Short-term movement of Phlebotomus argentipes (Diptera: Psychodidae) in a visceral leishmaniasis-endemic village in Bihar, India

Abstract

Visceral leishmaniasis (VL), transmitted by the sand fly, Phlebotomus argentipes, is frequently reported on the Indian subcontinent where its basic ecology is largely unknown. Our objective was to evaluate the effectiveness of sugar solution (10%), containing colored food dye (0.5%) applied to peridomestic vegetation, to mark P. argentipes and subsequently estimate horizontal movement by capturing dye‐marked specimens in CDC light traps in a village in Bihar, India. From September 30 to November 27, 2016, a total of 667 captured sand flies were successfully marked using sugar baits, of which 608 were P. argentipes (~91.2%). Although the majority of P. argentipes were captured <100 m from the respective marking sites, a significantly greater proportion of females (15.7%) was captured >100 m from marking sites when compared to males (3.1%). Sand flies that ingested sugar bait were only collected from areas containing >eight vegetation types and mature banana plants. The average number of marked P. argentipes captured per trap‐night (±SD) <100 m from respective marking sites was greatest in peridomestic vegetation (Males: 0.9 ± 1.97; Females: 0.63 ± 1.44), followed by areas with livestock (Males: 0.66 ± 2.75; Females: 0.24 ± 0.69), and areas with humans only (Males: 0.1 ± 0.36; Females: 0.11 ± 0.31). To our knowledge, this is the only study in Bihar in which sand flies have been marked with food dyes, and the results demonstrate the potential usefulness of food dyes in estimating short‐term movement of P. argentipes. Limitations of this experiment are that the number of each trap location type, vegetation composition at marking sites, and distance of all trap sites from marking sites were not homogenous, and the total number of marked sand flies collected were relatively low. In spite of the above limitations, these data should prove useful in developing a large‐scale study addressing the caveats. Results of such a study could provide important information regarding the dynamics of VL transmission and inspire managers to pursue alternative means of sand fly control on the Indian subcontinent.

Inferring transmission trees to guide targeting of interventions against visceral leishmaniasis and post–kala-azar dermal leishmaniasis

“…This is consistent with findings from a spatial analysis of occurrence of VL cases around index cases in Muzaffarpur, Bihar, India (38), which found a combination of short and long distances (from tens to hundreds of meters) from the closest index case for secondary VL cases diagnosed close together in time. The inferred transmission distances are also consistent with limited available data on the flight range of the P. argentipes sandfly vector, which suggests a short-term (0.5 to 2.5 d) flight range of around 300 m (39), and with the flight range of fed females of a species in the same genus of a few hundred meters (up to a maximum of nearly 1 km) (40). Considering that index cases are often detected after a longer delay than subsequent cases and there will be some delay in mounting reactive interventions, such as active case detection and/or targeted IRS around the index case(s), interventions will need to be applied in a large radius (up to 500 m) around index cases to be confident of capturing all secondary cases and limiting transmission.…”

Spatial modelling of sand fly vector’s response to a synthetic sex-aggregation pheromone: impact on the incidence of visceral leishmaniasis in rural and urban settings

“…The parallel situation for anthroponotically transmitted L. donovani causing human VL in the Indian subcontinent, is illustrated by the increased risk of infection and VL in humans living with, or within similarly close proximity of, active VL case households (Chapman et al 2018; Chapman et al, 2020). Within-household and/or near neighbour aggregation patterns are likely to arise in part due to the usual short range dispersal (<100m) of the respective sand fly vectors, measured by mark-release-recapture studies (Poché 2018; Dye 1991; Morrison 1993; Galvis-Ovallos 2018).…”

Towards a Sustainable Vector-Control Strategy in the Post Kala-Azar Elimination Era

“…In fact, sand fly abundance in traps placed in vegetation and the outskirts of endemic villages support the contention that Ph. argentipes in Bihar are now exophilic (Poche et al, 2018b).…”

“…argentipes has been assumed to be almost exclusively endophilic and endophagic (Chowdhury et al, 2016). However, recent reports from Bihar highlight its exophilic and exophagic behavior, suggesting that to be effective, vector control must also encompass outdoor sand fly populations, especially in places where many residents sleep outdoors (Poche et al, 2011;Poche et al, 2012;Poche DM et al, 2017;Govil et al, 2018;Poche et al, 2018b).…”