Onchocerciasis hyperendemic in the Unturán mountains: an extension of the endemic region in southern Venezuela

Abstract

A new region with human onchocerciasis is reported in the Unturán mountains, South Venezuela, affecting Yanomamö populations not surveyed in previous studies conducted in the Venezuelan-Brazilian border area. Its distribution probably extends towards the Upper Toototobi endemic area in Brazil. The age-standardized prevalence of Onchocerca volvulus microfilariae (mf) (67%), the prevalence of infection in those aged > or = 20 years (86%), and the community microfilarial load (CMFL) (24 mf/mg), are consistent with hyperendemic transmission. Both prevalence and mean intensity increased monotonically with age without reaching a plateau, the highest values being recorded in the > or = 45 years age class (respectively, 95% and 42 [geometric mean of Williams] or 172 [arithmetic mean] mf/mg). The degree of parasite overdispersion (measured by the variance/mean ratio) also increased with host age. The CMFL value, the presence of sclerosing keratitis, hanging groin, and severe skin lesions, indicated that the infection poses an important public health problem in the region.

Phosphoglucomutase and trehalase isoenzymes of Venezuelan Simulium vectors of Onchocerca volvulus

“…Recent reports indicate that the Amazonian focus actually extends further north than previously thought, into the northerly flowing Río Caura basin ( Godoy et al . 1989 ), and further south into the Unturan mountain range ( Botto et al . 1997 ).…”

Human Onchocerciasis in the Amazonian Area of Southern Venezuela: Spatial and Temporal Variations in Biting and Parity Rates of Black Fly (Diptera: Simuliidae) Vectors

“…HUMAN ONCHOCERCIASIS IN the Amazonian area of southern Venezuela is found between the lowlands and the highlands of the Orinoco, Caura, and Siapa river basins (Rassi et al 1977, Godoy 1982, Botto et al 1997, affecting mainly the indigenous Yanomami Amerindian group. In the highlands of this area, Simulium guianense Wise s.l.…”

“…The results presented here form part of a more extensive study in southern Venezuela with the purpose of obtaining entomological, parasitological, and clinical indicators appropriate to the evaluation of onchocerciasis endemicity and severity, and for epidemiological modeling (Botto et al 1997(Botto et al , 1999Basáñ ez et al 1998, Basáñ ez andBoussinesq 1999;Vivas-Martṍnez et al 1998, 2000a, 2000b. The entomological component of this project aimed at quantifying, before and during mass ivermectin distribution, the spatial and seasonal variations of various components of vectorial capacity: biting rate on humans, parity rate, vector competence, and vector survival, as well as natural infection levels in the less studied species of the Amazonian area, namely, S. oyapockense s.l.…”

Filariosis por onchocerca volvulus , loa loa y mansonella pers tans. Analisis epidemiológico, clínico, anal ítico y parasitológico

“…De hecho, la relación entre las alteraciones oculares y la oncocercosis no fue reconocida inicialmente en África, sino en Guatemala, por Rodolfo Robles (Robles 1917). La patología ocular atribuible a oncocercosis aún ocurre en algunos de los focos americanos, especialmente en el sur de Venezuela y Brasil (Botto et al 1997), pero la ceguera es muy rara. La enfermedad cutánea y el prurito son las principales manifestaciones clínicas en esta zona.…”