Study of house-level risk factors associated in the transmission of Indian Kala-azar

<p>Abstract</p> <p>Background</p> <p>In visceral leishmaniasis (VL), phlebotomine vectors are the main target to reduce for control measures. An attempt has been taken to delineate the association between <it>Phlebotomous argentipes </it>and housing characteristics between two districts e.g. endemic and non-endemic.</p> <p>Methods</p> <p>A cross-sectional survey was conducted on 240 households for both the endemic (Vaishali district) and non-endemic (Lohardaga district) site. Logistic regression analysis was used to identify factors related to housing characteristics influencing suitable habitats for <it>P. argentipes</it>. Vector density estimated using a CDC light trap.</p> <p>Results</p> <p>The proportion of <it>P. argentipes </it>in both endemic and non-endemic areas was significantly much higher (P < 0.001) when compared with the proportion of <it>Sergentomiya </it>and <it>P. papatasi</it>. The results of multilevel logistic regression analysis showed that mud plastered wall (<it>P value = 0.001)</it>, mixed dwelling (<it>P value = 0.002</it>) and area (<it>P value = 0.001</it>) were strongly associated with the presence of vectors.</p> <p>Conclusion</p> <p>Result of the studied household characteristics provides an accurate, rapid assessment of house-level variation in risk. The results also have implications for maximizing surveillance efficacy of sandflies, which is likely to become increasingly important while formulating any control strategy.</p

Seasonal relationship between normalized difference vegetation index and abundance of the Phlebotomus kala-azar vector in an endemic focus in Bihar, India

Remote sensing was applied for the collection of spatio-temporal data to increase our understanding of the potential distribution of the kala-azar vector Phlebotomus argentipes in endemic areas of the Vaishali district of Bihar, India. We produced monthly distribution maps of the normalized difference vegetation index (NDVI) based on data from the thematic mapper (TM) sensor onboard the Landsat-5 satellite. Minimum, maximum and mean NDVI values were computed for each month and compared with the concurrent incidence of kala-azar and the vector density. Maximum and mean NDVI values (R2 = 0.55 and R2 = 0.60, respectively), as well as the season likelihood ratio (X2 = 17.51; P <0.001), were found to be strongly associated with kala-azar, while the correlation with between minimum NDVI values and kala-azar was weak (R2 = 0.25). Additionally, a strong association was found between the mean and maximum NDVI values with seasonal vector abundance (R2 = 0.60 and R2 = 0.55, respectively) but there was only a marginal association between minimum NDVI value and the spatial distribution of kala-azar vis-à-vis P. argentipes density

Effect of Village-wide Use of Long-Lasting Insecticidal Nets on Visceral Leishmaniasis Vectors in India and Nepal: A Cluster Randomized Trial

Visceral leishmaniasis (VL) is a vector-borne disease causing at least 60,000 deaths each year amongst an estimated half million cases, and until recently there have been no significant initiatives to reduce this burden. However, in 2005, the governments of India, Bangladesh and Nepal signed a memorandum of understanding at the World Health Assembly in Geneva for the elimination of the disease by 2015. In the absence of an effective vaccine, the program will rely on the active detection and prompt treatment of cases throughout the endemic region, combined with a recurrent indoor residual spraying (IRS) of all villages at risk. Vector control programs based on IRS are notorious for failing to maintain comprehensive spray coverage over time owing to logistical problems and lack of compliance by householders. Long-lasting insecticidal nets (LNs) have been postulated as an alternative or complement to IRS. Here we describe how comprehensive coverage of LN in trial communities reduced the indoor density of sand flies by 25% compared to communities without LNs. This provides an indication that LNs could be usefully deployed as a component of the VL control program in the Indian subcontinent

Localization of kala-azar in the endemic region of Bihar, India based on land use/land cover assessment at different scales

Land cover, a critical variable in the epidemiology of kala-azar, can be remotely characterized by customizing and integrating “state-of-the-art” imagery at different spatial scales from different sensors onboard satellites. A study was conducted at four levels (national, state, district and village) investigating the role of land use/land cover (LULC) for leishmaniasis transmission resulting in a framework highlighting the links between LULC and areas endemic for the disease. Distribution maps were analysed by a probabilistic approach (Bayesian classifier) which produced a set of “suitability estimates” based on the probability of sand fly presence. The development of a sound knowledge of each link in the predicted sequence of satellite views offering an extraordinary opportunity to support the mapping of kala-azar endemicity and stratification of areas suitable for sand fly habitats across the country as well as at the local scal

Influence of topography on the endemicity of Kala-azar: a study based on remote sensing and geographical information system

Kala-azar, a fatal infectious disease in many Indian states, particularly in Bihar, West Bengal, Uttar Pradesh, and Jharkhand, is caused by the protozoan parasite Leishmania donovani and transmitted by the sandfly vector Phlebotomus argentipes. The vector is distributed all over the country but the disease is confined to particular zones since before the last century. In this study, parameters such as altitude, temperature, humidity, rainfall and the normalized difference vegetation index (NDVI) were investigated for correlation with the distribution of the disease in the northeastern corner of the Indian sub-continent. Data analysis on Kala-azar prevalence during the period 2005-2007 in the four states showed that the highest prevalence was below 150 m of altitude with very few cases located above the 300 m level. Low NDVI value ranges (0.03-0.015) correlated with a high occurrence of the disease. The maximum temperatures in the affected sites varied between an upper level of 25-29°C and a minimum of 16-20°C. The rainfall in these areas fluctuated between 1154 and 1834 mm. As the disease showed a high correlation with the prevailing topographic conditions, an attempt was made to improve the relative strength of the approach to predict the potential for endemicity of leishmaniasis by introducing satellite imagery complemented with a geographical information system database

Trends in spatio-temporal dynamics of visceral leishmaniasis cases in a highly-endemic focus of Bihar, India: an investigation based on GIS tools

Abstract Background Visceral leishmaniasis (VL) in Bihar State (India) continues to be endemic, despite the existence of effective treatment and a vector control program to control disease morbidity. A clear understanding of spatio-temporal distribution of VL may improve surveillance and control implementation. This study explored the trends in spatio-temporal dynamics of VL endemicity at a meso-scale level in Vaishali District, based on geographical information systems (GIS) tools and spatial statistical analysis. Methods A GIS database was used to integrate the VL case data from the study area between 2009 and 2014. All cases were spatially linked at a meso-scale level. Geospatial techniques, such as GIS-layer overlaying and mapping, were employed to visualize and detect the spatio-temporal patterns of a VL endemic outbreak across the district. The spatial statistic Moran’s I Index (Moran’s I) was used to simultaneously evaluate spatial-correlation between endemic villages and the spatial distribution patterns based on both the village location and the case incidence rate (CIR). Descriptive statistics such as mean, standard error, confidence intervals and percentages were used to summarize the VL case data. Results There were 624 endemic villages with 2719 (average 906 cases/year) VL cases during 2012–2014. The Moran’s I revealed a cluster pattern (P < 0.05) of CIR distribution at the meso-scale level. On average, 68 villages were newly-endemic each year. Of which 93.1% of villages’ endemicity were found to have occurred on the peripheries of the previous year endemic villages. The mean CIR of the endemic villages that were peripheral to the following year newly-endemic villages, compared to all endemic villages of the same year, was higher (P < 0.05). Conclusion The results show that the VL endemicity of new villages tends to occur on the periphery of villages endemic in the previous year. High-CIR plays a major role in the spatial dispersion of the VL cases between non-endemic and endemic villages. This information can help achieve VL elimination throughout the Indian subcontinent by improving vector control design and implementation in highly-endemic district

Incidence of visceral leishmaniasis in the Vaishali district of Bihar, India: spatial patterns and role of inland water bodies

The role of the distribution of inland water bodies with respect to the transmission of visceral leishmaniasis (VL) and its dominant vector, Phlebotomous argentipes, has been studied at the regional scale in Bihar, eastern India. The Landsat TM sensor multispectral scanning radiometer, with a spatial resolution of 30 m in the visible, reflective-infrared and shortwave-infrared (SWIR) bands, was used to identify water bodies using the normalized differential pond index (NDPI) calculated as follows: (Green – SWIR I)/(Green + SWIR I). Nearest neighbour and grid square statistics were used to delineate spatial patterns and distribution of the sandfly vector and the disease it transmits. The female P. argentipes sandfly was found to be associated with the distance from open water and particularly abundant near non-perennial river banks (68.4%; P <0.001), while its association with rivers was focused further away from the water source (X2 = 26.3; P <0.001). The results also reveal that the distribution of VL is clustered around non-perennial riverbanks, while the pattern is slightly random around the perennial river banks. The grid square technique illustrate that the spatial distribution of the disease has a much stronger correlation with lower density of open waters surfaces as well as with sandfly densities (X2 = 26.0; P <0.001). The results of our study suggest that inland water presence poses a risk for VL by offering suitable breeding sites for P. argentipes, a fact that should be taken into account when attempting to control disease transmissio