Background: Studies performed over the past decade have identified fairly consistent epidemiological patterns of risk
factors for visceral leishmaniasis (VL) in the Indian subcontinent.
Methods and Principal Findings: To inform the current regional VL elimination effort and identify key gaps in knowledge,
we performed a systematic review of the literature, with a special emphasis on data regarding the role of cattle because
primary risk factor studies have yielded apparently contradictory results. Because humans form the sole infection reservoir,
clustering of kala-azar cases is a prominent epidemiological feature, both at the household level and on a larger scale.
Subclinical infection also tends to show clustering around kala-azar cases. Within villages, areas become saturated over a
period of several years; kala-azar incidence then decreases while neighboring areas see increases. More recently, post kalaazar
dermal leishmaniasis (PKDL) cases have followed kala-azar peaks. Mud walls, palpable dampness in houses, and peridomestic
vegetation may increase infection risk through enhanced density and prolonged survival of the sand fly vector.
Bed net use, sleeping on a cot and indoor residual spraying are generally associated with decreased risk. Poor micronutrient
status increases the risk of progression to kala-azar. The presence of cattle is associated with increased risk in some studies
and decreased risk in others, reflecting the complexity of the effect of bovines on sand fly abundance, aggregation, feeding
behavior and leishmanial infection rates. Poverty is an overarching theme, interacting with individual risk factors on multiple
levels.
Conclusions: Carefully designed demonstration projects, taking into account the complex web of interconnected risk
factors, are needed to provide direct proof of principle for elimination and to identify the most effective maintenance
activities to prevent a rapid resurgence when interventions are scaled back. More effective, short-course treatment
regimens for PKDL are urgently needed to enable the elimination initiative to succeed.

/pdf/of-cattle-sand-flies-and-men-a-systematic-review-of-risk-vrnofb49ua.pdf

Of cattle, sand flies and men: a systematic review of risk factor analyses for South Asian visceral leishmaniasis and implications for elimination.

Background 
Known as ‘neglected disease’ because relatively little effort has been applied to finding cures, leishmaniasis kills more than 150,000 people every year and debilitates millions more. Visceral leishmaniasis (VL), also called Kala Azar (KA) or black fever in India, claims around 20,000 lives every year. Whole genome analysis presents an excellent means to identify new targets for drugs, vaccine and diagnostics development, and also provide an avenue into the biological basis of parasite virulence in the L. donovani complex prevalent in India.


Methodology/Principal Findings 
In our presently described study, the next generation SOLiD™ platform was successfully utilized for the first time to carry out whole genome sequencing of L. donovani clinical isolates from India. We report the exceptional occurrence of insect trypanosomatids in clinical cases of visceral leishmaniasis (Kala Azar) patients in India. We confirm with whole genome sequencing analysis data that isolates which were sequenced from Kala Azar (visceral leishmaniasis) cases were genetically related to Leptomonas. The co-infection in splenic aspirate of these patients with a species of Leptomonas and how likely is it that the infection might be pathogenic, are key questions which need to be investigated. We discuss our results in the context of some important probable hypothesis in this article.


Conclusions/Significance 
Our intriguing results of unusual cases of Kala Azar found to be most similar to Leptomonas species put forth important clinical implications for the treatment of Kala Azar in India. Leptomonas have been shown to be highly susceptible to several standard leishmaniacides in vitro. There is very little divergence among these two species viz. Leishmania sp. and L. seymouri, in terms of genomic sequence and organization. A more extensive perception of the phenomenon of co-infection needs to be addressed from molecular pathogenesis and eco-epidemiological standpoint.

/pdf/solid-sequencing-of-genomes-of-clinical-isolates-of-4uii5ggj7p.pdf

SOLiD™ sequencing of genomes of clinical isolates of Leishmania donovani from India confirm leptomonas co-infection and raise some key questions.

Visceral leishmaniasis (VL), caused by an intracellular parasite Leishmania donovani in the Indian subcontinent, is considered to be anthroponotic. The role of domestic animals in its transmission is still unclear. Although cattle are the preferred blood host for Phlebotomus argentipes, the sandfly vector of VL in the Indian subcontinent, very little information is available for their role in the disease transmission. In this study, we examined domestic cattle for serological and molecular evidence of Leishmania infection in a VL-endemic area in Bangladesh. Blood samples from 138 domestic cattle were collected from houses with active or recently-treated VL and post-kala-azar dermal leishmaniasis patients. The presence of anti-leishmanial antibodies in serum was investigated using enzyme-linked immunosorbent assay (ELISA) and then with direct agglutination tests (DAT). Nested PCR (Ln PCR) was performed to amplify the ssu-rRNA gene using the DNA extracted from Buffy coat. Recently-developed molecular assay loop-mediated isothermal amplification (LAMP) was also performed for further sensitive detection of parasite DNA. In this study, 9.4% (n = 13) of the cattle were found to be positive by ELISA. Of the 13 ELISA-positive cattle, only four (30.8%) were positive in DAT. Parasite DNA was not detected in either of the molecular assays (Ln PCR and LAMP). The study confirmed the presence of antibodies against Leishmania parasite in cattle. However, the absence of Leishmania DNA in the cattle indicates clearly that the cattle do not play a role as reservoir host. Similar study needs to be undertaken in the Indian subcontinent to determine the role of other domestic animals on which sandflies feed.

/pdf/survey-of-domestic-cattle-for-anti-leishmania-antibodies-and-1xq2cs85wg.pdf

R. K. Sanyal

Papers

Zoonotic reservoir in Indian kala-azar.