Community-based Chemotherapy Research Articles

The associations between water and sanitation and hookworm infection using cross-sectional data from Togo's national deworming program.

BackgroundSustainable control of soil-transmitted helminths requires a combination of chemotherapy treatment and environmental interventions, including access to safe drinking water, sufficient water for hygiene, use of clean sanitation facilities, and handwashing (WASH). We quantified associations between home-, school-, and community-level WASH characteristics and hookworm infection—both prevalence and eggs per gram of stool (intensity)—among Togolese school children in the context of community-based chemotherapy treatments administered in the country from 2010 through 2014.Methodology/Principal findingsWe analyzed data from two surveys conducted by the Togo Ministry of Health: a school-based survey of students aged 6–9 years across Togo conducted in 2009 and a follow-up survey in 2015, after four to five years of preventive chemotherapy. Data were available for 16,473 students attending 1,129 schools in 2009 and for 16,890 students from 1,126 schools in 2015. Between surveys, children in study schools received 0 to 8 rounds of deworming chemotherapy treatments. Few WASH conditions (only unimproved drinking water) were found to be significantly associated with the presence or absence of hookworms in an individual; however, quantitative eggs per gram of feces was associated with availability of unimproved drinking water, availability of improved drinking water either on or off school grounds, having a handwashing station with water available, and access to a sex-separate non-private or private latrine. The association between school WASH conditions and hookworm infection or burden often depended on the 2009 prevalence of infection, as more WASH characteristics were found to be significant predictors of infection among schools with high underlying endemicity of hookworm.Conclusions/SignificanceOur findings emphasize the complex and often inconsistent or unpredictable relationship between WASH and hookworm. Specifically, we found that while preventive chemotherapy appeared to dramatically reduce hookworm infection, WASH was associated with infection intensity.

Molluscicidal Effects of Aqueous Extracts of Selected Medicinal Plants from Makueni County, Kenya

Schistosomiasis (also known as Bilharzia) is a disease caused by species of parasitic worms or helminths of the genus Schistosoma. It continues to be a serious worldwide public health problem. The pathological changes in schistosome infestations are caused mainly by the deposition of the eggs into various tissues and organs where granulomas or pseudo tubercles are formed around them. Schistosomes and their intermediate snail hosts are integral parts of the freshwater aquatic environments in which they are found. Biomphalaria and Bulinus are the two primary genera of snails capable of harbouring infections with Schistosoma mansoni and S. haematobium. Some of the methods of controlling of schistosomiasis include: control of snails, public health education, sanitation, and community-based chemotherapy employing praziquantel. No single method, regardless of location, has been shown to work because of the large number of environmental variables involved in the parasitic transmission. Some of the control programmes have been those that include some method of curbing transmission, including mollusciciding. The objective of this study was to bioscreen aqueous extracts of five medicinal plants identified using ethnobotanical information gathered from traditional healers for molluscicidal activity. Molluscicidal activity was assessed by determining the ability of various concentrations of the aqueous plant extracts to kill adult Biomphalaria pfeifferi, the intermediate host of Schistosoma mansoni. Of the five plant extracts, only the aqueous extracts of Aloe secundiflora, Aspilia pluriseta, Balanites aegyptiaca, Azadirachta indica and Amaranthus hybridus showed molluscicidal activity. This study has established that five plants, that is, Aloe secundiflora, Aspilia pluriseta, Balanites aegyptiaca, Azadirachta indica and Amaranthus hybridus have molluscicidal activity and recommends that toxicity studies be conducted to establish their safety in bilharzia control.

Long term study on the effect of mollusciciding with niclosamide in stream habitats on the transmission of schistosomiasis mansoni after community-based chemotherapy in Makueni District, Kenya.

BackgroundSchistosoma mansoni infection is a persistent public health problem in many Kenyan communities. Although praziquantel is available, re-infection after chemotherapy treatment is inevitable, especially among children. Chemotherapy followed by intermittent mollusciciding of habitats of Biomphalaria pfeifferi, the intermediate host snail, may have longer term benefits, especially if timed to coincide with natural fluctuations in snail populations.MethodsIn this cohort study, the Kambu River (Intervention area) was molluscicided intermittently for 4 years, after mass chemotherapy with praziquantel in the adjacent community of Darajani in January 1997. The nearby Thange River was selected as a control (Non-intervention area), and its adjacent community of Ulilinzi was treated with praziquantel in December 1996. Snail numbers were recorded monthly at 9–10 sites along each river, while rainfall data were collected monthly, and annual parasitological surveys were undertaken in each village. The mollusciciding protocol was adapted to local conditions, and simplified to improve prospects for widespread application.ResultsAfter the initial reduction in prevalence attributable to chemotherapy, there was a gradual increase in the prevalence and intensity of infection in the non-intervention area, and significantly lower levels of re-infection amongst inhabitants of the intervention area. Incidence ratio between areas adjusted for age and gender at the first follow-up survey, 5 weeks after treatment in the non-intervention area and 4 months after treatment in the intervention area was not significant (few people turned positive), while during the following 4 annual surveys these ratios were 0.58 (0.39-0.85), 0.33 (0.18-0.60), 0.14 (0.09-0.21) and 0.45 (0.26-0.75), respectively. Snail numbers were consistently low in the intervention area as a result of the mollusciciding. Following termination of the mollusciciding at the end of 2000, snail populations and infections in snails increased again in the intervention area.ConclusionThe results of this study demonstrate that in the Kenyan setting a combination of chemotherapy followed by intermittent mollusciciding can have longer term benefits than chemotherapy alone.

Resolution and resurgence of schistosoma haematobium-induced pathology after community-based chemotherapy in ghana, as detected by ultrasound.

Community-based treatment is recommended for endemic populations with urinary schistosomiasis; however, the optimal target group for treatment and retreatment interval have not been established. Using ultrasound, this study identified subpopulations whose lesions were most likely to respond to treatment and characterized resurgence of pathology. Ultrasound examination of 1202 infected patients was followed by chemotherapy with praziquantel. A sample of 698 patients was followed for 18 months after treatment. Nearly all types of bladder pathologies resolved after treatment, regardless of patient's age or intensity of initial infection. However, many patients' upper urinary tract pathologies (62.5%) did not resolve. During the 18-month follow-up period, reappearance of severe bladder pathologies was rare, and <10% of persons had resurgence of mild bladder pathologies. For this population, retreatment is not needed annually but might be cost effective if given several years later. Confirmation from other areas is required before general policies can be formed.

The relationship between prevalence of Schistosoma haematobium infection and different morbidity indicators during the course of a control programme on Pemba Island

A long-term schistosomiasis control programme was initiated on Pemba Island,Tanzania in 1986 with the aim of eliminating morbidity due to Schistosoma haematobium infection. The programme used haematuria as a community indicator of morbidity for surveillance and for identifying individuals for selective population chemotherapy. Analysis of the first 3 evaluation studies showed that the prevalence of microhaematuria was linearly related to the prevalence of infection, and that visually detectable haematuria was a marker of the intensity of infection and risk of morbidity in a community. These relationships remained consistent during repeated community-based chemotherapy, suggesting that measures of haematuria may be useful tools for surveillance.

Schistosomiasis mansoni in Bahia, Brazil: historical trends and control measures

In order to aid the development of new approaches to schistosomiasis control, changes were analyzed in prevalence at the county level in the State of Bahia from the 1950s to the 1990s, as were determinants and the effect of community-based chemotherapy. In general, no substantial changes were observed in the basic pattern of spatial distribution of the prevalence of infection. However, during the period studied, there was an overall reduction in prevalence from 15.6% to 9.5% and an increase in prevalence rates in some counties from the western, southeastern, and northern areas of Bahia, indicative of new transmission areas. The effect of mass chemotherapy was analyzed. In the Paraguaçu Basin, where this control measure was used on a large scale, there was a reduction in prevalence similar to areas where this measure was not used. Correlation and regression analysis also failed to show links between mass chemotherapy and long term reduction in prevalence. The most powerful variables to explain these changes were those related with population dynamics. These findings strongly suggest that the reduction in prevalence observed in some areas of the State must be attributed to factors related with the spatial organization of this territory, causing a general decrease in the transmission rate, secondary to mass chemotherapy. At the same time, the incomplete form and the spatial inequalities that characterized the urbanization process created favorable conditions for the spread of schistosomiasis mansoni and the establishment of new foci.

Impact of repeated community-based selective chemotherapy on morbidity due to schistosomiasis mansoni.

The impact of repeated chemotherapy on morbidity due to schistosomiasis mansoni was evaluated in Gihungwe (initial prevalence 58%) and Buhandagaza/Kizina (33%), two village clusters in Burundi. Surveys were carried out with reference to the first treatment (month 0) at months -6, -3, 0, 3, 6, 9, 12, 24, and 36. Praziquantel (40 mg/kg) was given at months 0, 12, 24, and 36 to those showing eggs in the feces with a single 28-mg Kato slide. At each survey, duplicate Kato smears were examined, and all participants responded to a standardized medical history interview and underwent a clinical examination. In the three preintervention surveys, spleen and liver rates remained stable at the community and the individual level. The frequencies of diarrhea and abdominal pain varied to some extent, but they were consistently higher in the most heavily infected villages and age groups and remained relatively stable at the individual level. At the final survey, the prevalence of infection had decreased to 25%, and the frequency of diarrhea from 19-26% to 10% in both village clusters. This impact was strongest in the younger age groups. The frequency of abdominal pain was reduced only at the short term and in selected age groups. Organomegaly decreased only to a limited extent in those treated, and increased in those not treated, possibly due to the impact of malaria. The net result was that no measurable impact of the treatments on organomegaly at the community level could be demonstrated. In the light of these results, the relevance of community-based chemotherapy in moderate foci is questioned.

Repeated Community-Based Chemotherapy for the Control of Schistosoma Mansoni: Effect of Screening and Selective Treatment on Prevalences and Intensities of Infection

The impact of repeated selective chemotherapy on prevalences and intensities of infection with Schistosoma mansoni was evaluated in Gihungwe Transversals 1 and 2 (initial prevalence 60%) and Buhandagaza/Kizina (initial prevalence 35%), two village clusters in Burundi. Surveys were carried out at months -6, -3, 0, 3, 6, 9, 12, 24, and 36, with reference to the first intervention; treatment with praziquantel (40 mg/kg) was given at months 0, 12, 24, and 36 to subjects showing parasite eggs on a single 28-mg Kato slide. A second slide was examined for monitoring purposes only. Over the pre-intervention period, the overall prevalences and intensities remained relatively stable, but important increases were observed in specific groups. The cure rate three months after the first treatment in those treated was 73% (Gihungwe) and 83% (Buhandagaza/Kizina), but the prevalence at the community level was reduced only by 50% and 46%, respectively. Fifty-six percent and 79%, respectively, of the remaining positive cases had not been treated, largely because they were (falsely) negative at the screening. Reinfection occurred mainly in Gihungwe and in younger age groups. One year after the second treatment, prevalences and intensities were further reduced in Gihungwe only; one year after the third treatment prevalences were not reduced further in either village group. The final prevalence of infection was approximately 25%, with infections with an intensity of over 100 eggs per gram of feces approximately 5%, in all four villages. Over 80% of the remaining cases had not been treated at the previous intervention; the sensitivity of the screening method appears to be a major determinant of the outcome of repeated selective treatment.

Reliability of Detection of Microfilariae in Skin Snips in the Diagnosis of Onchocerciasis

To quantify the sensitivity of skin snips for the diagnosis of onchocerciasis, data collected over a 2 year period from 261 Liberians, 12-60 years of age, were examined. The overall sensitivity of 6 snips per person was estimated to be 91.6%. When the microfilariae density was greater than or equal to 3.5 microfilariae/mg skin, there were no false negatives. At lower microfilaria densities, the sensitivity declined markedly. Furthermore, it was found that smaller and lighter snips were more likely to be classified as being falsely negative. The load of infection at the community level may be reduced after intervention strategies, such as vector control or community-based chemotherapy. Interpretation of the impact of these programs on the prevalence of infection should take into account the lower sensitivity of the skin snips at lower levels of infection.

Community control of helminth infections of man by mass and selective chemotherapy.

The design of mass and targetted community-based chemotherapy programmes for the control of the major helminth infections of man is discussed in relation to the population and transmission dynamics of the parasites. Rapid reinfection following a single mass or targetted anthelmintic application is shown to be a universal feature of helminth transmission, as a consequence of the regulatory or feed-back mechanisms controlling population abundance within both individuals and the community as a whole. Control of reinfection requires repeated community treatment where the intensity of application and the interval between treatments are dependent on the reproductive life-expectancy of the adult worm, the net force of transmission prior to control (the basic reproductive rate) and the factors which create aggregation in the distribution of parasite loads within the population. Selective or targetted treatment is shown to be most effective for the control of morbidity as opposed to the control of transmission. The impact of targetted treatment depends critically on the factors that generate heterogeneity in parasite burdens and on whether or not selectivity is based on a single or repeated identification of the 'wormy' fraction of the community. Monte Carlo simulation studies are employed to assess the likely impacts of different control strategies on average parasite abundance/person and the distributions of parasite loads within populations. Future epidemiological research needs are discussed in relation to theoretical work and recent field studies of predisposition to heavy infection.