Sunday, 26 June 2011

Malaria: Amazon and Ethiopia

The following new articles have just been published in Malaria Journal

Population dynamics, structure and behaviour of Anopheles darlingi in a rural settlement in the Amazon rainforest of Acre, Brazil
Moutinho PR, Gil LH, Cruz RB, Ribolla PE Malaria Journal 2011, 10:174 (24 June 2011)

Anopheles darlingi is the major vector of malaria in South America, and its behaviour and distribution has epidemiological importance to biomedical research. In Brazil, An. darlingi is found in the northern area of the Amazon basin, where 99.5% of the disease is reported.

The study area, known as Ramal do Granada, is a rural settlement inside the Amazon basin in the state of Acre. Population variations and density have been analysed by species behaviour, and molecular analysis has been measured by ND4 mitochondrial gene sequencing.

The results show higher density in collections near a recent settlement, suggesting that a high level of colonization decreases the vector presence. The biting activity showed higher activity at twilight and major numbers of mosquitoes in the remaining hours of the night in months of high density. From a sample of 110 individual mosquitoes, 18 different haplotypes were presented with a diversity index of 0.895, which is higher than that found in other Anopheles studies.

Anopheles darlingi depends on forested regions for their larval and adult survival. In months with higher population density, the presence of mosquitoes persisted in the second part of the night, increasing the vector capacity of the species. Despite the intra-population variation in the transition to rainy season, the seasonal distribution of haplotypes shows no change in the structure population of An. darlingi.

Urban malaria and associated risk factors in Jimma town, south-west Ethiopia Alemu A, Tsegaye W, Golassa L, Abebe G
Malaria Journal 2011, 10:173 (24 June 2011)

Malaria kills millions around the world. Until recently it was believed to be a disease of rural areas, since the Anopheles mosquito, which transmits Plasmodium species breeds in rural areas. Urban malaria is emerging as a potential, but "avertable" crisis, in Africa. In view of the rapidly growing number of small and medium-sized towns in Ethiopia there is a pressing need to improve the understanding of the epidemiology of malaria. Therefore, the aim of this study was to determine malaria prevalence and associated risk factors in Jimma town.

A cross-sectional study was carried out in Jimma town from April 1 to May 28, 2010. 804 study participants were included from 291 households for microscopic examination of malaria parasites. Socio-demography data and risk factors were collected using structured questionnaires. Logistic regression analysis was done using SPSS 15.0 statistical software.

From a total of 804 study participants in current survey only 42 (5.2%) were positive for malaria parasites. Plasmodium vivax, Plasmodium falciparum and mixed infection accounted 71.4%, 26.2% and 2.4%, respectively. Higher malaria prevalence rate was observed among under-five children (11%). Those who do not use insecticide-treated bed nets (ITN) were more likely to be infected with malaria (OR=13.6; 95% CI 4.9-37.2, p<0.001) compared with those who use the ITN. Living in areas where stagnant water existed (OR=2.1; 95% CI 1.00-4.2, p=0.047) and its distance of existence <1 km from the house(OR=2.1; 95% CI 2.0-15.8, p=0.001) were more likely to be infected with malaria parasite compared with those who live away from stagnant at a distance greater than 1 km.

Malaria is a major health problem with P. vivax becoming a predominant species in the town. The prevalence was strongly associated with proximity of residence to potential mosquito breeding sites. Malaria is affecting significant proportions of the urban settlers and human activities nevertheless play an important role in bringing the mosquito breeding sites closer to residences.

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