Heartworm infection in cats: 50 cases (1985-1997)

Objective-To characterize risk factors, clinical findings, usefulness of di agnostic tests, and prognosis in cats with naturally occurring heartworm in fection (HWI). Design-Retrospective study. Animals-50 cats with Diroiilaria immitis infection. Procedure-Medical records, thoracic radiographs, and echocardiograms were r eviewed and findings compared with appropriate reference populations. Results-Findings suggested that male cats were not predisposed to HWI, dome stic shorthair cars were at increased risk, and indoor housing was only par tially protective. Fewer cases of HWI were identified in the final quarter of the year, compared with other periods, and prevalence is nor apparently increasing. Signs of respiratory tract disease were most common, followed b y vomiting. Infection was diagnosed incidentally in > 25% of cats, converse ly 10% of infected cats died suddenly without other clinical signs. Serolog ic tests were most useful for diagnosis, followed by radiography and echoca rdiography. Eosinophilia supported the diagnosis. Overall median survival t ime was 1.5 years but exceeded 4 years in cats surviving beyond the day of diagnosis. Conclusions and Clinical Relevance-Sex does nor appear to be a risk factor for HWI in cats, and indoor housing provides only incomplete protection. Si gns of respiratory tract disease (dyspnea and cough) are the strongest indi cators of HWI in cats, and some radiographic evidence of infection is detec ted in most cases. Antibody screening for HWI in cats is efficacious, and a ntigen testing and echocardiography are most useful for making a definitive antemortem diagnosis.