Comparison of black fly species (Diptera: Simuliidae) on an Amerindian reservation with a high prevalence of fogo selvagem to neighboring disease-free sites in the State of Mato Grosso do Sul, Brazil. The Cooperative Group on Fogo Selvagem Research.

Fogo selvagem is an autoimmune blistering skin disease that principally occurs among rural Brazilians living in geographically clumped disease foci. Exposure to hematophagous black flies possibly is related to the cause of the disease. We compared the occurrence, proportions, and richness of simuliid species immatures and the biting activity of adult females within a recently discovered, high prevalence focus of fogo selvagem, the Limão Verde Terena Reservation, to that of neighboring regions with no reported cases of fogo selvagem. Nine black fly species were collected from 12 stream sites during 5 trips to the fogo selvagem focus. The species showed longitudinal (upstream-downstream) trends in occurrence, proportions, and richness, and the abundance of simuliid immatures was greater at downstream sites. The most prevalent species at the focus, Simulium nigrimanum (Macquart), dominated the stream sites with highly abundant simuliid assemblages, and was the most common black fly in human bait collections. This species was absent or in very low numbers in neighboring valleys and villages that did not have cases of fogo selvagem.

An active focus of high prevalence of fogo selvagem on an Amerindian reservation in Brazil. Cooperative Group on Fogo Selvagem Research.

Fogo Selvagem (FS) is an autoimmune disease characterized by subcorneal vesicles and antidesmoglein-1 autoantibodies. Previous epidemiologic data have linked the onset of FS to exposure to an environmental antigen(s). This investigation describes a unique human settlement with an extraordinarily high prevalence of FS. This community is made up of Amerindians belonging to the Terena tribe, which has settled on the Limao Verde reservation in the state of Mato Grosso do Sul in Brazil. Twenty-six well-characterized FS cases have been identified within a total population of 998, yielding a prevalence of 2.6%. Seventeen of the patients (65 %) were males, and over 50% were older than 30 y of age. The incidence of the disease shows temporal periodicity, i.e., years with several cases of FS alternating with years with no cases. Over one-half of the cases occurred in genetically related family members. Another Terena reservation, the Ipegue/Taunay, located 90 km west of the Limao Verde reservation, was also evaluated as a control group. This reservation, with a population of 2203, had no recorded cases of FS. Thus, the Limao Verde reservation represents a new focus of FS in which the disease exhibits temporal, geographic, and familial clustering. These results suggest that the environmental antigen or antigens precipitating FS are endemic to the Limao Verde reservation. This reservation appears to be an ideal population for carrying out sero-epidemiologic, genetic, and environmental studies aimed at disclosing the etiology of FS.