Habitat and seasonality of Psychodopygus wellcomei help incriminate it as a vector of Leishmania braziliensis in Amazônia and northeast Brazil

Ecological niche modelling for predicting the risk of cutaneous leishmaniasis in the Neotropical moist forest biome

A major challenge of eco-epidemiology is to determine which factors promote the transmission of infectious diseases and to establish risk maps that can be used by public health authorities. The geographic predictions resulting from ecological niche modelling have been widely used for modelling the future dispersion of vectors based on the occurrence records and the potential prevalence of the disease. The establishment of risk maps for disease systems with complex cycles such as cutaneous leishmaniasis (CL) can be very challenging due to the many inference networks between large sets of host and vector species, with considerable heterogeneity in disease patterns in space and time. One novelty in the present study is the use of human CL cases to predict the risk of leishmaniasis occurrence in response to anthropogenic, climatic and environmental factors at two different scales, in the Neotropical moist forest biome (Amazonian basin and surrounding forest ecosystems) and in the surrounding region of French Guiana. With a consistent data set never used before and a conceptual and methodological framework for interpreting data cases, we obtained risk maps with high statistical support. The predominantly identified human CL risk areas are those where the human impact on the environment is significant, associated with less contributory climatic and ecological factors. For both models this study highlights the importance of considering the anthropogenic drivers for disease risk assessment in human, although CL is mainly linked to the sylvatic and peri-urban cycle in Meso and South America.

Aspects on the Ecology of Phlebotomine Sand Flies (Diptera: Psychodidae) From Guaraí, State of Tocantins, Brazil, Endemic Area for American Cutaneous Leishmaniasis

In Brazil, American cutaneous leishmaniasis (ACL) ecology involves a diversity of Leishmania species transmitted by different sand fly species. Workers involved in agricultural activities are those mainly affected by ACL in some regions from Tocantins State (TO), Brazil, where the disease can be established in new settlements. The objective of this study was to examine the seasonal and hourly frequency of sand fly species, focusing on the potential vectors of ACL, in a settlement in Guaraí (TO), an ACL transmission area. Sand flies were captured in forested area close to Pedra Branca Agricultural Project settlement, from March 2006 until December 2007, using Shannon trap. Monthly captures were made from 06:00 p.m. to 10:00 p.m., and 24-h captures were done twice per semester, from 06:00 a.m. to 06:00 a.m. A total of 10,089 specimens from 30 species were identified. Psychodopygus complexus Mangabeira, Psychodopygus llanosmartinsi Fraiha & Ward, and Nyssomyia antunesi Coutinho were the most abundant species. Nyssomyia antunesi was more frequent during the dry period, whereas Ps. complexus and Ps. llanosmartinsi had high frequencies during the rainy season. Precipitation was positively correlated with Ps. complexus and Ps. llanosmartinsi abundance, and negatively correlated with Ny. antunesi During 24-h captures, the majority of specimens were captured during the night followed by a decrease at dawn. The behavior and previous finding of natural infection by Leishmania (Viannia) braziliensis of Ps. complexus led us to the conclusion that this species can be a potential vector of L. (V.) braziliensis during the rainy season in Guaraí.

Phlebotomines (Diptera: Psychodidae) in a Hydroelectric System Affected Area from Northern Amazonian Brazil: Further Insights into the Effects of Environmental Changes on Vector Ecology

During 2012-2015, an entomological survey was conducted as part of a phlebotomine (Diptera: Psychodidae) monitoring program in an area influenced by the Santo Antônio do Jari hydroelectric system (Amapá State, Brazil). The purpose was to study aspects of Amazon/Guianan American cutaneous leishmaniasis (ACL) vectors subjected to stresses by anthropogenic environmental changes. For sampling, CDC light traps were positioned 0.5, 1, and 20 m above ground at five capture locations along the Jari River Basin. Fluctuations in phlebotomine numbers were analyzed to determine any correlation with rainfall, dam waterlogging, and/or ACL cases, from May 2012 to March 2015. We captured 2,800 individuals, and among 45 species identified, Bichromomyia flaviscutellata, Nyssomyia umbratilis, and Psychodopygus squamiventris s.l. were determined to be the main putative vectors, based on current knowledge of the Amazon/Guianan ACL scenario. Rainfall, but not complete flooding, was relatively correlated with phlebotomine fluctuation, mainly observed for Ps. squamiventris s.l., as were ACL cases with Ny. umbratilis. Behavioral changes were observed in the unexpected high frequency of Bi. flaviscutellata among CDC captures and the noncanopy dominance of Ny. umbratilis, possibly attributable to environmental stress in the sampled ecotopes. Continuous entomological surveillance is necessary to monitor the outcomes of these findings.

Natural Leishmania (Viannia) spp. infections in phlebotomine sand flies (Diptera: Psychodidae) from the Brazilian Amazon region reveal new putative transmission cycles of American cutaneous leishmaniasis

In Amazonian Brazil the etiological agents of American cutaneous leishmaniasis (ACL) belong to at least seven Leishmania species but little is known about the putative phlebotomine sand fly vectors in different biomes. In 2002–2003 a survey of the phlebotomine fauna was undertaken in the “Floresta Nacional do Tapajós”, Belterra municipality, in the lower Amazon region, western Pará State, Brazil, where we recently confirmed the presence of a putative hybrid parasite, L. (V.) guyanensis × L. (V.) shawi shawi. Sand flies were collected from Centers for Disease Control (CDC) light traps, Shannon traps and by aspiration on tree bases. Females were dissected and attempts to isolate any flagellate infections were made by inoculating homogenized midguts into Difco B⁴⁵ medium. Isolates were characterized by monoclonal antibodies and isoenzyme electrophoresis. A total of 9,704 sand flies, belonging to 68 species or subspecies, were collected. Infections were found in the following sand flies: L. (V.) naiffi with Psychodopygus hirsutus hirsutus (1) and Ps. davisi (2); and L. (V.) shawi shawi with Nyssomyia whitmani (3) and Lutzomyia gomezi (1). These results provide strong evidence of new putative transmission cycles for L. (V.) naiffi and L. (V.) s. shawi.

Ecology of Lutzomyia longipalpis in an area of visceral leishmaniasis transmission in north-eastern Brazil

Visceral leishmaniasis is a major public health issue in South America, where the disease is rapidly spreading. Changes in ecology and distribution of the principal vector, Lutzomyia longipalpis are among the factors accounting for the increasing incidence of the disease in this region. However, information about the ecology of L. longipalpis is still incipient, which may directly impair the implementation of effective control programs. Herein, the ecology of L. longipalpis was studied in a focus of visceral leishmaniasis in north-eastern Brazil. From August 2009 to August 2010, phlebotomine sand flies were monthly collected in four localities using CDC light traps (~37 per month) and a lantern-baited Shannon trap with mouth aspirators. A total of 24,226 phlebotomine sand flies were collected with light traps and 375 with mouth aspirators. The most abundant species was L. longipalpis, representing 97.9% of the specimens collected with light traps and 91.5% with the mouth aspirator. Other species (Lutzomyia evandroi, Lutzomyia lenti and Lutzomyia sallesi) were found in low numbers. Most phlebotomine sand flies (94.6%) were collected at chicken coops and corrals. No significant correlation was found between the monthly abundance of phlebotomine sand flies and the monthly averages of temperature, relative humidity or rainfall. However, interestingly enough, 82.4% of L. longipalpis specimens were collected in months when relative humidity surpassed 75%. This study points out that this vector is well adapted to live in different habitats and to different climate conditions. It also suggests that some north-eastern populations of L. longipalpis may be more xerotolerant than southern populations. Further studies to assess the relationship between microclimate and L. longipalpis density in different Brazilian regions are advised.

Biology of phlebotomine sand flies as vectors of disease agents

Phlebotomines are the sole or principal vectors of Leishmania, Bartonella bacilliformis, and some arboviruses. The coevolution of sand flies with Leishmania species of mammals and lizards is considered in relation to the landscape epidemiology of leishmaniasis, a neglected tropical disease. Evolutionary hypotheses are unresolved, so a practical phlebotomine classification is proposed to aid biomedical information retrieval. The vectors of Leishmania are tabulated and new criteria for their incrimination are given. Research on fly-parasite-host interactions, fly saliva, and behavioral ecology is reviewed in relation to parasite manipulation of blood feeding, vaccine targets, and pheromones for lures. Much basic research is based on few transmission cycles, so generalizations should be made with caution. Integrated research and control programs have begun, but improved control of leishmaniasis and nuisance-biting requires greater emphasis on population genetics and transmission modeling. Most leishmaniasis transmission is zoonotic, affecting the poor and tourists in rural and natural areas, and therefore control should be compatible with environmental conservation.

Dinâmica espaço-temporal de flebotomíneos (Diptera, Psychodidae) do município de Santa Quitéria, área de cerrado do Estado do Maranhão, Brasil

A flutuação sazonal, a freqüência horária e a ocorrência dos flebotomíneos nos ambientes intradomiciliar, peridomiciliar e extradomiciliar (cerrado), no município de Santa Quitéria, Estado do Maranhão foram estudados. Os espécimes foram capturados entre 18 e 6 horas, de maio de 1999 a abril de 2000, com armadilhas luminosas tipo CDC. Foram coletados 4.880 espécimes de 11 espécies. A riqueza e abundância foram maiores no peridomicílio (11 espécies; 50,1% dos espécimes), seguido pelo intradomicílio (9 espécies, 34%) e cerrado (7 espécies, 15,8%). Duas espécies foram encontradas na estação chuvosa, uma na estiagem e oito em ambas estações. Na estiagem foram registradas elevadas freqüências de Lutzomyia longipalpis Lutz & Neiva, 1912 (88,4%), L. evandroi Costa Lima & Antunes, 1936 (83,6%), L. lenti Mangabeira, 1938 (86%) e L. shannoni Dyar, 1929 (100%), enquanto as freqüências de L. quinquefer Dyar, 1929 (100%) e L. whitmani Antunes & Coutinho, 1939 (75%) foram maiores no período chuvoso. Os flebotomíneos foram encontrados a noite inteira, mas os horários de maior freqüência variaram de acordo com a espécie, observando-se picos no crepúsculo vespertino e primeiras horas da noite: L. quinquefer (18 h - 19 h); L. goiana Martins, Falcão & Silva, 1962 (18 h - 21 h); L. whitmani (19 h - 21 h) e L. longipalpis (20 h - 21 h) e ao longo da noite e no crepúsculo matutino: L. evandroi (21 h - 23 h e 3 h - 5 h), L. longipalpis (1 h - 3 h), L. lenti (22 h - 23 h e 4 h - 5 h). A ocorrência dos flebotomíneos nos diferentes ambientes, horários e estações vem sendo acompanhada por notificações de vários casos de leishmanioses cutânea e visceral.

Seasonal transmission of Leishmania (Leishmania) mexicana in the state of Campeche, Yucatan Peninsula, Mexico

In the Yucatan Peninsula, Mexico, localized cutaneous leishmaniasis (LCL) caused by Leishmania (Leishmania) mexicana is a typical wild zoonosis restricted to the forest, and humans are only accidentally involved. The transmission of L. (L.) mexicana has been related to the patient's occupation: "chicleros" (gum collectors) and agricultural workers. The objective of this study was to document L. (L.) mexicana seasonally of transmission in endemic areas of LCL in the state of Campeche, Yucatan Peninsula, Mexico. The timing of incidence of LCL in humans during 1993-1994, as well as the rate and time of infection in rodents and sand flies between February 1993 and March 1995 were analyzed. Rodents and sand flies were found infected between November and March, when men carried out their field activities and are exposed. Based on results analyzed, it is concluded that L. (L.) mexicana in the endemic area of LCL in the state of Campeche, Yucatan Peninsula, Mexico, presents a seasonal transmission restricted to the months of November to March. The knowledge of the timing of the transmission cycle in an endemic area of leishmaniasis is very important because intervention measures on the high-risk focus and population might be restricted.

Wild and synanthropic hosts of Leishmania (Viannia) braziliensis in the endemic cutaneous leishmaniasis locality of Amaraji, Pernambuco State, Brazil

Evidence of Leishmania infection was found in small mammals captured between 1996 and 2000 in the Amaraji region, Pernambuco State, Brazil. The kDNA polymerase chain reaction (PCR), using primers specific for subgenus L. (Viannia), was positive for 43/153 water rats (Nectomys squamipes), 13/81 black rats (Rattus rattus), 15/103 grass mice (Bolomys lasiurus), 1/14 marsh mice (Holochilus scieurus), 2/50 field mice (Akodon arviculoides), 2/12 woolly opossums (Marmosa sp.), and 5/37 common opossums (Didelphis albiventris). This same kDNA PCR was positive for 12/61 dog and 8/58 horse skin samples. In paired PCR tests of 203 small mammals, 18.7% were positive with the kDNA primers and 18.2% with rDNA primers. Amastigotes were seen in 26/460 and L. (V.) braziliensis was isolated from 5 grass mice and 1 black rat. We concluded that small mammals, particularly rodents, are infected with parasites of the subgenus L. (Viannia). The isolation of L. (V.) braziliensis zymodeme IOC/Z74 from 6 rodents and the fact that all the other described L. (Viannia) species that commonly infect humans have never been found in rodents or marsupials leads us to suggest that the positive PCRs indicate infections of L. (V.) braziliensis. The isolation of zymodeme IOC/Z74 from humans reinforces our hypothesis that small, ground-loving mammals, such as rodents are the primary reservoirs of L. (V.) braziliensis.

Genetic variation in populations of Leishmania species in Brazil

The population structure of strains of Leishmania (Viannia) braziliensis sensu lato from Pará State and Paraná State in Brazil, of L. (V.) shawi and L. (Leishmania) amazonensis from Pará State, and the relationships of type strains of the subgenera L. (Viannia) and L. (Leishmania) were examined by the random-amplified polymorphic deoxyribonucleic acid (RAPD) technique. Four different primers (M13-40, QG1, L15996 and delta gt11R) were used. The bands were analysed using the neighbor-joining (NJ) and unweighted pair-group method with arithmetic averages (UPGMA) algorithms of the MEGA package. The topology of the NJ and UPGMA trees was very similar but they were not always identical. Both trees differentiated the standard strains of the different species. Strains from the same location were grouped together only in the UPGMA phenogram of the M13-40 primer. L. (V.) braziliensis isolates from Paraná State were genetically closer to those from Paragominas, Pará State than to those from the Amazonian regions of Carajás in Pará State and Peru. The relationship was not dependent on geographical distance. It is postulated that the groups arose from different origins, in which the Amazonian stocks were related to Psychodopygus sand flies while the Paraná strains originated from a gene pool transmitted by Lutzomyia sand flies such as Lutzomyia (Nyssomyia) whitmani. Transmission by Ps. complexus in Paragominas is considered to be a secondary adaptation from the Lutzomyia leishmanial gene pool. Although the vectors of L. (V.) braziliensis are poorly known in the Amazon region, there is strong evidence that the major vectors are all Psychodopygus spp. There was a high degree of genetic variability amongst the L. (V.) shawi strains and there was no clear grouping according to the strains' origins. The genetic variability amongst L. (L.) amazonensis strains from the same locations was much lower but they formed 2 groups which coincided with their origin. Our results support the clonal population structure of Leishmania isolates and suggest that their distribution is related to the origin of the gene pool as well as to present vector and reservoir movements.

Distribution of sandflies (Diptera:Psychodidae) on tree-trunks in a non-flooded area of the Ducke Forest Reserve, Manaus, AM, Brazil

Sandflies were collected in the base of tree-trunks in the seasons of high and least rainfall in the Ducke Forest Reserve, near Manaus in the State of Amazonas. Lutzomyia umbratilis was the most abundant sandfly species. Caryocar villosum, Chrysophyllum amazonicum, Dinizia excelsa, Eschweilera atropetiolata and Parkia multijuga were the tree species on which most sandflies were collected and relative abundance were related to trunk characteristics. Seasonal patterns of sandfly distribution in the forest were observed.

Psychodopygus complexus, a new vector of Leishmania braziliensis to humans in Pará State, Brazil

This paper reports the finding of 4 specimens of Psychodopygus complexus, captured in the Paragominas region of Pará State, Brazil, naturally infected with trypanosomatids that were positively identified as Leishmania (Viannia) braziliensis. Attention is drawn to the importance of this species as a vector since it is highly anthropophilic and has a very extensive geographical distribution in the lower Amazon region of Pará State south of the Amazon river, including the island of Marajó.

Leishmaniasis in Brazil. XXIV. Natural flagellate infections of sandflies (Diptera: Psychodidae) in Pará State, with particular reference to the rôle of Psychodopygus wellcomei as the vector of Leishmania braziliensis braziliensis in the Serra dos Carajás

Between July 1983 and December 1984 natural flagellate infections were found in 114 (1%) of 11,586 female phlebotomine sandflies (Diptera: Psychodidae) of 21 species. A further 1084 females of 17 other species were not infected. Identification of the organisms on a number of occasions confirms the exclusive parasite/vector relationship of Leishmania mexicana amazonensis/Lutzomyia flaviscutellata and Le. braziliensis braziliensis/Psychodopygus "wellcomei". Undescribed or unidentified Leishmania spp. were isolated from Lu. shawi, Lu. ubiquitalis, Lu. whitmani, Ps. hirsutus, Ps. paraensis Ps. "wellcomei", and trypanosomes from Lu. nordestina and Lu. trinidadensis. Flagellate infections were recorded in 8 of 21 species examined for the first time, and some were isolated directly from insects into cultures. Le. b. braziliensis was transmitted to a hamster by the bite of a wild-caught, naturally infected Ps. "wellcomei". 7 of the 35 infected Ps. "wellcomei" were allowed to oviposit and the eggs were reared to adults. Four produced Ps. wellcomei males only, confirming the rôle of this species as the major vector of Le. b. braziliensis.