Viruses recently identified in China are infecting cattle ticks in Brazil

For the first time in South America, Brazilian researchers have described the Lihan tick virus and Wuhan tick virus 2. The study is published in Scientific Reports.

By Peter Moon  |  Agência FAPESP – Ticks are hematophagous ectoparasites that feed on the blood of vertebrates and are vectors of many types of microorganisms that cause diseases in horses, cattle, cats, dogs and rodents, as well as humans.

The cattle fever tick Rhipicephalus microplus transmits diseases that cause severe losses to Brazilian agriculture, reaching US$3.2 billion per year according to data for 2014. 

Research led by virologists at the University of São Paulo’s Ribeirão Preto Medical School (FMRP-USP) in Brazil has produced more detailed knowledge of the diversity of viruses that infest these ticks.

According to the results of a new study published in the journal Scientific Reports, pathogens previously found only in China have been detected for the first time in South America, including Lihan tick virus (LITV, Phenuiviridae family) and Wuhan tick virus 2 (WTV-2, Chuviridae family).

The authors also describe three novel tymoviruses (Tymovirales order), named guarapuava tymovirus-like 1, 2 and 3. They used a metagenomics approach to determine the diversity of viruses present in R. microplus parasitizing cattle in the South Region of Brazil. The study was supported by FAPESP.

“We identified two nearly complete sequences and four partial genomes of WTV-2, which belongs to a recently described family called Chuviridae. These viruses shared 97-98% of the amino acids with WTV-2 from R. microplus collected in China. The results showed that WTV-2 is present in R. microplus ticks throughout southern Brazil,” said William Marciel de Souza, a researcher at FMRP-USP’s Virology Research Center and the first author of the article.

The laboratory at which the study was conducted is headed by Professor Luiz Tadeu Moraes Figueiredo. The participants also included researchers at other Brazilian institutions, such as the University of the Center-West of Paraná (UNICENTRO), Evandro Chagas Institute and Federal University of the Southern Frontier (UFFS), as well as scientists affiliated with the University of Glasgow in Scotland (UK).

Similar results were found for LITV in Brazil. “We identified a nearly complete sequence for two strains and partial genomes for four strains of a unique species of a phlebovirus-like virus that shared 97-98% of the amino acids with an LITV described in R. microplus collected in China. As in the case of WTV-2, the results showed that LITV is present in R. microplus ticks throughout southern Brazil,” Souza said.

Metagenomics

“A major survey conducted since 2013 at the Virology Research Center with FAPESP’s support has searched for novel viruses that may be important to public health in Brazil,” Souza explained. “The project has so far identified more than 150 novel viruses in vertebrates – rodents, bats and others – and invertebrates. This latest article presents the first results of our investigation of arboviruses in ticks.”

Arboviruses are transmitted by arthropods. Many emerging viruses transmitted by ticks have caused outbreaks of devastating and often fatal diseases, representing a serious public and animal health problem in many parts of the world.

Some 900 tick species are currently known to science. They are grouped into three families: Argasidae, Ixodidae and Nuttalliellidae. Viruses transmitted to humans by infected tick bites are found mainly in the family Ixodidae, to which the genus Rhipicephalus belongs.

At least 38 species of viruses transmitted by ticks are currently known. They are grouped into eight families, including Flaviviridae and Phenuiviridae, to which the novel species discovered by the researchers at FMRP-USP belong.

“Despite the dissemination of ticks in Brazil and the significance of tick-borne viruses, only two viruses associated with ticks have previously been described in South America: cacipacoré virus and mogiana virus, hence our decision to look for more viruses,” Souza said.

“We want to identify unknown arboviruses that could potentially cause disease before the first outbreaks occur.”

The group collected engorged ticks and blood from infected cattle on farms in the three states of the South Region (Paraná, Santa Catarina and Rio Grande do Sul).

“We used metagenomics to determine the diversity of viruses present in R. microplus parasitizing cattle in southern Brazil. We analyzed the ticks’ viromes, the total collection of viruses in the bodies of these animals, and performed experimental infections using different in vitro host cell lines,” Souza said.

JMTV

Most of the ticks analyzed by the researchers proved to be infected by a known virus, Jingmen tick virus (JMTV), which belongs to the same family as the dengue and yellow fever viruses (Flaviviridae).

“Flaviviridae have a unique genome. The JMTV circulating in Brazil is different in that its genome is divided into four separate segments. Moreover, phylogenetic trees show that the JMTV circulating in Brazil could be a different genotype from those previously described in Africa and Asia,” Souza said.

“JMTV has been found in cattle ticks in China and in monkey ticks in Costa Rica. Our virus is 99% identical to the one found in China. Another highly similar JMTV has been found in Africa. JMTV is present in all three states of South Brazil, and we believe it’s widespread throughout Brazil. The virus is present wherever R. microplus is present, in our view.”

According to the virologists at FMRP-USP, the discovery that viruses previously known to exist only in China are also present in Brazil is evidence that the tick in question came to Brazil with the cattle on which it feeds.

“We infer that the viruses identified in our study and previously reported in Asia may have resulted from a deep [very ancient] association or coevolution with R. microplus and may be found in this tick species in subtropical and tropical regions worldwide,” Souza said.

The article “Viral diversity of Rhipicephalus microplus parasitizing cattle in southern Brazil” (doi: 10.1038/s41598-018-34630-1) by William Marciel de Souza, Marcílio Jorge Fumagalli, Adriano de Oliveira Torres Carrasco, Marilia Farignoli Romeiro, Sejal Modha, Meire Christina Seki, Janaína Menegazzo Gheller, Sirlei Daffre, Márcio Roberto Teixeira Nunes, Pablo Ramiro Murcia, Gustavo Olszanski Acrani and Luiz Tadeu Moraes Figueiredo can be read at www.nature.com/articles/s41598-018-34630-1.