Oropouche fever

Oropouche fever is a tropical viral infection, a zoonosis similar to dengue fever, transmitted by biting midge (species Culicoides paraensis) and mosquitoes from the blood of sloths to humans. It occurs mainly in the Amazonic region, the Caribbean and Panama. The disease is named after the region where it was first described and isolated at the Trinidad Regional Virus Laboratory, in 1955, the Oropouche River in Trinidad and Tobago and is caused by a specific arbovirus, the Oropouche virus (OROV), of the Bunyaviridae family.

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OROV was first described in Brazil in 1960, isolated from the blood of a sloth (Bradypus tridactylus) captured in the rain forest during the construction of the Belém-Brasília Highway. The Ochlerotatus serratus mosquito was implicated as a possible vector, because OROV was found in their blood too. According to Nunes et al. (2005), "the OROV genome consists of 3 partite, single-stranded, negative-sense RNAs, named large (L), medium (M), and small (S) RNA. These RNAs are predicted to encode a large protein (L: polymerase activity), viral surface glycoproteins (Gc and Gn), and nonstructural NSM protein, as well as both nucleocapsid (N) and NSS proteins. Complete nucleotide sequences have been determined for all 3 RNA segments, and previous studies of the molecular biology of the N gene (SRNA) of 28 different OROV strains indicated the existence of 3 genotypes, designated I, II, and III."

Large epidemies are common and very swift, one the earliest larger one having occurred at the city of Belém, in the Brazilian Amazon state of Pará, with 11,000 recorded cases. In the Brazilian Amazon, oropouche is the second most frequent viral disease, after dengue fever. Several epidemies have generated more than 263,000 cases, of which 130,000 alone occurred in the period from 1978 to 1980 [1]. Presently, in Brazil alone it is estimated that more than half million cases have occurred.

Oropouche fever has an abrupt onset fever, initially with generic symptoms similar to those seen in dengue fever. such as chills, headache, anorexia, muscle pain and joint pain and vomiting. Patients may develop symptoms of meningitis. Diagnosis is achieved by dosing the serum levels of the specific antibody to the virus.

The illness has no specific therapy, but usually symptomatic treatment is introduced, by using certain oral analgesic and anti-inflammatory agents. which should be prescribed by a physician, because some of them (such as aspirin) are dangerous because they reduce blood clotting activity and may aggravate the hemorrhagic effects;

The infection is usually self-limiting and complications are rare. Patients usually recover fully with no long term ill effects.

References

• Anderson, C. R., Spence, L., Downs, W. G. & Aitken, T. H. G. "Oropouche virus: a new human disease agent from Trinidad, West Indies." American Journal of Tropical Medicine and Hygiene 10, 1961; 574-578 PMID 13683183. Also in: The Caribbean Medical Journal, Vol. XXVI, Nos. 1-4, pp. 126-130;
• Nunes, MRT et al. "Oropouche virus isolation, Southeast Brazil." Emerging Infectious Diseases, Oct 2005. PMID 16318707
• Saeed MF, Wang H, Nunes MRT, Vasconcelos PFC, Weaver SC, Shope RE, et al. "Nucleotide sequences and phylogeny of the nucleo-capsid gene of Oropouche virus." J. Gen. Virol. 2000;81:743-8. PMID 10675412