Dispersal and Memory of Sand Flies in an Endemic Area of Cutaneous Leishmaniasis, Southern Brazil

Abstract

The dispersal of and the existence of memory in sand flies were measured in a transmission area of cutaneous leishmaniasis, in the municipality of Bandeirantes, Paraná, Brazil. Sand flies were caught in a rural area, with Shannon trap installed in the forest and three Falcão traps installed in a human-inhabited environment (HIE) and three others in an impacted environment presently uninhabited by humans (EUH), from 1800 to 0600 hours. The captured sand flies were marked with yellow, blue, or red fluorescent powder, according to the environments where they were captured. All marked sand flies were released at 0700 hours at a point between the three environments. The recaptures were made with 28 Falcão traps, distributed in the environments from for 10 consecutive days. The sand flies recaptured were examined under a stereomicroscope and later identified. It was concluded that sand flies are able to disperse over an average distance of 73 m, reaching 130 m in 24 h, showing that: 1) the sand flies were attracted with different intensities to each environment, and the ability to move among different environments allows the existence of enzootic cycle of Leishmania; 2) the sand flies possess a spatial memory, olfactory memory, or both, that enable them to return to the environment where they were captured initially, although the distances were different.

Learning and Memory in Disease Vector Insects

“…Using mark-recapture methods, Guerra-Silva et al [36] showed that sand flies, the vectors of the American cutaneous leishmaniasis, were able to return to their initial location after being released in an unknown area. The use of learned spatial, visual or olfactory cues by sandflies could be just one of the possible explanations for this behavior, but further work is still needed to assess whether or not sand flies rely on learned information.…”

Male Psyllids Differentially Learn in the Context of Copulation

“…Recent advances in disease vector pest management have highlighted the importance of understanding the effects of experience on insect behavior [23,24,25]. Human disease vectors, such as mosquitoes [26,27,28,29,30], kissing bugs [31,32], tsetse flies [33,34], and sandflies [35], demonstrate ecologically significant learning events, driving host selection and oviposition site preferences via visual, olfactory, and even thermal stimulus experiences [23]. Similarly, D. citri behaviors, ranging from host preference to mate choice, may be guided by experience-dependent visual and olfactory associations with the host environment and conspecifics [36].…”

Synthetic sex-aggregation pheromone of Lutzomyia longipalpis, the South American sand fly vector of Leishmania infantum, attracts males and females over long-distance

“…There are many different possible explanations for the marked differences observed in the distance that the males and females would travel and the recapture rates at the two sites. Attraction and capture of an insect is a complex process involving multiple components, several critical elements may individually or collectively be important; i) spatial memory/olfactory memory: one possibility is that sand flies were capable of learning a familiar area map to facilitate movement and specific routes between feeding, resting and breeding sites [ 53 – 56 ], ii) population density: a natural aggregation in the chicken shed producing large quantities of pheromone would compete with the synthetic pheromone, causing a reduction in the number of specimens attracted to pheromone-baited traps [ 53 , 57 ], iii) fidelity to specific hosts might influence the recruitment of sand flies in locations in which there is an availability of sources of blood [ 53 , 55 , 58 ], and iv) abiotic factors could explain the dispersal of Lu . longipalpis at the two sites, in particular high wind speed has been attributed to decreasing or failing collections as it interferes with sand fly flight [ 59 – 61 ].…”