ABSTRACT
Background & objectives: Malaria is a major public health problem in Tripura and focal disease outbreaks are of frequent occurrence. The State is co-endemic for both Plasmodium falciparum and P. vivax and transmission is perennial and persistent. The present study was aimed to review data on disease distribution to prioritize high-risk districts, and to study seasonal prevalence of disease vectors and their bionomical characteristics to help formulate vector species-specific interventions for malaria control. Methods: Data on malaria morbidity in the State were reviewed retrospectively (2008-2012) for understanding disease distribution and transmission dynamics. Cross-sectional mass blood surveys were conducted in malaria endemic villages of South Tripura district to ascertain the prevalence of malaria and proportions of parasite species. Mosquito collections were made in human dwellings of malaria endemic villages aiming at vector incrimination and to study relative abundance, resting and feeding preferences, and their present susceptibility status to DDT. Results: The study showed that malaria was widely prevalent and P. falciparum was the predominant infection (>90%), the remaining were P. vivax cases. The disease distribution, however, was uneven with large concentration of cases in districts of South Tripura and Dhalai coinciding with vast forest cover and tribal populations. Both Anopheles minimus s.s. and An. baimaii were recorded to be prevalent and observed to be highly anthropophagic and susceptible to DDT. Of these, An. minimus was incriminated (sporozoite infection rate 4.92%), and its bionomical characteristics revealed this species to be largely indoor resting and endophagic. Interpretation & conclusions: For effective control of malaria in the State, it is recommended that diseases surveillance should be robust, and vector control interventions including DDT spray coverage, mass distribution of insecticide-treated nets/ long-lasting insecticidal nets should be intensified prioritizing population groups most at risk to avert impending disease outbreaks and spread of drug-resistant malaria.
ABSTRACT
Background & objectives: the northeastern states of India are co-endemic for Plasmodium falciparum and P. vivax malaria. The transmission intensity is low-to-moderate resulting in intermediate to stable malaria. Malaria control prioritized P. falciparum being the predominant and life threatening infection (>70%). P. vivax malaria remained somewhat neglected. The present study provides a status report of P. vivax malaria in the northeastern States of India. Methods: Data on spatial distribution of P. vivax from seven northeastern states (Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland and Tripura) were analysed retrospectively from 2008–2013. In addition, cross-sectional malarial surveys were conducted during 1991-2012 in malaria endemic pockets across the states of Assam, Meghalaya, Mizoram and Tripura to ascertain the prevalence of P. vivax in different age groups. Results: Vivax malaria was encountered in all northeastern States but there existed a clear division of two malaria ecotypes supporting ≤30 and >30 per cent of total malaria cases. High proportions of P. vivax cases (60–80%) were seen in Arunachal Pradesh and Nagaland in the north with alpine environment, 42-67 per cent in Manipur, whereas in Assam it varied from 23-31 per cent with subtropical and tropical climate. Meghalaya, Tripura and Mizoram had the lowest proportion of P. vivax cases. Malaria cases were recorded in all age groups but a higher proportion of P. vivax consistently occurred among <5 yr age group compared to P. falciparum (P<0.05). P. vivax cases were recorded throughout the year with peak coinciding with rainy season although transmission intensity and duration varied. Interpretation & conclusions: In northeast India, P. vivax is a neglected infection. Estimating the relapsing pattern and transmission dynamics of P. vivax in various ecological settings is an important pre-requisite for planning malaria elimination in the northeastern states.
ABSTRACT
Background & objectives: Plasmodium falciparum is the leading cause of mortality and causes cerebral malaria associated with sequestration caused by cytoadherence of the trophozoite and schizont-infected erythrocytes to the endothelial cells of the deep vascular beds in the brain. Pathophysiology of malaria is complicated by rosetting. Rosetting is a process of binding of uninfected erythrocytes to the erythrocytes infected with mature asexual parasites and is controlled by expression of complement receptor 1 (CR1) on RBC surface. Various polymorphic forms of CR1 are known including molecular weight polymorphism, red blood cell expression levels/density polymorphism and Knops (KN) polymorphism. The Knops blood group includes several allelic pairs; Knops a and b (Kna and Knb), McCoy a and b (McCa, McCb), Swain-Langley (Sla), and Villien (Vil). Knops phenotype Sl (a–) has been found to rosette less effectively than Sl (a+) and hence suggested to be more protective. P. falciparum cases have not reduced much as compared to the reduction in the total number of malaria cases in the past few years. In addition, P. falciparum is the leading cause for all mortality and most of the morbidity in India. We, therefore, investigated the role of CR1 Knops polymorphism in the pathophysiology of malaria in Indian population. Methods: A case control approach was used for this study. CAPS (Cleaved amplified polymorphic sequence) methodology was adopted. A total of 100 normal individuals (free from any ailment) and 100 individuals suffering from P. falciparum infection (uncomplicated malaria) were recruited for this study. Results: We found that in Indian population (normal individuals and P. falciparum-infected individuals), only the wild type allele is present. Interpretation & conclusion: We concluded that the process of rosetting in the Indian context could be occurring independently of the effect of Knops polymorphism and in part could be controlled by other polymorphisms of the CR1 gene (density and structural polymorphism).
ABSTRACT
A standardised protocol has been developed by World Health Organization (CDS/RBM/2002) to assess the efficacy of common antimalarials in the treatment of clinically manifested infection with uncomplicated P. falciparum malaria for areas with low to moderate transmission. The therapeutic efficacy protocol is based on clinical and parasitological responses of the patients and it has the purpose of determining the practical efficacy of the drug regimen in study areas with the ultimate objective of ascertaining its continued usefulness or the necessity for replacing it in the routine treatment. Present study has been conducted at seven sites--Kathiatali and Simonabasti of District Nowgaon, Assam; Sonapur and Boko of District Kamrup, Assam; Keonjhar Town, Padampur and Basudebpur of District Keonjhar, Orissa. In order to reduce the patient recruitment time, health centre close to well-defined community was identified to conduct the activities at peak malaria season by selecting local pockets and organising mobile clinics. Microscopically confirmed cases of P. falciparum were enrolled according to the criteria for inclusion and exclusion. Treatment with recommended drug was given under supervision and a follow-up schedule at various intervals for 28 days was maintained. In chloroquine (CQ) study areas, wherever patients showed treatment failure, they were treated with second line drug--sulphadoxine-pyrimethamine (SP) combination and then followed-up as per study protocol. It was observed that 30% cases showed treatment failure to CQ in District Nowgaon, where revised drug policy has already been introduced. In Kamrup district, treatment failure with CQ was found to be less than 25%, which denotes the said regimen is still effective. Almost all the patients from Padampur and Basudebpur of District Keonjhar responded to CQ, treatment failure was noticed only in two patients (3%). The antifolate combination found to be fully effective as second line and also as first line wherever revised drug policy has been introduced.