Cats and dogs can be reservoirs for several zoonotic diseases, even when the infectious animal has no clinical signs. This study in Austria examined the role of cat or dog ownership in the incidence of seroprevalence to several bacterial diseases. Samples from 202 persons who owned cats, dogs, or both were compared with samples from 174 people who had no domestic pet contact for at least a year. A total of 88 (23%) had antibodies against Bartonella henselae, which causes cat-scratch disease. Pet ownership did not influence seroprevalence to B. henselae. IgG/IgM antibodies to Anaplasma phagozytophilum, human granulocytic ehrlichiosis, was 9% overall. There was no difference according to age, sex, urban or rural residence, or pet ownership. The 6 patients with positive IgM antibodies showed no clinical evidence of disease. Q fever (Coxiella burnetii) has been reported in persons with occasional contact with infected pets. In this study, 6% of the people had antibodies to C. burnetii, but once again no relation to pet ownership was seen.

COMMENTARY: While it is reassuring to read this study, the results should be interpreted cautiously. The sample size is small, and differences between the groups may not have been detectable. Flea and tick control programs will decrease risk for transmission of these and other diseases in all populations, including immunosuppressed patients.

Cat or dog ownership and seroprevalence of ehrlichiosis, Q fever and cat-scratch disease. Skerget M, Wenisch C, Daxboeck F, et al. EMERG INFECT DIS 9:1377-1340, 2003.