Sensitivity of diagnostic techniques in determining the prevalence of anuran trypanosomes

Two hundred thirty-three leopard frogs (Rana pipiens) from Oshkosh, Wisconsin, USA, were divided into two groups and their blood examined for trypanosomes. In Group I (n = 157), where the blood was examined by the hematocrit centrifuge technique (HCT), 36 (23%) were infected with trypanosomes. Eighteen were infected with Trypanosoma pipientis, 13 with Trypanosoma ranarum, three with Trypanosoma rotatorium and two with mixed infections of T. pipientis and T. ranarum. In Group II (n = 76) the blood was cultured and also examined by HCT and wet mounts. Trypanosomes (T. pipientis and T. ranarum) were detected in 24 frogs (33%) using all three techniques. Eleven T. pipientis were detected by HCT, however none by culture and two by wet mounts. Twelve T. ranarum were detected by culture while only 10 were found by HCT and five by wet mounts. One T. ranarum infection detected by HCT was missed by culture because of bacterial contamination. The HCT was consistently better than wet mount examinations. It is suggested that the HCT be used whenever possible in future trypanosome surveys.