Studies on the transmission potential of surviving microfilaremias after basic control of filariasis.

After filariasis was basically controlled (the microfilarial rate was lower than 1%) in Henan Province in 1987, longitudinal observation of the disease has been carried out in all the province in order to study the regular pattern of growth and decline or the transmission potential of the disease. According to the distribution of filaria species and original microfilarial rate, 7 administrative villages in 7 counties were selected as surveillance sites. From 1988 to 1995, etiological and mosquito vector surveys were made continuously in all sites where no control measure was conducted. 10 surviving microfilaremic individuals became negative gradually over the first 6 years and no new microfilaremia was found. Since then, the microfilarial rate was zero. During the 8 years, 19 vector mosquitos were positive, with a total of 33 filarial larva. Culex pipiens pallens was the predominant mosquito species inside human dwelling in all sites. The man-biting rate of mosquitos for outdoor sleepers fluctuated greatly, the highest was 360.60 mosquitos per man per night and the lowest 7.20. The man-biting rate of mosquitos for sleepers inside mosquito-nets was approximately 1. The proportion of multiparous mosquitos also fluctuated greatly, the highest was 88.10% and the lowest 27.27%. According to the data described above, the man-biting rate of mosquitos which contained filaria L3 was less than 1 mosquito per man per transmission season. It is suggested that after the microfilarial rate was lower than 1%, the surviving microfilaremias became negative gradually in 3-5 years, and the transmission of the disease was blocked. Therefore, in the districts where filariasis was basically controlled, elimination of the disease was attainable.

Seroprevalence and risk factors of human cysticercosis in a community of Shandong, China.

A community-based seroepidemiologic survey on Taenia solium cysticercosis in humans was carried out in Shandong Province, China. Blood specimens from 2,898 residents were collected and examined for anti-cysticercus antibody. Information on demographic and potential risk factors was obtained using a standardized questionnaire. The overall seroprevalence of cysticercosis was 3.2%. Seropositivity tended to increase with age ranging from 1.8% in children under 6 years of age to 5.7% in those over 60 years old. Distance between village residence and the town of the community was negatively associated with seropositivity (Chi-square for trend test p = 0.02). Multivariate logistic regression analysis identified four risk factors for cysticercosis infection in the community: defecating indiscriminately (OR = 1.35, 95% CI 1.01-1.81), being unable to identify diseased pork (OR = 4.09, 95% CI 1.53-10.97), raising pigs (OR = 1.36, 95% CI 1.09-1.69), and more than 60 years old (OR = 1.49, 95% CI 1.10-2.02. These findings have implications for developing appropriate strategies for the control of Taenia solium cysticercosis in the community.