Understanding the transmission dynamics of Leishmania donovani to provide robust evidence for interventions to eliminate visceral leishmaniasis in Bihar, India.

Visceral Leishmaniasis (VL) is a neglected vector-borne disease. In India, it is transmitted to humans by Leishmania donovani-infected Phlebotomus argentipes sand flies. In 2005, VL was targeted for elimination by the governments of India, Nepal and Bangladesh by 2015. The elimination strategy consists of rapid case detection, treatment of VL cases and vector control using indoor residual spraying (IRS). However, to achieve sustained elimination of VL, an appropriate post elimination surveillance programme should be designed, and crucial knowledge gaps in vector bionomics, human infection and transmission need to be addressed. This review examines the outstanding knowledge gaps, specifically in the context of Bihar State, India.The knowledge gaps in vector bionomics that will be of immediate benefit to current control operations include better estimates of human biting rates and natural infection rates of P. argentipes, with L. donovani, and how these vary spatially, temporally and in response to IRS. The relative importance of indoor and outdoor transmission, and how P. argentipes disperse, are also unknown. With respect to human transmission it is important to use a range of diagnostic tools to distinguish individuals in endemic communities into those who: 1) are to going to progress to clinical VL, 2) are immune/refractory to infection and 3) have had past exposure to sand flies.It is crucial to keep in mind that close to elimination, and post-elimination, VL cases will become infrequent, so it is vital to define what the surveillance programme should target and how it should be designed to prevent resurgence. Therefore, a better understanding of the transmission dynamics of VL, in particular of how rates of infection in humans and sand flies vary as functions of each other, is required to guide VL elimination efforts and ensure sustained elimination in the Indian subcontinent. By collecting contemporary entomological and human data in the same geographical locations, more precise epidemiological models can be produced. The suite of data collected can also be used to inform the national programme if supplementary vector control tools, in addition to IRS, are required to address the issues of people sleeping outside

Population genetics study of the imported fire ants (Formicidae: Solenopsis spp.)

The study was divided into three main sections. In the first section, temporal stability of genetic structure of red imported fire ant populations and effective population sizes were assessed with the help of microsatellites. The second part of the study was focused on the development of new microsatellite markers for the population genetics study of fire ants. The third part of the study was aimed at describing the association of phenotypic and genotypic characters of polygyne hybrid (Solenopsis invicta x richteri) fire ant in a colony and identifying the origin of polygyny in hybrid imported fire ant colony. Meridian, Yazoo City and Crystal Springs in Mississippi and Mobile, Alabama were selected for conducting the study. The overall FST estimates and the pairwise FST estimates between the populations of study, indicated little genetic differentiation and low spatial variation in the nuclear genetic structure of red imported fire ant. Gene flow estimates indicated that there is extensive movement between these populations. From 2006 to 2008 the FST estimates decreased and gene flow estimates increased, indicating that there is no equilibrium between genetic drift and migration in the populations studied. Effective population sizes ranged from 10 -17 in these populations.We have isolated and characterized an additional 11 polymorphic microsatellite loci in the invasive ant S. invicta from a population in Lauderdale County, Mississippi. The observed and effective number of alleles ranged from two to six (average 3.1818 ± S. E. 0.0486). Probability tests indicated significant deviations from the Hardy-Weinberg equilibrium at three loci. The polymorphism information content of the microsatellites ranged from 0.1482 to 0.6208.Identifying multiple inseminated queens in a colony and sequencing the critical region of Gp-9 locus (1600 base pairs) in individuals with the polygyne allele strongly indicate the association of phenotypic and genotypic characters of polygyny in a hybrid imported fire ant colony. A 100% match of Gp-9B and Gp-9b alleles and concordance in the critical amino acid substitutions of the Gp-9 locus in the hybrid fire ant with S. invicta Buren provides the evidence that polygyny in the hybrid imported fire ant colony is derived from S. invicta

Measures to Control Phlebotomus argentipes and Visceral Leishmaniasis in India

Visceral leishmaniasis is a deadly parasitic disease that is transmitted via the bite of a female sand fly, Phlebotomus argentipes. The highest burden of this disease is in northern India. In 2005, India embarked on an initiative with Ne­pal, Bangladesh, and the World Health Organization to eliminate visceral leishmaniasis by 2015. With the goal of 1 case in 10,000 people still unmet, it is prudent to evaluate the tools that have been used thus far to reduce vector numbers and cases of the disease. Herein, we present a review of studies conducted on vector-control strategies in India to combat visceral leishmaniasis including indoor residual spraying, insecticide-treated bed nets, environmental modification, and feed-through insecticides. This review suggests that the quality of indoor residual spraying may enhance control measures while a combination of spraying, nets, and feed-through insecticides would best confront the diverse habitats of P. argentipes

MOESM1 of Treatment of livestock with systemic insecticides for control of Anopheles arabiensis in western Kenya

Additional file 1. Survival curves for all treatment groups and time points

Bionomics of <i>Phlebotomus argentipes</i> in villages in Bihar, India with insights into efficacy of IRS-based control measures

<div><p>Background</p><p>Visceral leishmaniasis (VL) is a deadly vector-borne disease. Approximately 90% of Indian VL cases occur in Bihar, where the sand fly, <i>Phlebotomus argentipes</i>, is the principal vector. Sand fly control in Bihar consists of indoor residual spraying (IRS), the practice of spraying the inner walls of village dwellings with insecticides. Prior researchers have evaluated success of IRS-control by estimating vector abundance in village houses, but the number of sampling periods (<i>n</i> = 2–3) were minimal, and outdoor-resting <i>P</i>. <i>argentipes</i> were neglected. We describe a large-scale field study, performed in 24 villages within two Bihari districts, during which <i>P</i>. <i>argentipes</i> were collected biweekly over 47-weeks, in cattle enclosures, houses, and outdoors in peri-domestic vegetation. The objectives of this study were to provide updated <i>P</i>. <i>argentipes</i> ecological field data, and determine if program-initiated IRS-treatment had led to noticeable differences in vector abundance.</p><p>Principal findings</p><p><i>P</i>. <i>argentipes</i> (<i>n</i> = 126,901) relative abundance was greatest during the summer months (June-August) when minimum temperatures were highest. <i>P</i>. <i>argentipes</i> were most frequently collected from cattle enclosures (~46% total; ~56% blood fed). Many sand flies were found to have taken blood from multiple sources, with ~81% having blood fed on humans and ~60% blood feeding on bovines. Nonparametric statistical tests were determined most appropriate for evaluating IRS-treatment. Differences in <i>P</i>. <i>argentipes</i> abundance in houses, cattle enclosures and vegetation were detected between IRS-treated and untreated villages in only ~9% of evaluation periods occurring during the peak period of human-vector exposure (June-August) and in ~8% of the total observations. No significant differences were detected between the numbers of <i>P</i>. <i>argentipes</i> collected in vegetation close to the experimental villages.</p><p>Conclusion</p><p>The results of this study provide updated data regarding <i>P</i>. <i>argentipes</i> seasonal abundance, spatial distribution, and host preferances, and suggest vector abundance has not significantly declined in IRS-treated villages. We suggest that IRS be supplemented with vector control strategies targeting exophagic, exophilic <i>P</i>. <i>argentipes</i>, and that disease surveillance be accompanied by rigorous vector population monitoring.</p></div

Blood meal sources and trap placement of <i>P</i>. <i>argentipes</i> successfully analyzed using reverse-line blotting.

<p>Blood meal sources and trap placement of <i>P</i>. <i>argentipes</i> successfully analyzed using reverse-line blotting.</p

Summary of the total number of <i>P</i>. <i>argentipes</i> collected from houses (H), cattle enclosures (CE), and peri-domestic vegetation (V) between February 10-December 29, 2016.

<p>Summary of the total number of <i>P</i>. <i>argentipes</i> collected from houses (H), cattle enclosures (CE), and peri-domestic vegetation (V) between February 10-December 29, 2016.</p

Map of 24 study villages in two VL-endemic districts in Bihar, India.

<p>Map was generated in ArcGISusing ArcMap with a World Imagery base layer (Sources: Esri, DigitalGlobe, GeoEye, i-cubed, USDA FSA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community).</p