The community-based malaria control programme in Tigray, northern Ethiopia. A review of programme set-up, activities, outcomes and impact.

Tigray, the northernmost state of Ethiopia, has a population of 3.5 million, 86% rural, and 56% living in malarious areas. In 1992 a Community-Based Malaria Control Programme was established to provide region-wide and sustained access to early diagnosis and treatment of malaria at the village level. 735 volunteer community health workers (CHWs) serve 2,327 villages with a population of 1.74 million, treating an average of 489,378 patients yearly from 1994 to 1997. Recognition of clinical malaria is similar for CHWs and health staff at clinics where there is no access to microscopy. In 1996 a pilot community-financing scheme of insecticide-treated bednets was well accepted, but re-impregnation rates fell in 1998 because of war-related social upheaval. Indicators from health institutions show a progressive increase in malaria morbidity from 1994 to 1998. Repeated mortality surveys show a 40% reduction in death rates in under-5 children from 1994 to 1996 and a 10% increase from 1996 to 1998. These trends may be related to increased malaria transmission with water resources development, increased seasonal labour migration to malarious lowlands, prolongation of the transmission season with climate changes, and increasing chloroquine resistance throughout Ethiopia. Progressive extension of CHW services to ensure better coverage of women, children, migrant workers and communities near water development projects, change to first-line treatment with sulfadoxine-pyrimethamine, extension of the impregnated bednet initiative, and development of a regional warning system for epidemics should result in a greater impact on morbidity and mortality.

Opportunities, problems and perspectives for malaria control in sub-Saharan Africa.

Environments conducive to high malaria transmission and widespread poverty are at the roots of the 'malaria giant', which affects 46 countries in Africa. The recent interest in and momentum of work on malaria, in endemic countries and the international community, is unprecedented and opens new perspectives for controlling the disease. Significant steps included: (i) the allocation of US$20 million by WHO for accelerated implementation of malaria control in 34 African countries in 1997-98; (ii) the Declaration on Malaria by the Heads of States of the Organization of African Unity and the establishment of the African Initiative for Malaria Control in 1997; (iii) the concomitant mobilisation of the research community in the Multilateral Initiative on Malaria; (iv) the G8 Summit in 1998 in Birmingham asking for higher commitment to malaria control, particularly in Africa; and (v) the Roll Back Malaria initiative set as a WHO priority project in 1998. However, experiences have proved the alarming 'resilience' of the malaria system in Africa, showing devastating consequences when malaria returns to the original levels after intensive control is interrupted. Effective malaria control in Africa requires long-term action, firmly rooted in the social development of the country.

Community-based malaria control in Tigray, northern Ethiopia.

Community-based control activities have been a major component of the Tigray regional malaria control programme since 1992. A team of 735 volunteer community health workers treat on average 60,000 clinical malaria cases monthly during the high malaria transmission season. Ensuring access for the rural population to early diagnosis and treatment has contributed to a significant decrease in death rate in under-five children at the village level from 1994 to 1996. Mapping and geographic information system (GIS) technologies have been introduced to support planning for control by assessment of community-based coverage. With further development, GIS will be used in stratification, and to assess the impact of water resources development on malaria transmission and intensity.

Malaria, schistosomiasis, and intestinal helminths in relation to microdams in Tigray, northern Ethiopia.

A survey was undertaken in Tigray, Northern Ethiopia, to assess the prevalence of malaria, schistosomiasis, and intestinal helminths in relation to microdams. The survey took place from March to June 1995, during the dry season, at 41 microdams. At each site the village nearest the dam (within thirty minutes walk) was selected, ten households were randomly chosen, and all family members were examined for malaria and intestinal parasites. The overall study sample was 2271 people, of all age groups. Plasmodium falciparum infection was documented in four villages (at 10% of microdams); prevalence was 1.2% (range 0-20% by village). Larvae of Anopheles gambiae s.l. were found at one microdam. Infection with intestinal schistosomiasis was documented in 20 villages (at 49% of microdams), and one third of those infected had moderate to heavy infections. Biomphalaria species, the intermediate host snails of Schistosoma mansoni, were found at 16 microdams (39%), and snails infected by mammalian cercariae were found in one locality. Infections with soil-transmitted nematodes were prevalent: hookworm was detected in more than two thirds of the villages, and Ascaris lumbricoides and Trichuris trichiura were present in almost half of the villages. Out of 2078 stool examinations, the prevalence of S. mansoni infection was 7.2% (range 0-48% by village), of A. lumbricoides 2.3% (range 0-31%), of T. trichiura 2.4% (range 0-21%), and of hookworm 8.9% (range 0-78%). The prevalence of malaria, S. mansoni and hookworm was higher at altitudes below 2000 metres above sea level. S. mansoni was more prevalent in microdams built more than 5 years before the survey, while T. trichiura was more prevalent at recently constructed microdams. The widespread distribution of schistosomiasis and intestinal helminths, and the presence of malaria infection during the dry season confirm that microdams create favourable conditions for the transmission of these parasitic diseases. Health safeguards must be incorporated into the planning, construction, and operation of microdams and irrigation systems in order to prevent or reduce these diseases. In areas with high prevalence, control activities should be intensified.

Community participation in malaria control in Tigray region Ethiopia.

During the Ethiopian civil war from 1974 to 1991, the Tigrean People's Liberation Front established a primary health care system in Tigray in which community residents helped to plan and implement health services through health committees and community health workers (CHWs). To strengthen and update this system, a Community-Based Malaria Control Programme was initiated in 1992. The primary objectives of the Programme are to reduce malaria morbidity and mortality and to prevent malaria in pregnant women through early diagnosis and treatment of cases, chemoprophylaxis during pregnancy, and vector control by environmental management. A secondary objective is to introduce a cost-sharing scheme for eventual development of a village revolving fund. A total of 681 volunteers chosen by their communities have received malaria training and serve a rural population of 1,682319 (CHW/population ratio 1:2,500). The principal success of the programme at this stage is that a significant proportion of the rural population at risk for malaria is now being treated at the village level. During the last major transmission season from September through November 1993, each CHWs treated a mean of 45178 clinical malaria cases per month. Under-utilization of treatment services by women and children under 5 years and low chemoprophylaxis coverage of pregnant women have been documented. After focus group discussions with community members and CHWs to identify the reasons for these problems, changes in programme policies were made to improve coverage of these groups. Since 1992, considerable progress toward meeting programme objectives has been made, and continued evaluation will allow for interventions that should further strengthen the malaria control efforts in the region.

Temporal and spatial distribution of anopheline mosquitos in an Ethiopian village: implications for malaria control strategies.

The spatial and temporal distribution of Anopheles gambiae mosquitos in houses in the village of Sille in Ethiopia was monitored in 1990-91. Monthly mosquito densities in over 300 houses were obtained, and the data for each month were plotted on maps, which indicated clustering of mosquitos within the village. Spatial analysis using "kriging" techniques demonstrated clustering towards the edges of the village, the pattern of which changed with time. For example, the low density of mosquitos in one area in September increased as the nearby irrigation canals dried up during the following months. Since most entomological activity occurred at the periphery of the village, focal spraying of these areas could be a cost-effective procedure. If such clustering occurs in other villages, selective control of breeding sites and indoor spraying could provide a more efficient use of limited resources than traditional total coverage.

Prospects for the use of larvivorous fish for malaria control in Ethiopia: search for indigenous species and evaluation of their feeding capacity for mosquito larvae.

Because of problems with drug and insecticide resistance, the National Organization for the Control of Malaria and other Vectorborne Diseases, Ethiopia, has embarked on a programme of research on alternative malaria control methods, including the use of biological control agents, such as larvivorous fish. The objectives of the study were to identify indigenous larvivorous fish species which could be potential candidates for use as biological control agents; to extend knowledge of their distribution in Ethiopia; and to conduct laboratory tests to determine their feeding capacity. An extensive search resulted in the identification of 11 larvivorous fish species indigenous to Ethiopia, including five species previously unrecorded in the country. Seven species were assessed under standard laboratory conditions for their feeding capacity on larvae of Anopheles gambiae s.l. and Culex andersoni. All species tested were efficient larvivores in the laboratory. However, their larvivorous capacity should be tested further in field trials. Based on the findings of this study, two priority areas for the assessment of biological control using larvivorous fish were identified, the port city of Assab, using the local species Aphanius dispar, and the Ogaden, south-eastern Ethiopia, using the local species Oreochromis spilurus spilurus.

Control of mosquito larvae in the port city of Assab by an indigenous larvivorous fish, Aphanius dispar.

A randomized controlled trial was carried out in Assab under the auspices of the National Organization for the Control of Malaria and other Vectorborne Diseases of Ethiopia to assess the effectiveness of an indigenous cyprinodontid fish, Aphanius dispar, in controlling mosquito larvae, including the local malaria vector, Anopheles culicifacies adanensis. Cisterns, wells and barrels were found to be important breeding sites for the malaria vector and for culicine mosquitoes. Fish were equally effective in controlling mosquito larvae in all the types of breeding site investigated. The overall proportion of sites with fish that harboured mosquito larvae was 1.6%, ranging from 1.5 to 1.7% according to type of site, as compared to 34% in sites left unstocked, ranging from 17.9 to 60.0%. Monthly restocking of fish where necessary was found to be sufficient to maintain an adequate level of control. Stocking of larvivorous fish in wells and household water storage containers was well-accepted by the participants, who were aware of the role of the fish in malaria prevention and found the fish useful in keeping their water free of other aquatic organisms. Based on the results of this study, larvivorous fish were introduced on an operational scale for the control of malaria transmission in Assab, with the voluntary participation of the population and the collaboration of the Municipality and health authorities of Assab.

A parasitological and malacological survey of schistosomiasis mansoni in the Beles Valley, northwestern Ethiopia.

A survey of schistosomiasis mansoni infection was conducted in an area of northwestern Ethiopia which has been targeted for an irrigation project. The proximity of settlements to water-bodies infested with Biomphalaria pfeifferi, and used extensively for bathing and domestic purposes, indicated that the potential for transmission is high. Snails shedding S. mansoni cercariae were found in two localities. Stool specimens from a total of 7517 persons were examined, including specimens from 4915 children age 7-14 years in 29 localities, as well as from the total population of four of the more heavily infected localities. The 10-14 year age group had the highest transmission potential, in terms of prevalence (overall 25%), intensity of infection, and absolute numbers of infected individuals, suggesting that screening and chemotherapy would be most cost-effective in that age group.

Schistosoma mansoni infection in a new settlement in Metekel district, north-western Ethiopia: morbidity and side effects of treatment with praziquantel in relation to intensity of infection.

A study of morbidity and side effects of treatment with praziquantel in relation to intensity of infection with Schistosoma mansoni was conducted in 406 infected individuals from a newly-settled village in Metekel, north-western Ethiopia. Each subject was submitted to a standardized medical history and abdominal palpation. The frequencies of hepatomegaly and splenomegaly were low, 2% and 3%, respectively. A positive association was found between egg load and a history of blood in the stool. Interviews on side effects were conducted on the day following treatment with praziquantel (40 mg/kg body weight). Positive correlations with egg load were found for several side effects, including abdominal pain, diarrhoea, headache, back pain, and vomiting. Unusual side effects involving swelling of various parts of the body confirm 2 previous reports from a different region in Ethiopia and should be investigated further.

Malaria diagnosis by direct observation of centrifuged samples of blood.

We compared the effectiveness of malaria diagnosis by means of direct observation of centrifuged blood with that by conventional examination of Giemsa stained blood-films in a malaria clinic in Ethiopia. A commercially available, modified hematological apparatus (the QBC tube) was used for centrifugation. Red blood cells infected with diverse stages of Plasmodium falciparum and P. vivax are lighter than noninfected cells and somewhat heavier than granulocytes; thus they can readily be detected by direct inspection of UV-illuminated tubes. About 10% of infections diagnosed by direct centrifugal microscopy in a clinical setting were not detected by conventional examination of stained thick films. Diagnosis by direct centrifugation appears to be at least 8 times as sensitive as conventional microscopy when applied to serially diluted samples of malaria-infected blood. Superior sensitivity, together with the one step, solid state nature of the direct centrifugal procedure, provides important advantages for malaria diagnosis.

Characterization of Plasmodium falciparum cloned lines with respect to gametocyte production in vitro, infectivity to Anopheles mosquitoes, and transmission to Aotus monkeys.

The production of gametocytes in vitro and their subsequent infectivity to mosquitoes by 3 cloned lines of Plasmodium falciparum were studied. 2 of the cloned lines, Honduras I-clone B3 and Indochina III-clone W2, produced mature gametocytes (stage V) that were infective to Anopheles mosquitoes. The third clone, Sierra Leone I-clone D6, produced gametocytes, the majority of which did not develop beyond stage III. Fully mature gametocytes of Sierra Leone I-clone D6 were not infective to mosquitoes. Sporozoites collected from An. freeborni infected with Honduras I-clone B3 were used in transmission studies. Two of three Aotus monkeys were infected after prepatent periods of 19 and 20 d, respectively. This study supports previous reports that cloned lines of P. falciparum contain the full genetic capacity to produce morphologically mature gametocytes. The transmission to Aotus monkeys has also conclusively established that biologically competent gametocytes of both sexes are produced by clones.

Chloroquine-resistant Plasmodium falciparum malaria in Ethiopia.

Standard triple-dose therapy with chloroquine (25 mg base/kg) failed to clear asexual Plasmodium falciparum parasites from the blood of 22 of 98 patients infected in various parts of Ethiopia and evaluated in Addis Ababa, a malaria-free city. RI to RIII levels of resistance were demonstrated in those patients. The resistant isolates were confined to areas bordering Somalia, Kenya, and Sudan. In in-vitro tests 7 of 10 (70%) isolates were chloroquine-resistant.

Chloroquine-resistant falciparum malaria in northern Malawi.

An American Peace Corps volunteer contracted chloroquine-resistant Plasmodium falciparum malaria while serving in Malawi and taking regular chloroquine prophylaxis. Resistance was confirmed by in vitro testing of his parasites for chloroquine and pyrimethamine. The possibility of Fansidar-resistant falciparum malaria was also suggested in this case. American expatriates residing in or traveling to Malawi are advised to either take both chloroquine and Fansidar, or alternatively amodiaquine or doxycycline alone. Any breakthrough of slide-proven falciparum malaria in these individuals should be seriously suspected to be chloroquine- and Fansidar-resistant malaria, and should be treated with quinine and tetracycline.

Evaluation of sporontocidal compounds using Plasmodium falciparum gametocytes produced in vitro.

A test system that uses infective gametocytes from in vitro cultures was developed for evaluating the sporontocidal activity of antimalarial compounds. In evaluating the system, pyrimethamine and cycloguanil (dihydrofolate reductase inhibitors) and primaquine (8-aminoquinoline) were tested against pyrimethamine-sensitive and pyrimethamine-resistant strains of Plasmodium falciparum. The drugs were administered to Anopheles either in a blood meal containing infective gametocytes or in a noninfective meal 2-4 days later. The mosquitoes were dissected 9-10 days after they received the infective blood meal, and the sporontocidal effect of the drugs was evaluated by the number of oocysts found in the gut. Both cycloguanil and pyrimethamine had marked sporontocidal activity. The susceptibility pattern of the strains to the sporontocidal effect of pyrimethamine and cycloguanil was similar to the susceptibility of their asexual blood stages in vitro to the schizontocidal effect of the compounds. The sporontocidal effect was observed only when the compounds were administered at the same time as the infective blood meal, but not when they were given 2-4 days later. No sporontocidal activity was observed with primaquine. This system permits more reliable quantitative observations than have been possible with previous methods.