Potentially Zoonotic Helminthiases of Murid Rodents from the Indo-Chinese Peninsula: Impact of Habitat and the Risk of Human Infection

Abstract

In this study, we report the potential rodent-borne zoonotic helminths in wild-caught murid rodents from four categorized habitats-forest, nonflooded land, irrigated land, and human settlement in seven localities of Thailand, Cambodia, and Lao PDR. Out of 2478 rodent samples, 735 (29.7%) were infected by at least one of the following zoonotic helminth species: Echinostoma malayanum, Echinostoma ilocanum, Plagiorchis muris, Raillietina spp., Hymenolepis diminuta, Hymenolepis nana, Cyclodontostomum purivisi, and Moniliformis moniliformis. Raillietina spp. showed the highest prevalence (13.8%), followed by H. diminuta (8.6%), H. nana (6.7%), and C. purvisi (1.0%). Habitat affected the intensity of helminth infection in murid rodent hosts. Specific habitats favoring each zoonotic helminth species are discussed in relation to the risk of human infection. Season and host maturity influenced intensity of total zoonotic helminths, but there was no influence of host gender. However, in terms of individual helminth species, female rodents were more infected by E. malayanum, E. ilocanum, and C. purvisi than males. Among the rodent species, Rattus tanezumi seems to play the most important role as a reservoir by hosting seven zoonotic heminth species. This rat is ubiquitously found in all types of the habitats, suggesting that it can act as an important bridge species, carrying parasites across different habitats.

Helminths in rodents from Wet Markets in Thailand

“…Although the high prevalence of C. hepatica in commensal rodents may increase the health risk in humans, to date human seroprevalence has not been examined in SEA. Our study detected all the rodent-borne zoonotic nematodes and cestodes reported by Chaisiri et al (2015) except Cyclodontostomum purvisi. Thus, there can be no doubt that in the studied wet markets there is a potentially high risk of rodent-borne transmission.…”

“…The aforementioned studies of SEA markets (Claveria et al, 2005) (Paramasvaran et al, 2009;Tung et al, 2013), as well as in urban habitats (Mohd Zain et al, 2012), report the presence of the same zoonotic helminths as recovered in the present study (see details in Table 1). According to the review by Chaisiri et al (2015), four of our recovered helminths (H. diminuta, H. nana, Raillietina sp. and M. monoliformis) are potentially zoonotic species.…”

“…and M. monoliformis) are potentially zoonotic species. A fi fth gastrointestinal helminth (G. neoplasticum), not studied by Chaisiri et al (2015), is also a potentially zoonotic species and has been reported in humans in Thailand by Pasuralertsakul et al (2008). Nevertheless, reported cases of infestation in humans by this species worldwide are limited to just 40 -50 reports (Wilson et al, 2001).…”

“…Nevertheless, reported cases of infestation in humans by this species worldwide are limited to just 40 -50 reports (Wilson et al, 2001). We found a sixth zoonotic species, the lung nematode A. cantonensis, that was not included in the review by Chaisiri et al (2015) given that these authors only studied gastrointestinal helminths. This nematode causes human eosinophilic meningitis, and human cases have been reported in Thailand, mostly in the northeastern provinces (Eamsobhana, 2013) such as our study area.…”

“…The study of possible rodent-borne zoonoses is of interest as it has been reported previously that in the same study sites rodents are carriers and potential transmitters of Salmonella to humans. The role of rodents as reservoirs of helminth zoonoses in SEA has been reviewed by Chaisiri et al (2015). The prevalence of helminths in humans in Thailand should not be underestimated as a prevalence of 18.1 % was found by the last National Survey (Wongsaroj, 2015); some of these helminths are associated with rodents, the host species that are the object of the present study.…”