Physiographic and entomologic risk factors of malaria in Assam, India.
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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ABSTRACT: Anopheles annularis is one of the major vectors of malaria in Odisha, India. The present study was undertaken to determine the vectorial capacity and assess the genetic diversity of An. annularis collected from different endemic regions of Odisha. Mosquitoes were collected from thirteen endemic districts using standard entomological collection methods from 2009-2011. Sibling species of An. annularis were identified by PCR-RFLP and sequencing of D3 region of 28S ribosomal DNA (rDNA) region. Plasmodium falciparum (Pf) sporozoite rate and human blood fed percentage (HBF) were estimated by multiplex PCR using Pf and human specific primers. Genetic diversity of An. annularis was estimated by ISSR markers. Out of 1647 An. annularis collected, 1353 (82.15%) were collected by mechanical aspirators and 294 (17.85%) by light trap. 49 (2.97%) were positive for human blood and 18 (1.09%) were positive for Pf sporozoite. PCR-RFLP and sequencing analyses detected only An annularis A in the study areas. Overall genetic differentiation among An. annularis populations was moderate (FST=0.048) and showed significant correlation between genetic distance and geographic distance (r=0.882; P<0.05). Angul population proved to be genetically unique and was highly divergent FST>0.110) from other populations, suggesting low gene flow between them. The study indicated that only An. annularis A was found in Odisha with potential vectorial capacity that can play a major role in malaria transmission. ISSR markers proved to be useful molecular tools to evaluate genetic variability in An. annularis populations.Acta tropica 05/2014; · 2.79 Impact Factor
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ABSTRACT: WHO has reported that RDT and microscopy-confirmed malaria cases have declined in recent years. However, it is still unclear if this reflects a real decrease in incidence in Bangladesh, as particularly the hilly and forested areas of the Chittagong Hill Tract (CHT) Districts report more than 80% of all cases and deaths. PCR-confirmed surveillance and epidemiological data on malaria from the CHT are limited; existing data report Plasmodium falciparum and Plasmodium vivax as the dominant species. A cross-sectional survey was conducted in the District of Bandarban, the southernmost of the three Hill Tracts Districts, to collect district-wide malaria prevalence data from one of the regions with the highest malaria endemicity in Bangladesh. A multistage cluster sampling technique was used to collect blood samples from febrile and afebrile participants and malaria microscopy and standardized nested PCR for diagnosis were performed. Demographic data, vital signs and splenomegaly were recorded. Malaria prevalence across all subdistricts in the monsoon season was 30.7% (95% CI: 28.3-33.2) and 14.2% (95% CI: 12.5-16.2) by PCR and microscopy, respectively. Plasmodium falciparum mono-infections accounted for 58.9%, P. vivax mono-infections for 13.6%, Plasmodium malariae for 1.8%, and Plasmodium ovale for 1.4% of all positive cases. In 24.4% of all cases mixed infections were identified by PCR. The proportion of asymptomatic infections among PCR-confirmed cases was 77.0%, oligosymptomatic and symptomatic cases accounted for only 19.8 and 3.2%, respectively. Significantly (p < 0.01) more asymptomatic cases were recorded among participants older than 15 years as compared to younger participants, whereas prevalence and parasite density were significantly (p < 0.01) higher in patients younger than 15 years. Spleen rate and malaria prevalence in two to nine year olds were 18.6 and 34.6%, respectively. No significant difference in malaria prevalence and parasite density was observed between dry and rainy season. A large proportion of asymptomatic plasmodial infections was found which likely act as a reservoir of transmission. This has major implications for ongoing malaria control programmes that are based on the treatment of symptomatic patients. These findings highlight the need for new intervention strategies targeting asymptomatic carriers.Malaria Journal 01/2014; 13(1):16. · 3.49 Impact Factor
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ABSTRACT: Febrile illness is the most common symptom experienced by patients suspected of having malaria, especially in the malaria endemic areas of northeast India. Hospital-based data from two districts of upper Assam, namely Golaghat and Tinsukia, were analysed to assess the prevalence of malaria among inpatients who reported to health centres with febrile illness. A total of 16 hospitals were selected for the study. These included six government hospitals (three in rural and three in urban areas) and 10 private hospitals, which included four tea-garden hospitals. Selection was dependant on the availability of patients and inpatient treatment facilities. During the study, a total of 350 inpatients reported to the selected hospitals with fever; 324 were suspected of having malaria and were interviewed and included in the study. The average age of patients was 24.2±15.2 years and 63.3% (205/324) of them were male. The majority of patients (77.5%; 251/324) belonged to the lower household income category (<5000 Indian rupees) and travelled to the nearest town or city for treatment. Overall, the prevalence of malaria (as diagnosed by clinical examination and blood tests) across the different categories such as location, types of hospitals and household income was found to be 29.9% (97/324). Multivariate analysis revealed that the adjusted odds ratios (AOR) of malaria cases was higher based on location (2.13), type of health centre (1.75) and the distance travelled to a health centre (2.09). The mean duration of hospital treatment was 4.2±3.6 days and the delay in reporting to hospital was 3.9±2.6 days. The study emphasises the need to strengthen and improve the treatment facilities for malaria in government hospitals, and to create more awareness among people regarding early treatment, especially in the rural periphery villages of the endemic areas.International Health 05/2014; · 1.01 Impact Factor