ENTOMOLOGICAL AND SEROLOGICAL ASSESSMENT OF ONCHOCERCA VOLVULUS TRANSMISSION IN THE NORTHERN CHIAPAS FOCUS (MEXICO)

Entomological and serological surveys were performed during 2001 and 2005 in two communities (Altagracia and El Ambar) of the Northern Chiapas (Mexico) focus to assess the parasite transmission and incidence of exposure to onchocerciasis. In Altagracia in 2001, infective flies were detected, leading to an estimated transmission potential of 1.4 L3 per person per year. In 2005, no infec- tive flies were detected in Altagracia, leading to an estimated transmission potential of zero. No evi- dence for transmission was found during either year in El Ambar. Within a sentinel cohort in these com- munities, 12% (15/126) were serologically positive for antibodies recognizing a cocktail of O. volvulus recombinant antigens in El Ambar, while 7% (5/68) were serologically positive in Altagracia. The inci- dence in children five years old and younger (n = 27) within this sentinel cohort was 13% (2/15) in El Ambar, and 8% (1/12) in Altagracia. Although no evidence for parasite transmission was seen in El Ambar in the surveys conducted in 2001 and 2005, a few individuals in the sentinel cohort serocon- verted during this period.

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