Infestation and Distribution of Ectoparasitic Insects on the White-Footed Indochinese Rat (Rattus nitidus) in Southwest China.

Background: Ectoparasitic insects (fleas and sucking lice) on rodents can serve as vectors of some zoonotic diseases. Objective: To investigate the insect infestation and distribution on white-footed Indochinese rats (Rattus nitidus) in southwest China, a focus of zoonotic diseases. Methods: Field investigations were conducted at 116 survey sites between 2000 and 2024. Insects were identified under a microscope, and a series of calculations was conducted. Results: From 836 R. nitidus rat hosts, 3322 insects were identified as 24 species, including eight vector species. Fleas had more species (22) and fewer individuals (539) than sucking lice (two species with 2783 individuals). Male and adult hosts had higher insect infestations than females and juveniles (p < 0.05), and insect infestations varied in different environments. The insect spatial coefficients were higher than the critical values for determining aggregated distribution. The association coefficient between fleas and lice was V = 0.07 (p < 0.05). Conclusions:Rattus nitidus is susceptible to insect infestation, with the coexistence of multiple vector species. Fleas have much higher species diversity than sucking lice. Insect infestations exhibit sex and age biases of hosts as well as environmental heterogeneity. Fleas and lice are of aggregated and mutually independent distribution on R. nitidus. Multiple vector species on R. nitidus would probably increase the potential risk of transmission and focus persistence of related zoonotic diseases in southwest China.