Control of Schistosoma mansoni in the Blue Nile Valley of western Ethiopia by mass chemotherapy and focal snail control: a primary health care experience.

A simplified combination of human mass treatment with oxamniquine and focal snail control has been applied in a local Schistosoma mansoni control programme in a primary health care setting in the Dalati and Agallu Metti areas of the Ethiopian Blue Nile Valley. Teams of local health personnel and farmers did the daily work under intermittent supervision. Monthly snail surveys near the major villages disclosed a seasonal pattern with many infected snails during the dry season in upper stagnant sections of tributary rivers (1000-1200 m altitude) with favourable temperatures, and few snails in the rainy season. The highest prevalences and intensities of human infection were found in the 15-19 year age group living in the lower altitudes around 700 m. 5067 individuals (50-80% of the local population) were treated with 20-40 mg oxamniquine per kg body weight during the rainy seasons of 1985 (Dalati) and 1986 (Agallu Metti). In the Dalati area cross sectional surveys in 1985 and 1986, before and after the mass treatment, showed a reduction in prevalence from 42.4% to 11.4%, while in the Agallu Metti area a stratified random sample showed a prevalence reduction from 65.4% in 1986 to 7.8% in 1987 and a reduction in the prevalence of moderate to heavy infection (greater than 100 eggs per gram of stool) from 36.9% to 1.4%. Beginning in 1986 niclosamide was applied focally wherever infected snails were found and the monthly snail surveillance continued until 1989. As a result of this combined approach overall snail infection rates were reduced from 11.2% (Dalati) and 32% (Agallu Metti) to zero and 2% respectively. In 1989 the human prevalence was still only 8.6% in Agallu Metti. This programme has shown that it is feasible to control S. mansoni in these very remote localities through the primary health care system.

Praziquantel side effects and efficacy related to Schistosoma mansoni egg loads and morbidity in primary school children in north-east Ethiopia.

A total of 611 Schistosoma mansoni infected primary school children from three schools in north-east Ethiopia were treated with praziquantel at 40 mg/kg body weight in a single dose. Pre-treatment, 40.4% had no presenting symptoms and 30-40% had nausea, abdominal cramps and/or bloody-mucoid diarrhoea. None of the pre-treatment symptoms was related to nutritional status, intensity of S. mansoni egg excretion, or to the presence of other concomitant intestinal parasitic infections. During the first 4-6 h post-treatment observation period, 90 (14.7%) children self-presented with severe gastro-intestinal symptoms. Children who self-presented with severe symptoms had a higher mean age and mean S. mansoni egg excretion compared with children who did not self-present. The following day a total of 529 (86.6%) children, including all who self-presented during the first 4-6 h post-treatment, reported for clinical check-up and were subjected to a structured questionnaire interview on symptoms they had experienced over the time lapse following treatment. Among these, 91.5% reported one or more treatment related symptoms which were at times severe. Abdominal cramps (86.9%), diarrhoea with blood and/or mucus (49.5%), dizziness (31.2%) and vomiting (24.9%) were the most common treatment related symptoms. Skin rash with oedema were observed in four cases. Among treatment related symptoms, the combination of abdominal cramps with vomiting, bloody diarrhoea, vomiting alone and general weakness were significantly higher among the malnourished. A proportion of these symptoms increased with increasing categories of S. mansoni egg excretion before and after adjusting for nutritional status and concurrent intestinal parasitic infections. Overall, the cure rate of praziquantel, among 541 children who had stool examination 5 weeks after treatment was 83.2% and this rate decreased with increasing pre-treatment egg counts. In conclusion, most of the treatment related symptoms were mild. However, some of the objective symptoms were at times severe and may reduce drug compliance in primary health care based population chemotherapy.

Delayed reinfection of Schistosoma mansoni in the Blue Nile Valley of western Ethiopia 10 years after mass chemotherapy.

In the Blue Nile Valley of western Ethiopia a successful control programme against Schistosomiasis mansoni starting from 1985 was in 1989 interrupted by local guerrilla warfare. The control was based on human mass chemotherapy campaigns during the rainy season of 1985 and 1986 and a limited annual, focal molluscicidal activity where re-infection was demonstrated. In 1995 the area was revisited and selected schools in previously hyperinfected villages were examined for reinfection. The results were compared to re-calculated figures for the 5-19 year age group from previous pre-, per- and post-control surveys in the same localities. In 1995 prevalence rates in the 5-19 year age group had risen to 68% (Salba-Korka) and 63% (Sirba), which are very close to the 1985-1986 pre-control prevalences. Infection intensities, however, had not risen to the same degree. In Salba-Korka the 1986 pre-control geometric mean S. mansoni eggs per gram of faeces in the 5-19 year age group was 73, after mass treatment until 1989 it was close to 0, whereas in 1995 it was still only 27. In Sirba the result was similar. This might indicate a slower transmission rate after the control period than previously. The reported seasonality of transmission and the local use of the molluscicidal bark of the 'Bitza' tree might possibly have had some delaying effect.

Schistosomiasis in Ethiopia.

The literature on schistosomiasis in Ethiopia is reviewed with the objective of bringing together in one paper diverse sources which may not be available to those interested in schistosomiasis. Particular attention is given to the influence of altitude and climate, snail ecology and government economic programs on the distribution of schistosomiasis. Out of 365 communities studied between 1961 and 1986 for Schistosomiasis mansoni, cases were reported from 225 (62%), and in 85 (23%) the prevalence ranged from 10 to 92%. Most transmission sites and S. mansoni infections are in agricultural communities along streams between 1300 and 2000 m altitude infested with Biomphalaria pfeifferi, the major snail intermediate host. S. mansoni transmission above 2200 m and below 800 m is precluded in many parts of Ethiopia by low and high water temperatures, respectively. Schistosomiasis haematobium cases have been reported from 30 of the 54 communities studied, 17 of them with infection rates between 14 and 75%. Endemic S. haematobium appears to be confined in its distribution to lowlands below 800 m altitude. The highly focal distribution of S. haematobium transmission is largely due to the nonsusceptibility of most bulinine snails to the Ethiopian strain of the parasite and low water temperatures in the highlands. Water resources development, resettlement programs, refugee migration and other population movements may result in the spread of endemic S. mansoni. Lack of information on snail host/parasite relationships and the ecology of proven and suspected snail hosts does not permit predictions on the spread of endemic S. haematobium. Past and present schistosomiasis control programs in Ethiopia are reviewed and recommendations made for the national control program.

The use of reagent strips for detection of urinary schistosomiasis infection in the middle Awash Valley, Ethiopia.

Reagent strip test was carried out to detect haematuria in urinary schistosomiasis infection in ten schools (1114 children) in the middle Awash Valley, Ethiopia. In five schools (557 children), were compared with results of urine filtration technique conducted simultaneously. The prevalence of infection by reagent sticks and urine filtration was 19.5% and 3.1%, respectively. Haematuria, detected by the reagent strip, was highly related with the results of urine filtration at the 2+ limit rather than the 1+ limit. However, the intensity of infection of all children was highly associated with prevalence rate at both haematuria limits. The possible use of reagent strips in Ethiopia to monitor morbidity (haematuria) due to S. haematobium infection is discussed.

Intestinal helminthic infections in the southern Rift Valley of Ethiopia with special reference to schistosomiasis.

Nineteen communities located in the southern part of the Ethiopian Rift Valley were surveyed for S. mansoni infection and other helminth parasites of man. S. mansoni infected individuals were recorded in 11 communities and human prevalence reached more than 10% in 4 of them. The snail intermediate hosts were Biomphalaria pfeifferi in the lower Omo River basin and B. sudanica in the Rift Valley lakes. Other parasites encountered included A. lumbricoides (11.2%), T. trichiura (10.3%), hookworms (25.3%), Taenia sp. (8.1%), Strongyloides sp. (2.9%), H. nana (0.8%), Trichostrongylus sp (0.3%) F. hepatica (0.1%) and E. vermicularis (0.1%). In some communities the prevalence of hookworms, A. lumbricoides and T. trichiura reached 70%, 66.6% and 60%, respectively. A strong association (r = 0.9) was observed between altitude and parasite prevalence and burden. In nine communities located below 1200 metres, infected individuals harboured nearly two or less the number of parasite species while in 10 communities located at altitude above 1200 metres, multiple infection with three or more parasites reached as high as 53.2%. Similarly, the average parasite species per infected person ranged from 0 to 1.4 in the nine communities located at lower altitudes and from 1% to 2.6% in the 10 communities located at higher altitudes. By ages, both prevalence and multiparasitism are significantly in favour of those below 20 years of age (P < 0.005) although hookworms are prevalent in a wider age range. The widespread occurrence of intestinal schistosomiasis in the southern Rift Valley and the epidemiological pattern of other intestinal helminth parasites of man in this section of the Valley are discussed.

Comparison of urine filtration and a chemical reagent strip in the diagnosis of urinary schistosomiasis in Ethiopia.

The diagnostic efficacy of a chemical reagent strip (Ames Multistix) was compared with syringe-Nytrel urine filtration technique in the detection of S. haematobium infection at varying disease endemicity levels in the Awash Valley of Ethiopia. In low endemicity area (Afambo), the reagent strip showed highest sensitivity, specificity, positive predictive value and negative predictive value of 80%, 96%, 40% and 99% respectively at "1+ limit" of microhaematuria. In the moderate (Dahitele) to high (Enta Doyta) areas, the highest diagnostic values of 77%, 83%, 56% and 93% respectively and 78%, 67%, 51% and 87% respectively were obtained at "trace limit". Using these cut-off points of haematuria, the prevalence of S. haematobium were 4.5%, 30.8% and 47% at low, moderate and high endemicity areas compared to 3.2%, 21% and 31% respectively using the filtration technique. A highly significant (maximum Kendall's tau = 0.44271; p < 0.002) was observed between N + 1 transformed geometric mean egg counts and micro-haematuria in the 10-19 years of age at all levels of endemicity. The efficacy and simplicity of chemical reagent strips and limitations of single parasitological examinations are discussed.

Variability of egg excretion in Schistosoma mansoni infection in Ethiopia: a case report.

An Ethiopian boy, aged 18 years, and heavily infected with S. mansoni (1250 eggs per gram of faeces), gave stool sample for microscopy three times a day (at 9:00 am, 1:00 pm and 4:00 pm) for 5 consecutive days. Each time two slides were prepared by the modified Kato's thick-smear technique. The maximum egg count at each examination was converted to eggs per gram of faeces (EPG). There was no significant variability (at 10% level, F-value = 0.04) in in egg counts made at different times of the day. However, the coefficient of variations between the egg counts made on different days were fairly high ranging from nearly 61% to 73% and the differences being highly significant at 10% level (F value = 4.076). The implications of this day-to-day variability of S. mansoni faecal excretion in "selected" chemotherapy in Ethiopia is discussed.

Susceptibility of Ethiopian bulinid snails to Schistosoma haematobium from Somalia.

Susceptibility of four Ethiopian bulinid snails to a Somalian strain of S. haematobium was tested. Bulinus abyssinicus was highly susceptible and lowland B. africanus was partially susceptible while B. truncatus and B. forskalii were refractory to the parasite. It is suggested that Ethiopian refugees returning from Somalia and/or Somalian refugees entering Ethiopia should be screened and treated for S. haematobium before they are allowed to work/resettle in development areas where B. abyssinicus and B. africanus are known or ecologically suspected to occur.

Investigation into the cercariacidal and miracidiacidal properties of Endod (Phytolacca dodecandra) berries (type 44).

Aqueous extract of ground Endod (Phytolacca dodecandra) berries (Type 44) was investigated for its cercariacidal and miracidiacidal properties. Aqueous extract of the berries prevented snails from being infected by miracidia at a concentration of 4 ppm. Assessment of cercariacidal activity of Endod berries indicated that mortality of cercariae exposed to aqueous extract of Endod berries increased with increase in concentration of the test material and exposure time. Viability assessment test showed that pre-treatment of the cercariae with 12 ppm of the extract completely inhibited infection of mice by cercariae and significantly reduced tissue egg deposition and worm establishment in the mice (ANOVA, P < 0.05) The potential use of (Phytolacca dodecandra) berries against schistosome larval stages in fresh water in a schistosomiasis control program is discussed.

The efficacy of oxamniquine in selective population chemotherapy in Ethiopia.

Oxamniquine, at 40 mg/kg body weight, was used in a pilot schistosomiasis control programme in an endemic community in Ethiopia. After mass screening of the population using Kato's thick smear method, 1556 positive patients were treated in divided doses over two consecutive days. However, only 1183 (76%) persons completed the total dose. Three months later stool examination of about 20% of those who completed the total dose showed a cure rate of 68% and a significant reduction in the geometric mean egg counts. In those still positive redistribution of grades of infection took place; heavy infection, > 800 egg count per gram (epg), was reduced from 22.7% to 7.9% (p < .001) and light infection increased from 27.7% to 57.3% (p < .001) and light infection increased from 27.7% to 57.3% (p < .0001). The implications of this experience in the control of schistosomiasis in Ethiopia is discussed.

Colonization of irrigation canals by Bulinus abyssinicus and upsurge of urinary schistosomiasis in the middle Awash Valley of Ethiopia.

The current status of urinary schistosomiasis and snail intermediate 1 hosts in the middle Awash Valley was assessed. Examination of urine by the filtration method for one camp (Assoba) in the Amibara Irrigation scheme showed high human prevalence (70%) and snail infection (7%). Of interest is the fact that now B. abyssinicus, the snail intermediate host of urinary schistosomiasis, has started colonizing the irrigation canals and that our of the infected individuals, 30.3% are itinerant population, possible irrigation workers. The immediate measures to be taken are suggested.

Schistosomiasis in Addis Ababa.

With increased migration of infected people into cities schistosomiasis is increasingly becoming an urban disease in many endemic countries, including Ethiopia. Recently, 9 children (11-15 years of age) from an elementary school in Addis were found positive for S. mansoni by stool examination. Eight of the children reported to have never been outside Addis, information which was also confirmed from their parents/guardians. The possible occurrence of authochtonous transmission of intestinal schistosomiasis in Addis and the possible factors responsible for this are discussed and the need for more systematic survey suggested.

Elephantiasis in Pawe settlement area: podoconiosis or bancroftian filariasis?

During a pilot trial of animal trypanosomiasis control in 3 villages in Pawe settlement area of Region 6 found in northwest Ethiopia, a high frequency of people with swollen legs/feet was observed. House-to-house search in one of the villages (Village 24) indicated 68 persons, 28 males and 40 females (age ranging from 15 to 69 years) had elephantiasis of one kind or another. Based on the local population census the prevalence of elephantiasis was estimated to be 6%. Clinical examination of the 68 persons showed that about 63% had lymphoedema and/or groin lymph node swelling while parasitological examination of night blood collected between 21 and 23 hours turned to be negative. The type, magnitude and distribution of elephantiasis in Ethiopia are discussed and further study is suggested to elucidate the aetiology of the one in Pawe settlement area.

The status of Schistosoma mansoni and snail hosts in Tigray and northern Wello regions, northern Ethiopia.

A survey of Schistosoma mansoni infection and snail hosts was carried out in 1992 in six accessible schools and 11 water bodies respectively. Five to ten per cent of the students were randomly selected for stool examination by the Ritichie's method. In Adwa town, however, stools of 100 students out of the 199 selected were re-examined by Kato's method to assess intensity of infection. Results of stools examined by Ritichie's method showed that S. mansoni positive patients were present in four out of six (66.7%) schools, the prevalence for school ranging from 1% in Maychew to 61.8% in Adwa. In all the localities, there was significant male preponderance in the prevalence of infection (p < 0.05). Among those whose stools were examined by the Kato's method in Adwa town, both prevalence and geometric mean egg count per gram of faeces (EPG) were highest in the 10 to 14 years age group reaching 68% and 597 followed by 64% and 591 respectively in the 15 to 19 years of age. Of the S. mansoni positive students in Adwa, 86% excreted 200 or more EPG, 84% of those in the 10 to 14 years of age excreted as high as 1,600 EPG. Sexwise, no significant difference was observed in EPG (p > 0.05). Biomphalaria pfeifferi, the principal snail host of S. mansoni in Ethiopia, were collected from five out of the 11 waterbodies and were found shedding human schistosome cercariae in two of them, their infection rate reaching 0.7%. The ecological characteristics observed were found suitable for snail propagation.(ABSTRACT TRUNCATED AT 250 WORDS)

Decline of urinary schistosomiasis in Kurmuk town, western Ethio-Sudanese border, Ethiopia.

Urine examination of the residents of Kurmuk town, Western Ethio-Sudanese border, done in April 1993, showed that Schistosoma haematobium infection has now declined to 5.7% from 30.2% in 1981. The current intensity of infection is also as low as 20 eggs/10 ml urine. However, the finding of infected Bulinus africanus indicates resurgence of urinary schistosomiasis in the town. Possible factors that may have contributed to the decline and measures required to contain the disease are discussed.

Schistosoma haematobium infection among Ethiopian prisoners of war (1977-1988) returning from Somalia.

Fifty Ethiopian male prisoners of war aged 20-34 years returning from Somalia were examined at the Schistosomiasis Diagnostic Laboratory of the Institute of Pathobiology, Addis Abeba University, Addis Abeba in 1988. Medical history was obtained and their urine was examined by the filtration technique. Recovered eggs of S. haematobium were allowed to hatch as a test for viability. Positive patients were treated with praziquantel at a single dose of 40mg per kg. 94% of the prisoners gave history of haematuria and 96% gave history of treatment for schistosomiasis while in Somalia. S. haematobium egg positivity rate was 30% and all but one patient had viable eggs in their urine. The geometric mean egg count per 10ml urine was only 6.4. Urine examination of treated cases six weeks later showed 100% cure rate. A preliminary compatibility study between Ethiopian Bulinus snails and the Somalian strain of S. haematobium showed that B. abyssinicus and B. truncatus were susceptible to the parasite while B. africanus was only partially susceptible. The possibility that a foreign strain of S. haematobium may be introduced into ecologically and malacologically receptive areas in Ethiopia is discussed.

Helminth and snail survey in Harerge region of Ethiopia with special reference to schistosomiasis.

2300 persons from 25 communities in Harerge Administrative Region were examined for intestinal helminths. The overall prevalence rates were: Schistosoma mansoni 19.4%, Ascaris lumbricoides 13.4%, Trichuris trichiura 7.9%, and Taenia species 5.8%. Other parasites found in less than 3% included: Hymenolepis nana, Hymenolepis diminuta, Enterobius vermicularis, Strongyloides stercoralis and hookworms. Three age groups, 5-9, 10-14, and 15-19 years, had approximately similar prevalence (34.9-38.8%), but younger children had heavier egg loads (geometric mean egg output per gram of feces (EPG) of 347, 340 and 248, respectively). Boys had a higher prevalence of egg load than girls (42.4%, 395 EPG vs 26.5%, 277 EPG). Infection rates among Moslems were higher than Christians (45.5 vs 23.7%), but they had smaller egg output (333 vs 412 EPG). The frequency of light, moderate and heavy infections showed a normal distribution at 27, 46 and 27%. Biomphalaria pfeifferi was found to be infected with S. mansoni in Hirna (42/250), Esakly (6/80) and Genda Adem (20/200), the latter two in the Erer valley. Urine samples from 8 localities were negative for S. haematobium infection. The need for further study in several river valleys with agricultural potential is suggested.

Evaluation of reagent strips for detection of Schistosoma haematobium infection in the lower Awash valley, Ethiopia.

The use of reagent strips as indirect morbidity indicators in Schistosoma haematobium infection has been assessed in comparison with urine filtration technique in the lower Awash valley of Ethiopia in 1991. The prevalence of infection by reagent sticks and urine filtration was 16.0% and 3.6%, respectively. Reagent stick haematuria was highly related with urine filtration at the 2+ limit rather than the 1+ limit. A strong association was also obtained between prevalence rate and intensity of infection of all children at both haematuria limits. The prevalence of haematuria was not sex-related but there was age-associated infection and the prevalence was highest in the 10-13 year age group. The possible use of reagent stick haematuria in the monitoring of S. haematobium infection in Ethiopia is discussed.

Schistosomiasis in the Gumara and Ribb irrigation project area, Ethiopia.

A survey of intestinal schistosomiasis and vector snails was conducted in the Gumara and Ribb Irrigation project located on the eastern side of Lake Tana, northwest Ethiopia. Within the project area, stool specimens from 1273 people were examined by the thick smear method. The average infection rate for Schistosoma mansoni was 1.6%. Two localities, Addis Zemen and Yifag, located just outside the project area, were also examined, the former showing an S. mansoni prevalence of 34% (75/223) and the latter 18% (18/101) among school children. In Debre Tabor, the provincial capital 50 km away from the project site at an altitude of 2800 m., five S. mansoni cases were found among 111 school children, but they were considered to be imported cases. The possible establishment of intestinal schistosomiasis in the project area is discussed.