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.
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.
Flies are considered serious pests which cause health problems of human and animal, transmitting many pathogenic microbes. Pest management programs depend on proper identification of pests. The present research work is an initiative to identify the medically and veterinary important flies based on mitochondrial COI gene sequences. Eleven species of the fly pests were identified. Among them, four fly species were the first record from Bangladesh. The phylogenetic analysis of retrieved sequences confirmed that the evolution of these species occurred from a common ancestor. Highest AT percentage (69.9%) was found in Haematobia irritans exigua and lowest GC percentage (30.4%) was found in Haematobia irritans exigua. The substitution rate of codon was found 1.88 in 1st position, 0.73 in 2nd position and 1.22 in 3rd position, respectively. Interspecific genetic divergence range of flies sequences was 5-20%. Haplotype network showed that Atylotus agrestis was mostly diverged from its common ancestors by 37 mutational steps. This research is the first molecular approach to identify the medically and veterinary important flies based on MT-COI gene sequences along with the establishment of first DNA barcode dataset for accurate identification in Bangladesh.
Stored grain pests are discovered in food as immature stages, which further complicates the identification process. A DNA barcode dataset of some important pests that can be used for easy and confirm identification in stages of life is constructed. COI genes of three stored grain insect pests i.e,, Sitophilus oryzae, Callosobruchus chinensis and Oryzaephilus surinamensis were sequenced. The sequenced genes were submitted to NCBI GenBank and obtained accession numbers MG967331.1, MG967332.1, MG967333.1 and MK041216.1. BLAST analysis showed 99 to 100% homology with existing GenBank sequences. The nucleotide composition analysis revealed that the value of A+T (64.8%) is greater than G+C (35.2%). Genetic distance among four sequences of three store pests were ranged from 0.00293-0.32807. Phylogenetic analysis showed that these three species are originated from different clades. Haplotype analysis of mitochondrial COI gene of the stored grain insect pests showed high genetic diversity among them. C. chinensis, O. surinamensis and S. oryzae were separated from their common ancestor by 80, 73 and 64 mutational steps. These information may be helpful for attempting any successful control measures against the pest species. In conclusion, present author established the first DNA barcode dataset of three store grain pests and confirmed its efficiency for identifying these pests. Bangladesh J. Zool. 47(1): 1-11, 2019
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