Asymptomatic infection of visceral leishmaniasis in hyperendemic areas of Vaishali district, Bihar, India: a challenge to kala-azar elimination programmes

Abstract

A cohort of 91 asymptomatic individuals with visceral leishmaniasis (VL) were identified during base line screening using recombinant 39-aminoacid antigen (rk-39) and polymerase chain reaction (PCR) conducted from December 2005 to June 2006 involving 997 individuals of two highly endemic villages of Vaishali district, Bihar. The point prevalence of asymptomatic infection was 98 per 1000 persons at baseline. There was no statistically significant difference between rk-39 and PCR positivity rate (P>0.05), even though PCR positivity alone was found significantly higher (4.2%) than rk-39 positivity alone (2.6%). The monthly follow-up of the asymptomatic cohort revealed a disease conversion rate of 23.1 per 100 persons within a year. There was a statistically significant difference in conversion of disease when individuals were positive by both tests as compared to single tests by rk-39 and PCR (P<0.01). Disease conversion rate in the subjects residing in households with a history of VL (62%, 13/21) was higher than those residing in the households without a history of VL (38%, 8/21). Most of the identified asymptomatic individuals were from low socio-economic strata similar to that of VL cases in general. Apart from rk-39, PCR may be considered for screening of asymptomatic Leishmania donovani infection in large-scale epidemiological studies. Screening of asymptomatic cases and their close follow-up to ascertain early detection and treatment of VL may be considered in addition to the existing VL control strategies.

Evaluation of PCR procedures for detecting and quantifying Leishmania donovani DNA in large numbers of dried human blood samples from a visceral leishmaniasis focus in Northern Ethiopia

“…PCR -based methods for detecting parasites are highly sensitive and have the added advantage that they may be performed on dry specimens without the need for cold-storage [22,23]. In order to optimize our accomplishments from the current cohort studies, we experimented with primers for ITS1 and 7SL RNA gene [17,18].…”

Strong Association between Serological Status and Probability of Progression to Clinical Visceral Leishmaniasis in Prospective Cohort Studies in India and Nepal

“…In a study by Das et al 21 out of 91 polymerase chain reaction (PCR) and/or recombinant K39 (rK39) positive but asymptomatic individuals (23.1%) progressed to clinical VL over a follow-up period of one year [14]. Singh et al reported 38 VL cases among 55 asymptomatic seropositive subjects followed up for one year (69%) [15].…”

Towards elimination of visceral leishmaniasis in the Indian subcontinent—Translating research to practice to public health

“…The strategy needs a paradigm shift from preventing disease to preventing infection and interrupting transmission. The infectiousness of asymptomatic individuals infected with Leishmania , markers for progression to VL disease, the role of domestic animals in transmission, and the potential of PKDL as a reservoir for infection need to be better understood [92, 125–127]. The implications of HIV coinfection with VL for treatment failure and relapse, transmission dynamics, and development of parasite resistance to drugs need to be studied further, and strategies need to be developed and tested as appropriate [42].…”