Insecticide susceptibility status of Anopheles gambiae (s.l.) in and surrounding areas of Lake Tana, northwest Ethiopia.

BACKGROUND: Vector control is the most effective malaria control and prevention measure. Among these, IRS and LLINs are the most important chemical insecticide interventions used in malaria prevention and control strategies in Ethiopia. However, the long-term effectiveness of these strategies is under threat due to the emergency and spread of insecticide resistance in the principal malaria vector. Therefore, this study was carried out, under standardized laboratory conditions to assess the killing effect of some insecticides against An. gambiae s.l. METHODS: Mosquitoes in late instar larvae and pupae stages were collected from different breeding habitats of the study sites using a soup ladle (350 ml capacity). The immature was reared to adults at optimum temperature and humidity in a field insectary using the WHO protocol. Four insecticides representing three chemical classes were used against adult mosquitoes. These were permethrin, deltamethrin, pirimiphos-methyl and bendiocarb. Susceptibility tests were carried out from September to December 2021 using the WHO standard procedures. Mortality rate, variation, interaction effect and knockdown times (KDT50 and KDT95%) were computed using descriptive statistics, multivariate analysis of variance and log-probit regression model using SPSS version 20 software. RESULTS: Totally, 1300 Anopheles gambiae s.l. were tested to determine the susceptibility status to the four insecticides. Among these, 90.7% of them were susceptible to insecticides, whereas the remaining 9.3% of specimens were resistant to the insecticides. The results of the analysis of variance showed that mortality significantly varied between insecticides (F = 26.06, DF = 3, P < .0001), but not between study locations (F = 1.56, DF = 3, P = 0.212). On the other hand, the mean comparison of dead mosquitoes showed some signs of interaction between bendiocarb and locations, but not other insecticides and locations. CONCLUSIONS: This study revealed that the knockdown times and effectiveness of different insecticides varied in different study sites. Therefore, insecticide resistance information is very essential for concerned bodies to make informed and evidence-based decisions on vector control.

Prevalence of malaria and its risk factors in Lake Tana and surrounding areas, northwest Ethiopia.

BACKGROUND: In Ethiopia, malaria is a major concern to the health, and socio-economic development of the country because of its occurrence at the peak agricultural activities. Factors such as environmental, human host, parasite, and vector determine malaria transmission. Therefore, the present study was conducted to determine the prevalence and associated factors of malaria among febrile patients who visited selected health centres. METHODS: Institutional-based cross-sectional study was conducted between October 2020 to July 2021 in eight selected health centres located in Lake Tana and its surrounding areas. A simple random sampling technique was used to select febrile patients. Thick and thin blood films were prepared and processed according to the WHO guidelines. Socio-demographic and malaria risk factors were collected from study participants who could read and write using a self-administered questionnaire, whereas face-to-face interview was used to collect information from those participants who could not write and read. The strength of association between risk factors and malaria was assessed using univariate and multivariate logistic regression models. RESULTS: Of the total (531) febrile patients, 75.3% were malaria negative and 24.7% (overall prevalence) were malaria confirmed cases. Most of the infections were caused by Plasmodium falciparum (72.5%) followed by Plasmodium vivax (23.7%) and mixed-species (3.8%). The highest prevalence was recorded in Kidist Hana (51.5%) followed by Robit (34.8%), Gorgora (30.3%), and Wusha Tiris (25%) health centres. In terms of months, the highest prevalence (37.5%) was detected in October whereas the lowest (14%) was in March. Logistic regression analysis revealed that gender (p = 0.023), educational level (p = 0.025), study month (p = 0.036), presence of eave in the house (p = 0.002) and wall openings (p = 0.041), not using bed nets (p = 0.001), sleeping in the same house with cattle (p = 0.031) and the distance between mosquito-breeding site and living house (p = 0.020) were explanatory risk factors significantly associated with malaria among studied participants. CONCLUSIONS: In this study, we confirmed that the occurrence of malaria prevalence was high and continued against the Ethiopian malaria elimination plan of 2021-2025. Therefore, to meet the goals of this plan, the current prevention and control efforts should be stepped up even better in the coming years.

Larval Anopheles Species Composition and Diversity at Different Habitats and Seasons of Gondar Zuria District, Ethiopia.

Anopheles species' larval habitats are diversified and season dependent. Anopheles larvae can be found at different habitats and their preference may vary seasonally. Knowledge of species diversity and distribution helps plan malaria control interventions. Anopheles larvae were sampled using the WHO standard 350 ml dipper from breeding habitats of irrigation, pond, sewage, stream, and swamp. The collected sample larvae were identified microscopically to species using morphological keys. Among Anopheles species recorded, Anopheles gambiae complex was the most abundant followed by Anopheles christyi, Anopheles cinereus, Anopheles demeilloni, and Anopheles pharoensis in descending order. Anopheles species occurred more in January than in other months of the study period and less in March and April. For any particular mosquito species, larval abundance did not significantly vary between the habitats; in other words, all habitats contributed equally. In this study, we confirmed that Anopheles mosquito larval population varied more with respect to species than to habitats and months. Interventions could be launched targeting each habitat; during the month, numbers were high.

Prevalence of Intestinal Protozoa and Soil Transmitted Helminths Infections among School Children in Jaragedo Town, South Gondar Zone of Ethiopia.

Background: Parasitism is a relationship where one, the parasite, harms the host or lives at the expense of the host. Intestinal parasites (protozoa and STHs-soil-transmitted helminths) cause gastrointestinal tract infection in humans and animals. Intestinal parasitic infections (IPIs) predominate the tropics and subtropics and affect poor countries, where school children suffer the most. To prevent and control these infections, local risk factors must first be identified. The aim of the study was to determine the prevalence of intestinal parasitic infections and associated risk factors among school children in Jaragedo town schools, South Gondar Zone of Ethiopia. Methods: A cross-sectional study was conducted from October 2018 to April 30, 2019, involving 396 students from one elementary and one secondary school. Stratified simple random sampling method was used. A questionnaire was prepared to collect sociodemographic and socioeconomic data of the study subjects. Stool samples were collected and examined using formalin-ether concentration technique. Data were analyzed using SAS software version 9.4. Descriptive statistics were used to give a clear picture of population characteristics. Logistic regression was also used to determine the relationship between dependent variables (primary infection) with independent (explanatory) variables using SAS software. Results: Results showed that the overall prevalence of intestinal parasitic infections was 65.4%. E. histolytica was the most prevalent intestinal parasite (12-14%) followed by G. lamblia (8-9%); other parasites could not infect more than 5% of the study subjects. Generally, parasitism did not vary between the sexes. The logistic regression analysis showed that grade, level of students, water source, habit of consuming raw meat, and level of income had a strong effect on intestinal parasitic infection (P < 0.05). Other explanatory variables were not significant (P > 0.05). High prevalence of parasites indicates improper disposal of waste, low socioeconomic level, low living standard, and poor water quality. Conclusion: Therefore, short-term and long-term intervention strategies are required to minimize rates of infection.

Review of Anopheles Mosquito Species, Abundance, and Distribution in Ethiopia.

BACKGROUND: Malaria is a major mosquito-borne disease in Ethiopia, and it is one of the leading causes of morbidity and mortality. Plasmodium falciparum and P. vivax are the two malaria-causing parasitic species commonly known to cause human malaria in Ethiopia. To better manage and control vectors transmitting malaria parasites, the abundance, distribution, and updated annotated list of Anopheles species present in Ethiopia are very important. METHODS: In order to compile a list of the species recorded in Ethiopia, 33 original research articles were collected. This work gives an updated list of Anopheles mosquito species in Ethiopia and their abundance, distribution, and composition. RESULTS: According to this review, 110305 Anopheles mosquitoes were collected and 35 Anopheles species were recorded in different parts of Ethiopia. A. arabiensis was the most abundant when compared to other species, whereas A. maculipalpis and A. wilsonii were the least abundant species. The most abundant Anopheles species was recorded in central and the least abundant, from eastern Ethiopia. The second, third, and fourth abundant species were also collected from southern, northern, and western parts of Ethiopia.

Factors determining species richness patterns of breeding birds along an elevational gradient in the Horn of Africa region.

AIM: To document the species richness patterns of breeding birds along elevational gradients and explore its drivers in the Horn of Africa region. LOCATION: Horn of Africa region. TAXON: Breeding birds. METHODS: Distributional data for breeding birds were collected. Elevational distribution data were extracted, interpolated, and assembled for all birds, passerines, and nonpasserines. In order to tease apart how different environmental factors contributed to the variation in species richness, we found it is necessary to divide the area into four subregions with different climatic regimes and topographic structure, namely western slope, eastern slope, wet side, and dry side. Then, the species richness in each 100-m elevational band was counted along the elevational gradients of each subregion. Pearson's correlation analyses and ordinary least squares (OLS) regressions were used to examine the relationships between species richness and factors. RESULTS: The variation in species richness followed hump-shaped patterns for all subregions, although with peak values at different elevations. The bird species groups on the western and eastern slopes showed low and high plateaus with mid-elevation peaks, respectively, but very low species diversities at the highest elevations. Species richness was significantly correlated with temperature range and productivity in each subregion. The temperature range, area, and productivity explained 82% of the species richness variations for all birds on the western slope. MAIN CONCLUSIONS: The separate analyses of four area subdivisions provide strong indications of how various factors interact. Productivity and temperature range were the major driving factors for shaping the richness patterns, but deviations from expected patterns suggest modifying roles of mist formation zones in the valleys that deeply intersect the large highlands in the west and rich riparian vegetation where water from cool and humid environments at high elevation reaches lower elevations in the arid east. Conservation is recommended in each subregion based on the elevational richness scenarios.

Impact of insecticide-treated bednet use on malaria prevalence in Benishangul-Gumuz regional state, Ethiopia.

BACKGROUND & OBJECTIVES: In Ethiopia, nearly 10 million insecticide-treated bednets (ITNs) were distributed between 2004 and 2005; which touched 56 million in 2012. The study was aimed to determine the impact of these bednets on malaria prevalence, in Yaso district of Benishangul-Gumuz region, western Ethiopia. METHODS: A cross-sectional study was conducted during the peak malaria transmission season (October-November, 2014) in the Yaso district, Benishangul-Gumuz region. Data on demographic variables, ITN ownership and malaria infection rates were collected using structured questionnaires and blood film tests and analyzed using SAS for windows software. The probability of getting infected (questionnaire and the blood film results) was regressed against groups of explanatory variables, like age, sex, bednet use etc. using multiple logistic regressions. RESULTS: The results revealed that about 40% of the study subjects (384) were positive for Plasmodium falciparum; while P. vivax, P. falciparum and mixed infections accounted for 74.5% of the study subjects. All the 384 study subjects possessed insecticide-treated bednets; 50.5% possessed one, 39.3% two and 10.2% more than two. According to the logistic regression, there was significant association between illness due to malaria and at least one of the explanatory variables (χ26= 271.9, p<0.0001). For all Plasmodium species, education level, and age appeared to be significant beneficial factors (OR<1 and negative ß-values). Occupation was a significant risk factor. Proper ITN utilization improved with increasing educational status. INTERPRETATION & CONCLUSION: Schools may be appropriate for creating awareness and distribution of ITN instead of the current mass campaign, which is less effective. Efforts of stakeholders (schools, community health workers, and the government) should be integrated.