Occurrence of bovine giardiasis and endemic genetic characterization of Giardia duodenalis isolates in Heilongjiang Province, in the Northeast of China.

To determine the prevalence of bovine giardiasis in Heilongjiang Province in China and to molecularly characterize Giardia duodenalis, feces were collected from 814 dairy and beef cattle ranging in age from 6 days to 9 years. Clinical symptoms of diarrhea were recorded at the time of sampling. The G. duodenalis infection rate in cattle was 5.2 % (42/814) as determined by Lugol's iodine staining. G. duodenalis assemblages and subtypes were genetically diagnosed by sequence analysis of the triosephosphate isomerase (TPI) gene. Three assemblages were identified, representing A (n = 1), B (n = 18), and E (n = 24), with a mixed infection case of assemblages A and E. High heterogeneity was also observed within assemblages B and E at the TPI locus. Among the assemblages, eight subtypes of assemblage B and three subtypes of assemblage E were found to be novel subtypes. Findings on assemblages A and B are of public health importance. The zoonotic potential of bovine giardiasis needs to be further assessed by extensive genetic data of assemblages A and B from humans at the subtype level. The newly found subtypes of assemblages B and E imply that the evaluation of geographically distributed subtypes is of importance.