Detection of zoonotic pathogens in invasive black rats (Rattus rattus) inside and outside a coastal protected area in southern Peru

Introduction – This study investigates the occurrence of Leptospira spp., Toxoplasma gondii, and respiratory viruses in invasive black rats (Rattus rattus) from Punta San Juan (PSJ), a coastal protected area in southern Peru. Rodents can harbor zoonotic pathogens at the wildlife–human interface, posing ecological and public health risks. Methods – Fifty-three rats were trapped inside and outside PSJ in June 2025 from two contrasting zones: inside PSJ (n = 29), corresponding to the protected coastal habitat within the reserve, and outside PSJ (n = 24), including adjacent urban and human-impacted coastal areas. Serum, blood, and tissues were analyzed for T. gondii using Western blot and quantitative PCR. Leptospira spp. detection was performed by real-time PCR targeting the lipL32 gene in blood samples. Respiratory viruses, including influenza A and B, were screened using the Illumina Respiratory Virus Panel through next-generation sequencing (NGS) technology in respiratory tract and lung swabs. Results – One adult female (1/49, 2.0%) captured inside PSJ was seropositive for T. gondii, but all PCR tests were negative in blood and tissues. Leptospira spp. DNA was detected in 18/53 rats (34.0%), with higher frequency outside the reserve (54.2%) than inside (17.2%) (p = 0.008). No amplifications were obtained for respiratory viruses. Discussion – The higher Leptospira frequency outside PSJ suggests that human-associated environments increase infection risk in the study area. In contrast, evidence for other zoonotic pathogens was limited, with only a single serological detection of T. gondii and no respiratory viruses identified. Although these findings are restricted to a local context, they highlight Leptospira spp. as the primary zoonotic pathogen detected and support the need for broader surveillance to better assess the epidemiological role of invasive rodents in coastal protected areas.