Yellow Fever Virus, Southern Brazil | CDC EID

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Volume 16, Number 12–December 2010
Research
Yellow Fever Virus in Haemagogus leucocelaenus and Aedes serratus Mosquitoes, Southern Brazil, 2008

Jáder da C. Cardoso, Marco A.B. de Almeida, Edmilson dos Santos, Daltro F. da Fonseca, Maria A.M. Sallum, Carlos A. Noll, Hamilton A. de O. Monteiro, Ana C.R. Cruz, Valéria L. Carvalho, Eliana V. Pinto, Francisco C. Castro, Joaquim P. Nunes Neto, Maria N.O. Segura, and Pedro F.C. Vasconcelos Comments to Author
Author affiliations: Secretaria da Saúde do Estado do Rio Grande do Sul, Porto Alegre, Brazil (J. da C. Cardoso, M.A.B. de Almeida, E. dos Santos, D.F. da Fonseca, C.A. Noll); Universidade de São Paulo, São Paulo, Brazil (J. da C. Cardoso, M.A.M. Sallum); Instituto Evandro Chagas, Ananindeua, Brazil (H.A. de O. Monteiro, A.C.R. Cruz, V.L. Carvalho, E.V. Pinto, F.C. Castro, J.P. Nunes Neto, M.N.O. Seguara, P.F.C. Vasconcelos); and Universidade do Estado do Pará, Belém, Brazil (P.F.C. Vasconcelos)

Suggested citation for this article

Abstract
Yellow fever virus (YFV) was isolated from Haemagogus leucocelaenus mosquitoes during an epizootic in 2001 in the Rio Grande do Sul State in southern Brazil. In October 2008, a yellow fever outbreak was reported there, with nonhuman primate deaths and human cases. This latter outbreak led to intensification of surveillance measures for early detection of YFV and support for vaccination programs. We report entomologic surveillance in 2 municipalities that recorded nonhuman primate deaths. Mosquitoes were collected at ground level, identified, and processed for virus isolation and molecular analyses. Eight YFV strains were isolated (7 from pools of Hg. leucocelaenus mosquitoes and another from Aedes serratus mosquitoes); 6 were sequenced, and they grouped in the YFV South American genotype I. The results confirmed the role of Hg. leucocelaenus mosquitoes as the main YFV vector in southern Brazil and suggest that Ae. serratus mosquitoes may have a potential role as a secondary vector.

Yellow fever is an acute, often fulminant, disease caused by Yellow fever virus (YFV), the prototype member of the family Flaviviridae, genus Flavivirus. YFV is endemic to tropical regions of Africa and South America (1,2). The virus is transmitted through the bite of mosquitoes belonging to the family Culicidae to vertebrate hosts, especially nonhuman primates and humans.

In South America, the urban cycle involves the mosquito Aedes aegypti and humans, whereas in the jungle cycle, the virus is transmitted to nonhuman primates by mosquitoes in the genera Haemagogus and Sabethes, especially Hg. janthinomys, Hg. albomaculatus, Hg. leucocelaenus, Sa. chloropterus, Sa. glaucodaemon, Sa. soperi, and Sa. cyaneus (2,3).

Currently in Brazil, 2 yellow fever–endemic areas have been described. The area where vaccination is recommended or risk for yellow fever is recognized includes the northern and central regions, as well as Maranhão State and the eastern part of Bahia, Minas Gerais, São Paulo, Paraná, Santa Catarina, and Rio Grande do Sul states. The area where vaccination has not been recommended includes the coastal region between Piauí and Rio Grande do Sul states (4). During 1989–2008, a total of 546 human cases of yellow fever and 241 deaths were recorded in Brazil (5).

In Rio Grande do Sul, the southernmost state in Brazil, the last cases of sylvatic yellow fever were recorded in the 1960s (6). After 40 years without detectable activity, the virus was isolated from mosquitoes (Hg. leucocelaenus) collected in 2001, during an epizootic involving free-living nonhuman primates of the species Alouatta caraya (black howler monkey) in the northwestern region of the state (7). These YFV hosts spend most of their time in the trees and only go down to the ground to feed during the day; they are extremly sensitive to YFV and die of the disease after they are infected naturally or experimentally even in lower doses.

The confirmation of YFV in nonhuman primates and in mosquitoes led to vaccination campaigns in 44 municipalities to prevent human cases and the initiation of a program of environmental surveillance for yellow fever and other arboviruses authorized by Brazil's state Ministry of Health. The goal of this program was to detect the early presence of YFV in mosquitoes and nonhuman primates (through the detection of specific antibodies). The monitoring program was improved and, in 2002, a new epizootic was recorded with virus circulation in the central region of the state, including 9 additional municipalities in the vaccination area. Subsequently, no YFV activity was recorded for 6 years.

In October 2008, the state health secretary reported an increase in the number of deaths of black howler monkeys in the northwestern region, and intensified surveillance began immediately, before the deaths from yellow fever were even confirmed (8). This study describes the results obtained in 2008 during entomologic surveillance in areas with records of yellow fever epizootics in 2 municipalities of the northwest region of Rio Grande do Sul State.

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Yellow Fever Virus, Southern Brazil | CDC EID

Suggested Citation for this Article

Cardoso JC, de Almeida MAB, dos Santos E, da Fonseca DF, Sallum MAM, Noll, CA, et al. Yellow fever virus in Haemagogus leucelaenus and Aedes serratus mosquitoes, southern Brazil, 2008. Emerg Infect Dis [serial on the Internet]. 2010 Dec [date cited]. http://www.cdc.gov/EID/content/16/12/1918.htm

10.3201/eid1612.100608

Comments to the Authors

Please use the form below to submit correspondence to the authors or contact them at the following address:

Pedro F.C. Vasconcelos, Departamento de Arbovirologia e Febres Hemorrágicas. Instituto Evandro Chagas, SVS/MS, Rod. BR 316, Km 07, SNº, Bairro, Levilândia 66030-000, Belém, Brazil; email: pedrovasconcelos@iec.pa.gov.br