Tadesse Dejenie

Infection prevalence of Schistosoma mansoni and associated risk factors among schoolchildren in suburbs of Mekelle city, Tigray, Northern Ethiopia

Effective and sustainable control of Schistosomamansoni infection requires identifying subpopulations that are at risk of infection. A cross-sectional epidemiological survey was conducted in children of four primary schools in Raya Alamata District of Ethiopia to determine the prevalence and intensity of infection, and index of potential contamination of intestinal schistosomiasis. Fecal samples of 500 (266 males and 234 females) subjects aged 6-19 years were processed using Kato Katz thick smear field technique. Questionnaire survey was also deployedto assess associated risk factors among infected children. Out of the examined children, 101(20.2%) were infected by S. mansoni. The prevalence of infection differed significantly among the age groups (χ 2 = 6.93; P<0.05). High prevalence of infection was observed among children of 10-14 years old. Intensity of S. mansoni infection was low, only 3.96% had heavy infection intensity. Children of 10-14 years age have high infection intensity than any age group (χ 2 = 12.5; P<0.05). Index of potential contamination value showed that to a great extent children of 10-14 years were responsible to contaminate the environment with the bulk of S. mansoni eggs and for the transmission and maintenance of the disease in the area. Swimming habit (AOR= 3.66; P<0.05), frequency of water contact (AOR= 8.15; P<0.05) and treatment history (AOR 2.1; CI 1.3-3.3, P= 0.002) were the potential associated risk factors for S. mansoni infection. Schistosomamansoni infection did not show any significant association with gender, household water source, bathing and family occupation. Intestinal schistosomiasis is a public health problem, and to a great extent children of 10-14 years age group were responsible in the transmission and maintenance of the infection.

Genetic diversity of Microcystis blooms (Cyanobacteria) in recently constructed reservoirs in Tigray (Northern Ethiopia) assessed by rDNA ITS

The cyanobacterium Microcystis is notorious for forming extensive and potentially toxic blooms in nutrient-rich freshwater bodies worldwide. However, little is known about the factors underlying the genetic diversity and structure of natural Microcystis populations, despite the fact that this knowledge is essential to understand the build-up of blooms. Microcystis blooms are common and occur year-round in Africa, but are underinvestigated in this continent. We studied the genetic diversity and structure of Microcystis populations in 30 man-made reservoirs in Tigray (Northern Ethiopia) using Denaturing Gradient Gel Electrophoresis of the 16S–23S rDNA internal transcribed spacer (ITS) region and assessed the importance of local environmental conditions and geographic position of the reservoirs for the observed patterns. The analyses showed that both regional and local Microcystis ITS diversity in these recently constructed reservoirs was relatively low, with several dense blooms containing only a single ITS type. Especially one non-toxic ITS type dominated a considerable fraction of Microcystis blooms, but appeared restricted in its geographic distribution. The relationship between Microcystis ITS population structure and abiotic variables (water clarity, pH) and with zooplankton (Daphnia biomass) indicates a (limited) influence of environmental conditions on Microcystis population structure in the reservoirs of Tigray.

Index of Potential Contamination for Intestinal Schistosomiasis among School Children of Raya Alamata District, Northern Ethiopia

Effective and sustainable control of Schistosomamansoni infection requires identifying subpopulations that are at risk of infection. A cross-sectional epidemiological survey was conducted in children of four primary schools in Raya Alamata District of Ethiopia to determine the prevalence and intensity of infection, and index of potential contamination of intestinal schistosomiasis. Fecal samples of 500 (266 males and 234 females) subjects aged 6-19 years were processed using Kato Katz thick smear field technique. Questionnaire survey was also deployedto assess associated risk factors among infected children. Out of the examined children, 101(20.2%) were infected by S. mansoni. The prevalence of infection differed significantly among the age groups (χ 2 = 6.93; P<0.05). High prevalence of infection was observed among children of 10-14 years old. Intensity of S. mansoni infection was low, only 3.96% had heavy infection intensity. Children of 10-14 years age have high infection intensity than any age group (χ 2 = 12.5; P<0.05). Index of potential contamination value showed that to a great extent children of 10-14 years were responsible to contaminate the environment with the bulk of S. mansoni eggs and for the transmission and maintenance of the disease in the area. Swimming habit (AOR= 3.66; P<0.05), frequency of water contact (AOR= 8.15; P<0.05) and treatment history (AOR 2.1; CI 1.3-3.3, P= 0.002) were the potential associated risk factors for S. mansoni infection. Schistosomamansoni infection did not show any significant association with gender, household water source, bathing and family occupation. Intestinal schistosomiasis is a public health problem, and to a great extent children of 10-14 years age group were responsible in the transmission and maintenance of the infection.

The ecology of the riverine Garra species (Teleostei, Cypriniformes) in reservoirs of the semi-arid highlands of northern Ethiopia: temporal dynamics of feeding activity

Abstract Garra species are among the most abundant fish in small rivers of northern Ethiopia. Many manmade reservoirs in the region have been colonized by Garra, which often are the only fish species present and have become very abundant. Little is known about the ecology of these reservoir populations of riverine species. In this study we investigated the distribution patterns and gut fullness of 2 dominant species, G. blanfordii and G. geba, in 3 recently created reservoirs (Gereb Awso, Tsinkanet, and Mai Gassa I) in Tigray, northern Ethiopia. Species composition differed among reservoirs. Our data on fish catch densities and the fullness of the foregut suggest that the ecology of the Garra populations in the reservoirs is likely influenced by the avoidance of predation by birds. G. blanfordii, and to a lesser extent G. geba, foraged most actively after sunset.