Non-adherence to community directed treatment with ivermectin for onchocerciasis control in Rungwe district, southwest Tanzania.

BACKGROUND: Community directed treatment with ivermectin (CDTI) for onchocerciasis control was developed as a strategy for achieving sustained high coverage in endemic communities. This strategy for over a short period of time has radically altered the consequences of infection with Onchocerca volvulus. The present challenge is maintaining the high therapeutic coverage especially in some of the impoverished endemic countries. One of these challenges is non-adherence to ivermectin treatment and this provides compelling reason for data collection at community level. OBJECTIVE: To describe the factors associated with non-adherence to CDTI. DESIGN: Cross-sectional descriptive study. SETTING: Communities participating in CDTI activities in Ndubi village, Rungwe district, southwest Tanzania. RESULTS: A high proportion (66%) of respondents were aware of onchocerciasis, and this was more significant in males than females (X2 = 9.17; p< 0.002). Knowledge on causes of the disease was low, only 29.3% associated it with the bite of Simulium fly, 17% associated it with mosquitoes, 17.1% to houseflies, and 30% had completely no idea. Knowledge on signs and symptoms of onchocerciasis was also observed to be equally low (20.4%) among the respondents. Similarly, only 35.4% of the respondents knew itching, swelling of the body, diarrhoea and vomiting as associated side effects of ivermectin. There was, however, no sex difference in knowledge levels (X2 = 0.01; p>0.939). Low knowledge levels on causes of the disease, signs and symptoms and side effects of ivermectin were attributed to inadequate health education in the communities. However, some other factors associated with non-adherence were local beliefs and the lifestyle of alcoholism. CONCLUSIONS: Factors identified to affect programme implementation and associated with non-adherence were inadequate knowledge on causes of the disease and sign/symptoms, side effects of ivermectin, local beliefs and lifestyle of alcoholism in the communities.

The transmission dynamics of bancroftian filariasis: the distribution of the infective larvae of Wuchereria bancrofti in Culex quinquefasciatus and Anopheles gambiae and its effect on parasite escape from the vector.

The anatomical distribution of the infective larvae (L3) of Wuchereria bancrofti in Culex quinquefasciatus and Anopheles gambiae, and its influence on L3 escape, was evaluated by exposing the vectors to human individuals infected with W. bancrofti. After the extrinsic incubation period of W. bancrofti, a random sample of the infected mosquitoes was dissected to determine the distribution of infective larvae in the body of the mosquitoes and the proportion of mosquitoes that were infected. The remaining mosquitoes were exposed to an experimental definitive host (mouse skin). The infective larvae on and in the host tissues were counted. The engorged mosquitoes were dissected to determine the proportion infected and the distribution of L3 in mosquitoes after exposure. The results show that 53.4% of L3 escaped from Cx. quinquefasciatus to enter the experimental host whereas only 4% of L3 escaped from An. gambiae. Analysis of the results indicates that the number of L3 in the vector and the proportion of L3 in the head and mouthparts influence the number of L3 escaping from the vector to enter the definitive host and consequently the number that gain access to host tissues. The implication of these findings on the transference of the parasite from the vector to the definitive host is discussed.

Acute adenolymphangitis due to bancroftian filariasis in Rufiji district, south east Tanzania.

A longitudinal prospective surveillance for acute adenolymphagitis (ADL) was carried out in three villages in Rufiji district. A sample population of 3000 individuals aged 10 years and above was monitored fortnightly for a period of 12 months. The annual incidence of ADL was found to be 33 per 1000 population and was significantly higher in males than females (52.7/1000 and 18.7/1000 respectively). ADL episodes were more frequent in the age group of 40 years and above. Individuals with chronic manifestations seemed to be more vulnerable to ADL attacks with 62.2% of the total episodes occurring in this group. Furthermore, individuals with lymphoedema experienced more frequent acute episodes compared to those with hydrocele and 'normal exposed'. ADL episodes ranged from one to five per annum and the majority of the affected (60.4%) experienced a single episode. The average duration of an ADL episode was 8.6 days and in 72.5% of the episodes the affected individuals were incapacitated and unable to do their normal activities for an average duration of 3.7 days. The physical incapacitation associated with ADL episodes emphasizes the significance of lymphatic filariasis as a major public health problem of substantial socio-economic consequences.