The clinical-epidemiological profile of malaria patients from Southern Venezuela, a critical hotspot in Latin America.

BACKGROUND: Venezuela accounted for 55% of the cases and 73% of the malaria deaths in the Americas in 2019. Bolivar state, in the southeast, contributes > 60% of the country's Plasmodium vivax and Plasmodium falciparum cases every year. This study describes the clinical-epidemiological characteristics of clinical malaria patients in this high-transmission area. METHODS: A prospective study was conducted on patients seeking medical attention in three medical centres in the state capital, Ciudad Bolivar, between June and October 2018. Malaria diagnosis was carried out using microscopy following national standards. Malaria-positive patients were examined for clinical symptoms, and haematological tests were performed at the time of diagnosis. Patients were followed up by telephone to evaluate malaria recurrences. RESULTS: Out of 287 patients, 200 (69.7%) were positive for P. vivax, 69 (24%) for P. falciparum, and 18 (6.3%) had mixed (P. vivax/P. falciparum) infections. Patients' median age was 33 years (IQR 20), 168 (69%) were men, and 40% practiced gold mining as the main occupation. Fever (96.5%), chills (91.3%), and headaches (90.6%) were the most frequent symptoms. At least one symptom associated with severe malaria was observed in 69 out of 161 patients with complete clinical evaluation (42.9%). Plasmodium vivax infections were found in 42 out of 69 (60.9%) severe cases; by contrast, P. falciparum and mixed malaria caused 34.8% (24/69) and 4.4% (3/69) of infections, respectively. Two patients died of cerebral malaria. Mean hemoglobin was lower in the patients infected with P. falciparum than those infected with P. vivax. Regardless of the parasite causing the infection, patients presented high levels of total bilirubin, aminotransferases (AST, ALT), and lactate dehydrogenase (LDH). Out of the 142 patients followed up by phone for three months (49.5% of the 287 patients), 35 (24.7%) reported recurrences. CONCLUSIONS: The high malaria prevalence among young male adults practicing gold mining suggests that this occupation is a significant risk factor. The unexpected high prevalence of P. vivax patients with at least one criteria of severe clinical disease is a matter of concern. Whether it is the result of a lack of timely diagnosis and effective treatment should be explored.

Prevalence of Intestinal Parasite Infections and Their Associated Factors among Food Handlers Working in Selected Catering Establishments from Bule Hora, Ethiopia.

Intestinal parasites are responsible for one of the major health problems like food contamination with socioeconomic effects in the world with a prevalence rate of 30-60%, in developing countries that lie within tropical and subtropical areas. They pose a reasonable public health burden, particularly in low- and middle-income countries, including Ethiopia. Globally, due to intestinal parasitic infections, around 3.5 billion people are affected and more than 200,000 deaths are reported annually. Around 50000 deaths yearly are caused by intestinal parasites in Ethiopia. As such, intestinal parasites perceived global and local burdens to various countries. The risk of food contamination depends largely on the health status of the food handlers, their hygiene, knowledge, and practice of food hygiene. Food handlers with poor personal hygiene and sanitation conditions are the major potential sources of intestinal helminthes and protozoa worldwide. The proposed study was aimed at evaluating prevalence of intestinal parasitic infections and their associated factors among food handlers working in selected catering establishments. A cross-sectional study was conducted in Bule Hora Town from March to April 2020. A total of 136 catering establishments were selected using a systematic sampling technique. Data analysis was done using SPSS version 20. The prevalence of intestinal parasites in this study was 46.3%. Entamoeba histolytica was the most predominant parasite (33.3%, i.e., 21/63) while Giardia lamblia was the least (11.1%, i.e., 7/63). Consumption of vended or borehole water and hygienic practices such as hand washing before eating, after using toilet, before cooking and trimming of finger nail and wearing proper working clothes and shoes were statistically significant with intestinal parasitic infection (P < 0.05). Generally, the prevalence of intestinal parasitic infection in this study was high and contributed by low socioeconomic status and poor environmental and personal hygiene. Measures including education on personal hygiene, environmental sanitation, drinking water supply, regular medical checkups, and treatment should be taken into account to reduce the prevalence of intestinal parasites.

Seroprevalence and risk factors of Toxoplasma gondii infection among veterinary personnel and abattoir workers in Central India.

Toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii, is an important zoonotic infection. Veterinary personnel and abattoir workers are considered to be at a high risk of T. gondii infection owing to their occupational exposure. However, the association of T. gondii infection with occupational exposure to animals has not been determined in India. Hence, we analysed 139 and 126 blood samples of veterinary personnel and abattoir workers, respectively, for anti-T. gondii antibodies using enzyme-linked immunosorbent assay (ELISA), modified agglutination test (MAT) and indirect fluorescent antibody test (IFAT). The association of seroprevalence with sociodemographic profiles, work activities and dietary habits was determined in the study population. MAT, ELISA and IFAT results demonstrated nearly 46%, 48% and 47% seropositivity, respectively. MAT (kappa = 0.924) and IFAT (kappa = 0.962) results showed good agreement with ELISA results. Of the ELISA positive samples, 46% was copositive for IgG antibody, 1.5% for IgM antibody and 1.5% for both IgG and IgM antibodies. High IgG avidity was observed only in IgG+ IgM- and IgG+ IgM+ samples and not in IgM+ IgG- samples, indicating chronic T. gondii infection in most of the cases. Furthermore, multivariate analysis revealed that T. gondii seropositivity was associated with age > 30 years (odds ration [OR] = 1.992), cat at home (OR = 1.991), not wearing gloves (OR = 1.886), not wearing safety glasses (OR = 1.985) and contact with soil (OR = 1.695). These findings support the presence of a potentially significant association between T. gondii seropositivity and occupational exposure to animals.

Update: Malaria, U.S. Armed Forces, 2020.

Malaria infection remains an important health threat to U.S. service members who are located in endemic areas because of long-term duty assignments, participation in shorter-term contingency operations, or personal travel. In 2020, a total of 28 service members were diagnosed with or reported to have malaria. This was the lowest number of cases in any given year during the 10-year surveillance period and represents a 15.2% decrease from the 33 cases identified in 2019. The relatively low numbers of cases during 2012-2020 mainly reflect decreases in cases acquired in Afghanistan, a reduction largely due to the progressive withdrawal of U.S. forces from that country. The number of malaria cases caused by Plasmodium falciparum in 2020 (n=8) was the second lowest observed during the surveillance period. The percentage of 2020 cases of malaria caused by Plasmodium vivax (53.6%; n=15) was the highest during any given year of the surveillance period. The remaining 5 malaria cases were labeled as associated with other/unspecified types of malaria (17.9%). Malaria was diagnosed at or reported from 13 different medical facilities in the U.S., Germany, Africa, and Korea. Providers of medical care to military members should be knowledgeable of and vigilant for clinical manifestations of malaria outside of endemic areas.

Defining malaria risks among forest workers in Aceh, Indonesia: a formative assessment.

BACKGROUND: Following a dramatic decline of malaria cases in Aceh province, geographically-based reactive case detection (RACD) was recently evaluated as a tool to improve surveillance with the goal of malaria elimination. While RACD detected few cases in households surrounding index cases, engaging in forest work was identified as a risk factor for malaria and infections from Plasmodium knowlesi-a non-human primate malaria parasite-were more common than expected. This qualitative formative assessment was conducted to improve understanding of malaria risk from forest work and identify strategies for targeted surveillance among forest workers, including adapting reactive case detection. METHODS: Between June and August, 2016, five focus groups and 18 in-depth interviews with forest workers and key informants were conducted in each of four subdistricts in Aceh Besar and Aceh Jaya districts. Themes included: types of forest activities, mobility of workers, interactions with non-human primates, malaria prevention and treatment-seeking behaviours, and willingness to participate in malaria surveys at forest work sites and using peer-referral. RESULTS: Reported forest activities included mining, logging, and agriculture in the deep forest and along the forest fringe. Forest workers, particularly miners and loggers, described often spending weeks to months at work sites in makeshift housing, rarely utilizing mosquito prevention and, upon fever, self-medicating and seeking care from traditional healers or pharmacies rather than health facilities. Non-human primates are frequently observed near work sites, and most forest work locations are within a day's journey of health clinics. Employers and workers expressed interest in undertaking malaria testing and in participating in survey recruitment by peer-referral and at work sites. CONCLUSIONS: Diverse groups of forest workers in Aceh are potentially exposed to malaria through forest work. Passive surveillance and household-based screening may under-estimate malaria burden due to extended stays in the forest and health-seeking behaviours. Adapting active surveillance to specifically target forest workers through work-site screening and/or peer-referral appears promising for addressing currently undetected infections.

Avian mite bites acquired from pigeons: Report of three cases and review of the literature.

BACKGROUND: Skin lesions caused by avian mite bites are uncommon and often misdiagnosed. They are usually caused by bites from avian mites that have infested domestic poultry or birds nesting in or near human habitation. We report three cases of human skin lesions from avian mites infesting pigeons. OBSERVATIONS: Three persons working in the same place developed similar skin pruritic papules simultaneously. The diagnosis remained unknown until Dermanyssus gallinae (chicken mite) was found on the computer's table of the three individuals workplace, situated near a window where pigeons used to live. Antihistaminic treatment was carried out with a skin disinfestation. In two cases, symptoms resolved after one week of treatment. In the third case, corticosteroids were needed. CONCLUSIONS: Avian mite bites skin lesions can remain unrecognized or misdiagnosed. Inquiry about contact with pigeons or poultry may be helpful in patients with nonspecific skin lesions.

Paludismo importado en docente / Malaria from a foreign country in a teacher

En Europa, las enfermedades infecciosas transmitidas por vectores, en particular el paludismo, siguen constituyendo un problema de salud importante, sobre todo a través de viajeros infectados que regresan de países en los que estas enfermedades son endémicas. OBJETIVO: presentar un caso clínico de paludismo importado en España en relación a un desplazamiento de origen profesional. MATERIAL Y MÉTODOS: un profesor que viaja como cooperante a Guinea Ecuatorial y regresa a España. Se valora la historia clínico-laboral en relación a su cuadro clínico de paludismo. CONCLUSIÓN: en caso de viajes profesionales se insiste en la necesidad de medidas preventivas como son un completo asesoramiento en consulta médica, valorando la posible necesidad quimioprofilaxis frente a paludismo y la administración de distintos tipos de vacunas

In Europe the infectious diseases with transmission by vectors, as malaria, constitute an important health problem, mostly in the cases of travelers from endemic areas. OBJECTIVE: it shows a clinic case of imported malaria in Spain after a professional travel. MATERIAL AND METHODS: it is included a Spanish cooperating teacher who travelled from Equatorial Guinea to Spain, considering his clinical-occupational record and his malaria symptoms and signs. CONCLUSION: if it will be a professional travel, it is necessary preventive measures as a complete clinic information, including the possibility of chemoprophylaxis against malaria and the administration of different types of vaccines

Old friends and friendly fire: Pregnancy, hookworm infection, and anemia among tropical horticulturalists.

OBJECTIVES: Despite public health concerns about hookworm infection in pregnancy, little is known about immune profiles associated with hookworm (Necator americanus and Ancylostoma duodenale) infection during pregnancy. Fetal tolerance requirements may constrain maternal immune response to hookworm, thereby increasing susceptibility to new infections or increasing hemoglobin loss. To explore this possibility, we study systemic immune response and hemoglobin levels in a natural fertility population with endemic helminthic infection. METHODS: We used Bayesian multilevel models to analyze mixed longitudinal data on hemoglobin, hookworm infection, reproductive state, eosinophils, and erythrocyte sedimentation rate (ESR) to examine the effects of pregnancy and hookworm infection on nonspecific inflammation, cellular parasite response, and hemoglobin among 612 Tsimane women aged 15-45 (1016 observations). RESULTS: Pregnancy is associated with lower eosinophil counts and lower eosinophil response to hookworm, particularly during the second and third trimesters. Both hookworm and pregnancy are associated with higher ESR, with evidence for an interaction between the two causing further increases in the first trimester. Pregnancy is moderately associated with higher odds of hookworm infection (OR: 1.23, 95% CI: 0.83 to 1.83). Pregnancy and hookworm both decrease hemoglobin and may interact to accentuate this effect in the first-trimester of pregnancy (Interaction: ß: -0.30 g/dL; CI: -0.870 to 0.24). CONCLUSIONS: Our findings are consistent with a possible trade-off between hookworm immunity and successful pregnancy, and with the suggestion that hookworm and pregnancy may have synergistic effects, particularly in the first trimester.

Effect of malaria on productivity in a workplace: the case of a banana plantation in Zimbabwe.

BACKGROUND: Malaria is known to contribute to reduction in productivity through absenteeism as worker-hours are lost thus impacting company productivity and performance. This paper analysed the impact of malaria on productivity in a banana plantation through absenteeism. METHODS: This study was carried out at Matanuska farm in Burma Valley, Zimbabwe. Raw data on absenteeism was obtained in retrospect from the Farm Manager. Malaria infection was detected using malaria Rapid Diagnostic Test. Measures of absence from work place were determined and included; incidence of absence (number of absentees divided by the total workforce), absence frequency (number of malaria spells), frequency rate (number of spells divided by the number of absentees), estimated duration of spells (number of days lost due to malaria), severity rate (number of days lost divided by number of spells), incapacity rate (number of days lost divided by the number of absentees), number of absent days (number of spells times the severity rate), number of scheduled working days (actual working days in 5 months multiplied by total number of employees), absenteeism rate. RESULTS: A total of 143 employees were followed up over a 5-month period. Malaria positivity was 21%, 31.5%, 44.8%, 35.7% and 12.6% for January 2014 to May 2014, respectively. One spell of absence [194 (86.6%)] was common followed by 2 spells of absence [30 (13.4%)] for all employees. Duration of spells of absence due to malaria ranged from 1.5 to 4.1 working-days, with general workers being the most affected. Incidence of absence was 143/155 (93.3%), with total of spells of absence of over a 5-month period totalling 224. The frequency rate of absenteeism was 1.6 with severity rate of absence being 2.4. and incapacity rate was 3.7. CONCLUSION: Malaria contributes significantly to worker absenteeism. Employers, therefore, ought to put measures that protect workers from malaria infections. Protecting workers can be done through malaria educative campaigns, providing mosquito nets, providing insecticide-treated work suits, providing repellents and partnering with different ministries to ensure protection of workers from mosquito bites.

Prevalence of glucose-6-phosphate dehydrogenase deficiency, U.S. Armed Forces, May 2004-September 2018.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an inherited genetic disorder most commonly associated with hemolytic anemia. Among those with G6PD deficiency, hemolytic anemia may be triggered by bacterial or viral infections and by certain foods and drugs, including the 8-aminoquinoline (8-AQ) class of antimalarials. Because 8-AQ drugs remain the only drugs approved by the U.S. Food and Drug Administration for malaria relapse prevention, the Department of Defense (DoD) requires testing of all service members' G6PD status. To estimate prevalence of G6PD deficiency among DoD service members, Composite Health Care System-generated, Health Level 7-formatted laboratory records for all service members (n=2,311,223) dated between May 2004 and September 2018 were queried for G6PD testing. Corresponding demographic data were obtained from the Defense Enrollment Eligibility Reporting System. Overall prevalence of G6PD deficiency among this cohort was low, at 2.2%. Demographic trends mirrored U.S. statistics; the cohort prevalence among males (2.3%) was higher than among females (1.5%), and the prevalence among non-Hispanic blacks (9.5%) was higher than among those in any other race/ethnicity group.

Rubber plantations and drug resistant malaria: a cross-sectional survey in Cambodia.

BACKGROUND: The ongoing spread of artemisinin resistant Plasmodium falciparum malaria is a major threat to global health. In response, countries in the Greater Mekong Sub-region, including Cambodia, have declared ambitious goals to eliminate malaria. Major challenges include the lack of information on the at-risk population-individuals who live or work in or near the forest where the malaria vectors are found, including plantation workers. This study aimed to address this knowledge gap through a cross-sectional survey conducted in rubber plantations in Cambodia in 2014. METHODS: The survey was conducted in two rounds in four provinces and included a malaria prevalence survey, analysis for the K13 genetic mutation, and a comprehensive behavioural questionnaire. Forty plantations were included in each round, and 4201 interviews were conducted. An additional 701 blood samples were collected from family members of plantation workers. RESULTS: Overall malaria prevalence was relatively low with adjusted PCR prevalence rate of 0.6% for P. falciparum and 0.3% for Plasmodium vivax, and was very heterogenous between plantations. There was little difference in risk between permanent residents and temporary workers, and between the two rounds. The main risk factors for P. falciparum infection were smaller plantations, age under 30 years, lack of self-reported use of a treated net and recent travel, especially to the Northeastern provinces. Proximity of plantations to the forest was also a risk factor for malaria in round one, while male gender was also a risk factor for malaria by either species. CONCLUSIONS: With Cambodia's P. falciparum elimination target on the horizon, identifying every single malaria case will become increasingly important. Plantations workers are relatively accessible compared to some other at-risk groups and will likely remain a high priority. Ongoing surveillance and adaptive strategies will be critical if malaria elimination is to be achieved in this setting.

Porcine cysticercosis in slaughtered pigs and factors related to Taenia solium transmission amongst abattoir workers in Ibadan, Nigeria.

INTRODUCTION: porcine cysticercosis is under-reported particularly in Nigeria, despite the reportedly high prevalence of epilepsy and associated life-threatening health implications. This study was aimed at determining the prevalence of porcine cysticercosis and factors related to Taenia solium transmission to humans. METHODS: slaughtered pigs at a major abattoir, south-western Nigeria were randomly inspected and questionnaire was administered to pig workers/consumers while the data were analysed using Stata 12.0. RESULTS: a 4.4% (11/250) prevalence of porcine cysticercosis was obtained; the age, breed, sex and body conditions of pigs were not significant for infection (p < 0.05). Further, none (0.0%) of the respondents knew that T. solium could cause epilepsy in man and 39.5% often defaecated on neighbouring open fields and farmlands. Respondents purchasing pork from home slaughter were about four and ten times less likely to demonstrate good knowledge (OR = 0.24; 95% CI: 0.08-0.74) and practice (OR = 0.10; 95% CI: 0.05-0.22) than those purchasing from abattoir. Moreover, those lacking toilet facility were about four and five times less likely to demonstrate good knowledge (OR = 0.24; 95% CI: 0.07-0.86) and practice (OR = 0.19; 95% CI: 0.08-0.45) than those who had it. Other factors associated with practices related to T. solium transmission included age (p = 0.000), sex (p = 0.000) and duration (p = 0.003). CONCLUSION: the increased odds of poor knowledge and practices related to Taenia solium transmission especially among respondents purchasing home slaughter pork and lacking toilet facility provides insights into the parasite epidemiology. Above findings are important in lowering the infection prevalence in pigs and humans in this endemic area.

Update: Malaria, U.S. Armed Forces, 2018.

Malaria infection remains an important health threat to U.S. service members who are located in endemic areas because of long-term duty assignments, participation in shorter-term contingency operations, or personal travel. In 2018, a total of 58 service members were diagnosed with or reported to have malaria. This represents a 65.7% increase from the 35 cases identified in 2017. The relatively low numbers of cases during 2012-2018 mainly reflect decreases in cases acquired in Afghanistan, a reduction due largely to the progressive withdrawal of U.S. forces from that country. The percentage of cases of malaria caused by unspecified agents (63.8%; n=37) in 2018 was the highest during any given year of the surveillance period. The percentage of cases identified as having been caused by Plasmodium vivax (10.3%; n=6) in 2018 was the lowest observed during the 10-year surveillance period. The percentage of malaria cases attributed to P. falciparum (25.9%) in 2018 was similar to that observed in 2017 (25.7%), although the number of cases increased. Malaria was diagnosed at or reported from 31 different medical facilities in the U.S., Afghanistan, Italy, Germany, Djibouti, and Korea. Providers of medical care to military members should be knowledgeable of and vigilant for clinical manifestations of malaria outside of endemic areas.

Re-evaluation of the MSMR Case Definition for Incident Cases of Malaria.

The MSMR has been publishing the results of surveillance studies of malaria since 1995. The standard MSMR case definition uses Medical Event Reports and records of hospitalizations in counting cases of malaria. This report summarizes the performance of the standard MSMR case definition in estimating incident cases of malaria from 2015 through 2017. Also explored was the potential surveillance value of including outpatient encounters with diagnoses of malaria or positive laboratory tests for malaria in the case definition. The study corroborated the relative accuracy of the MSMR case definition in estimating malaria incidence and provided the basis for updating the case definition in 2019 to include positive laboratory tests for malaria antigen within 30 days of an outpatient diagnosis.

Modeling asymptomatic infections and work-related human circulation as drivers of unstable malaria transmission in low-prevalence areas: A study in the Northern Peruvian Amazon.

BACKGROUND: Despite relatively successful control campaigns, malaria remains a relevant public health problem in the Peruvian Amazon. Several studies suggest that malaria persistence in the area can be connected with a high prevalence of asymptomatic infections, which were subsequently shown to be connected with work-related exposure in areas of hyperendemic transmission. In this study, we tested the hypothesis that the infection reservoir represented by asymptomatic carriers in the northern Peruvian Amazon, combined with circular human movement to and from hyperendemic working areas, can capture the observed hypoendemic malaria transmission. METHODS: We designed a set of agent-based models that represent local-scale malaria transmission in a typical riverine community in the northern Peruvian Amazon. The models include asymptomatic individuals as well as a full representation of human movements within the community and between the community and external hyperendemic working places. Several theoretical scenarios are explored to verify if and how malaria clinical immunity prevalence and human work-related movements influence the malaria morbidity registered in the community. RESULTS: Agent-based simulations suggest that malaria incidence observed through passive case detection can be reproduced as exclusively generated by the asymptomatic infection reservoir. Scenarios analysis also show that, even if asymptomatic infections are completely eliminated, human movements to and from hyperendemic working areas generate a flow of imported cases that is enough to permit the persistence of transmission in the community. Simulation results were verified over a wide range of clinical immunity prevalence values and over a wide range of percentages of people working in remote hyperendemic areas. This context of unstable malaria transmission is observed to be vulnerable to severe outbreaks. CONCLUSIONS: Asymptomatic malaria infection and occupational circular human movement to hyperendemic transmission areas are designated by agent-based models as possible exclusive causes of residual hypoendemic malaria transmission observed in the Peruvian Amazon. Control strategies are proposed to decrease asymptomatic infection prevalence and to block transmission from asymptomatic individuals to the malaria susceptible population.

Screening municipal waste collectors for cystic echinococcosis and toxocariasis in southwestern Iran.

INTRODUCTION: Cystic Echinococcosis (CE) and toxocariasis caused by the larval stages of intestinal dog worms including Echinococcus granulosus and Toxocara spp. are among the most widespread zoonotic diseases. METHODOLOGY: Four hundred municipal waste collectors were serologically evaluated for CE and toxocariasis. To identify the seropositive cases of CE, an ELISA test was performed using native AgB. Toxocara IgG detection was carried out using ELISA DRG kit (USA), and the seropositive cases were then examined by a Western blot kit (LDBIO, France) to confirm the positive ELISA results. RESULTS: 15 (3.7%) workers were seropositive for CE according to the ELISA. A significant relationship was observed between being seropositive and having contact with soil and dogs. No significant correlations were observed between education and the prevalence of these diseases. Of the 15 seropositive workers for CE, ten worked in district 5 of Ahvaz. Toxocara IgG was identified in 11 (2.7%) cases using the ELISA; however, none of them were confirmed by Western blotting. CONCLUSION: The 3.7% rate of seroprevalence for CE in asymptomatic municipal waste collectors living in urban regions of Ahvaz suggests a high rate. The higher rate of infection among workers in district 5 is likely associated with the presence of stray and owned dogs in that area of the city. A prolonged exposure to contaminated soil, the lack of awareness about the risk of diseases that can be transmitted through waste and the lack of general availability of suitable personal protective equipment for waste collectors might cause infectious 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.