Vinicius Ferreira (IOC/Fiocruz)
The Amazon Rainforest and the Brazilian Cerrado (savanna region) together amount to more than seven thousand square kilometers in extension. Despite the numerous scientific investigations undertaken in these regions, this vast stretch of territory still holds surprises. Two of them have just come to light: Brazilian scientists have identified two species of virus that had never been described in the world. Denoted as Xapuri and Aporé, in reference to the remote locations of Acre and Mato Grosso do Sul where they were located, the micro-organisms belong to the mammarenavirus genus of the arenavirus family. There are still no data about the magnitude of the circulation of these species in the country and the possibility of infection in humans is also unknown.
The findings bring light to a class of viruses that in South American and African nations is responsible for causing symptoms of hemorrhagic fever, similar to that which occurs with dengue or yellow fever. In Brazil, information about the circulation and cases associated with arenaviruses are very limited. "We are working on a fundamental aspect of health surveillance, which is the identification of the emergence of new pathogens. This has an immediate impact on the management of cases: if a patient with hemorrhagic fever lives in a region with a circulation of arenaviruses, it is necessary to perform differential diagnoses at the times when the tests are negative for arboviruses. As arenaviruses can lead to death in three out of every ten infected people, it is essential to act quickly”, says Elba Lemos, head of the Osvaldo Cruz Institute's Laboratory of Hantavirus and Rickettsiosis (IOC/Fiocruz) and coordinator of the study. The findings about the virus Xapuri were published in the journal Emerging Microbes & Infections and the publication documenting the discovery of the Aporé virus can be found in the journal “Memórias” of the Oswaldo Cruz Institute.
The identification of the viruses started from an investigation comparable to looking for a needle in a haystack. The scientists were studying rodents from both regions, looking for new microorganisms. The route of discovery of the Xapuri virus occurred from the collection of samples in three cities in the state of Acre (the municipalities of Porto Acre and Rio Branco were also included in the analysis). The researchers found that the examinations of a rodent of the species Neacomys musseri presented changes never seen before. With the complete sequencing of the virus and subsequent comparison with genetic sequences available in public databases, it was possible to identify that it was a mammarenavirus. "However, it was necessary to discover which virus was this and which mammalenavirus group it belonged to: the group called the Old World, which includes viruses from Africa and Asia, or the New World group formed by pathogens native of the Americas," comments Jorlan Fernandes, the first author of the research and postdoctoral fellow of the Postgraduate Program in Tropical Medicine of the IOC/Fiocruz, under the supervision of Lemos.
"When we perceived that the genetic sequencing did not correspond to any pathogens cataloged in the world database dedicated to the subject - called GenBank - we realized that we were dealing with a new virus," added Alexandre Guterres, co-author of the study. At that moment, it was baptized Xapuri, after a town in the interior of Acre where it was located. Another new characteristic was soon observed: although it falls within the group called New World, Xapuri did not fit into any of the four strains already described in the Americas: groups A, B, C and D. "Our suggestion is that Xapuri be included in a new strain. Popularly speaking, it would be a sister strain of groups B and C, which may represent the first identification of a natural recombinant of the arenavirus family that arose from two groups of mammarenaviruses that are not closely related”, says Fernandes.
Risk under evaluation
The second discovery came from Mato Grosso do Sul. From the samples of a rodent of the species Oligoryzomys mattogrossae, it was possible to identify the Aporé virus - an allusion to the river in Mato Grosso do Sul near to where the collection was made. The genetic analysis indicated that the virus belongs to class B mammarenaviruses. “Aporé is closely related to two arenaviruses of South America capable of infecting humans and which are highly pathogenic”, says Fernandes. "However, like Xapuri, it is not yet possible to say whether or not these viruses are pathogenic to people. It will be necessary to carry out specific tests ", completes Lemos. The gene sequencing of the Aporé and Xapuri viruses were deposited in GenBank.
Researcher at the IOC/Fiocruz Hantavirus and Rickettsiosis Laboratory, Renata Carvalho de Oliveira explains that an arenavirus is found in nature in wild rodents and transmitted from the inhalation of aerosols contaminated with saliva particles, urine or feces from infected rodents. "People who are exposed to these animals are at greater risk of infection during their daily, professional or recreational activities, especially residents and workers in rural areas," says Lemos.
The clinical condition is characterized by fever associated with muscular pain, among other symptoms, and then it develops into hemorrhage, with or without neurological signs. "Generally, with a rapid and increasingly serious development, the disease, which is little known even by health professionals, can have a fatal outcome," explains Lemos. Without a vaccine and without specific treatment, prevention is based on avoiding or reducing direct or indirect exposure to rodents and the material excreted by them.
The identification of new viruses has been submitted and approved by the International Committee of Virus Taxonomy, which regulates and organizes the description, identification and classification of viruses. The research was supported by the Biology and Parasitology Laboratories of Wild Mammal Reserves and Computational Biology and Systems of the IOC/Fiocruz, the Sequencing Platform of the IOC/Fiocruz, the National Cancer Institute, the National Infection Service of the United Kingdom and the Julio Maiztegui National Institute of Human Viral Diseases, of Argentina.