[Entomology of onchocerciasis in Soconusco, Chiapas, México. VII. Quantitative variations in the transmission of Onchocerca volvulus (Nematoda: Filaroiidea) according to human activity space].

In this research we tried to demonstrate differences in transmission intensities of onchocerciasis by Simulium ochraceum in the community of Golondrinas, Municipality of Acacoyagua in the Soconusco area of the state of Chiapas. Adult females of this species were captured in the center of the villages, the coffee plantation, and the corn bean planted plots, during 7 to 10 consecutive days of the months of June, August, November and December of 1983, and January, March, and May of 1984. Captures were made from 7:00 to 11:00 h, by two persons (a human bait and a collector) in each of the mentioned areas. Variations in densities of S. ochraceum were not statistically significant among the different areas, although there was a predominance in the center of the villages during all the time periods. There was not a statistical significance in the number of oviparous females, although again the center of 50 villages showed the highest percentages (43.5%), as compared to the coffee plantation (37.8%), and the corn-bean plots (33.8%). Regarding the ratio infection: infectivity, only the infective mosquitoes with L3 showed a statistical significance in the three types of areas, being highest in the center of the villages. Transmission potentials were: center of the village 28.5 L3/human/period; coffee plantation, 73 L3/human/period; corn-bean plot, 5.8 L3/human/period. We discuss the possibility that the differences in densities among the various areas might depend on the variations of the breeding sites, mobility or permanence of the individuals during the hours of greater activity of S. ochraceum, and the wind and light local conditions.(ABSTRACT TRUNCATED AT 250 WORDS)