Relationships between leukocytes and Hepatozoon spp. In green frogs, Rana clamitans

There are few published data on amphibian leukocyte profiles, and relationships between amphibian leukocytes and parasites are even less well known. Using counts from 35 pairs of blood smears taken 2 days apart, we tested for correlations between leukocyte proportions and infection intensities of Hepatozoon spp. (either Hepatozoon catesbianae or Hepatozoon clamatae) in green frogs (Rana clamitans). On average (SE), we counted 65.4 (1.7) lymphocytes, 14.0 (1.3) neutrophils, 19.3 (1.6) eosinophils, 0.9 (0.1) monocytes, and 0.4 (0.1) basophils per 100 leukocytes. All frogs harbored Hepatozoon spp. (median seven parasites per 100 leukocytes; range 1-250). Significant relationships were not observed between numbers of leukocytes and infection intensities of Hepatozoon spp. Among the possible explanations for these null results are that Hepatozoon spp. is benign, that Hepatozoon spp. is able to evade detection by the immune system, that Hepatozoon spp. is able to manipulate leukocyte investment, or that other unmeasured or undetected parasites were more important in affecting immune response.