Epidemiology and control of schistosomiasis mansoni in communities living on the Cuando River floodplain of East Caprivi, Namibia.

The Cuando River area of eastern Caprivi, Namibia, is highly endemic for Schistosoma mansoni whereas S. haematobium transmission, due to the scarcity of its intermediate host snail, Bulinus africanus, does not occur. Chemotherapy (6-monthly blanket treatments with praziquantel) combined with focal mollusciciding (monthly application of niclosamide) was used in a project in the area to control the disease. Although as many adults and pre-school children as possible were tested and treated, the project concentrated largely on school-age children. It took 3 years for prevalence to decline from > 80% to 20% because of a lack of proper sanitary facilities and piped water supplies and high rates of absenteeism and re-infection. However, intensity of infection decreased more rapidly, from an arithmetic mean of > 200 to < 5 eggs/g faeces. Hepatomegaly was common among school children when the project started but could be seen in only a small percentage of them after 3 years of control. Neither the bovine schistosome, S. mattheei, nor the lechwe schistosomes, S. margrebowiei and S. leiperi, were observed in the excreta of humans living in the area.

Observations on the techniques used in the qualitative and quantitative diagnosis of schistosomiasis.

For many years, the Visser filter has been used in various laboratories in South Africa for the qualitative and quantitative diagnosis of human schistosomiasis. In the present study, the effectiveness of the Visser filter was compared with those of the urinalysis method for urine (involving the use of small transparent filters in Millipore filter holders attached to 10-ml syringes) and the Kato-Katz thick smear method for faeces. The Visser filter was the most sensitive in detecting ova in human excreta. Furthermore, there was little agreement between the egg counts obtained using the Visser filter and those obtained with the other two techniques. The Visser filter owes its effectiveness and superior sensitivity to the fact that, compared with the other two techniques, larger quantities of urine (total bladder contents) and stool (up to 5 g) can be easily processed.

Nutritional status of primary school children with endemic goitre in Caprivi, Namibia.

The nutritional status of primary school children living in an endemic goitre area in eastern Caprivi, Namibia, was assessed by means of clinical, biochemical, anthropometrical and dietetic observations. An approximately 20 pc sample, consisting of 380 primary school children, aged six to 18 years and representing eight schools in the Cuando River area of eastern Caprivi, was included in the study. Their goitre prevalence of 34.5 pc has been reported earlier. A significantly lower mean thyroxine level in goitrous compared to non-goitrous children indicated that dietary iodine deficiency was the primary cause of the endemic goitre. The present paper focuses on the nutritional status of these primary school children. Anthropometrically, these children were severely undernourished, as indicated by a high prevalence of low (below the third NCHS percentile) weight and height for age values, ranging from 38.0 pc to 55.9 pc. Dietary analysis revealed a low energy intake as well as dietary deficiencies in folic acid (only girls), ascorbic acid, vitamin A, nicotinic acid, iron, riboflavin and calcium. A high percentage (43.9 pc of boys and 33.7 pc of girls) of the children were biochemically anaemic whilst less than one pc of the children showed clinical signs of anaemia. Nutritional intervention programmes in this area should not only treat and prevent the endemic goitre but also attend to the energy and micro-nutrient deficiencies in these children.

PIP: In Namibia, a nutrition survey was conducted among 380 children aged 6-18 years at 8 primary schools along the Cuando River over about a 100 km stretch, in eastern Caprivi. This is a goiter-endemic area. 34.5% of the children had a goiter, which was the most significant nutritional condition in primary school children. This high prevalence of goiter indicated a dietary iodine deficiency. Iodine deficiency disorder can cause neurological damage ranging from mild intellectual impairment to full-blown cretinism. 38% were underweight and 55.9% were stunted (i.e., 3rd percentile of the National Center for Health Statistics). 2% had clinical signs of either kwashiorkor or marasmus. 43.9% of boys and 33.7% of girls were biochemically anemic, but less than 1% were clinically anemic. Mean standard hemoglobin level was 12.46 for girls and 12.31 for boys. Maize made up most of the diet and was eaten 2.7 times/day/child. Few children ate bread. Caloric intake was poor (39% and 45% of WHO recommendations for boys and girls, respectively). The diet did not contain enough folic acid for girls. Nutritional deficiencies in the diet also included ascorbic acid, nicotinic acid, iron, vitamin A, riboflavin, and calcium. Adequate nutritional intakes were limited to protein, thiamin, and vitamin B12 and, for boys, folic acid. These findings suggest that subsistence farming does not provide these children enough energy to maintain normal growth in children. This goiter-endemic area along the Cuando River needs educational and agricultural intervention programs to reverse endemic goiter and poor nutritional status. They should include treatment and prevention of goiter but also treatment and prevention of energy and nutrient deficiencies.

Malaria control and longitudinal changes in levels of DDT and its metabolites in human serum from KwaZulu.

Blood samples were obtained on four occasions over a 12-month period from individuals living in KwaZulu, South Africa, who had been exposed to DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) as a consequence of its use in their homes to control transmission of malaria. The longitudinal changes in serum DDT and its major metabolities, DDE and DDD, were determined. No additional risk was considered to have been presented by the increases that occurred following application of the pesticide. There were significant increases in DDT, DDE and sigma DDT (DDT + its metabolites) for the age group > or = 21 years, but for the age group 3-20 years a reduction in serum levels occurred over 12 months. Two concurrent processes probably govern the increase and decrease in serum levels, and the relative contributions of each interchange as the individual becomes older. The results suggest that children in KwaZulu experience conditions that differ from those of their parents, as well as from those that affect children in developed countries. In consequence, it is desirable that risk assessments of vector control chemicals consider all sectors of a population.

PIP: The indoor application of DDT is successfully used to interrupt the transmission of malaria parasites in many developing countries. In South Africa, it is employed in the northern and eastern Transvaal and northern KwaZulu, where malaria is endemic. DDT was applied biannually to all homesteads in these areas over the period 1957-77, with regular applications made annually thereafter between January and March. The stable, lipophilic properties of DDT, however, enable the insecticide to accumulate in biological systems. This study was designed to determine longitudinal changes in levels of DDT and its metabolites in the serum of a population protected against malaria by DDT, and to examine differences in the rates of change of serum levels of DDT and DDE between younger and older age groups. Blood samples were collected on four occasions over a 12-month period from 71 individuals living in KwaZulu, South Africa, who had been exposed to DDT during malaria control interventions. 29 were 21 years old or older, while the remainder were 3-20 years old. Researchers determined the longitudinal changes in serum DDT and its major metabolites, DDE and DDD. There were significant increases in DDT, DDE, and DDT and its metabolites for people aged 21 years and older, but for the age group 3-20 years, a reduction in serum levels occurred over the 12-month period. Two concurrent processes probably govern the increase and decrease in serum levels, and the relative contributions of each interchange as an individual ages. These results suggest that children in KwaZulu experience conditions which differ from those of their parents, as well as from those which affect children in developed countries. A need therefore exists to assess the risk presented by vector control chemicals in all sectors of a given population.

Ubombo and the site of David Bruce's discovery of Trypanosoma brucei.

The site and remains believed to be those of the camp where Sir David Bruce and his wife Mary worked between 1894 and 1897, and where Bruce discovered the causative agent of nagana and its transmission by the tsetse fly, have recently been discovered at the small village of Ubombo in northern KwaZulu (Zululand), South Africa. The site where these remnants were found fits the meagre, albeit significant, information presented by Bruce in his writings on the location of the camp.

Endemic goitre among undernourished schoolchildren in eastern Caprivi, Namibia.

A cross-sectional study on a 20% random sample of 380 children, aged 6-18 years, from 8 primary schools in the Cuando River area of eastern Caprivi, Namibia, was done to determine the prevalence of goitre and to investigate related hormonal and nutritional factors. Of the children 34.5% had goitre. Reduced plasma free thyroxine concentrations in the more severely goitrous children, compared with matched non-goitrous children (P = 0.0007), implicated dietary iodine deficiency as the causative factor. Their diet was inadequate in energy and most nutrients according to World Health Organisation criteria. Retarded growth, indicated by their low body weight and height in relation to age, were observed in a large proportion (45.6-73%) of the children. These findings suggest that dietary iodine deficiency was the most likely cause for the endemic goitre in these children, who were predisposed to nutritional disorders by long-term undernourishment.

Urinalysis reagent strips in the screening of children for urinary schistosomiasis in the RSA.

The use of urinalysis reagent strips (Labstix; Ames) in screening for Schistosoma haematobium infection in various schistosomiasis-endemic areas of the RSA was assessed in 941 children. Sensitivity, specificity, false-positive and false-negative rates and the positive predictive value for haematuria and proteinuria were calculated. Both haematuria and proteinuria were positively correlated with the presence of S. haematobium eggs in the urine. Intensity of infection correlated positively with the degree of haematuria and proteinuria (P less than 0.001). The presence and intensity of S. haematobium infection were more closely related to the presence and degree of haematuria than to proteinuria. Screening for haematuria alone enabled 83.1% of S. haematobium-positive and 89.7% of negative subjects to be detected accurately. The false-positive rate was 2.7%. It was found that a single parameter, haematuria, could be used to identify infected children in endemic areas. It was also found to be possible to use the reagent strips to select out S. haematobium-infected children with egg counts greater than 200 ova/10 ml urine. The simple model developed allows rapid identification of moderately to heavily infected children and can be used by paramedical staff in field situations.

A radioimmunoassay for the diagnosis of malaria.

A newly developed radioimmunoassay for the diagnosis of malaria has been tested in South Africa. The radioimmunoassay is an antibody binding-inhibition assay, based on a monoclonal antibody (D5) cross-reacting with Plasmodium berghei and P. residual binding activity was tested on antigen-coated microtiter plates. A sample was considered positive if it inhibited binding of the antibodies to an extent exceeding that of the microscopically negative blood samples. Blood was collected on 3 separate occasions from a total of 530 individuals living in a malaria-endemic area and was examined by radioimmunoassay and microscopy. Group 1, consisting of 194 samples, yielded 12 samples positive by microscopy and 10 of these (83%) were also positive by radioimmunoassay. One sample in this group was "positive" in the radioimmunoassay but negative on microscopy (false positive). In the 320 samples of group 2, 13 were positive by microscopy and 6 (46%) by radioimmunoassay. Group 3, which included 16 samples preselected as positive by microscopic examination and 16 controls, was examined after 4 weeks storage at -20 degrees C. Twelve samples (75%) were positive by radioimmunoassay. Tests carried out to determine the effect of blood storage on the activity of the antigen indicated that activity was preserved with little loss over a 3-month period.

Mseleni joint disease. Part II. Low serum calcium and magnesium levels in women.

Low calcium and magnesium levels were found in serum from women domiciled in an area where an osteo-arthrosis with a female preponderance is endemic. Despite decreased serum calcium, the methodology used indicated low circulating parathyroid hormone, while values for phosphorus, total alkaline phosphatase and the serum proteins were not remarkable. Alcoholism was excluded as a factor influencing the measured variables. The results reported, together with previous findings, justify intensified investigation into the link between diet-induced mineral deficiencies and endemic osteo-arthrosis at Mseleni.

Morbidity from urinary schistosomiasis in relation to intensity of infection in the Natal Province of South Africa.

Morbidity from urinary schistosomiasis was assessed on clinical, radiological, parasitologic and biochemical evidence in 510 schoolchildren living in a Schistosoma haematobium endemic area. The results were viewed against the background of the prevalence and intensity of infection in the subjects. Clinical morbidity correlated well with the intensity of infection, the latter in turn being influenced by factors such as water contact pattern, sex and water source. A surprisingly high prevalence (42%) of abnormalities was observed in the urinary tract of subjects, but no relationship could be demonstrated between the intensity of infection and structural damage to the urinary tract. Urographic changes were more severe in the 11-15 year age group than in the 6-10 year group. Significant rectal involvement (76%) in S. haematobium-infected subjects was regarded as a reflection of the heavy worm burdens borne by these children. The morbidity described in this study indicates a definite degree of pathology in the infected children but the impression was that they suffered only mild disability. However, given the structural lesions seen on urography and the limited sensitivity of the biochemical tests used for the assessment of renal function, renal pathology cannot be ruled out. Further studies on the renal status of these subjects are essential.

Phenotypic differences in Schistosoma mattheei ova from populations sympatric and allopatric to S. haematobium.

Schistosoma mattheei ova were collected from cattle in different localities in South Africa and after hatching, miracidia were used to infest Bulinus (Physopsis) globosus. Cercariae harvested from these snails were used to infest the definitive host Praomys (Mastomys) coucha and eggs from the resulting female S. mattheei were collected. These ova were compared with a Schistosoma haematobium X S. mattheei hybrid similarly collected from an infested P. (M.) coucha. The results indicate that S. mattheei populations which are sympatric to S. haematobium possess S. haematobium characteristics. It is suggested that the gene pools of populations of the parasite in these areas are infiltrated with S. haematobium genes via the S. mattheei X S. haematobium hybrid originating from human hosts.

Scanning electron microscopy of the teguments of males from five populations of Schistosoma mattheei.

The teguments of males from 5 populations of S. mattheei, of which 3 were sympatric and 2 allopatric with S. haematobium, were studied by means of scanning electron microscopy (SEM). A certain percentage of the males of each sympatric population bore tubercle spines while the allopatric populations were spineless. It is postulated that the presence of tubercle spines is a characteristic inherited from S. haematobium.

Specificity of the Testryp CATT card agglutination test in a non-sleeping-sickness area of Africa.

A card agglutination test (CATT), recently developed for the diagnosis of trypanosomiasis, has been evaluated in certain southern African localities; 179 blood specimens and 63 serum samples from black patients of both sexes and widely ranging ages, suffering from a variety of generalized and parasitic disorders, were tested. False-positives were minimal (2.9%) and there were no cross-reactions with any of the parasitic infections. The CATT is therefore regarded as a highly specific and sensitive test, which can be performed effectively in the field by non-specialist personnel.

The role of human water contact patterns in the transmission of schistosomiasis in an informal settlement near a major industrial area.

Human contact with schistosome-infested water was studied in a rapidly growing community near an industrial area: water-contact was observed and categorized; interviews concerning water usage were conducted and schoolchildren and adult women were tested for schistosome infections. Results indicated that swimming amongst certain young people was an important contact activity in summer. To a lesser extent the washing of clothes and blankets was found to be an activity of importance, providing a focus for the social gathering of women and young children in contact with the water throughout the year. One of the aims of the study was to develop cost-effective methods for use in this and other endemic areas to provide guidelines for control programmes. A comparison was made between methods of assessing exposure to the infection in their ability to predict the prevalence of Schistosoma haematobium and S. mansoni across age-sex classes of the human host; an exposure index which included an assessment of body surface area was found to be preferable to one based on duration of contact only. The differing relationships between exposure to infested water and prevalence of the two schistosome species were in accordance with reports from other areas, thus supporting the choice of minimum requirements for a survey prior to control.