Trypanosoma dionisii in China: ecology and tentative epidemiology

Trypanosoma dionisii, one of several species that parasitizes Chiroptera worldwide, was first reported in a 30 year-old pregnant woman in China. It is important to improve our understanding of ecological and epidemiological patterns to identify potential transmission vectors and to estimate the risk of T. dionisii infection in the local population as well as in various species of domestic and wild animals.

We performed an ecological survey with epidemiological features in the area where the first T. dionisii case was found, including parasitological and serological tests and local demographic information for six surrounding villages. Sylvatic and domestic mammals and potential vector organisms in the same locality were investigated by nested-PCR for Trypanosoma and the phylogenetic analysis was performed.

A total of 241 samples from the local population were screened for trypanosomiasis by parasitological and serological tests with no positive cases identified. However, 11 out of 18 bats collected from the village tested positively for Trypanosoma spp. by microscopy and nested-PCR, while 9 were positive for T. dionisii and 2 for T. vespertilionis. With regard to cats, 5 from a pet hospital in local showed 3 were co-infected with of T. dionisii and T. vespertilionis, and one having T. dionisii only, as well as one of the 29 animals examined was found infected with T. vespertilionis. Other animals seemed even less affected as all 163 blood samples collected from livestock and poultry, such as cows, sheep, chickens, ducks and geese, tested negative. Also 35 mosquito and mite pools tested negatively, while 4 out of 30 tick pools tested positive by nested-PCR with their sequences close to T. conorhini.

The survey indicates that a natural epidemic foci of T. dionisii, exists in Dongying Region, Shandong Province, China. Although no evidence of a high risk for human epidemic was found, the widespread presence of this parasites in bat species and a relatively high infection rate observed in the surveyed cats and dogs emphasize the emerging threat it poses to human health. Further surveillance and analysis are warranted to evaluate the transmission risk.