Capybara found dead from rabies on Brazilian island, highlighting the need for virus surveillance

Between December 2019 and January 2020, three capybaras (Hydrochoerus hydrochaeris) died from rabies on Anchieta Island in Ubatuba, São Paulo state, Brazil. One dog was found dead and two showed paralysis in their hind limbs before death. Brain analysis performed at the Pasteur Institute in São Paulo determined that the cause of death was rabies encephalitis.

An article reporting the findings of this study is published in the journal Veterinary Research Communication. This is the third reported case of rabies in a capybara in the world, and the second in Brazil.

The study also detected that the strain of rabies found in the three animals was the same as a variant present in the vampire bat (Desmodus rotundus).

“In recent years, there has been an increase in reported cases of rabies in wild animals. This may be related to environmental disturbances that cause an imbalance in the ecosystem in which D. rotundus lives,” said the study’s lead author. said researcher Enio Mori. Dr. Mori is a researcher at the Institut Pasteur, a division of the São Paulo State Health Authority, and a professor at the Graduate Program in Experimental and Comparative Pathology at the Faculty of Veterinary Medicine and Animal Sciences of the University of São Paulo (FMVZ-USP). ).

In another recent incident, an opossum (Didelphis albiventris) infected with the rabies virus was found dead in Campinas, one of the state’s largest cities.

Anchieta Island is a state natural park. Shortly after repairs were made to the roof of the previously abandoned building, the capybara died there, forcing the bat colony to roost elsewhere.

“At times like this, bat colonies are under extreme stress, fights are frequent, and they can transmit rabies to each other and to other wild animals that feed on their blood, such as capybaras. It will increase,” Mori said.

Generally speaking, deforestation also contributes to the increase in rabies. Deforestation reduces wildlife, which is the vampire bat’s only food source. Bats must find other prey and frequently turn to livestock and even humans, potentially transmitting rabies in the process.

variations

The infected capybara was discovered by employees of the Florestal Foundation, which manages São Paulo’s conservation sites, including Anchieta Island State Park. Samples of the animal’s brain tissue were sent to the Pasteur Institute, part of the region’s rabies surveillance laboratory network. Researchers and technical staff there first tested samples for rabies virus antigen for triage purposes and concluded that all three cases tested positive.

The virus was then isolated for confirmatory testing. One of the samples was in poor condition, making this test impossible, but they were able to sequence the virus particle’s genome. The test confirmed the presence of a variant of the rabies virus found in vampire bats, indicating the possibility of infection through bites.

The only known case of rabies in a capybara in Brazil was published in 1985. In other parts of the world, only one case has been reported, which occurred in northern Argentina in 2009. The virus variant in question has only been typed in this latest study.

There are no reports of capybaras transmitting rabies to humans. However, bites by these animals usually result in serious injuries. It is unclear whether capybara saliva, like bat saliva, contains the virus (bats are the main reservoir of rabies in South America).

“Therefore, we need to continue epidemiological surveillance to find out, for example, what role capybaras play in the virus cycle. There’s a good chance they’ll die. But further research is needed to confirm that,” Mori said.