Impact of cattle keeping on human biting rate of anopheline mosquitoes and malaria transmission around Ziway, Ethiopia.

OBJECTIVE: To assess the impact of livestock keeping on the human biting rate (HBR) of anopheline mosquitoes and malaria transmission around Ziway in the middle course of the Ethiopian Rift Valley. DESIGN: As a passive experiment, man landing captures were done in homesteads with mixed dwelling, separate cattle shed and without livestock; and as an active experiment, captures were in experimental tukuls (huts) of cattle, goats, and without livestock. Parasite and spleen rates of children were compared among those residents under variable living conditions mentioned for passive experiment. SUBJECTS: For entomological study, human-baits were used for man-landing captures of mosquitoes. Study subjects for parasitological and clinical studies were children below 10 years old. MAIN OUTCOME MEASURES: Human-biting rate (HBR) of anopheline mosquitoes; and the parasite and spleen rates of the study subjects in different living conditions. RESULTS: In the passive experiment, the mean HBR of Anopheles arabiensis in mixed dwelling, separate cattle shed and without livestock was 8.45, 4.64 and 5.97, respectively. Similarly, the HBR of An. pharoensis was 2.88, 1.79 and 1.61, respectively. In the active experiment, the mean HBR of An. arabiensis in tukuls with cattle, goats, and without livestock was 3.50, 3.38 and 1.43 respectively; while that of An. pharoensis was 0.37, 0.70 and 0.55 respectively. Parasitologically, mean parasite rates of 26.67%, 15.05% and 23.85% were, respectively, recorded from children living under the above conditions stated for passive experiment. Similarly, the mean spleen rates of 50.0%, 26.9%, and 47.37% were recorded, respectively. CONCLUSION: These observations in the present study indicate that the presence of cattle in homesteads tends to increase the man biting rate of An. arabiensis, although differences in the mean HBR of vector mosquitoes were not statistically significant for all groups. In contrast, cattle keeping in separate cattle sheds outside of the human dwellings tends to reduce the man biting rate of An. arabiensis and malaria transmission in the study area.

Implication of Papio anubis in the transmission of intestinal schistosomiasis in three new foci in Kime area, Ethiopia.

Epidemiological studies were conducted in the Lake Langano area in the Rift Valley of Ethiopia to determine the occurrence of schistosomiasis and assess factors involved in its transmission. Microscopic examination of faecal specimens from free ranging Papio anubis (anubis baboon) troops from Bishan Gari and Burka Dita forest reserves revealed Schistosoma mansoni eggs with a prevalence of 12.1% (11/91) and 26.2%(34/130), respectively. The eggs were viable as confirmed by miracidial hatching and infectivity tests. Out of the total 12 communities (three schools, five villages and one herdsmen community) surveyed for schistosomiasis around Lake Langano, individuals excreting S. mansoni eggs were found in nine communities with prevalence of infection ranging from 1.4 to 43%. The intensity of infection ranged from 24 EPG (eggs per gram of faeces) to 243 EPG. Excretion of viable eggs by the baboons indicate that they play a role in maintenance of S. mansoni infection in the locality. The detection of S. mansoni eggs in young children, collection of cercarial-infected Biomphalaria pfeifferi in water bodies, and establishment of S. mansoni infection in lab-bred mice have confirmed establishment of transmission foci in Kime area, south-east of Lake Langano. However, the lake itself does not seem to support transmission of schistosomiasis since no snails were found along the shore of the Lake. Further investigations are indicated to fully elucidate the role baboons play in the epidemiology of schistosomiasis in the Rift Valley of Ethiopia. The risk of introduction of water-based development projects in these new endemic foci in relation to S. mansoni infection in the baboons is discussed.

Field trial of the RTM dipstick method for the rapid diagnosis of malaria based on the detection of Plasmodium falciparum HRP-2 antigen in whole blood.

The performance of the Quorum RapidTest Malaria (RTM) dipstick method that detects Plasmodium falciparum histidine-rich protein-2 (PfHRP-2) antigen in whole blood was evaluated in a malaria endemic area. Results were compared with conventional Giemsa-stained blood films. Of 306 people tested 37.9% (116/306) were found to be parasitaemic; of these 66.4% (77/116) were P. vivax and 32.8% (38/116) were P. falciparum infections. There was only one (0.9%) mixed P. falciparum plus P. vivax infection. The RTM test was positive in 35/36 patients with P. falciparum identified on blood smear examination, resulting in a sensitivity of 97.2% [95% confidence interval (CI): 91.6-102.8%]. Specificity was 96.3% (95% CI: 93.9-98.6%). The RTM test had a positive predictive value of 77.8% (95% CI: 65.7-89.9%) and a negative predictive value of 99.6% (95% CI: 98.4-100.8%). Of the 10 false positives, seven reported recent malaria episode and treatment, indicating persistence of antigenaemia. If these were assumed truly infected, the positive predictive value is increased to 93.3% (95% CI: 85.8-100.8%). The RTM test was positive in all seven P. falciparum infections with gametocytes and one mixed infection, but was negative in all falciparum gametocytes and relapsing fever cases. All but one P. vivax infection gave negative result on the RTM test. The RTM test missed one patient with parasitaemia. The test is highly sensitive and specific requiring no instrument or trained personnel. It appears to be a very useful tool for rapid diagnosis of malaria, especially in the rural health institutions with limited diagnostic facilities.

Clinical presentation of onchocerciasis among indigenous and migrant farmers in southwest Ethiopia.

OBJECTIVE: To show the magnitude of the problem and give a systematic account of the clinical manifestations of onchocerciasis in a rain forest ecology in southwest Ethiopia. DESIGN: A cross sectional clinico-epidemiological study. SETTING: Teppi Health Centre and Endris-Goji Clinic, Ethiopia. SUBJECTS: Four hundred and twenty one individuals aged ten years and above. RESULTS: Eighty four per cent of the examined people had a macrofilarial load ranging from one to 855 microfilariae per mg of skin snip. If the presence of any of skin microfilaria, nodule and/or leopard skin were taken as diagnostic criteria, the overall prevalence rate of onchocerciasis would be 88%. However, if we strictly followed stringent diagnostic criteria such as presence of unprompted itching, nodule(s), microfilaraedermia and skin dermatitis, the prevalence rate of onchocerciasis would be 23% (98/421). Hanging or pendular scrotum, which has been rarely reported in Africa but not until now in Ethiopia, was found in 19% (46/246) of the male patients. There was neither negative nor positive correlation between microfilarial load and severity of clinical manifestations of the disease. CONCLUSION: Onchocerciasis has been found to be one of the major health problems in this community and its diagnosis should not be based on selected signs and symptoms such as nodules and leopard skin alone that could undermine the magnitude of the problem.

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.

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.

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.

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.

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.