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Prevalence of naturally occurring Dirofilaria immitis infection among nondomestic cats housed in an area in which heartworms are endemic

Clarke AtkinsDepartment of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606.

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 DVM, DACVIM
,
Anneke MorescoCarnivore Preservation Trust, 1940 Hanks Chapel Rd, Pittsboro, NC 27312.
Present address is the Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616.

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 MS, DVM
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Annette LitsterCentre for Companion Animal Health, School of Veterinary Science, University of Queensland, Brisbane, Queensland 4072, Australia.

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 BVSc, PhD

Abstract

Objective—To determine prevalences of heartworm exposure (ie, positive heartworm antibody test results) and heartworm infection (ie, positive heartworm antigen test results or identification of mature heartworms at necropsy) among nondomestic cats housed in an area in rural North Carolina where Dirofilaria immitis is known to be endemic and among nondomestic cats housed in areas with a low prevalence of dirofilariasis or in an area considered to be free from heartworms.

Design—Cross-sectional prevalence survey.

Animals—97 nondomestic cats in North Carolina (study population) and 29 nondomestic cats in Colorado; Queensland, Australia; or Auckland, New Zealand (control population).

Procedure—Results of serologic tests and postmortem examinations were reviewed.

Results—Results of heartworm antibody tests were positive for 57 of 75 (76%) study cats and 1 of 29 (3%) control cats. Male study cats had a significantly higher risk of heartworm exposure than did female study cats (relative risk, 1.3). Results of heartworm antigen tests were negative for all 47 study cats and 16 control cats that were tested. Postmortem examinations were performed on 21 study cats, and 1 (5%) was found to be infected with heartworms.

Conclusions and Clinical Relevance—Results suggested that nondomestic cats housed outdoors in the southeastern United States are at risk for heartworm exposure and infection, with male cats having a greater risk of exposure than female cats. (J Am Vet Med Assoc 2005;227:139–143)

Abstract

Objective—To determine prevalences of heartworm exposure (ie, positive heartworm antibody test results) and heartworm infection (ie, positive heartworm antigen test results or identification of mature heartworms at necropsy) among nondomestic cats housed in an area in rural North Carolina where Dirofilaria immitis is known to be endemic and among nondomestic cats housed in areas with a low prevalence of dirofilariasis or in an area considered to be free from heartworms.

Design—Cross-sectional prevalence survey.

Animals—97 nondomestic cats in North Carolina (study population) and 29 nondomestic cats in Colorado; Queensland, Australia; or Auckland, New Zealand (control population).

Procedure—Results of serologic tests and postmortem examinations were reviewed.

Results—Results of heartworm antibody tests were positive for 57 of 75 (76%) study cats and 1 of 29 (3%) control cats. Male study cats had a significantly higher risk of heartworm exposure than did female study cats (relative risk, 1.3). Results of heartworm antigen tests were negative for all 47 study cats and 16 control cats that were tested. Postmortem examinations were performed on 21 study cats, and 1 (5%) was found to be infected with heartworms.

Conclusions and Clinical Relevance—Results suggested that nondomestic cats housed outdoors in the southeastern United States are at risk for heartworm exposure and infection, with male cats having a greater risk of exposure than female cats. (J Am Vet Med Assoc 2005;227:139–143)