American Cutaneous Leishmaniasis in Panama: a historical review of entomological studies on anthropophilic Lutzomyia sand fly species

Abstract

We review existing information on the epidemiology of American Cutaneous Leishmaniasis (ACL) in Panama, with emphasis on the bionomics of anthropophilic Lutzomyia sand fly species. Evidence from Panamanian studies suggests that there are six anthropophilic species in the country: Lutzomyia trapidoi, Lu. panamensis, Lu. gomezi, Lu. ylephiletor, Lu. sanguinaria and Lu. pessoana (Henceforth Lu. carrerai thula). In general, these taxa are abundant, widespread and feed opportunistically on their hosts, which make them potential transmitters of pathogens to a broad range of wildlife, domesticated animals and humans. Furthermore, nearly all man-biting species in Panama (with the exception of Lu. gomezi) expand demographically during the rainy season when transmission is likely higher due to elevated Leishmania infection rates in vector populations. Despite this, data on the distribution and prevalence of ACL suggest little influence of vector density on transmission intensity. Apart from Lu. trapidoi, anthropophilic species seem to be most active in the understory, but vertical stratification, as well as their opportunistic feeding behavior, could vary geographically. This in turn seems related to variation in host species composition and relative abundance across sites that have experienced different degrees of human alteration (e.g., deforestation) in leishmaniasis endemic regions of Panama.

Figure 1

Epidemiological patterns of Leishmania ( Viannia ) panamensis in Panama: (A) Sylvatic focus of American Cutaneous Leishmaniasis; (B) Non-stable transmission – farmers and hunters; (C) Endemic transmission – indigenous communities; (D) Epidemic transmission – military personnel, tourists and teachers; (E) Tree buttresses; (F) Forest leaf-litter; (G) Potential secondary reservoirs Proechimys semispinosus (Spiny rat), Didelphis marsupialis (Opossum), Dasyprocta punctata (Agoutis), Odocoileus virginianus (White-tail deer); and (H) Primary reservoir Choloepus hoffmanni (Two-toed sloth).

Figure 2

The chart shows the number of studies carried out in Panama about American Cutaneous Leishmaniasis (ACL) and the bionomic (ecology + behavior) of anthropophilic Lutzomyia sand fly species from 1920 to the present. The information is broken down by time period and research area (in numbers at the bottom and words and different colors on the right side, respectively).

Figure 3

The graphs show the chronological distribution of American Cutaneous Leishmaniasis (ACL) cases in Panama in two different periods of time: (A) represents the number of clinical cases recorded from 1953 to 1965 and (B) from 2000 to 2013. Information in A and B was obtained directly from Walton et al., (1968) and from the department of epidemiology of the Panamanian Ministry of Health (MINSA - as it is abbreviated in Spanish), respectively.