Infestation patterns and ecological distribution of fleas and sucking lice on Rattus tanezumi in southwest China: Evidence from a long-term multi-provincial study (2000-2024).

BACKGROUND AND AIM: The oriental house rat (Rattus tanezumi) is a dominant commensal rodent in southwest China and an important reservoir host for multiple zoonotic pathogens. Fleas and sucking lice that parasitize this species play a critical role in the maintenance and transmission of flea-borne and louse-associated diseases. However, long-term, large-scale evidence on the infestation patterns, ecological distribution, and host-parasite relationships of these ectoparasites remains limited. This study aimed to comprehensively characterize the infestation status, community structure, and ecological determinants of fleas and sucking lice on R. tanezumi across southwest China.

MATERIALS AND METHODS: A retrospective analysis was conducted using data from systematic field investigations conducted at 116 survey sites across five provincial regions of southwest China between 2000 and 2024. Rodents were captured using standardized trapping protocols in indoor and outdoor habitats. Fleas and sucking lice were collected, mounted, and taxonomically identified under a microscope. Infestation indices, including prevalence, mean abundance, and mean intensity, were calculated. Community diversity indices, host-related factors (sex, age, and relative fatness), environmental gradients (latitude, longitude, and altitude), and habitat types were analyzed. Association coefficients and Spearman's rank correlation were used to assess interspecific and intergroup relationships.

RESULTS: A total of 3,069 R. tanezumi were examined, of which 40.40% were infested with ectoparasitic insects. Overall, 12,539 insects belonging to 34 species were identified, comprising 30 flea species and four sucking louse species. Fleas exhibited markedly higher species diversity but lower individual abundance than sucking lice. Ten flea species are known or potential vectors of zoonotic pathogens. Sucking lice showed significantly higher infestation prevalence and intensity than fleas (p < 0.05). Male, adult, and low-fatness hosts harbored significantly heavier louse infestations, whereas flea infestation showed no clear sex or age bias. Infestation indices varied significantly across environmental gradients and habitats. The association coefficient between fleas and lice was close to zero, indicating mutual independence.

CONCLUSION: R. tanezumi harbors a diverse assemblage of ectoparasitic insects, including multiple zoonotic flea species. Fleas and sucking lice exhibit contrasting community structures, host associations, and ecological patterns. These findings provide long-term, multi-regional evidence supporting targeted surveillance and control strategies for rodent-associated ectoparasites and related zoonoses in southwest China.