Predictive modeling of sand fly distribution incriminated in the transmission of Leishmania (Viannia) braziliensis and the incidence of Cutaneous Leishmaniasis in the state of Paraná, Brazil

Southern Brazil concentrates a considerable number of cases of cutaneous leishmaniasis reported since 1980, and Paraná is the state that most records CL cases in the region. The main sand fly species incriminated as vectors of Leishmania (Viannia) braziliensis (Vianna,1911) are Migonemyia (Migonemyia) migonei (França, 1920), Nyssomyia (Nyssomyia) neivai (Pinto, 1926) and Nyssomyia (Nyssomyia) whitmani (Antunes & Coutinho, 1936). In this study, we evaluated areas with climatic suitability for the distribution of these vectors and correlated these data with CL incidence in the state. The occurrence points of Mg. migonei, Ny. neivai, and Ny. whitmani were extracted from a literature review and field data. For CL analysis in the state of Paraná, data were obtained from the Informatics Department of the Unified Health System of Brazil (DATASUS), covering the period from 2001 to 2019. The layers of bioclimatic variables from the WorldClim database were used in the study. Species distribution modeling was developed using the MaxEnt Software version 3.4.4. ArcGIS software version 10.5 was used to develop suitability maps and the graphical representation of disease incidence. The AUC values were acceptable for all models (> 0,8). Bioclimatic variables BIO13 and BIO14 were the most influential in the distribution of Mg. migonei, while BIO19 and BIO6 were the variables that most influenced the distribution of Ny. neivai, and Ny. whitmani was most influenced by variables BIO5 and BIO9. During 19 years, 4992 cases of CL were reported in the state by 286 municipalities (71,6%). Northern Paraná showed the highest number of areas with very high and high climatic suitability for the occurrence of these species, coinciding with the highest number of CL cases. The modeling tools allowed analyzing the association between climatic variables and the geographical distribution of CL in the state. Moreover, they provided a better understanding of the climatic conditions related to the distribution of different species, favoring the monitoring of risk areas, the implementation of preventive measures, risk awareness, early and accurate diagnosis, and consequent timely treatment.

Effects of Migonemyia migonei salivary gland homogenates on Leishmania (Viannia) braziliensis infection in BALB/c mice

Cutaneous leishmaniasis caused by Leishmania (Viannia) braziliensis is the most widespread clinical form of leishmaniasis in the Americas. Migonemyia migonei is a widely distributed phlebotomine sand fly species in Brazil and has been implicated as a vector for L. (V.) braziliensis. In the present study, we investigated the effects of salivary gland homogenates (SGH) of Mg. migonei on the course of L. (V.) braziliensis infection in BALB/c mice. Mice were separated into four groups (six mice per group): CTRL (uninfected mice); SGH (mice inoculated with Mg. migonei SGH); SGH+LEISH (mice inoculated with Mg. migonei SGH plus L. (V.) braziliensis promastigotes); LEISH (mice inoculated with L. (V.) braziliensis promastigotes). Mice were followed up for 8 weeks and the cellular immune response was evaluated by flow cytometry at the end of the experiment. Analysis of cytokine production by splenic cells stimulated with 0.5 SGH, 0.25 SGH of Mg. migonei or L. (V.) braziliensis soluble antigen stimulation (LSA) demonstrated that upon stimulation with SGH 0.25, the production of IL-17A and TNF was not sustained in the SGH group, with decreasing levels of these cytokines after 5 days compared to 3 days of incubation. Analyzing the production of cytokines after LSA stimulation, we observed lower levels of IL-17A in the SGH group after 5 days compared to 3 days. The same was observed for IFN-γ in the SGH group. Yet, the levels of TNF were significantly higher in the LEISH group after 5 days compared to 3 days. Among SGH+LEISH and LEISH mice, three animals in each group developed skin lesions on the tail, the mean lesion size was significantly higher in the LEISH group. Our study suggests that Mg. migonei SGH may modulate BALB/c immune response, as reflected by the low production or early decrease of pro-inflammatory cytokines in splenic cell cultures following stimulation with L. (V.) braziliensis antigen. Our data also suggest that Mg. migonei saliva may reduce the lesion size in BALB/c mice, but further research with a larger sample size is needed to confirm this hypothesis.

Landscape effects on the abundance of Lutzomyia longipalpis and Migonemyia migonei (Diptera: Psychodidae: Phlebotominae) in Corrientes city, northern Argentina

We analyses the relationship between landscape and environmental variables estimated from high-resolution satellite images with the temporal variation of the abundance of Lutzomyia longipalpis and Migonemyia migonei, vectors of leishmaniasis, in Corrientes city. At 8 collection sites, 14 samples were conducted between March 2012 to February 2014. Proportion of land cover classes derived from high resolution satellite images as: water, bare soil, urban areas, low vegetation and high vegetation, as well as average, maximum and minimum values of Normalized Difference Vegetation Index and Normalized Difference Water Index) in buffer areas of 50 m, 100 m and 150 m were used to characterize and identify suitable environmental conditions for the development of sand flies through Generalized Linear Mixed Models. The most frequently collected species during the sampling period was Lu. longipalpis and followed by Mg. migonei. The models showed that high Lu. longipalpis abundance were related to low proportion of high vegetation coverage, while a negative association was among Mg. migonei abundance and with values of Normalized Difference Water Index and with the interaction between urban areas and minimum values of Normalized Difference Water Index, and a positive association with the interaction between low vegetation and average values of Normalized Difference Water Index.

Temporal distribution of, and effect of anthropic modifications on, phlebotomine populations in the Chaco Bioregion, Argentina

Migonemyia migonei is the predominant species in the dry ecoregion and Nyssomyia neivai in the humid region, although co-dominance in humid highly modified areas could be observed. Vector abundance seems to be modulated by environmental anthropization, as the abundance and predominance of Ny. neiviai and Mg. migonei increased in highly modified areas. In Humid Chaco, the risk of human-vector contact would be present throughout the year, being particularly high in spring/summer, and in Dry Chaco, the risk would be restricted to temperate and humid months.

Performance of light-emitting diode traps for collecting sand flies in entomological surveys in Argentina

The performance of two light-emitting diode traps with white and black light for capturing phlebotomine sand flies, developed by the Argentinean Leishmaniasis Research Network (REDILA-WL and REDILA-BL traps), were compared with the traditional CDC incandescent light trap. Entomological data were obtained from six sand fly surveys conducted in Argentina in different environments. Data analyses were conducted for the presence and the abundance of Lutzomyia longipalpis, Migonemyia migonei, and Nyssomyia whitmani (106 sites). No differences were found in presence/absence among the three types of traps for all sand fly species (p>0.05). The collection mean of Lu. longipalpis from the REDILA-BL didn´t differ from the CDC trap means, nor were differences seen between the REDILA-WL and the CDC trap collection means (p>0.05), but collections were larger from the REDILA-BL trap compared to the REDILA-WL trap (p<0.05). For Mg. migonei and Ny. whitmani, no differences were found among the three types of traps in the number of individuals captured (p>0.05). These results suggest that both REDILA traps could be used as an alternative capture tool to the original CDC trap for surveillance of these species, and that the REDILA-BL will also allow a comparable estimation of the abundance of these flies to the CDC light trap captures. In addition, the REDILA-BL has better performance than the REDILA-WL, at least for Lu. longipalpis.

First description of Migonemyia migonei (França) and Nyssomyia whitmani (Antunes & Coutinho) (Psychodidae: Phlebotominae) natural infected by Leishmania infantum in Argentina

Leishmania infantum is the etiological agent of the Visceral Leishmaniasis (VL) disease in America, with Lutzomyia longipalpis phlebotomine sandflies as its proven vectors in Argentina, and infected dogs as its main urban reservoir. In Puerto Iguazú City (Misiones province, Argentina), human and canine cases of VL were recorded. Additionally, in the rural area known as "2000 Hectáreas", less than 10km away from the city, several human cases of Tegumentary Leishmaniasis (TL) were registered determining an endemic area with Leishmania braziliensis as the etiological agent. Because of this, several phlebotomine captures were done in this site showing that Nyssomyia whitmani is the most abundant sandfly followed by Migonemyia migonei. In this study, three of the sandflies captured were found infected whit L. infantum parasites, detected by PCR and sequencing. Two of them were N. whitmani and the other one was a M. migonei specimen, being this the first report of L. infantum natural infection for Argentina in these sandfly species. N. whitmani is the main vector of L. braziliensis in this area, and M. migonei has been suggested as a putative vector in other locations where human and canine cases of VL where reported with L. longipalpis apparently absent. In this context, we consider necessary further studies that could define the role of M. migonei and N. whitmani as specific or permissive vectors of L. infantum, their vectorial competence and capacity, and their actual role in the transmission of both Tegumentary and Visceral Leishmaniasis in the study area.