Characteristics of naturally acquired Plasmodium relictum capistranoae infections in naive Hawaiian crows (Conrus hawaiiensis) in Hawaii

Indigenous to Hawaii, the Hawaiian crow (Corvus hawaiiensis) is the world's most severely endangered species with only 3 reproductively active pairs remaining in the wild. Seven captive-reared, avian malaria-naive C. hawaiiensis were exposed in an outdoor aviary and hematologically and serologically monitored for 9 wk. Three birds showed Plasmodium relictum capistranoae parasitemia (6.35%, 2.15%, and 0.60%). All birds were seroconverted for malaria on week 7 as determined by enzyme-linked immunosorbent assay (ELISA). Malaria IgG levels of exposed parasitemic birds did not differ from those of exposed nonparasitemic C. hawaiiensis and were not significantly correlated with the level of parasitemia. Four of 9 hematological parameters, e.g., white blood cell count (WBC), relative and absolute lymphocytosis, and total solids (TS), showed significant increases related to ELISA-determined malarial infection. The sensitivity, specificity, and the positive predictive values of these 4 parameters for malarial infections in C. hawaiiensis were higher than 66%, with the WBC and TS sensitivity reaching 100%. The reference range of 9 hematological parameters was established based on uninfected, clinically healthy C hawaiiensis. Seven birds were successfully treated and released, increasing the total wild C. hawaiiensis world population by approximately 50%.