LIGHT-MICROSCOPY DIAGNOSIS OF BABESIA-BOVIS AND BABESIA-BIGEMINA KINETES IN THE HEMOLYMPH OF ARTIFICIALLY INFECTED BOOPHILUS-MICROPLUS ENGORGED FEMALE TICKS

The length, width and position of the nucleus of Babesia bovis and Bab esia bigemina kinetes from the haemolymph of Boophilus microplus engor ged female ticks were recorded. Additionally, the shape of Babesia bov is kinetes were registered as curved, semi-curved or straight. To this aim Boophilus microplus tick larvae from a colony free of Babesia wer e fed on splenectomised calves artificially infected with either Babes ia bovis or Babesia bigemina pathogenic strains. Six engorged female t icks showing an infection of at least ten mature kinetes of Babesia bo vis in a sample of haemolymph 5 days after detachment were also monito red 7, 9 and 10 days after collection. The same procedure was followed with six engorged female ticks infected with Babesia bigemina. One hu ndred and twenty kinetes of each species of Babesia were evaluated. Th e mean length +/- standard deviation and ranges for Babesia bovis kine tes were 14.30 +/- 0.922 mu m and 11.9-16.3 mu m, while the correspond ing measures for the kinetes of Babesia bigemina were 11.27 +/- 0.900 mu m and 9.0-13.1 mu m (P < 0.001, t-test). The width was 3.33 +/- 0.3 15 mu m, 2.6-4.0 mu m for Babesia bovis and 2.24 +/- 0.287 mu m, 1.5-2 .8 mu m for Babesia bigemina kinetes (P < 0.001). The most common posi tion of the nucleus was central for both species of Babesia. A total o f 58% of Babesia bovis kinetes showed the typical curved tail. No effe ct of time post-collection and individual host ticks in the kinete of Babesia bigemina was found while an unexpected influence of individual host tick in the width of Babesia bovis kinetes was detected (P < 0.0 1, analysis of variance). The overlap in the sizes of kinetes from bot h species of Babesia makes it difficult to apply the results to ticks of unknown babesial infection status. This finding is further complica ted by the intra-specific size variations of Babesia kinetes from diff erent geographical origins.