Canine babesiosis: indirect fluorescent antibody test for a North American isolate of Babesia gibsoni.

A sensitive and reproducible indirect fluorescent antibody test for a North American isolate of Babesia gibsoni was described. In blind tests (coded samples), titer reproducibility was within two 4-fold dilutions and the appropriate positive and negative sera were identified as such. Babesia gibsoni antisera reacted with homologous antigen at one to three 4-fold dilutions greater than with the following heterologous species: B bigemina, B argentina, B equi, Plasmodium falciparum, and P brasilianum. The titer of B canis antiserum to B gibsoni antigen was 1:1,024. low parasitemia (less than 0.01%) of B gibsoni preceded development of minimum significant titer (1:64) by 10 days in a splenectomized dog. Maximum titer was detected 25 days later. In a nonsplenectomized dog, low parasitemia (less than 0.01%) was noted 6 days after injection; it reached 8% at 5 weeks and decreased to and remained below 1% at 7 weeks. A titer of 1:256 occurred at 25 days and increased to 1:65,536 at 18 weeks. Thereafter, it fluctuated to 1:4,096 until the experiment was ended at 24 weeks. organismic antigen retained its reactivity for 5 days at 5 C. This indirect fluorescent antibody test should be useful in the diagnosis of dogs infected with B gibsoni.