Evaluation of the hemagglutination test for epidemiologic studies of leptospiral antibodies in wild mammals.

Sera from 153 wild animals of 18 species were tested for antibodies against 12 serovars of Leptospira by the microscopic agglutination (MA) test. Seventy-five percent of the animals tested were seropositive against one or more of the 12 serovars used. The most commonly found serovars were pomona, autumnalis, pyrogenes, icterohaemorrhagiae, australis, and canicola. Of 62 carnivores representing 7 species, 55 (89%) were seropositive, as were 46 (60%) of 77 rodents from 9 species. Leptospira of the serovar copenhageni serogroup icterohaemorrhagiae were recovered from kidney tissues of a Norway rat (Rattus norvegicus). Of 443 wildlife sera tested by the indirect hemagglutination (IHA) test using cells sensitized with L. illini antigen, 47 (11%), mainly carnivores and deer, gave a heterophile reaction. Of the remaining 396 sera, 164 (41%) were seropositive for leptospirosis by the IHA test. To compare the IHA test with the MA test, 143 serum samples were tested by both methods. There was 84% concordance between the two tests.