Emerging threat: Rabies virus from marmosets found in Brazilian bats

A recent study has revealed a startling link between rabies virus variants found in bats and those present in white-tufted marmosets in Northeast Brazil. 

This finding is significant due to the potential risk of rabies transmission to humans, and is particularly concerning since a man died in May after a marmoset bite.

Emergence in wildlife 

Rabies, a deadly disease for humans, is increasingly being detected in various wildlife species, including marmosets found in Brazilian forests and urban areas. 

Marmosets, often captured as pets and later abandoned, have been implicated in human rabies cases. This emergence is a pressing public health concern.

Study insights

The study was conducted by researchers from the Federal University of São Paulo’s Medical School (EPM-UNIFESP) and supported by FAPESP. The results highlight the similarity between rabies variants in marmosets and bats. 

Fruit- and insect-eating bats, which are not typically associated with rabies, were found carrying the virus, indicating a complex transmission dynamic. Bats that feed on blood are the more likely hosts. 

Deadly encounters

“Seven marmosets have recently tested positive for rabies. Rabies is endemic in Ceará, where people have been attacked by marmosets and died from rabies. One such death occurred in May,” said study lead author Larissa Leão Ferrer de Sousa.

In February, a 36-year-old farm worker near a town called Cariús was bitten by a rabid marmoset. “The marmoset fell into his backyard. It was semi-paralyzed, which is one of the symptoms of rabies. The man tried to help it, and it bit him,” said Sousa.

“Animals with rabies aren’t always aggressive and don’t necessarily foam at the mouth, the symptom most people associate with rabies. Sometimes there are no apparent symptoms at all.”

Public warning

Sousa advises against touching wild animals, including bats, and suggests contacting local animal health surveillance for dead wildlife. Immediate medical attention and vaccination are crucial following animal contact, as rabies symptoms typically signal a fatal outcome.

“Rabies incubates for 45 days on average, so it’s extremely important for anyone who’s infected to get post-exposure prophylaxis [serum and vaccine] immediately. When symptoms appear, it’s normally too late, and the patient will die,” said Ricardo Durães-Carvalho, a researcher at EPM-UNIFESP and principal investigator of the study.

Genetic sequencing 

The researchers sequenced RNA from 144 brain tissue samples of 15 bat species. These samples, collected as part of a national surveillance program, revealed rabies virus variants in bats closely related to those in marmosets. 

Next, the team traced the evolutionary history of the viruses they found using computer-assisted tools.

The first set of sequences was compatible with rabies virus variants found in two insectivorous bat species from Southeast Brazil in 2010. 

However, another group of variants found in two insectivorous and one frugivorous species of bats were evolutionarily related to the virus detected in marmosets from the Northeast.

Study implications 

“Our results allowed us to infer that the different rabies virus variants that were closely related in evolutionary terms were originally from the same animal, revealing complex spillover dynamics and multiple viral transmission between hosts,” said Durães-Carvalho.

While bats and marmosets play key roles in rabies transmission, they are also crucial for ecological balance and are threatened by habitat loss. Respecting and protecting these animals in their natural habitats is essential for maintaining ecosystem health.

The discovery of rabies virus variants in bats linked to marmosets in Brazil serves as a reminder of the intricate relationships between wildlife, humans, and diseases. 

Wildlife conservation and public health vigilance are crucially important for preventing future outbreaks.

White-tufted marmosets

White-tufted marmosets, also known as common marmosets or white-tufted-ear marmosets, are New World monkeys native to South America. They were originally found along the northeastern coast of Brazil, in various states including Piaui, Paraiba, Ceará, Rio Grande do Norte, Pernambuco, Alagoas, and Bahia​​​​.

In terms of appearance, these marmosets are quite small, with a body length of approximately 12 to 15 centimeters and a tail length ranging from 29.5 to 35 centimeters. They are distinguished by their white ear tufts and a white blaze on their forehead. Their head fur is usually dark brown, while their back fur is a greyish brown color with light transverse striping​​.

The white-tufted marmoset lives in stable extended families, indicative of their social nature​​. An interesting aspect of their behavior is their feeding habits. They primarily feed on gums and saps from trees, using their lower incisors to create holes in gum-producing trees. This action induces a flow of gum from the trees, which serves as an important food source for them​​.

The study is published in the Journal of Medical Virology.

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