Detection of haemoparasites in selected Australian reptiles using archived blood smears

Haemoparasites of Australian reptiles remain poorly documented, with much of the available knowledge derived from studies conducted several decades ago. Using archived blood smears, this study examined the occurrence, morphology, and host associations of haemoprotozoans in two gecko species (Gehyra dubia and Hemidactylus frenatus), two freshwater turtle species (Emydura macquarii krefftii and Muchelys latisternum), and an associated turtle leech (Placobdelloides bancrofti) from northern Queensland, Australia. A total of 332 gecko blood smears were examined, with no blood parasites detected, suggesting that infections were absent, rare, or below the detection threshold at the time of sampling. In contrast, protistan parasites were detected in 93% of 15 freshwater turtles examined, with high prevalence of both haemogregarines and trypanosomes and frequent co-infections. Morphological characteristics and developmental stages of haemogregarines were consistent with the genus Haemogregarina, and similar with Haemogregarina clelandi, representing a new geographic record. Trypanosome infections occurred as multiple trypomastigote morphotypes consistent with previous descriptions of Trypanosoma chelodinae and related forms. All 38 leech crop smears examined were positive for Trypanosoma spp., predominantly at the epimastigote stage, supporting the role of P. bancrofti as a vector of turtle trypanosomes in Australian freshwater systems. This study highlights marked contrasts in haemoprotozoan occurrence between terrestrial and aquatic reptiles, reinforces the importance of leeches in turtle parasite transmission, and demonstrates the value of archived blood smears for establishing historical baselines and addressing knowledge gaps in Australian reptile parasitology.