory cytokines and other molecules may assist in reducing the progression of pathology in the lung. This type of approach may benefit in diminishing morbidity associated with this infectious disease.—Kelly St. Denis, MSc, DVM, DABVP (Feline Practice)


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