Characterization and monitoring of deltamethrin-resistance in Anopheles culicifacies in the presence of a long-lasting insecticide-treated net intervention.

BACKGROUND: Deltamethrin-impregnated, long-lasting insecticidal nets (LLINs) were distributed in the study area from November 2014 to January 2015 to evaluate their impact on malaria transmission in the presence of insecticide-resistant vectors. Studies were carried out in 16 selected clusters in Keshkal sub-district, Chhattisgarh State, India to monitor and characterize deltamethrin resistance in Anopheles culicifacies sensu lato. RESULTS: Deltamethrin susceptibility of An. culicifacies decreased in a post-LLIN survey compared to a pre-LLIN survey and was not significant (p > 0.05) while, the knockdown values showed significant increase (p < 0.05). Pre-exposure to piperonyl butoxide, triphenyl phosphate showed synergism against deltamethrin (p < 0.001). Biochemical assays showed significantly (p < 0.05) elevated monooxygenases in 3 of 5 clusters in post-LLIN survey-I that increased to 10 of 11 clusters in post-LLIN survey-II, while esterases were found significantly elevated in all clusters and both enzymes were involved in conferring pyrethroid resistance, not discounting the involvement of kdr (L1014L/S) gene that was heterozygous and at low frequency (4-5%). CONCLUSION: This field study, in a tribal district of India, after distribution of deltamethrin-impregnated LLINs showed decrease in deltamethrin susceptibility in An. culicifacies, a major vector of malaria in this study area and in India. Results indicated development of resistance as imminent with the increase in insecticide selection pressure. There is an urgent need to develop new vector control tools, with insecticide classes having novel mechanisms of resistance, to avoid or delay the onset of resistance. Regular insecticide resistance monitoring and mechanistic studies should be the priority for the malaria control programmes to suggest strategies for insecticide resistance management. The global commitment to eliminate malaria by 2030 needs various efforts that include development of combination vector control products and interventions and few are becoming available.

Monitoring of long-lasting insecticidal nets (LLINs) coverage versus utilization: a community-based survey in malaria endemic villages of Central India.

BACKGROUND: Despite the known effectiveness of long-lasting insecticidal nets (LLINs) in providing protection against malaria, high level of ownership and use are very difficult to achieve and maintain. Nearly 40,000 LLINs were distributed in 2014 as an intervention tool against malaria transmission in 80 villages of Keshkal sub-district in Chhattisgarh, India. This study assessed LLIN coverage, access, utilization pattern, and key determinants for the net use 1 year after mass distribution. METHODS: In 2015, a cross-sectional household survey was carried out in 80 study clusters (whole village or part of village). From each cluster, 40 households were randomly selected and interviewed using a structured questionnaire adapted from the malaria indicator survey of Roll Back Malaria guidelines. Information on demographic characteristics, LLIN ownership, and its use on the night before the survey, and physical condition of LLINs were recorded. RESULTS: 2970 households were interviewed with a total of 15,003 individuals present in the households during the night before the survey. Nearly 98% of households had at least one LLIN and 59.4% of the surveyed population reportedly used an LLIN the previous night. LLIN use varied from 41 to 94% between the study clusters. Nearly 89% of the LLINs were found in good physical condition (without holes). However, proportion of household with at least one LLIN per two persons was only 39%. CONCLUSION: Universal coverage of LLINs was inadequate in the study clusters making it difficult for all household members to use an LLIN. LLIN use varied between clusters and was highest in children under 5 years of age. Health education campaigns and creating awareness about the benefit of sleeping under the LLINs in providing protection against malaria is required not only to high risk groups of pregnant women and children below 5 years of age but all the members of the family to have an epidemiological impact of this intervention at the community level. Relatively high net use despite poor access to LLINs indicates an overall desire to use nets when they are available. The main barrier to increased use of nets is the low coverage at household level.

Additional burden of asymptomatic and sub-patent malaria infections during low transmission season in forested tribal villages in Chhattisgarh, India.

BACKGROUND: The burden of sub-patent malaria is difficult to recognize in low endemic areas due to limitation of diagnostic tools, and techniques. Polymerase chain reaction (PCR), a molecular based technique, is one of the key methods for detection of low parasite density infections. The study objective was to assess the additional burden of asymptomatic and sub-patent malaria infection among tribal populations inhabiting three endemic villages in Keshkal sub-district, Chhattisgarh, India. A cross-sectional survey was conducted in March-June 2016, during the low transmission season, to measure and compare prevalence of malaria infection using three diagnostics: rapid diagnostic test, microscopy and nested-PCR. RESULTS: Out of 437 individuals enrolled in the study, 103 (23.6%) were malaria positive by PCR and/or microscopy of whom 89.3% were Plasmodium falciparum cases, 77.7% were afebrile and 35.9% had sub-patent infections. CONCLUSIONS: A substantial number of asymptomatic and sub-patent malaria infections were identified in the survey. Hence, strategies for identifying and reducing the hidden burden of asymptomatic and sub-patent infections should focus on forest rural tribal areas using more sensitive molecular diagnostic methods to curtail malaria transmission.

Involvement of Mitanins (female health volunteers) in active malaria surveillance, determinants and challenges in tribal populated malaria endemic villages of Chhattisgarh, India.

BACKGROUND: Accredited Social Health Activists (ASHA), female health volunteers working at village level have become an integral component of National Health Mission (NHM) in India in the past two decades. Mitanin (meaning female friend in local dialect), a precursor of ASHA, play an indispensable role in early detection of health related problems and are helping in improving overall community health status in Chhattisgarh state. The current study was carried out to evaluate the feasibility of involving Mitanin in active malaria surveillance work in 80 tribal villages of Chhattisgarh and to explore the challenges and determinants to perform malaria surveillance activities by the Mitanins. METHODS: A total of 162 Mitanins were selected and divided into two age and village matched groups. The first group (training plus) of Mitanins were given additional training in malaria surveillance activities in whilst the second (standard) group received routine training. All Mitanins were interviewed using a structured questionnaire. In-depth interviews were also conducted among randomly selected sub groups of Mitanins (five from each group) after the completion of the quantitative survey. Performance of Mitanins was evaluated using pre-defined grading scores (A-E) which included various factors such as educational qualifications and knowledge about malaria, its signs and symptoms and knowledge, attitude and treatment practices. RESULTS: More number of Mitanins in training plus group has showed better performance (≥ B) than those in the standard group of Mitanins (80% vs 43.5%, p = 0.001) after adjusting for socio-demographic factors. Based on the outcome of in-depth interviews, Mitanin's lack of adequate support from supervisors, delayed payment of incentives and lack of appreciation were the major challenges mentioned. CONCLUSION: Mitanins can play an effective role in active fever surveillance for malaria besides performing other health related tasks at sub-village level after focused education on malaria related activities and proper supervision.

Impact of long-lasting insecticidal nets on prevalence of subclinical malaria among children in the presence of pyrethroid resistance in Anopheles culicifacies in Central India.

BACKGROUND: Subclinical (asymptomatic) cases of malaria could be a major barrier to the success of malaria elimination programs. This study has evaluated the impact of long-lasting insecticidal nets (LLINs) on the prevalence of subclinical malaria in the presence of pyrethroid resistance in the main malaria vector Anopheles culicifacies on malaria transmission among a cohort of children in villages of the Keshkal sub-district in Chhattisgarh state. METHODS: A cohort of 6582 children ages less than 14 years was enrolled from 80 study clusters. Post monsoon survey was carried out at baseline before LLIN distribution, and 5862 children were followed up in the subsequent year. Study outcomes included assessment of subclinical malarial infections and use of LLINs among the study cohort in the presence of varied levels of pyrethroid resistance. FINDINGS: In the baseline survey, the proportion of subclinical malaria was 6·1%. LLIN use during the previous night was 94·8%. Overall, prevalence of subclinical malaria was significantly reduced to 1% (p<0·001) in the second survey. LLIN users were protected from malaria (OR: 0·25, 95% CI=0·12-0·52, p<0.001) and subclinical malaria (OR: 0·25, 95% CI=0·11-0·58, p=0·001) despite the presence of pyrethroid resistance in the study area. INTERPRETATION: In this low transmission area, sleeping under LLINs significantly reduced the burden of malaria among children. In the presence of pyrethroid resistant malaria vector, a high LLIN use of 94·5% was observed to have significantly brought down the proportion of subclinical malaria among the cohort children.

Effect of ß-glucan on the immune response of early stage of Anabas testudineus (Bloch) challenged with fungus Saprolegnia parasitica.

The present study was carried out to study the effect of different dosages of ß-glucan suspension on immune response and disease resistance in Anabas testudineus spawns against a fungal pathogen Saprolegnia parasitica. Eight day old spawns were exposed for 3 h in four different dosages of ß-glucan suspension in phosphate buffered saline at the rate of 0, 5, 10, 15 mg l(-1). The cell suspension of spawn was assayed for total protein, acid phosphate, lysozyme, bactericidal and NBT activity. The spawns were then challenged with 3x10(5) CFU ml(-1) of S. parasitica. The survivability percentage and immunological parameters were assayed upto day 7. Exposure of fish for 3h to all the concentrations of ß-glucan recorded a significant enhancement in the immunological parameters such as lysozyme activity, bactericidal activity and NBT activity by the end of day 7. The challenge study indicated least mortality in the groups exposed to 10 mgl(-1) and 15 mgl(-1) but 15 mgl(-1) gives little higher survivability. Thus 3 h exposure of ß-glucan suspension could reduce the mortality and increase the immunity of A. testudineus spawns against S. parasitica.

Effect of beta-glucan on immunity and survival of early stage of Anabas testudineus (Bloch).

The present experiment was carried out to study the effect of different dosages of beta-glucan suspension derived from barley on the innate immune response and disease resistance of Anabas testudineus spawns against infection caused by Aeromonas hydrophila. Four different dosages of beta-glucan suspension in phosphate buffered saline at the rate of 0, 5, 10, 15 mg l(-1) were taken and 8 days old spawn were exposed for 2 h and 3 h. The cell suspension of spawn was assayed for total protein, acid phosphatase activity, lysozyme activity, bactericidal and NBT. Further, the spawns were challenged with 3 x 10(5) cells ml(-1) of A. hydrophila and survivability percentage and immunological parameters were assayed upto day 7. On day 7, most of the immunological parameters such as lysozyme activity, bactericidal activity and NBT activity were significantly enhanced after exposing the fish to all the concentrations of beta-glucan. Challenge study indicated least mortality in the group of spawns immersed in 15 mg l(-1) beta-glucan suspension for 3 h. Thus, 3 h exposure to beta-glucan suspension could reduce the mortality and increase the immunity of A. testudineus spawns.