TIME-SERIES ANALYSIS OF THE PREVALENCE OF ENDOPARASITIC INFECTIONS INCATS AND DOGS PRESENTED TO A VETERINARY TEACHING HOSPITAL

The apparent prevalence of endoparasitic infections of cats and dogs p resented to the small animal Veterinary Hospital of the University of Pennsylvania was measured between 1984 and 1991. Two thousand feline a nd 8077 canine fecal samples were examined along with 6830 canine bloo d samples. The overall mean monthly prevalence of feline infections wa s 16% for ascarids, 0.9% for hookworms, 4.0% for tapeworms, 2.4% for G iardia spp. and 4.2% for coccidia. The overall mean monthly prevalence of canine infections was 5.7% for ascarids, 9.7% for hookworms, 9.7% for whipworms. 1.8% for tapeworms, 4.7% for Giardia spp. and 3.1% for coccidia, There was a significant downward trend in the prevalence of hookworms and heartworms in dogs (P < 0.001 in both cases). There was a significant upward trend in the prevalence of tapeworms in cats (P < 0.05). There were no significant long-term trends in any of the other time series. The smoothed data were analyzed for seasonal trends. Non e of the autocorrelation analyses gave incontrovertible evidence of se asonality. The repeated peaks at the 6, 12 and 24 month lags in the ca se of ascarid infections were suggestive of a 12 month seasonality wit h a peak prevalence in December, but the results were not statisticall y significant at the 5% level. Hookworms and whipworms in dogs occurre d together more than would be expected by chance in 4 out of the 6 yea rs for which data were available.