Inputs to the hormonal control of egg development in Rhodnius prolixus

This paper re-examines existing data on the environmental inputs governing egg production in Rhodnius prolixus. Feeding has a direct effect on egg production such that the product of the unfed weight of the female times the weight of the blood meal is a good predictor of the number of eggs produced. Mating modifies this input, so that mated females produce more eggs. Egg production is governed by the corpus allatum, and indirect evidence suggests that the number of eggs producted by a female is a function of the length of time that juvenile hormone is secreted by the corpus allatum. The input which determines the times at which the corpus allatum is switched off originates in the stretch induced by the amount of the meal remaining in the crop, modified by the matedness status of the female. The precise nature of the sensors detecting stretch is not yet clear, but the integrity of the dorsal aorta is essential to the transmission of the information. These data are related to the survival strategy for Rhodnius.

The Venezuelan experience in the control of Schistosomiasis mansoni

Schistosomiasis mansoni endemic zone of Venezuela is located in the valleys of the north central mountain region, with an extension of 15,000 km2 and inhabited by 5.1 million persons. The disease was discovered in 1906, but an organized Control Program was not established until 1943. Its basic activity has been the control of the snail vector, but prevention of man-water contact, prevention of snail infection, treatment of infected people and sanitary instruction, have also been carried out. Prevalence has diminished from 14.7% (1943-60) to 0.9% (1981-84). At present few active foci still persist, but a low transmission rate and low morbidity makes it difficult to know the exact number of infected people, which has been estimulated to be about 50,000.

Health education for children in the control of Schistosomasis

Health education for children is an important measure in the control of schistosomiasis especially considering the characteristics of the disease during childhood, such as high prevalence, high percent of treatment resistance, high rates of egg elimination and high level of reinfection, as reported in studies conducted in endemic areas. All of these facts indicate that children play a role in the maintenance and transmission of schistosomiasis. Historically in Brazil, Health Education concerning the major Brazilian endemies consists of a kind of vertical, interventionist and temporary action. An alternative would be to create a permanent health education process by assigning health education teachers to elementary schools. This would require expansion and improvement of teacher training and the development of programs taking into account: 1) the cognitive aspects of the child, the child's perception of reality and of the health/illness process; 2) the adaptation of instruction means and materials to the age group; 3) a "pedagogy of liberation" approach emphasizing the possibility of transforming life conditions since schistosomiasis is related to the lack of public services such as basic sanitation and clean domestic water supply.

Control of schistosomiasis in the Gezira

For the control of schistosomiasis in irrigated agricultural schemes, the inhabitants must have: 1) Enough potable water. 2) Latrines. 3) Proprer health education to motivate the community to participate in the control. 4) Proper diagnostic facilities. 5) Proper availabel chemotherapy. 6) Focal mullusciciding. 7) If possible trial of biological and environmental methods control. Following the above methods, we could reduce the prevalence of schistosomiasis from over 50% to about 13%. The important achievement, is the improvement of the health of the community; therefore more production and reduced morbidity and mortality.