An outbreak of Mayaro virus disease in Belterra, Brazil. III. Entomological and ecological studies

Walter Reed Army Medical Center. Walter Reed Army Institute of Research. Washington, D.C.Universidade de Brasilia. Faculdade de Ciências da Saúde. Brasília, DF, Brazil.Gorgas Memorial Laboratory. Miami, Flórida, USA.Ministério da Saúde. Fundação Serviços de Saúde Pública. Instituto Evandro Chagas. Belém, PA, Brasil.Results of entomological and vertebrate host investigations made during dual outbreaks of Mayaro (MA Y) and yellow rever (YF) viroses in Belterra, Pará, Brazil in 1978 are reported. Over 9,000 insects representing 26 species were assayed in 396 pools for the presence of arboviruses. Pools of Haemagogus janthinomys Dyar yielded the only isolares of either MA Y or YF virus. The minimum field infection rate for nine isolates of MA Y virus from Hg. janthinomY$ was 1:82, and for two isolares of YF virus was 1:368. Analysis of collection data showed Hg. janthinomys to be attracted to man as a blood source and present in alI habitats sampled, although most abundant in the forest canopy. Twelve hundred bird gera and 584 mammal gera were tested by hemagglutination-inhibition (HI) tests for antibody to MA Y virus. Highest MA Y antibody prevalence rates were found among marmosets (Callithrix argentata, 32 positive of 119 tested, 27%). Mayaro virus was algO isolated from the blood of a sylvan marmoset captured at the peak of the MA Yvirus outbreak. Experimental infection of marmosets with MA Y virus confirmed that a substantial viremia follows infection with this virus. Marmosets were algO found with HI antibody to YF virus (5/119,4%). The results presented indicate that Hg. janthinomys was the principal vector of both MAY and YF viruses and that marmosets were the main ampliJying hosts for MA Y virus, and perhaps for YF virus as well