Rabies in urban opossums, health warning signal for São Paulo

Female white-tailed opossum (Didelphis albiventris) According to a group of researchers from the University of São Paulo (USP) and Adolfo University, a man was found dead in 2021 in Bosque dos Jequitibas Park in the center of Campinas, one of the largest cities in the Brazilian state of São Paulo. It was announced that he died of rabies meningoencephalitis. The Lutz Institute (IAL) is a regional reference institute that collaborates with health professionals from public institutions in the City of São Paulo and Campinas.

Reported in an article published in a magazine emerging infectious diseasesthis discovery serves as a warning against the presence of a virus deadly to humans in urban environments.

Thanks to a successful vaccination campaign for livestock, canine rabies is no longer present in the state of São Paulo. Therefore, it is important to monitor other mammals that may be vectors of the virus, especially animals such as opossums, which have been neglected in this type of surveillance. ”

Eduardo Ferreira Machado, lead author of this article

He received a scholarship from FAPESP to carry out research for his doctoral studies at the Faculty of Veterinary Medicine, Department of Animal Sciences (FMVZ-USP).

Neurological signs of the disease detected in the animal were indicative of a form of rabies that causes paralysis and is transmitted by bats. Viral particles identified in other organs also indicated that the infection was in the systemic stage of dissemination.

The opossum is one of 22 animals the group tested for rabies and other diseases in 2021 as part of an epidemiological surveillance project carried out in partnership with the São Paulo City Health Department and the Center for Zoonosis Control of Campinas. It was one of us.

That same year, the team analyzed 930 bats, 30 of which tested positive for rabies. More than half of these (17 or 56.7%) belonged to frugivorous species of this genus. Artibeus. The remainder (13 or 43.4%) were insectivorous and belonged to three different genera.

bridge to humanity

Transmission between bats and opossums can occur through their interactions as these animals compete for habitat in natural areas such as tree canopies and in artificial environments such as roof gables and backyards.

In 2014, there were reports of rabies in cats in Campinas. The cause of the infection was determined to be a virus variant found in bats. Both cats and opossums can prey on bats, and this was the most likely route of infection.

The researchers also noted the fact that 15 of the 22 opossums analyzed were killed by dogs. “Dogs act as a bridge between opossums and humans and can carry rabies and other diseases to humans, so it's important to monitor urban wildlife,” Machado said.

According to José Luis Caton Diaz, co-author of this article and Dr. Machado's thesis advisor at FMVZ-USP, opossums adapt well to urban environments without necessarily ceasing to interact with forested areas. This is said to be the key to this type of surveillance.

“Yet, they are neglected. Little is known about the diseases they suffer from and can transmit to us,” says “A Comparison of Diseases in Neotropical Marsupials.” said Caton Diaz, principal investigator and grant recipient of the “Pathology and Investigation'' project. , “Diderphimorphiae: A Surveillance Proposal for a Neglected Group of Mammals in Wildlife Health Research”, supported by FAPESP.

The authors note in their paper that research conducted in the 1960s led to the first suggestion of resistance to rabies virus in opossums, a hypothesis strengthened by the paucity of rabies reports in these animals. .

The low incidence of rabies in opossums in North America, where wild carnivorous mammals are a natural reservoir of the virus, is due to the low body temperature of opossums (34.4°C to 36.1°C) and their ability to survive attacks by opossums. This is explained as the possibility is minimal. ferocious animal. However, the Brazilian study shows that infections are occurring and need to be monitored.

Researchers continue to analyze animal carcasses brought to IAL's pathology center to monitor for the presence of rabies and other diseases. They plan to partner with agencies in other countries, such as Australia, so they can carry out monitoring of opossums and other marsupials.

“Australians have a lot of experience in this area. We can make comparisons that are useful for both countries,” Mr Cattan-Diaz said.