Everything we know about the Oropouche virus, the pathogen that spreads with deforestation

The Oropouche virus has been circulating in the Amazon for decades. This year, 11,634 cases occurred, the majority in Brazil (9,563) and Peru (936), where it is an old acquaintance. However, it also spread to Bolivia, Colombia, Ecuador, Guyana, Panama and even Cuba, where its first endemic transmission was reported with 603 cases.

This year, infected travelers crossed borders. The virus was found twice in Canada, once in the Cayman Islands, and 94 times in the United States — the majority in Florida (90) and the rest in California, Colorado, Kentucky and New York. Europe reported its first 30 imported cases in Spain, Italy and Germany. The disease is not only expanding (in 2023 Brazil reported 835 cases), but it also claimed its first two fatalities, serious cases increased, and it was confirmed that there is transmission during pregnancy.

For those who study arboviruses such as oropouche – pathogens that are transmitted through arthropods such as mosquitoes and ticks – the situation is not surprising, but it is worrying, because despite having clues about its transmission cycle, there is a lack of information to predict its future behavior. . “We have some pieces of the puzzle, but there is no complete certainty as to what role each one plays,” this is how Juan Carlos Navarro, professor at the SEK International University and Director of Research at the same institution, where he leads the group, summarizes the situation. of emerging diseases and epidemiology.

A natural cycle with gaps

In 1955, a young chickadee fell ill after spending two weeks working and sleeping in the forest near the Oropouche River in Trinidad and Tobago. He had a fever for three days. That was the first documented case of the Oropouche virus. Since then, dozens of outbreaks have been reported, the majority (30) occurring in the Amazon basin.

Navarro has dedicated 30 years to the study of arboviruses such as dengue, equine encephalitis, Mayaro and, since 2016, Oropouche, which has two transmission cycles. In the rainforest, the reservoirs, animals that keep the virus circulating—even if they themselves do not get sick—are believed to be non-human primates (such as neotropical marmosets and capuchin monkeys), sloths, rodents, and birds from which the virus was isolated or They found antibodies. In fact, the disease is known as “sloth fever,” although it is not known “what role these or non-human primates play in the transmission cycle. “They are probably amplifying hosts,” says the researcher.

In the epidemic cycle, people are the amplifying hosts and the virus is transmitted through the bites of blood-eating insects. The main vector, that which transports the pathogen between humans, is Culicoides paraensis, which is the same size as the head of a pin and lives from Argentina to the United States. Insects of this species are called gnats in Spanish and biting midges in English.

Sloth fur could hide future antibiotics

The stable health of sloths and the multitude of organisms on their bodies led scientists in Costa Rica to study the medical potential of their fur.

Some studies suggest that Culex quinquefasciatusinsects present in almost all countries, as well as several species of the genus Culex and Aedes (a very common type of mosquito) can transmit it. In fact, the first isolation of the virus in Trinidad and Tobago occurred in Coquillettidia venezuelensis, another mosquito. Without the complete map of wildlife reservoirs, the ecology of their vectors and all their interactions, it is difficult to predict future scenarios.

Culicoides paraensis It is associated with rural jungle areas, it is found near bodies of water and banana crops, “but in the new cases in urban areas it is not known what role it plays,” says Navarro. Meanwhile, in Cuba, where today they have endemic transmission , Culicoides paraensis is not reported. “If infected people are bitten by a competent mosquito, it can start a local cycle of transmission as is happening with dengue in southern Europe. That could happen with Oropouche because species like Culicoides, They transmit other viruses of veterinary importance in Spain, Italy and France. Before, it happened with diseases that came to America: yellow fever, malaria and Mayaro.”