Sand flies on Paraná River Islands and natural infection of Nyssomyia neivai by Leishmania in southern Brazil

Leishmania (Leishmania) infantum DNA detection in Nyssomyia neivai in Vale do Ribeira, Paraná, Brazil

BACKGROUND

The incidence of visceral leishmaniasis (VL) has increased in the Southern region of Brazil in recent years, especially in the State of Paraná. New species have been suggested with potential to act as vector in VL endemic areas.

OBJECTIVES

Identify the Leishmania species in sand fly specimens collected from 2016 to 2018 in the municipality of Itaperuçu, Vale do Ribeira, Paraná, Brazil.

METHODS

Light traps were used for collections and for the analysis of sand fly were used the multiplex polymerase chain reaction (PCR) methodology and subsequent sequencing.

FINDINGS

Among the collected specimens, 88.62% were attributed to the species Nyssomyia neivai, which were grouped into 176 pools. Three positive pools were detected: two with Leishmania (Viannia) braziliensis and one with L. (Leishmania) infantum. The positivity rate for the parasite was 0.25% based on the presence of at least one infected insect in the pool.

MAIN CONCLUSIONS

The detection of L. infantum in Ny. neivai draws attention due to its abundance and anthropophily in the State of Paraná. Moreover, this finding is considered as an alert and suggests that the vector competence of Ny. neivai and the criteria for its incrimination should be carried out, given its wide distribution in southern of Brazil.

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.

Characterization of a municipality as free of canine visceral leishmaniasis in the context of One Health

Dogs are the main urban reservoir of Leishmania infantum, the causative agent of visceral leishmaniasis (VL), which is transmitted by sand flies. In the state of Paraná, the first detection of a positive dog for VL was in 2014, this year Paraná lost free status for this disease (VL). The objectives of this study were to determine the prevalence of canine visceral leishmaniasis in Palotina, the occurrence of vectors that may transmit Leishmania infantum, and the number of notifications of human visceral leishmaniasis cases from period 2010 to 2020. To determine the occurrence of canine visceral leishmaniasis, blood samples from 204 dogs were analyzed using the rapid test DPP® to detect anti-L. infantum antibodies. To investigate the occurrence of potential vectors, monthly collections were made at 18 points within the urban area of the municipality. The number of human visceral leishmaniasis cases was investigated from Epidemiological Surveillance records. None of the serologically tested dogs showed positive titration. Only two specimens of Lutzomyia neivai, one of Lutzomyia sp. and four of Brumptomyia brumpti specimens were collected. No human visceral leishmaniasis cases were reported. These results suggest that there is no evidence of circulation of L. infantum in Palotina.

Use of the high-content imaging system equipment to evaluate in vitro infection by Leishmania braziliensis in response to sand fly Nyssomyia neivai saliva

Earlier research has shown that in vivo immunization with sand fly saliva protects the host against infection by parasites of genus Leishmania, and inoculation of saliva along with Leishmania promastigotes favors infection in the host. In this study, High-Content Imaging System was used to demonstrate in vitro that sand fly saliva also promotes infection by these parasites. THP-1 cells were cultured in 96-well microplates and challenged with three strains of Leishmania braziliensis plus four dilutions of Nyssomyia neivai salivary gland extract. High-Content Imaging System equipment (Operetta CLS, Perkin Elmer) was configured to automatically count both cells and parasites inside the microplates and subsequently calculate the Infection Index (II). Results demonstrate that the extract concentration of 1 gland showed greater infection than other dilutions. These findings suggest that sand fly N. neivai saliva has potential for increasing the parasite infection, reinforcing the importance of studying its components. A new method to evaluate Leishmania infection in vitro assays was also presented, broadening this area of study.

Ecology and Molecular Detection of Leishmania infantum Nicolle, 1908 (Kinetoplastida: Trypanosomatida) in Wild-Caught Sand Flies (Psychodidae: Phlebotominae) Collected in Porto Alegre, Rio Grande do Sul: A New Focus of Visceral Leishmaniasis in Brazil

Phlebotomine sand flies are hematophagous insect vectors of the protozoan parasites of the genus Leishmania Ross, 1903 (Kinetoplastida: Trypanosomatida) that infect mammals, including humans, causing leishmaniasis. In Porto Alegre, Brazil, three autochthonous cases of human visceral leishmaniasis were reported in 2016 through 2017. We analyzed for the presence of Leishmania DNA in sand flies collected at the neighborhood of Agronomia, Porto Alegre, Brazil. Phlebotomine sand flies were collected at three sites from October 2014 to September 2015. Female sand flies were pooled in numbers from 1 to 20 depending upon species, locality, and date; all were screened for Leishmania infection by the amplification of the ITS1 region. In total 518 phlebotomine sand flies were collected: Psathyromyia lanei (Barretto and Coutinho, 1941) (Diptera: Psychodidae) (30.5%), Brumptomyia sp. (França and Parrrot, 1921) (Diptera: Psychodidae) (25.7%), Migonemyia migonei (Franca, 1920) (Diptera: Psychodidae) (21.4%), Pintomyia fischeri (Pinto, 1926) (Diptera: Psychodidae) (21.4%), and Nyssomyia neivai (Pinto, 1926) (Diptera: Psychodidae) (1.0%). Most sand flies were collected during the hot and rainy season from October 2014 to April 2015. Of the 113 pools analyzed, five pools of Pi. fischeri were PCR-positive with the amplicons possessing sequences similar (>95%) to that of Leishmania infantum Nicolle, 1908 (Kinetoplastida: Trypanosomatida). These results represent the first molecular detection of Le. infantum in Pi. fischeri. It is possible that Pi. fischeri is involved in the transmission cycle of Le. infantum in the studied area; however, further studies are needed to establish the true role of Pi. fischeri in the visceral leismaniasis cycle.

Predominance of Nyssomyia neivai (Pinto) on the Islands of the Paraná River, Southern Brazil

Leishmaniasis is a vector-borne disease caused by the protozoan Leishmania and it is one of the six most important infectious diseases in the world. The aim of this study was to conduct a research on the fauna and most frequented ecotopes by sandflies on islands of the Paraná River. The sandflies were collected with Falcão light traps in 10 islands in the municipalities of São Pedro do Paraná, Porto Rico, and Querência do Norte, in Paraná State, Brazil, from November 2012 to November 2014. In total, 76,145 specimens of Nyssomyia neivai, the only species found, were collected, of which 63,015 were female and 13,130, male. The largest number of sandflies was collected mainly in domiciles and peridomiciles. The islands of the Paraná River showed predominance of Ny. neivai, which is largely involved in the transmission of Leishmania and a risk of human leishmaniasis to the island inhabitants and tourists.