Plant-feeding phlebotomine sand flies, vectors of leishmaniasis, prefer Cannabis sativa.

Blood-sucking phlebotomine sand flies (Diptera: Psychodidae) transmit leishmaniasis as well as arboviral diseases and bartonellosis. Sand fly females become infected with Leishmania parasites and transmit them while imbibing vertebrates' blood, required as a source of protein for maturation of eggs. In addition, both females and males consume plant-derived sugar meals as a source of energy. Plant meals may comprise sugary solutions such as nectar or honeydew (secreted by plant-sucking homopteran insects), as well as phloem sap that sand flies obtain by piercing leaves and stems with their needle-like mouthparts. Hence, the structure of plant communities can influence the distribution and epidemiology of leishmaniasis. We designed a next-generation sequencing (NGS)-based assay for determining the source of sand fly plant meals, based upon the chloroplast DNA gene ribulose bisphosphate carboxylase large chain (rbcL). Here, we report on the predilection of several sand fly species, vectors of leishmaniasis in different parts of the world, for feeding on Cannabis sativa We infer this preference based on the substantial percentage of sand flies that had fed on C. sativa plants despite the apparent "absence" of these plants from most of the field sites. We discuss the conceivable implications of the affinity of sand flies for C. sativa on their vectorial capacity for Leishmania and the putative exploitation of their attraction to C. sativa for the control of sand fly-borne diseases.

A fine scale eco-epidemiological study on endemic visceral leishmaniasis in north ethiopian villages.

Visceral Leishmaniasis (VL) is a disseminated protozoan infection caused by Leishmania donovani that affects almost half a million people annually. In Northern Ethiopia, VL is common in migrant agricultural laborers returning from the lowland sesame fields of Metema and Humera. Recent VL foci have emerged in resident rural populations near the town. In the current study, we evaluate multilevel entomological, epidemiological and ecological factors associated with infection and disease through fine-scale eco-epidemiological analyses in three villages. Satellite images showed that villages constructed in or close to vertisols, were likely to become endemic for VL. Vertisols or black-cotton soil, are characterized by high contents of smectitic clay minerals, which swell when hydrated and shrink upon desiccation, causing extensive deep cracking during the dry season. The population densities of Phlebotomus orientalis, the vector, were negatively correlated with distance from vertisols and persons living close to vertisols were more likely to be bitten by sand flies, as evidenced by sero-positivity to Ph. orientalis saliva. Apparent (albeit non-significant) clustering of VL cases and abundant asymptomatic infections close to vertisols, suggest anthroponotic transmission around houses located close to vertisols. Comparable rates of male and female volunteers, mostly under 15 years of age, were infected with L. donovani but a significantly higher proportion of males succumbed to VL indicating a physiological gender-linked male susceptibility. Our data suggest that the abundant infected persons with high parasitemias who remain asymptomatic, may serve as reservoir hosts for anthroponotic transmission inside villages. Only limited insights on the transmission dynamics of L. donovani were gained by the study of environmental factors such as presence of animals, house structure and vegetation cover.

Minimally invasive microbiopsies: a novel sampling method for identifying asymptomatic, potentially infectious carriers of Leishmania donovani.

Visceral leishmaniasis (VL) is a potentially lethal, sand fly-borne disease caused by protozoan parasites belonging to the Leishmania donovani species complex. There are several adequate methods for diagnosing VL, but the majority of infected individuals remain asymptomatic, comprising potential parasite reservoirs for transmission of the disease. The gold standard for assessing host infectiousness to biting vector insects is xenodiagnosis (i.e. scoring infection rates among insectary-reared insects that had fed on humans suspected of being infected). However, when it comes to sand flies and leishmaniasis, xenodiagnosis is an intricate operation burdened by logistical hurdles and ethical concerns that prevent its effective application for mass screening of widely dispersed communities, particularly in rural regions of underdeveloped countries. Minimally invasive microbiopsy (MB) devices were designed to penetrate the skin to a depth of ∼200µm and absorb blood as well as skin cell lysates, mimicking the mode by which phlebotomine sand flies acquire blood meals, as well as their composition. MBs taken from 137 of 262 volunteers, living in endemic VL foci in Ethiopia, detected Leishmania parasites that could potentially be imbibed by feeding sand flies. Although the volume of MBs was 10-fold smaller than finger-prick blood samples, Leishmania DNA detection rates from MBs were significantly higher, implying that skin, more often than blood, was the source of parasites. Volunteers with histories of VL were almost as likely as healthy volunteers to test positive by MBs (southern Ethiopian focus: 95% CI: 0.35-2.59, P=1.0. northern Ethiopian focus 0.87: 95% CI: 0.22-3.76, P=1), suggesting the importance of asymptomatic patients as reservoirs of L. donovani. Minimally invasive, painless MBs should be considered for reliably and efficiently evaluating both L. donovani infection rates among large numbers of asymptomatic carriers and their infectiousness to blood-feeding sand flies.