Lutzomyia Sand Fly Diversity and Rates of Infection by Wolbachia and an Exotic Leishmania Species on Barro Colorado Island, Panama

Abstract

BackgroundSand flies (Diptera, Psychodidae, Phlebotominae) in the genus Lutzomyia are the predominant vectors of the protozoan disease leishmaniasis in the New World. Within the watershed of the Panama Canal, the cutaneous form of leishmaniasis is a continuous health threat for residents, tourists and members of an international research community. Here we report the results of screening a tropical forest assemblage of sand fly species for infection by both Leishmania and a microbe that can potentially serve in vector population control, the cytoplasmically transmitted rickettsia, Wolbachia pipientis. Knowing accurately which Lutzomyia species are present, what their evolutionary relationships are, and how they are infected by strains of both Leishmania and Wolbachia is of critical value for building strategies to mitigate the impact of this disease in humans.Methodology and FindingsWe collected, sorted and then used DNA sequences to determine the diversity and probable phylogenetic relationships of the Phlebotominae occurring in the understory of Barro Colorado Island in the Republic of Panama. Sequence from CO1, the DNA barcoding gene, supported 18 morphology-based species determinations while revealing the presence of two possible “cryptic” species, one (Lu. sp. nr vespertilionis) within the Vespertilionis group, the other (Lu. gomezi) within the Lutzomyia-cruciata series. Using ITS-1 and “minicircle” primers we detected Leishmania DNA in 43.3% of Lu. trapidoi, 26.3% of Lu. gomezi individuals and in 0% of the other 18 sand fly species. Identical ITS-1 sequence was obtained from the Leishmania infecting Lu. trapidoi and Lu. gomezi, sequence which was 93% similar to Leishmania (viannia) naiffi in GenBank, a species previously unknown in Panama, but recognized as a type of cutaneous leishmaniasis vectored broadly across northern and central South America. Distinct strains of the intracellular bacterium Wolbachia were detected in three of 20 sand fly species, including Lu. trapidoi, in which it frequently co-occurred with Leishmania.ConclusionsBoth morphological and molecular methods were used to examine an assemblage of 20 sand fly species occurring in the forests of the Panama Canal area. Two of these species, members of separate clades, were found to carry Leishmania at high frequency and hence are likely vectors of leishmaniasis to humans or other mammal species. A single Leishmania species, identified with high confidence as Le. naiffi, was carried by both species. That Le. naiffi is known to cause cutaneous lesions in South America but has hitherto not been reported or implicated in Panama opens the possibility that its range has recently expanded to include the Isthmus or that it occurs as a recent introduction. The occurrence of Leishmania and Wolbachia in Lu. trapidoi identifies one important vector of the disease as a potential target for gene introductions using Wolbachia population sweeps.

New human case reports of cutaneous leishmaniasis by Leishmania (Viannia) naiffi in the Amazon region, Brazil

“…trapidoi and Lu. gomezi (Azpurua et al 2010). In the Amazonian region of Ecuador, natural infection of Lu.…”

Prevalence of Sand Flies andLeishmania donovaniInfection in a Natural Population of FemalePhlebotomus argentipesin Bihar State, India

“…In recent years, different methods have been developed to screen pools or clusters of insects, which can efficiently estimate the infection potential of disease spread by a vector species (Yameogo et al 1999;Martin-Sanchez et al 2006;Bhattarai et al 2009;Severinsson, et al 2010). The rates of sand fly infection varied in accordance with the transmission of the disease, as observed in other studies reported from Panama (Azpurua et al 2010), Athens (Aransay et al 2000), and Turkey (Svobodova et al 2009). The prevalence of infection with Leishmania in the vector female P. argentipes may be exploited as a tool for the surveillance of these infections, and for measuring the success of control programs.…”

“…Molecular methods such as PCR are highly sensitive and easy to perform compared to optical microscopy. Using PCR for the detection of Leishmania has proven useful (Cabrera et al 2002;Bhattarai et al 2009;Azpurua et al 2010). This technique would be expensive and highly labor-intensive if individual insects are analyzed, as the number of sand flies collected could be in the thousands.…”

PRESENCIA DE Wolbachia y Leishmania EN UNA POBLACION DE Lutzomyia evansi PRESENTE EN LA COSTA CARIBE DE COLOMBIA

“…La detección de la infección natural de Wolbachia por la presencia de su ADN en poblaciones silvestres de insectos vectores presentes enáreas donde se reportan enfermedades infecciosas, es importante porque este endosimbionte puede ser usado como control biológico para disminuir las tasas de infección al bloquear la actividad patogénica de diversos microorganismos (virus y pará-sitos) (Ono et al, 2001;Azpurua et al, 2010;Rodriguero & Marcela, 2013;Wallace, 2013). Este estudio reporta y confirma la presencia de Wolbachia en un grupo de machos de Lu.…”