ABSTRACT
ABSTRACT The emergence of insecticide resistance in different mosquito populations underscores the pressing need for alternative approaches to control vector-borne diseases. Among several technological strategies, the employment of bacterial symbionts, such as the Wolbachia pipientis strains wMel and wAlbB to inhibit the ability of Aedes aegypti (Linnaeus, 1762) to transmit dengue and Zika viruses in endemic regions worldwide is promising. This investigation examines both the bacterial diversity associated with Culex quinquefasciatus and the genetic diversity of Wolbachia in females collected in Coari, Amazonas State, Brazil. Both 16S rRNA and Wolbachia surface protein (wsp) gene sequences were generated and examined. Proteobacteria was the dominant phylum. Wolbachia was the predominant genus, followed by Providencia, unclassified Erwiniaceae, and Acinetobacter. The presence of Delftia in Cx. quinquefasciatus need further investigations to identify the strains and if any of them can inhibit the transmission of arboviruses by this mosquito. Wolbachia 16S rRNA sequences were detected in all samples analyzed. The wsp sequences from Coari specimens were identified as Wolbachia wPip strain of the supergroup B. These sequences are identical and share 100% similarity with those of other Cx. quinquefasciatus populations from Brazil. Our findings suggest the hypothesis of previous studies that the Wolbachia invasion in Cx. quinquefasciatus was recent.
ABSTRACT
Introdução - Nyssorhynchus darlingi e outros mosquitos da subfamília Anophelinae atuam como vetores dos parasitos da malária humana. Alterações na paisagem podem alterar a distribuição, abundância e comportamento desses mosquitos. Bactérias presentes no intestino médio de vetores de Plasmodium são capazes de modular a infecção por Plasmodium spp. no mosquito. Objetivos - Ampliar o conhecimento sobre os mosquitos que atuam na dinâmica de transmissão da malária em áreas rurais e periurbanas da Amazônia brasileira e investigar a diversidade bacteriana associada ao abdômen de Ny. darlingi e Nyssorhynchus braziliensis. Métodos - Capturas de mosquitos foram realizadas em áreas rurais e periurbanas da Amazônia brasileira. Testes de detecção de Plasmodium spp. foram realizados nos mosquitos. Análises de correlação e de regressão foram realizadas entre métricas de paisagem e as variáveis: incidência acumulada de malária, número de Ny. darlingi, mosquitos infectados e taxa de picada humana. Sequenciamento da região V4 do gene 16S rRNA foi realizado para explorar a diversidade bacteriana associada ao abdômen de Ny. braziliensis e de Ny. darlingi naturalmente infectado e não infectado por Plasmodium spp. Resultados - Nyssorhynchus darlingi, Nyssorhynchus rangeli, Nyssorhynchus benarrochi B e Nyssorhynchus konderi B foram encontrados infectados com Plasmodium. Plasmodium vivax e Plasmodium falciparum foram as espécies do parasito encontradas nos vetores. Foram encontradas correlações positivas entre incidência acumulada de malária e as variáveis taxa de picada humana, densidade de borda e número de Ny. darlingi. Porcentagem de cobertura florestal e taxa de picada humana apresentaram correlação negativa. O período entre 0 h:00 e 3 h:00 foi o que apresentou maior número de mosquitos infectados. Não houve diferença estatística entre a diversidade bacteriana de Ny. darlingi infectado e não infectado. Asaia e Serratia estavam presentes em ambas as espécies de Nyssochynchus. Enterobacter foi encontrado apenas em abdômen de Ny. darlingi não infectado e Pseudomonas foi o gênero mais abundante. Conclusão - Este estudo reporta pela primeira vez a infecção natural por Plasmodium em Ny. konderi B e Ny. benarrochi B em regiões da Amazônia brasileira. Os resultados obtidos sugerem que mudanças na paisagem podem favorecer a ocorrência de novos vetores e consequentemente, aumentar o número de casos de malária em regiões endêmicas. O encontro de maior número de mosquitos infectados após a meia-noite contribui para as medidas de controle do vetor e confirma a importância do uso de mosquiteiros impregnados com inseticida. A presença de Asaia e Serratia em ambas as espécies de Nyssorhynchus e a alta prevalência de Pseudomonas em Ny. darlingi indicam a necessidade de outros estudos sobre a possível utilização destas bactérias no controle da malária através da paratransgênese. A presença do gênero Enterobacter apenas em abdômen de Ny. darlingi não infectado sugere que bactérias deste gênero possam oferecer proteção a infecção por Plasmodium e outros estudos devem ser realizados para verificar essa hipótese.
Introduction - Nyssorhynchus darlingi and other mosquitoes of the subfamily Anophelinae act as vectors of human malaria parasites. Landscape changes can alter the distribution, abundance and behavior of these mosquitoes. Bacteria present in the midgut of Plasmodium vectors are able to modulate infection by Plasmodium spp. in the mosquito. Objectives - To broaden the knowledge about mosquitoes that act on the dynamics of malaria transmission in rural and peri-urban areas of the Brazilian Amazon and to investigate the bacterial diversity associated with abdomen of Ny. darlingi and Nyssorhynchus braziliensis. Methods - Mosquito collections were carried out in rural and peri-urban areas of the Brazilian Amazon. Detection tests for Plasmodium spp. mosquitoes were carried out. Correlation and regression analyzes were performed between landscape metrics and the following variables: cumulative incidence of malaria, number of Ny. darlingi, infected mosquitoes, and human biting rate. Sequencing of the V4 region of the 16S rRNA gene was performed to explore the bacterial diversity associated with abdomen of Ny. braziliensis and Ny. darlingi naturally infected and not infected by Plasmodium spp. Results - Nyssorhynchus darlingi, Nyssorhynchus rangeli, Nyssorhynchus benarrochi B and Nyssorhynchus konderi B were found infected with Plasmodium. Plasmodium vivax and Plasmodium falciparum were the parasite species found in the vectors. Positive correlations were found between cumulative incidence of malaria and the variables human biting rate, edge density and number of Ny. darlingi. Percentage of forest cover and human biting rate presented negative correlation. The period from 0 h: 00 to 3 h: 00 was the one with the highest number of infected mosquitoes. There was no statistical difference between bacterial diversity in Ny. darlingi infected and uninfected. Asaia and Serratia were present in both species of Nyssochynchus. Enterobacter was found only in abdomen of Ny. darlingi uninfected and Pseudomonas was the genus most abundant. Conclusion - This study reports for the first time the natural infection by Plasmodium in Ny. konderi B and Ny. benarrochi B in regions of the Brazilian Amazon. The results suggest that changes in the landscape can favor the occurrence of new vectors and, consequently, increase the number of malaria cases in endemic regions. The finding of a greater number of infected mosquitoes after midnight contributes to vector control measures and confirms the importance of insecticide-treated nets. The presence of Asaia and Serratia in both species of Nyssorhynchus and the high prevalence of Pseudomonas in Ny. darlingi indicate the need for further studies on the possible use of these bacteria in the control of malaria through paratransgenesis. The presence of the Enterobacter only in abdomen Ny. darlingi uninfected suggests that bacteria of this genus can offer protection to Plasmodium infection and other studies should be performed to verify this hypothesis.