Risk factors for visceral leishmaniasis in a new epidemic site in Amhara Region, Ethiopia

We conducted a case-control study to evaluate risk factors for visceral leishmaniasis during an epidemic in a previously unaffected district of Ethiopia. We also collected blood and bone marrow specimens from dogs in the outbreak villages. In multivariable analyses of 171 matched case-control pairs, dog ownership, sleeping under an acacia tree during the day, and habitually sleeping outside at night were associated with significantly increased risk. Specimens from 7 (3.8%) dogs were positive by immunofluorescent antibody test (IFAT) and both enzyme-linked immunosorbent assays (ELISAs), whereas Leishmania DNA was detected in 5 (2.8%) bone marrow aspirates (from 3 seropositive and 2 seronegative dogs). Insecticide-treated nets may only protect a portion of those at risk. Further research on the vectors, the role of the dog in the transmission cycle, and the effect of candidate interventions are needed to design the best strategy for control

Risk Factors for Visceral Leishmaniasis among Residents and Migrants in Kafta-Humera, Ethiopia

<div><p>Background</p><p>Visceral leishmaniasis is a lethal parasitic disease transmitted by phlebotomine sand flies. The largest focus of VL in Ethiopia is located in the lowland region bordering Sudan, where the epidemiology is complicated by the presence of thousands of seasonal agricultural workers who live under precarious conditions.</p><p>Methodology/Principal Findings</p><p>We conducted two parallel case-control studies to identify factors associated with VL risk in residents and migrants. The studies were conducted from 2009 to 2011 and included 151 resident cases and 157 migrant cases, with 2 matched controls per case. In multivariable conditional regression models, sleeping under an acacia tree at night (odds ratios (OR) 5.2 [95% confidence interval 1.7–16.4] for residents and 4.7 [1.9–12.0] for migrants), indicators of poverty and lower educational status were associated with increased risk in both populations. Strong protective effects were observed for bed net use (OR 0.24 [0.12–0.48] for net use in the rainy season among residents, OR 0.20 [0.10–0.42] for any net use among migrants). For residents, living in a house with thatch walls conferred 5-fold and sleeping on the ground 3-fold increased risk. Among migrants, the risk associated with HIV status was borderline significant and sleeping near dogs was associated with 7-fold increased risk.</p><p>Conclusions/Significance</p><p>Preventive strategies should focus on ways to ensure net usage, especially among migrant workers without fixed shelters. More research is needed to understand migration patterns of seasonal labourers and vector bionomics.</p></div

Multivariable conditional logistic regression models for factors associated with risk of visceral leishmaniasis among residents and migrants in Humera, Tigray, Ethiopia.

1<p>Odds ratios (OR) and 95% confidence intervals (CI).</p>2<p>Data on HIV status missing for at least one member of 21 case-control sets; these sets therefore excluded from analysis.</p

Demographic characteristics of participants in matched case-control studies of visceral leishmaniasis among long-term residents and migrants in Humera, Tigray region, Ethiopia.

<p>Demographic characteristics of participants in matched case-control studies of visceral leishmaniasis among long-term residents and migrants in Humera, Tigray region, Ethiopia.</p

Resident analysis: Behavioral risk factors for visceral leishmaniasis, Humera, Tigray region, Ethiopia.

1<p>Odds ratio (OR), 95% confidence intervals (CI) and p values derived from univariable conditional logistic regression models. Number and percentage for each factor provided for reference only.</p

Resident analysis: household-level risk factors for visceral leishmaniasis, Humera, Tigray region, Ethiopia.

1<p>Odds ratios (OR), 95% confidence intervals (CI) and p values derived from univariable conditional logistic regression models. Number and percentage for each factor provided for reference only.</p

Typical Humera shelter with walls of grass thatch and nearby acacia tree.

<p>Typical Humera shelter with walls of grass thatch and nearby acacia tree.</p

Migrant analysis: risk factors for visceral leishmaniasis in Humera, Tigray region, Ethiopia.

1<p>Odds ratios (OR), 95% confidence intervals (CI) and p values derived from univariable conditional logistic regression models. Number and percentage for each factor provided for reference only.</p