Roger H. Webber

Prevalence of hydrocele as a rapid diagnostic index for lymphatic filariasis

The real burden of lymphatic filariasis in most endemic areas remains unknown even thought it is a major public health problem in many tropical countries, particularly in sub-saharan African. The nocturnal periodicity of the parasite requires parasitological examinations to be done at night. The aim of this study was to develop and validate rapid epidemiological assessment tools for the community diagnosis of lymphatic filariasis, that may be used in the future to determine the distribution of the disease and identify high risk communities in Ghana. Twenty communities with varying endemicity of filariasis were sampled from 3 endemic districts. Community members were selected for the study using a modified Expanded Programme for Immunization (EPI) cluster sampling technique. The prevalence of hydrocele was high (range 4.5-40.75%, mean = 17.78%) and the community prevalence of microfilaraemia correlated well with that of hydrocele (r = 0.84). The findings suggest that it is possible to obtain reliable and valid estimates of the community burden of lymphatic filariasis using the prevalence of hydrocele as a diagnostic index.

Infectious reservoir of Plasmodium infection in Mae Hong Son Province north-west Thailand.

BackgroundIt was unknown whether the main reservoir of Plasmodium falciparum and Plasmodium vivax, which infects mosquitoes in Thailand, was (a) in people feeling sufficiently ill with malaria to come to a clinic or (b) in people who had remained in their home villages with some fever symptoms or with none.MethodsMass surveys were carried out in Thai villages to identify people with Plasmodium infections and with fever. Malaria patients were also located at a clinic which served these villages. Adults from both sources whose blood slides registered positive for Plasmodium spp. were requested to allow laboratory-bred Anopheles minimus to feed on them. Seven to nine days after the blood feeds the mosquitoes were dissected and checked for presence of oocysts.Results and DiscussionThere were higher rates of Plasmodium infection among people in the villages with fever than without fever and much higher rates of infection among clinic patients than among people who had remained in the villages. People with malarial infections identified via the clinic and the village surveys could infect mosquitoes, especially, but not only, if their blood slides showed visible gametocytes. Because only a very small minority of the village populations were visiting the clinic on any one day, assessment indicated that the main reservoir of infection was not primarily among clinic patients but among those in the villages, especially those feeling feverish.ConclusionsEfficient use of an anti-gametocyte drug to suppress the parasite reservoir in a population requires that it be given, not just to clinic patients, but to infected people located by mass surveys of the villages, especially those feeling feverish.

Evaluation of the filter paper blood collection method for detecting Og4C3 circulating antigen in bancroftian filariasis

Serological diagnosis of filariasis is generally known to be more reliable than detection of microfilariae. The recently developed Og4C3 enzyme-linked immunosorbent assay (ELISA) for detecting Wuchereria bancrofti circulating antigen has been shown to be very sensitive in diagnosing filiariasis using serum samples. The commercially available form of this ELISA, using whole blood collected on filter paper, has not been validated independently. We evaluated the sensitivity of this new method against standard 20 microL night blood films in 1808 paired samples from 18 communities in different endemic areas of Ghana. The diagnostic performance of the method was consistently low in all but 2 communities (sensitivity = 50.3%). This method of diagnosing filariasis is not suitable for field use in its present form.

Comparison of the effect of insecticide-treated bed nets and DDT residual spraying on the prevalence of malaria transmitted by Anopheles anthropophagus in China

In order to improve the control of malaria in a problem part of Hubei Province, China, where Anopheles anthropophagus is the vector of Plasmodium vivax, insecticide treatment of bed nets was introduced. The people were given the choice of DDT residual spraying, which had been used for many years, or deltamethrin treatment of their bed nets. Two counties, in which these 2 different methods had been introduced, and an untreated area were evaluated. DDT house spraying and insecticide treated bed nets were equally effective, but deltamethrin treatment was cheaper and so was considered the method of choice.

A Community-based Study of Acute Respiratory Infections Among Preschool Children in Syria

A longitudinal community-based study of the epidemiology of acute respiratory infections (ARI) in children less than 5 years old was carried out in a low income peri-urban area of Syria. A total of 1030 children were followed up by weekly morbidity surveillance for a period of 24 weeks, starting September 1989. The results revealed that, on average, a child suffered 3.4 episodes of ARI per 100 child-days at risk. The average prevalence of ARI was 23 per cent of time of observation. The peak age-specific incidence occurred in children 6-12 months old for cough/cold, and in children 0-5 months for pneumonia. Male children experienced higher incidence and prevalence of ARI. The most frequently reported symptoms were nasal discharge and cough.

Surveillance for low-level malaria.

Due to good detection and control, malaria has reached very low levels in China with the result that existing methods of surveillance, taking blood slides from all fever cases and those with a common cold, are finding very few malaria cases among the millions of persons examined. Passive case detection agents in areas of moderate and low endemicity in Hubei Province, China, were instructed to indicate on the form associated with each slide whether the patient was considered to be a clinical case of malaria (group 1), was thought to have malaria but did not have all the features (group 2), had fever alone and was not thought to be a case of malaria (group 3), or merely had a common cold (group 4). In the low endemic area (slide positivity rate 0.23%), only 5 cases in group 3 and 4 in group 2 were detected per 10,000 examinations. It is recommended that these categories be discontinued in malarious areas of low endemicity, to encourage greater efficiency in detecting cases in groups 1 and 2. In the moderately endemic area, with a slide positivity rate of 4.19%, all categories, including group 4, were considered valuable for detecting malaria cases.

A successful control programme for lymphatic filariasis in Hubei, China

This paper describes the epidemiology and control of human lymphatic filariasis in Hubei province, China from the 1950s to the 1990s. Brugia malayi, transmitted by Anopheles sinensis, and Wuchereria bancrofti, transmitted by Culex quinquefasciatus, were found in 69 of 78 counties and cities. The distribution of filaria species was distinct, with B. malayi endemic in the plains, mixed infections in hilly areas, and W. bancrofti in the mountains. Before 1979, the microfilaria rate (mfr) in some villages was as high as 30.69%. Since 1979, large scale control programmes have been carried out and 27,875,267 blood examinations have been made. Up to 1988, the mfr in all endemic villages decreased to below 1%. From 1989 to 1991 about 200,000 people had their blood examined yearly and few cases were detected. The continued use of mass blood examination for filariasis surveillance is not economic at such low levels of infection, and it is suggested that selective treatment of microfilaremic persons should be the main control measure at this stage.

The potential role of peripheral health workers and community key informants in the rapid assessment of community burden of disease: the example of lymphatic filariasis

Data for planning disease control programs in most developing countries is often not available because they are usually expensive to gather. This study explored the potential use of peripheral health staff and community key informants in gathering community‐level data about lymphatic filariasis. Agreement between findings of health workers and those of physicians was very high (κ 0.66–0.87) for the clinical conditions examined. The prevalence of hydrocele was found to be a good predictor of communities at risk of filariasis. Community key informants provided very useful qualitative and quantitative data on the prevalence of clinical filariasis. The need to use nontraditional health professionals in gathering data for planing control programs is discussed.