Serology and PCR for Apicomplexa and SARS-CoV-2 in feral cats from a Brazilian island

Feral cats in insular environments represent a relevant interface between wildlife, environmental contamination, and zoonotic risk under a One Health perspective, as feralization increases exposure to infections and facilitates pathogen transmission. Herein, we surveyed Toxoplasma gondii, Sarcocystis spp., Neospora caninum, and SARS-CoV-2 in Furtada Island, Mangaratiba, Rio de Janeiro, Brazil, where there has been a feral cat population since the 1950s. This study aimed to investigate serological, molecular, and morphological indicators of infection in feral cats by assessing antibodies against Toxoplasma gondii, Sarcocystis spp., Neospora caninum, and SARS-CoV-2, detecting Apicomplexa DNA in reproductive tissues, and evaluating the morphology of the uterus, ovaries, testes, and epididymides. It was demonstrated that 40.4% (21/52) were exposed to T. gondii, 13.7% (7/52) were exposed to Sarcocystis spp., and no cats were seropositive for N. caninum. Additionally, no feline was positive for SARS-CoV-2 through serological investigation. No histological changes were observed in the reproductive tissues, and the DNA of the agents was not detected using molecular methods. This is the first investigation of host-pathogen interaction in feral cats from Furtada Island in southeastern Brazil. The data confirm that Toxoplasma gondii and Sarcocystis spp. are circulating within this feral cat population. These findings highlight the importance of feral cats as sentinels of environmental contamination and support the need for One Health-based surveillance strategies in insular ecosystems.