To characterize the number of granulocytes needed to count on peripheral smear to identify diagnostic anaplasmosis morulae.
Retrospective case study where the peripheral smears of 14 confirmed cases of anaplasmosis were examined. The granulocytes were counted up to 100 and 200 until a morula was identified. The mean counts of three pathologists were calculated to determine the minimum number of granulocytes needed to count for identifying diagnostic morulae.
Morulae were identified before a count of 100 granulocytes in 11 (78.6%) cases and between 100 and 200 granulocytes in 3 (21.4%) cases. All 14 (100%) cases had morulae identified before counting 200 granulocytes.
Peripheral smears are a useful, cost-effective, and time-effective tool for diagnosing anaplasmosis. In positive cases, diagnostic morulae can be identified with a count of 200 granulocytes.