Intensely clustered outbreak of visceral leishmaniasis (kala-azar) in a setting of seasonal migration in a village of Bihar, India

Abstract

Background: A visceral leishmaniasis outbreak was reported from a village in a low-endemic district of Bihar, India. Methods: Outbreak investigation with house-to-house search and rapid test of kala-azar suspects and contacts was carried out. Sandfly collection and cone bio-assay was done as part of entomological study.Results: A spatially and temporally clustered kala-azar outbreak was found at Kosra village in Sheikhpura district with 70 cases reported till December 2018. Delay of more than a year was found between diagnosis and treatment of the index case. The southern hamlet with socio-economically disadvantaged migrant population was several times more affected than rest of the village (attack rate of 19.0% vs 0.5% respectively, OR MH = 39.2, 95% CI 18.2-84.4). The median durations between onset of fever to first contact with any health services, onset to kala-azar diagnosis, diagnosis to treatment were 10 days (IQR 4-18), 30 days (IQR 17-73) and 1 day (IQR 0.5 to 3), respectively, for 50 kala-azar cases assessed till June 2017. Three-fourths of these kala-azar cases had out-of-pocket medical expenditure for their condition. Known risk factors for kala-azar such as illiteracy, poverty, belonging to socially disadvantaged community, migration, residing in kutcha houses, sleeping in rooms with unplastered walls and nonuse of mosquito nets were present in majority of these cases. Only half the dwellings of the kala-azar cases were fully sprayed. Fully gravid female P. argentipes collected post indoor residual spraying (IRS) and low sandfly mortality on cone-bioassay indicated poor effectiveness of vector control. Conclusions:There is need to focus on low-endemic areas of kala-azar. The elimination programme should implement a routine framework for kala-azar outbreak response. Complete case-finding, use of quality-compliant insecticide and coverage of all sprayable surfaces in IRS could help interrupt transmission during outbreaks.

Predicted Impact of COVID-19 on Neglected Tropical Disease Programs and the Opportunity for Innovation

“…While it is unlikely that new vector-control activities can be introduced during the COVID-19 pandemic, continuation of existing measures may help, as evident during program disruptions due to the West African Ebola outbreak in Guinea, where areas with vector control saw fewer gHAT cases after normal activities resumed [ 14 ]. For VL, the effect of suspending indoor residual spraying efforts should be expected to be more variable at local village levels, ranging from very limited impact to outbreaks as observed in Kosra, India [ 15 , 16 ]. For LF, the use of bednets has a small impact relative to MDA and, in addition, bednets will not be effective in areas where the predominant vector species bites during the day [ 17 , 18 ].…”

Time for a village-level strategy for the elimination of kala-azar (visceral leishmaniasis) in India: analysis of potential kala-azar outbreak situation in 2018

“…20 An explosive kala-azar outbreak of 74 cases in Kosra village situated in a low-endemic area, provides an appropriate example. 7 A village-level strategy for the prompt identification and outbreak response is not only likely to help reduce the kala-azar burden but would also help sustain the reduction of cases in the maintenance phase of any kala-azar elimination programme.…”

“…6 This contributes to the characteristic clustering of cases and outbreaks of kala-azar evolving focally and quickly within a few months. 7…”

Costs and outcomes of active and passive case detection for visceral leishmaniasis (Kala-Azar) to inform elimination strategies in Bihar, India

“…Clustered outbreaks have been recently documented in previously low-incidence settings in Bihar, possibly in part due to decreased host competence in areas with few VL infections [ 35 ]. In these populations, a greater proportion show decreased immunity over time and are disproportionately susceptible to transmission from acute VL infections [ 36 , 37 ].…”