Identification of transmission foci of Schistosoma mansoni: narrowing the intervention target from district to transmission focus in Ethiopia.

BACKGROUND: Schistosoma mansoni (S. mansoni) infection is a significant public health problem in Ethiopia, and has wide distribution in the country. The impact of the disease is particularly high on school-age children. Nationwide 385 endemic districts were identified, whereby control and elimination interventions are underway using school-based annual mass drug administration (MDA) with praziquantel. The national elimination program targets endemic districts as a whole. The aim of this study was to identify the transmission foci of Schistosoma mansoni and determine prevalence of soil-transmitted helminths (STHs) in Abeshge district. METHODS: The study was conducted from April to May, 2019 among school-age children randomly selected from public elementary schools in Abeshge district, South-central Ethiopia. Demographic information and data on risk factors of S. mansoni infection were gathered using pre-tested questionnaire. Moreover, a stool sample was collected from each child and examined using Kato-Katz thick smear technique. The data were analyzed using STATA_MP version 12. RESULTS: A total of 389 school-age children from five public elementary schools were included in the study. The overall prevalence of S. mansoni and STHs was 19.3% (75/389) and 35% (136/389), respectively. The prevalence of S. mansoni was 60.6% in Kulit Elementary school, while it was zero in Geraba. The prevalence of S. mansoni was significantly higher among males (AOR = 2.6, 95% CI 1.3-5.1), those with habit of swimming and/or bathing in rivers (AOR = 2.9, 95%CI 1.3-5.1) and involved in irrigation activities (AOR = 2.9, 95% CI 1.0-8.3). Overall, the prevalence of S. mansoni was significantly higher among school children attending Kulit Elementary School compared to those attending the remaining schools (AOR = 12.5, 95%CI 6.2-25.1). CONCLUSION: A wide variation of S. mansoni prevalence was observed among the school children in the different schools. Control interventions better identify and target foci of S. mansoni transmission, instead of targeting the district homogenously.

Transmission studies of intestinal schistosomiasis in Lake Albert, Uganda and experimental compatibility of local Biomphalaria spp.

Despite ongoing preventive chemotherapy campaigns, intestinal schistosomiasis is hyper-endemic in shoreline communities living along Lake Albert, Uganda. To provide a deeper insight into the local epidemiology of Schistosoma mansoni, a variety of field-based studies were undertaken focusing upon schistosome-snail interactions and confirmation of transmission foci. Cercarial shedding patterns of field-caught Biomphalaria spp., as identified by morphology, were hourly observed over a ten day period and showed that Biomphalaria stanleyi produced significantly more cercariae than Biomphalaria sudanica. Peak production times in both species were between 12.00 and 14.00h indicating greatest infection risk from lake water exposure is during the early afternoon. Laboratory-bred snails were exposed to locally hatched miracidia and susceptibility of Biomphalaria spp. was confirmed experimentally. Biomphalaria stanleyi was a more permissive host. After ascertaining appropriate conditions for infection of laboratory mice, 28 groups of between 5 and 6 naïve mice were placed in floatation cages at four suspected shoreline transmission sites for a 30 minute period of exposure. Eight weeks later, mice (n=142) were culled and S. mansoni adult worms were retrieved from 10 animals. Taken as a whole, these observations highlight the local importance of B. stanleyi in transmission of intestinal schistosomiasis and clearly demonstrate the risk of infection on the Lake Albert shoreline. To mitigate this risk local environmental modification(s), i.e. improvement in sanitation and hygiene and control of snail populations, is needed to bolster the impact of chemotherapy-based interventions.

Molluscicidal and schistosomicidal activities of a steroidal saponin containing fraction from Dracaena fragrans (L.).

The steroidal saponin-containing fraction from methanolic extract of Dracaena fragrans (Family: Agavaceae) was tested for molluscicidal and ovicidal activities against Biomphalaria alexandrina and Bulinus truncatus, the snail vectors of Schistosoma mansoni and S. haematobium in Egypt, respectively. It was also tested for schistosemicidal activity in vitro on adult S. mansoni and against the free-living miracidia and cercariae of the parasite. The homogenated soft body of B. alexandrina was used to determine the effect of the saponin fraction on total protein, albumen, aminotransferase enzymes and acetylcholin esterase. The results showed that the saponin fraction had considerable molluscicidal activity; LC50 & LC90 were 2.7 ppm & 3.7 ppm for B. alexandrina and 2 ppm & 2.5 ppm for B. truncatus, respectively. Snail eggs did not hatch in concentration as low as half molluscicidal LC50 (1.35 ppm). The LC50 killed all miracidia and cercariae in 30 seconds and after 22 & 40 minutes at a very low concentration (0.165 ppm) respectively, and had in vitro lethal effect on adults with LC50 18.4 microg/ml 4 days post-exposure. The snail tissue homogenate showed significant increase in total protein content & albumen, in aminotransferases and acetylcholinesterase activities.

Laboratory assessment of molluscicidal activity of crude aqueous and ethanolic extracts of Dalbergia sissoo plant parts against Biomphalaria pfeifferi.

BACKGROUND: In the continued search for molluscicidal compounds from plants, crude aqueous and ethanolic extracts from different parts of Dalbergia sissoo Roxb. 1832, were evaluated against egg masses and adults of Biomphalaria pfeifferi (Krauss, 1848), the snail intermediate host of Schistosoma mansoni (Sambon, 1907) in Nigeria. METHODS: Laboratory-bred adult B. pfeifferi and their viable 0-24 h old egg masses were separately exposed to five different concentrations (7.81-2000 mg l(-1)) each, of the crude aqueous and ethanolic extracts of the fruits, leaves, roots and stem bark of D. sissoo, for 24 h. The LC50 and LC90 values of each extract for the target organisms were calculated using probit analysis. RESULTS: Only the ethanolic extracts of the fruits and roots showed significant activities against the adult snails (24 h LC90<100 mg l(-1): 74.33 and 93.93 mg l(-1), respectively) and their egg masses (LC90: 89.29 and 114.29 mg l(-1), respectively) while all other extracts demonstrated weak molluscicidal and ovicidal activities (24 h LC90 > 100 mg l(-1)). There were concentration-dependent behavioural changes in snails exposed to test extracts, while egg mortalities, manifested at the gastrula/exogastrula stage and or the prehatch snail stage of development, were similarly concentration-dependent. CONCLUSIONS: The crude ethanolic extracts of D. sissoo fruits and roots exhibited promising molluscicidal activities (LC90 values<100 mg l(-1)) against adult B. pfeifferi with additional toxicities towards its 0-24 h-old egg masses.

Effect of the plant Cupressus macro-carpa (Cupressacea) on some haematolo-gical and biochemical parameters of Biomphalaria alexandrina snails.

The dry powder of the plant aereal part; Cupressus macro-carpa (Cupressacea) was tested against Biomphalaria alexandrina. LC50 & LC90 values were 59.5 & 98.8 ppm, respec-tively. Exposure of B. alexandrina to sublethal concentrations (LC0, LC10 & LC25) of C. macrocarpa for three weeks signi-ficantly decreased the number of circulating hemocytes. The magnitude of reduction was increased with increasing of the tested concentration. The main type of cell in the hemolymph of B. alexandrina was the granulocyte (71.8%), followed by large round cells or hyalinocytes (19.0%) and small round cells or undifferentiate cells (9.2%). The percentage of different hemocyte categories was changed in treated snails. In snails maintained at LC25, showed significantly higher percentages of small round cells than controls, 56.2% & 9.2% respectively. Maintainence of B. alexandrina in sublethal concentrations for three weeks significantly reduced protein & hemoglobin content in the hemolymph. Reduction in enzyme activities occurred in the hemolymph and tissues of treated snails. The enzymes were pyruvate kinase (PK), lactat dehydrogenase (LDH), hexokinase (HK) and phosphoenol pyruvate carboxy kinase (PEPCK) which are very important in metabolism of the protein and carbohydrate. The infectivity of Schistosoma mansoni miracidia was greatly reduced by exposure to the sublethal concentrations (LC0, LC10 & LC25) of Cupressus. Infection rate of B. alexandrina reached to 54.5%, 37.5% & 16.7%, respectively compared to control (81.25%). Duration of cercarial shedding and the total periodic cercarial production/snail showed significant reduction while the parasite incubation period was significantly longer (p<0.05).

Control of Biomphalaria pfeifferi population and schistosomiasis transmission in Ethiopia using the soap berry endod (Phytolacca dodecandra), with special emphasis on application methods.

The endod (Phytolacca dodecandra)-based schistosomiasis mansoni control project was implemented in Ethiopia between 1994 and 1999. The aim was to develop an effective, cheap and sustainable method of controlling schistosomiasis. First, different formulations of the Ethiopian endod strain 44 (E-44) were compared for potency in the laboratory. Secondly, spray and drip-feeding methods were compared for simplicity and effectiveness in the field. Lastly, the efficacy of endod powder soap was compared with the endod spray method. In Bati stream, endod powder soap was distributed to the residents every weekend at laundry sites. In Worke stream, endod was sprayed along a 1-km stretch of the stream at 3-month intervals. No endod was applied in Harbu stream. The immediate and long-term effects of endod application on the snail population and schistosomal infection were determined. Using the spray method, 100% snail mortality could be obtained, and it was simpler and more effective than the drip-feeding method. Snail mortality ranged from 20 to 100% using endod soap. There was a progressive decline in the snail population and infection in Bati stream compared with Worke stream, mainly due to sustained use of endod soap. The advantages and disadvantages of the different endod delivery systems are discussed.

Control of Schistosoma mansoni by the soapberry Endod (Phytolacca dodecandra) in Wollo, northeastern Ethiopia: post-intervention prevalence.

OBJECTIVES: To record the effect of Endod soap and spraying of soaked Endod suspension on the prevalence of human schistosomiasis. DESIGN: A cross-sectional epidemiological study in which pre- and post-intervention parasitological results were compared. SETTING: Kemise, Bati and Harbu towns in northeastern Ethiopia. SUBJECTS: The study subjects included all members of the five per cent households systematically selected from the three towns. RESULTS: In Kemise town, where suspension of ground Endod was sprayed on the stream containing infected snails, the prevalence of the disease was reduced from 59% to 53% and the mean intensity of infection was reduced from 239 eggs per gram (EPG) of faeces to 99 EPG (p < 0.05). In Bati town where Endod soap approach was used, the respective reduction in the prevalence and intensity of infection was from 51% to 43% and from 195 EPG to 162 EPG (p < 0.05). There was also a significant reduction of the disease in the control town probably due to the effects of praziquantel treatment and other factors. CONCLUSION: The reduction achieved in the prevalence and intensity of schistosomiasis after an intervention period of four years was limited. This observation corroborates the fact that molluscicides must always be considered as supplementary to chemotherapy in the control of schistosomiasis. Although both approaches can be used, the spraying approach appears to be simpler and more feasible because two or three times yearly application of Endod suspension would suppress snail population and reduce transmission. Nevertheless, the choice as to what approach to use must be made on the basis of community preference, and for some soap-effect of Endod would be attractive

Some aspects in the control of schistosomosis and soil-transmitted helminthosis in Yemeni children.

OBJECTIVE: Prevalence, intensity and incidence of schistosomosis and soil-transmitted helminthosis among school children in an ignored area in Yemen were determined. The study aimed to investigate the impact of single doses of Praziquantel or Albenedazole or both, relating to sanitary, socioeconomic and behavioral practices on the prevalence and intensity of infections. METHODS: Out of a total number of 897 pupils, 453 were randomly selected from AlMahweet town and 444 from rural surrounding areas. Millipore filtration, modified Kato and precipitation techniques were applied for urine and stool analysis. RESULTS: Prevalence rates were 27% for schistosomosis, 61% for ascariosis, 21% for trichuriosis, 2% for fascilosis, 0.3% for entrobiosis, 0.7% for hook worm infection and 0.2% for strongloydiosis. Factors found confounding the relationship between schistosomosis and residence, under logistic regression analysis, were sex and frequency of water contact. Probability of infection by Bilharzia for boys who reside in rural AlMahweet and visit the water source is 0.52, compared to 0.30 for their mates who reside in AlMahweet town. Odds ratio estimates accounted for via residence was 2.5, via water contact 1.7 and via boys 3.2. With regards to other helminthic infections, availability of latrines remained the only significant factor under ANOVA. CONCLUSION: In conclusion, annual campaigns for treatment as a single control measure can reduce the infection rate of S. mansoni by 62.5%, T. trichura by 48% and A. lumbricoides by 24%. Whereas for S. hematobium the appropriate time interval for intervention should be shortened according to the findings of a properly designed intervention study before used as a single control measure. Since 77% of the children were infected by other helminthes, therefore mass treatment should be extended to cover all children. For those boys in rural AlMahweet who visited the water source during the week before the interview, mass treatment for schistosomosis is recommended since the prediction of infection rate reached 52%.

The molluscicidal activity of Crown of Christ (Euphorbia splendens var. hislopii) latex on snails acting as intermediate hosts of Schistosoma mansoni and Schistosoma haematobium.

The present study describes the action of the latex of Euphorbia splendens var. hislopii (E. milli) on species of the genus Bulinus and on Biomphalaria pfeifferi, intermediate hosts of schistosomiasis in Africa, and the Brazilian snails B. glabrata, B. tenagophila, and B. straminea, intermediate hosts of schistosomiasis in Brazil. The impact of the latex on the egg masses and embryos of B. glabrata was also evaluated. Using the standardized methodology of the World Health Organization for testing plant-derived molluscicides, we obtained a 90% lethal dose (LD90) ranging from 0.13 ppm for B. glabrata subjected to lyophilized latex to 4.0 ppm for B. pfeifferi tested with the natural latex. This material has proved to be one of the most potent and specific plant molluscicides discovered thus far, presenting advantages in terms of application so that it could be used in programs involving community participation in endemic areas in both Brazil and Africa.

Uma concepçäo popular sobre a esquistossomose mansonica: os modos de transmissäo e prevençäo na perspectiva de gênero / A popular concept of schistosomiais mansoni: modes of transmission and prevention in the perspectives of gender differences

Estudo sobre as concepçoes e práticas populares acerca da transmissäo e prevençäo das parasitoses, com ênfase para a esquistossomose mansônica. Explora a existência de um sistema popular de cuidados de saúde que mescla elementos da biomedicina e da medicina tradicional como forma de compreender e manejar os fenômenos de saúde/doença. Descreve as diferenças entre sexo e morbidade e sexo/gênero na concepçäo dos sujeitos entrevistados. Apresenta o discurso popular sobre as parasitoses, discutindo as dificuldades das açoes de controle. Considera as contradiçoes entre hábitos e valores culturais e as medidas de controle conhecidas, criticando a imprecisäo das açoes educativas nos programas oficiais de intervençäo.