BackgroundThe relationship between climatic factors and mosquito abundance is very important to determine parasite activity levels and, therefore, disease risk. Therefore, this study was conducted to investigate the seasonal abundance of anophelines and their association with meteorological variables and disease transmission in two malaria endemic areas of Bangladesh.MethodsMonthly sampling was done from both indoors and outdoors in 12 selected houses using light traps (LTs) and pyrethrum spray (PS) during January, 2011 to January, 2012 in two malaria endemic areas of Bangladesh. Outdoor rainfall, temperature, and relative humidity data of the study areas were collected from the meteorological department of Bangladesh. Mosquitoes were killed with chloroform and identified morphologically under stereoscopic microscopes using taxonomic keys. Samples were tested for CSP of P. falciparum, P. vivax 210 and P. vivax 247 using ELISA. Pearson correlation and canonical correspondence analyses (CCA) were computed to investigate the associations with species abundance and rainfall, temperature, humidity and malaria cases.ResultsA total of 2,443 female anophelines, representing 22 species were captured. Every female Anopheles were tested for P. falciparum, P. vivax 210 and P. vivax 247 CSP, of which 10 species were found positive. The CSP positive species were An. annularis, An. baimaii, An. barbirostris, An. jeyporiensis, An. karwari, An. minimus s.l., An. philippinensis, An. umbrosus, An. vagus and An. wilmori. Anopheles vagus and An. philippinensis were the dominant species present almost throughout the year with highest peaks in March and smallest peaks in September but An. baimaii and An. willmori were found during monsoon (July -September) only. Lag rainfall and relative humidity were the most significant variables influencing An. baimaii, An. willmori, An. vagus, and An. subpictus density in Kumari area. Abundance of these four species positively related to malaria cases. The effects of temperature were not found as a significant variable on the abundance of anophelines mosquitoes in Bangladesh.ConclusionsOur study demonstrates that the nature of relationship between malaria vector and climatic variables were multifaceted. Detailed studies of vector bionomics, continuous monitoring and malaria transmission dynamics is essential for predicting disease outbreaks and vector control in the region.
BackgroundBlood-feeding patterns of mosquitoes are crucial for incriminating malaria vectors. However, little information is available on the host preferences of Anopheles mosquitoes in Bangladesh. Therefore, the objective of the present study was to determine the hematophagic tendencies of the anophelines inhabiting a malaria-endemic area of Bangladesh.MethodsAdult Anopheles mosquitoes were collected using light traps (LTs), pyrethrum spray (PS), and human bait (HB) from a malaria-endemic village (Kumari, Bandarban, Bangladesh) during the peak months of malaria transmission (August-September). Enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) were performed to identify the host blood meals of Anopheles mosquitoes.ResultsIn total, 2456 female anopheline mosquitoes representing 21 species were collected from the study area. Anopheles vagus Doenitz (35.71%) was the dominant species followed by An. philippinensis Ludlow (26.67%) and An. minimus s.l. Theobald (5.78%). All species were collected by LTs set indoors (n = 1094), 19 species were from outdoors (n = 784), whereas, six by PS (n = 549) and four species by HB (n = 29). Anopheline species composition significantly differed between every possible combination of the three collection methods (χ2 test, P < 0.001). Host blood meals were successfully detected from 1318 (53.66%) Anopheles samples belonging to 17 species. Values of the human blood index (HBI) of anophelines collected from indoors and outdoors were 6.96% and 11.73%, respectively. The highest values of HBI were found in An. baimai Baimaii (80%), followed by An. minimus s.l. (43.64%) and An. annularis Van den Wulp (37.50%). Anopheles baimai (Bi = 0.63) and An. minimus s.l. (Bi = 0.24) showed strong relative preferences (Bi) for humans among all hosts (human, bovine, goats/sheep, and others). Anopheles annularis, An. maculatus s.l. Theobald, and An. pallidus Theobald exhibited opportunistic blood-feeding behavior, in that they fed on either humans or animals, depending on whichever was accessible. The remaining 12 species preferred bovines as hosts.ConclusionsThe observed high anthropophilic nature of An. baimai, An. minimus s.l., and An. annularis revealed these species to be important malaria vectors in hilly areas of Bangladesh. Higher values of HBI in outdoor-resting mosquitoes indicated that indoor collection alone is not adequate for evaluating malaria transmission in the area.
Mosquito larvae are purely aquatic and develop in water bodies, the type of which is more or less specific to each species. Therefore, a study was carried out to identify the habitat characters of different mosquito species along with their species composition in semi-urban area of Dhaka in Bangladesh during the month of May and June 2012. A total of 6088 mosquito larvae belonging to 12 species (Aedes aegypti, Aedes albopictus, Anopheles barbirostris, Anopheles peditaeniatus, Anopheles vagus, Culex gelidus, Culex hutchinsoni, Culex quinquefasciatus, Culex tritaeniorhynchus, Mansonia annulifera, Mansonia uniformis, and Toxorhynchites splendens) under 5 genera were collected from 14 different types of habitats. Culex quinquefsciatus was the dominant (21.7/500 ml) species followed by Cx. tritaeniorhynchus (10.53/500 ml). Dissolved oxygen and chlorophyll a were the preeminent predictors for the abundance of all collected mosquito larvae except Ae. aegypti. Water temperature was positively associated with the breeding of An. vagus (r = 0.421, p = <0.001), An. barbirostris (r = 0.489, p = <0.001) and An. peditaeniatus (r = 0.375, p = <0.001). Water depth, distance from nearest house, emergent plant coverage, and alkalinity were found as the basis of larval abundance. Every Culex species and Tx. splendens (r = 0.359, p = 0.001) were found positively associated with chemical oxygen demand, while Mn. annulifera showed negative association (r = -0.115, p = 0.0297). This study also highlighted that various physicochemical factors affect the presence or abundance of mosquito larvae.
BackgroundA clear understanding of the social and behavioral risk factors, and knowledge gaps, related to exposure to malaria are essential when developing guidelines and recommendations for more effective disease prevention in many malaria endemic areas of the world including Bangladesh and elsewhere in the South East Asia. To-date, the level of knowledge that human populations, residing in moderate to high malaria risk zones, have with respect to the basic pathogen transmission dynamics, risk factors for malaria or disease preventative strategies, has not been assessed in Bangladesh. The purpose of this study was to address this gap by conducting surveys of the knowledge, attitudes and practices (KAP) of people, from variable socio-demographic backgrounds, residing in selected rural malaria endemic areas in Bangladesh.MethodsThe KAP survey was conducted in portions of six different malaria endemic districts in Bangladesh from July to October 2011. The survey consisted of interviewing residence of these malaria endemic districts using a structured questionnaire and interviewers also completed observational checklists at each household where people were interviewed. The study area was further divided into two zones (1 and 2) based on differences in the physical geography and level of malaria endemicity in the two zones. Data from the questionnaires and observational checklists were analysised using Statistical Package for Social Sciences 16.0 (SPSS, Inc., Chicago, IL, USA).ResultsA total of 468 individuals from individual households were interviewed, and most respondents were female. Monthly incomes varied within and among the zones. It was found that 46.4% and 41% of respondents’ family had malaria within the past one year in zones 1 and 2, respectively. Nearly 86% of the respondents did not know the exact cause of malaria or the role of Anopheles mosquitoes in the pathogen’s transmission. Knowledge on malaria transmission and symptoms of the respondents of zones 1 and 2 were significantly (p<0.01) different. The majority of respondents from both zones believed that bed nets were the main protective measure against malaria, but a significant relationship was not found between the use of bed net and prevalence of malaria. A significant relationship (p<0.05) between level of education with malaria prevalence was found in zone 1. There was a positive correlation between the number of family members and the prevalence of malaria. Houses with walls had a strong positive association with malaria. Approximately 50% of the households of zones 1 and 2 maintained that they suffered from malaria within the last year. A significant association (p<0.01) between malaria and the possession of domestic animals in their houses was found in both zones. People who spent time outside in the evening were more likely to contract malaria than those who did not.ConclusionTo address the shortcomings in local knowledge about malaria, health personnel working in malaria endemic areas should be trained to give more appropriate counseling i...
Circumsporozoite protein enzyme-linked immunosorbent assays (CSP-ELISA) are widely used for malaria vector identification throughout the world. However, several studies have reported false-positive results when using this method. The present study was conducted to estimate the frequency of false positives among anopheline species in malaria endemic areas of Bangladesh. In total, 4,724 Anopheles females belonging to 25 species were collected and tested for Plasmodium falciparum, Plasmodium vivax-210, and P. vivax-247 CSP. Initially, 144 samples tested positive using routine CSP-ELISA, but the number of positive results declined to 85 (59%) when the samples were tested after heating at 100 0 C for 10 min to remove false-positive specimens.
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