Comparison of findings using ultrasonography and cystoscopy in urogenital schistosomiasis in a public health centre in rural Angola.

BACKGROUND: Schistosomiasis is a chronic disease caused by infection with parasitic worms of the genus Schistosoma. In sub-Saharan Africa, infections with S. haematobium are most common. Cystoscopic examination (CE) has been accepted as the goldstandard test for detecting the late manifestations of schistosomiasis, including urothelial cancer of the bladder. However, this procedure is invasive and 10-40% of tumours may remain undetected. A non-invasive examination and a new generation of biomarkers are needed for better monitoring of the disease. OBJECTIVE: To assess the usefulness of ultrasound (US) scans for monitoring of structural urinary tract disease by local public health services in areas of Angola in which urogenital schistosomiasis is endemic. METHODS: A cohort of 80 S. haematobium-infected patients was selected in order to compare changes in the bladder wall detected by US with those observed on CE. RESULTS: There was a notable correlation between the findings observed on CE and US. Patients with lesions of the bladder mucosa such as neoplasms, ulcers or granulomas detected by CE also had changes in bladder wall thickness on US. The results support increased use of portable US machines for non-invasive examination of the bladder by local general practitioners. CONCLUSION: US examination should be an integral part of the investigation of haematuria and used in all S. haematobium control programmes. General practitioners may find it useful for more accurate diagnosis of haematuria and to identify bladder wall alterations in both adults and children in schistosomiasis-endemic regions.

Genetic diversity of a population of Schistosoma haematobium derived from schoolchildren in east central Zimbabwe.

To characterize the extent of genetic diversity of Schistosoma haematobium within and among its definitive host (intra- and interhost parasite diversity), 133 individual isolates from 25 infected schoolchildren were compared using randomly amplified polymorphic DNA markers. With 4 primers, 53 unambiguous loci were identified, and of these, 22 were polymorphic. Mean heterozygosity in the population was 0.116 +/- 0.043. Analysis of molecular variance showed the majority of variance occurred within, rather than between, hosts. Frequencies of certain alleles segregated the parasite population into 13 distinct clusters of associated genotypes, with 4 of these first appearing 10 mo after the initial survey. Considering the level of diversity within this limited geographical area and the possibility of rapid turnover of genotypes, parasite variance may impact acquired immunity and clinical outcome of the infection.

Environmental and geographical factors contributing to watershed contamination with Cryptosporidium parvum oocysts.

Cryptosporidium parvum is a waterborne parasite which infects cattle and produces life-threatening zoonosis in people with impaired immune systems. Digital maps of 100-year floodplain boundaries, land use/cover, and livestock operations were used to select and characterize cattle farms in the floodplain area in Lancaster County, Pennsylvania, U.S.A. Over 21% of the cattle farms were located within 100-year floodplain boundaries. On average, a single farm comprised 12.8 ha of pasture (including buildings and farmyard) at risk of inundation. In all farms cattle had unlimited access to the creek. Manure samples collected from closed-in calf pens, cow/heifer yard runoff, and cattle paths through the creek were tested for C. parvum. On 64% of the farms (n=50) at least one sample was positive for C. parvum, and 44% of the farms had oocysts in all manure samples. Concentration varied from 90 to 371 oocysts/g and was significantly higher (P<0.02) in calf samples than in manure from cow and cow/heifer.

Recovery of avian schistosome cercariae from water using penetration stimulant matrix with an unsaturated fatty acid.

Avian schistosome cercariae that emerge from aquatic snails can penetrate human skin causing cercarial dermatitis resulting in serious skin disease in sensitized and immunocompromised people. A trap developed for Schistosoma mansoni cercariae was tested for recovery of avian schistosome cercariae. A matrix with an unsaturated fatty acid, linoleic acid stimulates attachment and penetration of Trichobilharzia spp. cercariae, and the immobilized larvae can be subsequently visualized. The number of trapped cercariae exceeded by 3 to 7 times the number of larvae expected on the surface of the trap, based on their random distribution in the water. Recognition, attachment, and penetration of Trichobilharzia spp. cercariae led to injection of more secretory products into the stimulant matrix than by Schistosoma mansoni cercariae. This method can assist in the identification of waters infected with avian schistosome cercariae so that human exposure to these parasitic larvae can be minimized.

Schistosomiasis in newly reclaimed areas in Egypt. 2--Patterns of transmission.

The distribution, abundance and seasonality of infected Biomphalaria alexandrina and Bulinus truncatus were studied for 2 years (1992-1994) in two newly reclaimed areas, namely El Manayef and El-Morra areas located on both sides of Suez Canal near Ismailia City. The results confirm the occurrence of transmission of both Schistosoma mansoni and S. haematobium since infected snails of both species were recovered in these areas. This consequently proves that reclamation of parts of the desert utilizing Nile water had led to spread of schistosomiasis to these areas. Analysis of the data shows that the infected snails, especially B. alexandrina, were found clustered in a relatively few numbers of transmission sites and furthermore the greater majority of these sites were found located within a less number of transmission foci. This pattern of focality is clearly demonstrated by Geographical Information System (GIS) produced maps. Infected B. alexandrina snails fluctuated seasonally showing 2 peaks, a minor peak in August and a higher one in November. Only one peak of infected B. truncatus was recognized in July.

Schistosomiasis in newly reclaimed areas in Egypt. 1-distribution and population seasonal fluctuation of intermediate host snails.

Two newly reclaimed areas located west & east of Suez Canal, namely El Manayef area and El Morra area, were studied for patterns of distribution and population seasonal fluctuation of Biomphalaria alexandrina and Bulinus truncatus, the intermediate host snails of Schistosoma mansoni and S. haematobium, respectively. In this study Geographic Information System (GIS) techniques were utilized for producing maps and analyzing the results. Habitats of the two vector snail species were categorized into suitability levels depending on the frequency with which snails were collected over a 12 months period. Data obtained from the most suitable habitats were only used for studying the seasonal fluctuation of snail population. The results showed that both study areas were almost similar in major physico-chemical parameters. However, oxygen content in canals was higher than in drains and conductivity was higher in drains than in canals. As regards snail distribution and density, most snails of both considered species were clustering in much fewer numbers of sites, more pronouncedly in the case of Biomphalaria than Bulinus. Population density of snails was significantly higher in El-Manayef area than in El-Morra area and in canals than in drains. Both species exhibited 2 population peaks/year, the peaks of Biomphalaria were in March-April & August in both study areas, while for Bulinus these peaks occurred in March-May and August in El-Manayef area and in May and March, respectively, in El-Morra area.

Vector control: methods for use by individuals and communities.

by Jan A. Rozendaal, World Health Organization, 1997. pound85.00 (xii +412 pages) ISBN 92 4 154494 5.

Post treatment sensitivity studies with the ParaSight-F test for malaria diagnosis in Zimbabwe.

The post-treatment diagnostic performance of the Plasmodium falciparum histidine-rich protein (HRP-II) antigen detection test, ParaSight-F test, was assessed on 55 falciparum malaria cases treated with chloroquine during in vivo drug sensitivity studies. The post-treatment sensitivity of the test remained high, except for an insignificant decline on day 1. However, specificity dropped sharply by day 1, subsequently increasing linearly with time to satisfactory values by day 10. As expected, from its inverse relationship to specificity, the false positive rate was high on day 1 and decreased linearly to low level by day 10. The temporary increase in false positive rate-following treatment was due to persistent parasite antigen, rather than subpatent parasitaemia. Thus findings showed that positive readings by the test within 10 days post-treatment may occur in cured cases and will not necessarily imply treatment failure. Furthermore it will be important to take patient antimalarial history into consideration during routine usage of the test for malaria diagnosis. The trend of Youden's J-index for the ParaSight-F test showed that from 10 days post-treatment, the test was generally reliable, with positive readings indicating active infection. It was concluded that the ParaSight-F test was not only valuable at confirming malaria diagnosis on clinical cases in seasonal transmission areas, but had potential for application to detect recrudescent infections within 2 weeks of chloroquine treatment.

Social and cultural factors affecting rates of regular retreatment of mosquito nets with insecticide in Bagamoyo District, Tanzania.

Insecticide-treated mosquito nets have an impact on mortality and morbidity in young children under controlled conditions. When integrated into larger control programs, there is the danger that rates of regular retreatment of the nets with insecticide will drop, greatly limiting their effectiveness as a public health intervention. In Bagamoyo District, Tanzania, rates of retreatment dropped significantly when payment for the insecticide was introduced. A series of neighbourhood (hamlet) meetings were held in all study villages to discuss people's concerns about the insecticide and ways to increase rates of retreatment. Although changes were made in the procedure for retreatment, rates of retreatment remained lower than expected and showed marked variation within as well as between villages. We then conducted unstructured key informant interviews as well as informal discussions in a village with strong variation between different sectors of the villages in rates of retreatment. While logistical problems were most frequently cited as reasons not to bring nets for retreatment, political and social divisions within the community provided a better explanation. This is borne out by the low response to rearrangements in logistics which made retreating the nets significantly easier for households, and the higher response when changes were made in the channels of communication as well as the logistic features. It is clearly more difficult for villagers to appreciate the benefits of the insecticide than those of the nets. Great emphasis needs to be placed on the insecticide and its beneficial effects from the outset for any large-scale programme to be sustainable.

Trial of the ParaSight-F test for malaria diagnosis in the primary health care system, Zimbabwe.

Rapid diagnosis of Plasmodium falciparum malaria remains one of the main limitations to prompt treatment. Diagnosis based on clinical symptoms is decidedly unreliable, especially in areas of seasonal transmission like Zimbabwe. In view of this, the Plasmodium falciparum histidine rich protein (HRP-II) antigen detection assay (ParaSight-F test) was tried at 10 health centres in 3 malaria endemicity zones of Zimbabwe, as a malaria diagnostic tool for primary health care. Parasitological evaluations were conducted using thick and thin film microscopy as gold standard, and ease of test operation and practicability to nurses were ascertained by questionnaire. The sensitivity of the test did not vary substantially by endemicity zone and was approximately 93%. Specificities were 85, 72 and 92% in the hyperendemic, mesoendemic and hypoendemic zones, respectively. Positive predictive values varied considerably with endemicity, the lowest being in the hypoendemic zone (56%). However, negative predictive values did not change significantly, with a mean of 94%. It was found that the ParaSight-F test reduced mistreatment for malaria, relative to clinical diagnosis, by up to 81%, especially in the hypoendemic region. Test acceptability evaluations were good.

Schistosoma mansoni: the immune response against cercarial glycocalyx.

Schistosoma mansoni cercarial glycocalyx was separated and purified by Sephacryl-300 SR. It was found to stimulate the humoral immune response in mice injected with it. Antiglycoalyx antibodies raised in CD/1 mice were found to be cytotoxic to schistosomula in vitro. But conversely, no protective effect was demonstrated in vivo. Eosinophil-mediated cytotoxicity was found to have no effector function in the murine immune response against schistosomes. A monoclonal antiglycocalyx IgM was prepared during our study. It was found to have no cytotoxic effect on schistosomules in vitro. However, it was found to have an inhibitory activity blocking the cytotoxic effect of other antiglycocalyx isotypes in the immune mouse. The contradiction between the result of antiglycocalyx antibody-mediated cytotoxicity obtained in vivo and that obtained in vitro is in itself revealing and suggests that the effect is crucially dependent upon factors as yet poorly understood.

Community based studies on childhood mortality in a malaria holoendemic area on the Tanzanian coast.

Demographic surveillance of children under 5 years of age was undertaken over a 2 year period in a rural area of coastal Tanzania where holoendemic malaria conditions exist. The mean annual entomological innoculation rate (EIR) during the period under study was 234 infective bites per person. There were 192 deaths in children and 1130 live births during the 2 years. Of these, 148 were infant deaths giving an infant mortality rate of 131/1000 live births (95% CI 101, 154). There were 44 deaths in children 1-4 years of age and the overall child mortality rate was 10/1000 (95% CI 6.1, 14.3). Using verbal autopsy questionnaires, 56% of the deaths under 4 years were tentatively attributed to malaria.

Cercariometry in the study of Schistosoma mansoni transmission in Egypt.

The recovery of Schistosoma mansoni cercariae was studied in experimental ditches and natural irrigation canals using a continuous operating centrifuge and a water suction sampling technique. Recovery of cercariae from static water in the ditches where caged infected Biomphalaria alexandrina snails were placed showed that cercariae recovered were more with increase of infected snails and decrease of water volume and were most abundant in the proximity of the snails which produced them. Shade or heavy vegetation cover reduced the recovery of cercariae. Results suggest also strong seasonal differences in diurnal patterns of cercarial recovery. An early morning peak with large number of cercariae occurred during hot weather while in cooler seasons cercariae appear in fewer numbers but persist for most of the day. Obtained information, beside contributing to knowledge of cercarial behaviour, should help to optimize taking water sample and consequently to increase efficiency of cercariometry techniques. In the natural irrigation system, cercariometry was significantly more sensitive in detecting transmission foci than snail sampling by a dip net.

Treatment practices for degedege, a locally recognized febrile illness, and implications for strategies to decrease mortality from severe malaria in Bagamoyo District, Tanzania.

Malaria remains one of the chief causes of mortality among young children in sub-Saharan Africa. Verbal autopsies for cases of childhood mortality in Bagamoyo District, Tanzania demonstrated that degedege, a locally defined illness of children characterized by fever and convulsions, is frequently treated by traditional healers. To investigate this further, an ethnographic study was carried out in one village that included in-depth interviews with 14 traditional healers and 3 focus groups with parents. Parents and traditional healers were unanimous in their conviction that degedege requires traditional treatments, at least initially, and that these treatments are effective. While traditional healers do refer cases that are not improving to the District Hospital, this frequently occurs late in the course of the illness, after one or more stages of traditional treatments. The prognosis will thus be poor for those children who are suffering from severe malaria. Consideration should be given to enlisting the support of traditional healers in efforts to improve treatment for severe malaria, including teaching them how to distinguish febrile convulsions from cases of severe malaria.