In Ceará, marmoset rabies is found in bats – 09/21/2023 – Balance and Health

Variants of the rabies virus detected in bats closely related to variants present in white-tufted marmosets (Callithrix jacchus) were found in Ceará, raising an alert about the circulation of the virus, which is deadly to humans. Marmosets are quite common in wild and urban areas in Brazil, often being captured and kept as pets.

Supported by Fapesp, the study was coordinated by researchers from EPM-Unifesp (Escola Paulista de Medicina da Universidade Federal de São Paulo). The results were published in the Journal of Medical Virology.

In addition to the similarity between the variants found in the bats analyzed, the presence of the rabies virus in frugivorous and insectivorous species of flying mammals caught the attention of researchers. Blood-feeding bats are best known for being hosts and important transmitters of the rabies virus.

“Up until August this year, seven marmosets were found positive for rabies. In Ceará, the disease is endemic and we have a history of attacks on humans by marmosets and deaths from rabies, one of which occurred in May”, says Larissa Leão Ferrer de Sousa, Servant at the Central Public Health Laboratory of Ceará (Lacen), in Fortaleza, and doctoral student at EPM-Unifesp.

Sousa refers to the death of a 36-year-old farmer, attacked by a marmoset in February in the municipality of Cariús. The man only sought care in April, when symptoms began to appear, but he did not survive. Infection with the virus causes progressive encephalitis, an inflammation of the brain that leads to death in almost 100% of cases.

“The marmoset fell in his yard with difficulty in moving around. The man tried to help him and was bitten. The animal already showed signs of paralysis, one of the symptoms of rabies. The sick animal does not always show aggression and foaming at the mouth, which population normally associates it with rabies. Sometimes, there are not even apparent symptoms”, explains the veterinarian.

Sousa also warns that bats and other wild mammals should not be touched. When you find these dead animals, you must notify the municipality’s zoonosis service so that they can be sent for analysis.

Furthermore, the person who had direct contact with the animal must seek medical attention so that anti-rabies serum and vaccine can be administered, depending on the case.

“The incubation time of the rabies virus is 45 days on average. Therefore, it is extremely important that the individual undergoes post-exposure prophylaxis immediately. Without carrying out this treatment [soro e vacina antirrábicos]when symptoms appear, the prognosis is usually fatal”, explains Ricardo Durães-Carvalho, researcher at EPM-Unifesp supported by FAPESP and coordinator of the study.

Sequencing

The researchers analyzed 144 tissue samples taken from the brains of bats belonging to 15 species. The animals arrived in Lacen do Ceará between January and July 2022, as part of the national epidemiological surveillance program. As part of this program, health professionals collect mammals found dead or showing symptoms of virus infection in the State.

The samples had RNA extracted for analysis of the viruses found. Then, the genetic sequences of the rabies virus were compared with others deposited in public databases. Own tools were used to trace the evolutionary history of the viruses found.

The first set of sequences was compatible with rabies virus variants found in two Southeastern bat species in 2010, the insectivores Tadarida brasiliensis and Nyctinomops laticaudatus.

However, another group of variants, found for the first time in bats (two insectivorous and one frugivorous species), has a very close evolutionary relationship with the rabies virus detected in white-tufted marmosets from Northeastern Brazil.

“Our results allow us to infer the presence of distinct variants of the rabies virus, evolutionarily close and originally present in a given animal, in others. This reveals a complex spread dynamics [spillover] and multiple viral transmission between hosts”, explains Durães-Carvalho.

With the intensification of vaccination of domestic animals, wild animals have become the main source of human rabies in the Americas. The first case of death from rabies associated with a marmoset was reported in 1991, also in Ceará. After that, another 14 deaths in the State were attributed to transmission by these primates.

Bats and marmosets, prominent actors in the rabies transmission chain in Brazil, have important ecological functions and suffer from the loss of habitat resulting from the expansion of cities and agriculture.

Bats, in particular, are important for the balance of ecosystems and fundamental in seed dispersal, pollination and pest control. “The best thing is to respect these animals and keep them in the wild”, concludes Sousa.

The study was also supported by Fapesp through five other projects (20/08943-5, 19/14526-0, 22/09684-9, 22/08748-3 and 21/05661-1).

The article Rabies virus variants from bats closely related to variants found in marmosets (Callithrix jacchus), a neglected source of human rabies infection in Brazil can be read here.