Visceral leishmaniasis outbreaks in Bihar: community-level investigations in the context of elimination of kala-azar as a public health problem

Abstract

Background With visceral leishmaniasis (VL) incidence at its lowest level since the 1960s, increasing attention has turned to early detection and investigation of outbreaks. Methods Outbreak investigations were triggered by recognition of case clusters in the VL surveillance system established for the elimination program. Investigations included ascertainment of all VL cases by date of fever onset, household mapping and structured collection of risk factor data. Results VL outbreaks were investigated in 13 villages in 10 blocks of 7 districts. Data were collected for 20,670 individuals, of whom 272 were diagnosed with VL between 2012 and 2019. Risk was significantly higher among 10–19 year-olds and adults 35 or older compared to children younger than 10 years. Outbreak confirmation triggered vector control activities and heightened surveillance. VL cases strongly clustered in tolas (hamlets within villages) in which > 66% of residents self-identified as scheduled caste or scheduled tribe (SC/ST); 79.8% of VL cases occurred in SC/ST tolas whereas only 24.2% of the population resided in them. Other significant risk factors included being an unskilled non-agricultural laborer, migration for work in a brick kiln, living in a kuccha (mud brick) house, household crowding, habitually sleeping outside or on the ground, and open defecation. Conclusions Our data highlight the importance of sensitive surveillance with triggers for case cluster detection and rapid, careful outbreak investigations to better respond to ongoing and new transmission. The strong association with SC/ST tolas suggests that efforts should focus on enhanced surveillance in these disadvantaged communities.

Optimizing Village-Level Targeting of Active Case Detection to Support Visceral Leishmaniasis Elimination in India

“…Given the many small and large outbreaks in the eight-year time window of KAMIS data, an appropriate threshold could be empirically derived and then prospectively tested. To date, initiation of outbreak investigations has required reporting of case clusters by astute local staff (Priyamvada et al, 2021).…”

“…The well-documented clustering of VL cases at the village and sub-village levels provides the basis for developing ACD targeting strategies (Bulstra et al, 2018;Chapman et al, 2020;Priyamvada et al, 2021). It is not possible to cover all villages in the affected districts of the affected states using any ACD method, particularly the more intensive ones such as house-to-house searches, since Bihar alone has more than 43,000 villages in 33 endemic districts.…”

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“…Canines, marsupials, edentates and rodents (Mann et al, 2021;Tejaswi and Rajan, 2020;Rijal et al, 2019;Aronson et al, 2016). Leishmaniasis is a vector-borne protozoan disease caused by an intracellular parasite which globally affected 350 million people and found endemic in 98 countries, India, Bhutan, Sri Lanka, Nepal, Bangladesh, Indonesia, Pakistan, East African countries including Sub-Saharan Africa, Ethiopia, Eritrea, Somalia, South Sudan and North Sudan, Nigeria, Egypt, South America, Peru, Syria, Brazil, Iraq, Kenya Iran, Saudi Arabia, Middle East, and South East Asia (Karimi et al, 2021;Mann et al, 2021;Priyamvada et al, 2021;Rijal et al, 2019;;Brindha et al, 2021;Murray et al, 2005;Alvar et al, 2012;Zeleke et al, 2021;Tejaswi and Rajan, 2020).…”

“…The parasite is then internalized via macrophages in the liver, spleen, and bone marrow (Rijal et al, 2019;Tejaswi and Rajan, 2020;Karimi et al, 2021). Over 90 sandfly species are known to transmit leishmania parasites (Priyamvada et al, 2021;Rijal et al, 2019;Karimi et al, 2021;Brindha et al, 2021;Mann et al, 2021;Murray et al, 2005;Kamhawi, 2006;Croft et al, 2006;Croft and Olliaro, 2011).…”

“…For all the three forms of leishmaniasis, the infection can range from asymptomatic to severe (Mann et al, 2021;Murray et al, 2005;Herwaldt, 1999;Karimi et al, 2021). Cutaneous and mucosal leishmaniasis can cause substantial morbidity, whereas visceral leishmaniasis (VL) (Kala Azar) can be life threatening and killed many people if it is not detected and treated at the early stage (Priyamvada et al, 2021;Mann et al, 2021;Kumar et al, 2020aKumar et al, , 2020bChappuis et al, 2007;Medley et al, 2015;Rijal et al, 2019;Murray et al, 2005;Karimi et al, 2021;Sundar et al, 2018;Tejaswi and Rajan, 2020;Sundar and Murray, 2005;Sundar et al, 2002Sundar et al, , 2007Zeleke et al, 2021). Therefore, treatment of leishmaniasis can be challenging (Rijal et al, 2019).…”