Sand fly population dynamics and cutaneous leishmaniasis among soldiers in an Atlantic forest remnant in northeastern Brazil

Abstract

Outbreaks of cutaneous leishmaniasis are relatively common among soldiers involved in nocturnal activities in tropical forests. We investigated the population dynamics of sand flies in a military training camp located in a remnant of Atlantic rainforest in northeastern Brazil, where outbreaks of cutaneous leishmaniasis have sporadically been described. From July 2012 to July 2014, light traps were monthly placed in 10 collection sites, being nine sites located near the forest edge and one near a sheep and goat stable. Light traps operated from 5:00 pm to 6:00 am, during four consecutive nights. Leishmania infection in sand flies was assessed using a fast real-time PCR assay. Cases of cutaneous leishmaniasis among soldiers were also investigated. In total, 24,606 sand flies belonging to 25 species were identified. Males (n = 12,683) predominated over females (n = 11,923). Sand flies were present during all months, being more numerous in March (n = 1,691) and April 2013 (n = 3,324). Lutzomyia choti (72.9%) was the most abundant species, followed by Lutzomyia longispina (13.8%), Lutzomyia complexa (5.3%), representing together >90% of the sand flies collected. Forty cases of cutaneous leishmaniasis were recorded among soldiers from January 2012 to December 2014. Leishmania isolates were obtained from eight patients and were all characterized as Leishmania braziliensis. Soldiers and anyone overnighting in Atlantic rainforest remnants should adopt preventative measures such as the use of repellents on bare skin or clothes and insecticide-treated tents.

Home sweet home: sand flies find a refuge in remote indigenous villages in north-eastern Brazil, where leishmaniasis is endemic

“…Similar studies conducted in Pernambuco reported a species richness ranging between 4–25 species [6, 27, 30–32]. Until this study, 41 sand fly species were considered to be present in Pernambuco [29].…”

“…Monthly average temperature (°C), relative humidity (%) and rainfall (mm) data were obtained from station 82900 of the Technology Institute of Pernambuco (ITEP). The saturation deficit (SD) was calculated as follows: SD = (1 – RH/100) × 4.9463 × e 0.0621 × T , where RH is relative humidity and T is temperature [ 6 ].…”

“…forest rodents) and domestic dogs, respectively, being involved as reservoirs in their zoonotic transmission cycles [ 4 , 5 ]. Outbreaks of zoonotic CL in Brazil are commonly detected among males at working age who enter the forest for various reasons, such as for military training [ 6 ]. Deforestation (e.g.…”

Pathogen spillover during land conversion

“…; Dantas‐Torres et al . ). The impact of edge habitats on interspecies contact is the most important mechanism influencing transmission, as demonstrated by yellow fever that transmits from primate reservoirs into humans via mosquito vectors in both highly deforested landscapes and intact natural habitats (Bicca‐Marques & de Freitas ; Almeida et al .…”

“…For frequency-dependent pathogens (such as vector-borne arboviruses), increased land conversion and contact between reservoir and recipient hosts will lead to increased disease incidence in the matrix and increased probability of spillover over a large range of parameter space. For example, in the Neotropics, cutaneous leishmania spillover tends to occur in landscapes where forests dominate deforested matrices, suggesting high densities of core species are necessary to facilitate spillover (Chaves et al 2008;Dantas-Torres et al 2017). The impact of edge habitats on interspecies contact is the most important mechanism influencing transmission, as demonstrated by yellow fever that transmits from primate reservoirs into humans via mosquito vectors in both highly deforested landscapes and intact natural habitats (Bicca-Marques & de Freitas 2010;Almeida et al 2012;Romano et al 2014).…”