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.

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 (kappa 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.

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.

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.

Permethrin-impregnated bednets are more effective than DDT house-spraying to control malaria in Solomon Islands.

A field trial compared DDT house-spraying with permethrin-impregnated bednets for malaria control in Solomon Islands from 1987 to 1991. Mortality-rates of malaria vector Anopheles farauti in exit window traps were 11.6% from an untreated hut, 10.1% from a hut sprayed with DDT 2 g/m2, and 98% of those from a hut in which the occupants used bednets treated with permethrin 0.5 g/m2. Since bioassays of the DDT-sprayed walls (15 min exposure in W.H.O. standard test cones) gave 77% mortality of An.farauti, it was concluded that the insignificant impact of DDT could be explained by the exophilic behaviour of endophagic vectors, whereas the greater impact of permethrin was attributed to the more effective exposure of An.farauti females to the impregnated bednets-attracted by the occupants. The parous rate was higher indoors, except in the area with permethrin-impregnated bednets. It was therefore concluded that permethrin-impregnated bednets reduced the mean longevity of An.farauti and hence its vectorial capacity. The circumsporozoite (CS) antigen positivity rate of An.farauti in the DDT area was 0.18% outdoors, significantly less than 1.42% indoors. In the comparison area CS rates were 0.65% outdoors and 0.75% indoors. CS antigen was not detected in An.farauti from the bednet area, indicating the apparent prevention of malaria transmission. As DDT spraying was so much less effective, it was discontinued in 1993 and permethrin-impregnated bednets are now the principal malaria control method in Solomon Islands.

Malaria in Hubei Province, China: approaching eradication.

In the last six years, there has been a steady reduction of Plasmodium vivax malaria in Hubei Province with an API (annual parasite incidence) of 0.134 per thousand by 1992. This is especially so in the south, east, west and north-west parts of the province. Much of this reduction has been produced by a policy of repeated radical treatment in the non-malaria season. In the centre of Hubei, where Anopheles anthropophagus is the chief vector, malaria is still a problem. The key factors in destabilizing malaria are a sudden increase in the number of An. anthropophagus, introduction of non-immunes into the endemic area, and the village doctors' diminished interest in malaria surveillance activities. Impregnated bed nets are possibly the best strategy for reducing malaria, but where the prevalence is reduced to a sufficiently low level efficient case finding and detection are able to contain malaria and produce a continued reduction.

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.

The economic impact of Plasmodium falciparum malaria on education investment: a Pacific Island case study.

A small but intensive study was carried out adopting a simple method which attempts to quantify the economic consequences Plasmodium falciparum malaria on education investment through school pupil absenteeism in a community in Solomon Islands. In a randomized sample of 4,920 cases of P. falciparum malaria in a community, 2,886 occurred in children of primary school age group of 7 to 13 years. On average a case gave rise to a mean school absenteeism of 5.3 days. In the final analysis a total of 11,028 pupil days schooling were lost due to the sampled cases of malaria caused by the species. This is equivalent to 55.14 school pupil years as a child is expected to attend school for 200 days in a year. A primary school teacher with an average annual salary of US$3,990.00 is expected to teach 6,500 school pupil days a year. When this is adopted as an economic indicator for investment in education the loss is calculated to be US$6,769.57 or equivalent to US$1.38 per case. When this is applied nationally, assuming that rates are similar for 79,203 cases of P. falciparum reported in 1990, the total consequence for investment in education is US$108,966.00, which is equivalent to 27.31 teachers being paid for not teaching, an unacceptable impact for a small nation like the Solomon Islands.

Measuring effectiveness of malaria control: a simplified method for primary health care. Preliminary report.

Based on the infant parasite rate where an increasing number of infants become positive for each month of age (until a plateau is reached) a measure is developed using surveillance blood slides of all cases of malaria at the start of the transmission season. The fortnightly PCD returns from the beginning of the malaria transmission season are plotted on log-log paper and the angle the slope of the line makes with the axis is compared with similar results obtained from the intervention. The difference between the angles measures the effectiveness. The measure can be used in places that have a marked seasonal pattern (for all ages). Where immunity is shown to be a factor, only positive children should be utilized. In areas where malaria is not seasonal, the infant parasite rate, using the rate of acquiring infection rather than the overall value, will provide an alternative indicator. This evaluation tool is being tried in seasonal and non-seasonal parts of the world.

Structured short-answer questions: an alternative examination method.

A structured short answer (SSA) examination has been developed for the MSc, Community Health in Developing Countries, to test competence in international public health. Questions can test knowledge or aim to assess problem-solving ability, but have the advantage that the candidates construct their own answer (rather than choosing from pre-formed answers in an MCQ), yet encourage sufficient precision for answers to be easily marked. The SSA more closely reflects participatory teaching and self-directed learning. Illustrated material is widely used.

Immunohistochemistry of biogenic polypeptides in nerve cells and fibres of the guinea pig inferior mesenteric ganglion after perturbations.

Immunohistochemistry of peptide- and dopamine-beta-hydroxylase-(DBH)-containing varicose nerve fibres and ganglion cells, respectively, in the guinea pig inferior mesenteric ganglion was investigated following a) transsection of mesenteric (colonic) branches, b) transsection of central (lumbar splanchnic, intermesenteric and hypogastric) branches, and c) transplantation into the spleen. The findings indicate that pathways of different opioid peptides are not identical. Met-enkephalin- and met-enkephalin-arg-phe- (cleavage products from pre-proenkephalin) containing fibres course in central branches to make contact in the inferior mesenteric ganglion. Dynorphin- and alpha-neo-endorphin- (deriving from pre-prodynorphin) containing fibres as well as leu-enkephalin- (included in the dynorphin sequence) fibres appear to rise not only from central and from enteric somata, but also from intraganglionic noradrenergic neurons. Similar pathways seem to be used by VIP- and by neurotensin-immunoreactive fibres, although intraganglionic neurotensin-immunoreactive cell bodies are rare. Practically all substance P- and most CGRP-immunoreactive fibres enter the ganglion via central branches and, to a large extent, traverse it, but some CGRP-immunoreactive influx appears to come from the intestine. The origin of intraganglionic substance P- and CGRP-immunoreactive fibres after ganglion transplantation remained unidentified. Somatostatin- and neuropeptide Y-immunoreactive fibres predominantly have an intraganglionic origin as have DBH-immunoreactive noradrenergic fibres. The demonstrated alterations in neuropeptide immunoreactivity of intraganglionic and periganglionic nerve fibres following the applied transsection procedures contribute to the present knowledge on origin and destination of peptidergic transmitter segments in the guinea pig inferior mesenteric ganglion. Moreover, the present study provides evidence that intrinsic participation in intraganglionic fibre supply is more extensive than hitherto believed.

Anthrax in Lake Rukwa Valley, Tanzania: a persistent problem.

An epidemic of 239 human cases of anthrax is reported in the Rukwa Valley area of Tanzania. Although the infecting source was meat from animals dying of the disease, no intestinal cases occurred. Those infected were predominantly males between 15 and 35. The epidemic was seasonal, reaching a peak towards the end of the dry period when cattle were close grazing, and declining rapidly once the rains started and the grass began to grow. The increasing magnitude of annual epidemics suggests that the problem will get worse unless major efforts are made to vaccinate cattle before the epidemic period.

A poliomyelitis survey the simple way: the Tanzanian experience.

A simple cost effective survey to assess the need for a rehabilitation service for individuals disabled by poliomyelitis was carried out making the maximum use of the existing government administration. The field team consisted solely of a medical officer and a health officer. The prevalence rate for paralytic poliomyelitis in the Mbeya region of Tanzania was 2.95/1000 persons. The rate for children under 10 years was 1.15/1000, suggesting that the expanded immunisation programme started in 1977 was being successful. With approximately 4000 cases of paralytic poliomyelitis in the Mbeya region a rehabilitation service would seem to be justified. If poliomyelitis surveys are required for rehabilitation purposes they must include all age groups. In this survey, had only school children been considered, as recommended by the World Health Organisation, two thirds of the cases would have been excluded, thereby hardly justifying a rehabilitation service.

Chemoprophylaxis of malaria in non-immune residents in Dar es Salaam, Tanzania.

The malaria infection rates in non-immune residents of Dar es Salaam on various chemoprophylactic regimens were compared with that (37.1%) in those not taking prophylactic antimalarials. Among 647 people resident in Dar es Salaam for 1-6 years the two groups with the lowest infection rates by person-episodes (2.0% and 1.5%) were those taking proguanil 200 mg daily alone or with chloroquine base 300 mg weekly. Infection rates (16.9% and 14.0%) were also significantly lower than in the no-prophylaxis group in those taking chloroquine base 300 mg weekly combined with 'Fansidar', 'Maloprim' (each one tablet weekly), or proguanil 100 mg daily. No significant reduction in the malaria attack rate was found in those taking chloroquine base 300 mg or 600 mg weekly (31.2%), pyrimethamine 25 mg weekly (27.3%), proguanil 100 mg daily (46.4%), maloprim one tablet weekly (40.4%), or a combination of chloroquine base 300 mg weekly and pyrimethamine 25 mg weekly (27.1%). Similar results were obtained when the infection rates per year of exposure were compared. Proguanil was associated with fewest user complaints and fansidar with most.

The maximum density of anopheline mosquitoes that can be permitted in the absence of continuing transmission of filariasis.

Using two years of mosquito collections from two fixed stations on Guadalcanal it was possible to compare the average man-biting rate with the prevalence of microfilaraemia. One area was found to be free of infection while the other still had one positive case. The DDT residual spraying had caused a change in biting habits of A. farauti No. 1 allowing a greater density of mosquitoes to bite man at times when they had lower microfilaria densities. This difference was compared with the pre-spray density so that the maximum permissible number of mosquitoes biting man without transmission of filariasis taking place, could be calculated. A theoretical value for m of 19.84 had been worked out previously; this study gave a corrected observed value of m of approximately 20, very close to the calculated theoretical value. The situation studied here probably showed incomplete interruption of transmission, so it was considered preferrable to recommend a figure of 0.66 average vector man-biting rate per hour indoors for the critical value.