A field evaluation of PCR for the routine detection of Babesia equi in horses

We report on a study that evaluated the usefulness of PCR for the routine detection of Babesia equi in horses. The blood from a total of 105 horses comprising both sick and apparently healthy animals were examined for the presence of B. equi using both Wright-Giemsa-stained blood smears and PCR. Microscopic analysis of Giemsa-stained blood smears revealed 101105 animals positive for Babesia, compared to 16/105 for the primary PCR and 36/105 for the nested PCR. Three of the 10 samples positive by Wright-Giemsa-stain were negative by PCR for B. equi. However, evidence is presented that these samples contained B. caballi and not B. equi. The Wright-Giemsa-stain was shown to identify Babesia in mostly clinically ill animals while the nested PCR detected the organism in a large number of apparently healthy animals. The results of this study suggest that the nested PCR is superior to both Wright-Giemsa-stained and primary PCR methods, and should be considered for the routine detection of B. equi in both healthy and clinically ill horses. (C) 2003 Elsevier Science B.V. All rights reserved.