Trypanosomes and Gut Microbiota Interactions in Triatomine bugs and Tsetse Flies: A vectorial perspective.

Triatomines (kissing bugs) and tsetse flies (genus: Glossina) are natural vectors of Trypanosoma cruzi and Trypanosoma brucei, respectively. T. cruzi is the causative agent of Chagas disease, endemic in Latin America, while T. brucei causes African sleeping sickness disease in sub-Saharan Africa. Both triatomines and tsetse flies are host to a diverse community of gut microbiota that co-exist with the parasites in the gut. Evidence has shown that the gut microbiota of both vectors plays a key role in parasite development and transmission. However, knowledge on the mechanism involved in parasite-microbiota interaction remains limited and scanty. Here, we attempt to analyse Trypanosoma spp. and gut microbiota interactions in tsetse flies and triatomines, with a focus on understanding the possible mechanisms involved by reviewing published articles on the subject. We report that interactions between Trypanosoma spp. and gut microbiota can be both direct and indirect. In direct interactions, the gut microbiota directly affects the parasite via the formation of biofilms and the production of anti-parasitic molecules, while on the other hand, Trypanosoma spp. produces antimicrobial proteins to regulate gut microbiota of the vector. In indirect interactions, the parasite and gut bacteria affect each other through host vector-activated processes such as immunity and metabolism. Although we are beginning to understand how gut microbiota interacts with the Trypanosoma parasites, there is still a need for further studies on functional role of gut microbiota in parasite development to maximize the use of symbiotic bacteria in vector and parasite control.

An Overview on the Impact of Microbiota on Malaria Transmission and Severity: Plasmodium-Vector-Host Axis.

PURPOSE: Malaria, which is a vector-borne disease caused by Plasmodium sp., continue to become a serious threat, causing more than 600,000 deaths annually, especially in developing countries. Due to the lack of a long-term, and effective vaccine, and an increasing resistance to antimalarials, new strategies are needed for prevention and treatment of malaria. Recently, the impact of microbiota on development and transmission of Plasmodium, and the severity of malaria has only begun to emerge, although its contribution to homeostasis and a wide variety of disorders is well-understood. Further evidence has shown that microbiota of both mosquito and human host play important roles in transmission, progression, and clearance of Plasmodium infection. Furthermore, Plasmodium can cause significant alterations in the host and mosquito gut microbiota, affecting the clinical outcome of malaria. METHODOLOGY: In this review, we attempt to summarize results from published studies on the influence of the host microbiota on the outcome of Plasmodium infections in both arthropods and mammalian hosts. CONCLUSION: Modifications of microbiota may be an important potential strategy in blocking Plasmodium transmission in vectors and in the diagnosis, treatment, and prevention of malaria in humans in the future.

Host-Parasite Interactions: Regulation of Leishmania Infection in Sand Fly.

PURPOSE: Sand flies are the only proven vectors of leishmaniases, a tropical neglected disease endemic in at least 92 countries. Vector-parasite interactions play a significant role in vector-borne disease transmission. There are various bottlenecks to Leishmania colonization of the sand fly midgut. Such bottlenecks include the production of innate immune-related molecules, digestive proteases, parasite impermeable peritrophic membrane, and resident gut microbiota. These barriers determine the parasite load transmitted and, consequently, the disease outcome in mammalian host. Therefore, it is important to understand the molecular responses of both sand fly and Leishmania during infection. METHOD: Here, we reviewed the published literature on sand fly-Leishmania interactions bringing together earlier and current findings to highlight new developments and research gaps in the field. CONCLUSION: Recent research studies on sand fly-Leishmania interaction have revealed contrasting observations to past studies. However, how Leishmania parasites evade the sand fly immune response still needs further research. Sand fly response to Leishmania infection can be best understood by analyzing its tissue transcriptome. Better characterization of the role of midgut components could be a game changer in development of transmission-blocking strategies for leishmaniasis.

Entomological Survey of the Sand Fly Fauna of Kayseri Province: Focus on Visceral and Cutaneous Leishmaniasis in Central Anatolia, Turkey

Objective: In Turkey, leishmaniasis occurs in two clinical forms: cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL). CL has been reported mainly from south-eastern Anatolia and the eastern part of the Mediterranean region, whereas VL is sporadic in almost all geographical regions of Turkey. Both clinical forms of the disease have been recorded in Kayseri province for decades, but no study has been conducted on the sand fly fauna in this area. Therefore, we determine the species composition and population dynamics of sand flies prevalent in Kayseri province and identify possible vector species. Methods: Data related to the recent locations of CL and VL cases were obtained from the Ministry of Health, and sand flies were collected in 14 localities of different districts using CDC light traps. The specimens were transferred to the laboratory in 70% ethanol, and morphological identification to the species level was performed using previously written keys. Results: A total of 1,636 sand fly specimens were collected. Morphological identification revealed eight species of the genus Phlebotomus (P. perfiliewi s.l., P. halepensis, P. simici, P. major s.l., P. papatasi, P. tobbi, P. sergenti and P. mascittii) and one species of the genus Sergentomyia (S. dentata). Among all specimens, members of subgenus Adlerius (54.58%) formed the dominant group, followed by the subgenus Larroussius (43.76%). Conclusion: Our results showed that P. halepensis, belonging to subgenus Adlerius, and P. perfiliewi, belonging to the subgenus, are probable vectors of cutaneous and VL in the province, respectively.

Toxicity of Thiamethoxam on Field-Collected Sand Flies (Diptera: Psychodidae) From Different Regions of Turkey.

Phlebotomine sand flies (Diptera: Psychodidae) are the vectors of human and canine leishmaniasis, sand fly fever, and other arboviruses and bacteria. The control of sand flies is recommended by World Health Organization throughout the world. In this study, we investigated the susceptibility of field-collected sand flies against thiamethoxam in Turkey. The adult sand flies collected were from five different locations in three provinces; Yesilöz and Büyükpinar districts in Antalya province, Develi district in Kayseri province, and Üçpinar and Bayindirlik districts in Manisa province. They were investigated using two different doses (0.125 and 0.25 g ai/m2) of thiamethoxam under laboratory conditions. After 1-h exposure, all sand flies were found highly susceptible to thiamethoxam and both test doses caused 100% mortality after 24 h. Considering the KDT50 time, flies collected from Yesilöz district in Antalya province were found to be most sensitive and flies collected from Üçpinar district in Manisa province were found as the most resistance to thiamethoxam. The results show that Turkish sand flies were highly susceptible to thiamethoxam and it can be used for the control of sand flies in the field.