Physiographic and entomologic risk factors of malaria in Assam, India

Malaria Research Centre (Indian Council of Medical Research), PO Sonapur, Kamrup, Assam 782 402, India.
The American journal of tropical medicine and hygiene (Impact Factor: 2.74). 11/2004; 71(4):451-6.
Source: PubMed

ABSTRACT Fever surveys were conducted in several districts of the Indian state of Assam to ascertain the prevalence of malaria in relation to vector abundance, entomologic inoculation rates (EIRs), and geographic location of human settlements. Anopheles minimus were incriminated, but their relative abundance and biting rates varied among districts, and no significant correlation was observed between these two indicators (r = 0.43, P = 0.34). Plasmodium falciparum was the predominant parasite species except in two districts where P. vivax was the majority parasite. The EIRs per person/night were 0.46-0.71 in P. falciparum-predominant areas and 0.12 in the district where P. vivax predominated. The correlation of percentage of fever cases positive for malaria infection in each district with the corresponding EIR was not significant (r = 0.6, P = 0.21). Malaria cases were detected in all months of the year but peaked during May-June, which corresponded to the months of heavy rainfall. These were also the months with highest incidence of infection with P. falciparum. Malaria cases were observed in all age groups of both sexes, and there was clustering of cases in villages near the vector-breeding habitat (perennial seepage streams), and foothill villages. However, malaria incidences were consistently lower in villages within 5 km of the nearest health care facility, which were in town areas. The data presented are indicative of low-to-moderate levels of malaria transmission by An. minimus, and would be of value for developing future intervention strategies.

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    • "The state of Assam and AP alone contributes 42% and 12% of malaria cases respectively in the NER [5] . Assam alone shares more than 5% of cases reported in India annually [6] . "
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    ABSTRACT: To depict mitochondrial genetic variation for the first time among Anopheles minimus (An.minimus) (Diptera: Culicidae) species from two malaria endemic states of NE India. Phylogeographic analysis was carried at 9 out of 12 sites of An.minimus confirmed malaria endemic places. All sequences were Adenine-Thymine rich regions. Transitions were observed in 6 sequences where 5 mutations were synonymous substitutions and in 1 case non synonymous mutation was observed. Three distinct clusters of haplotypes were generated. Haplotype diversity and low nucleotide diversity were studied. Overall negative values obtained from Tajima's D test and Fu'sFS test indicate a recent genetic population expansion. Network analysis has explained sequence diversity that was also shown by mutations in 6 sequences. High genetic diversity observed within the populations of An.minimus species has several possible implications for vector control in the region. Copyright © 2014 Hainan Medical College. Published by Elsevier B.V. All rights reserved.
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    • "The deforestation, human resettlement and developmental programmes singly or in combination increased the morbidity and mortality from emergent parasitic diseases (Patz et al. 2000). The state of Assam is very much vulnerable to malaria because of its location in the tropical region with humid climatic condition throughout the year (Mohapatra et al. 2001, Dev et al. 2004, Pardal et al. 2009, Dhiman et al. 2010). Despite of taking many preventive measures in Assam, the transmission of malaria continues to be uninterrupted and has increased in recent times. "
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    • "The declined chance of acquiring malaria infection with the increase in age of individual is due to progressive development of protective immunity (Sharma et al. 2004; Mayor et al. 2007). Significant variation of malaria prevalence among the different age groups has been reported in northeastern part of India (Dev et al. 2004). The persistence of P. falciparum is attributed to the emergence of drug resistant varieties, inadequate interventions and treatment seeking patterns in the communities (Singh et al. 2004; Mishra et al. 2002). "
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