Molecular and Biochemical Detection of Insecticide Resistance in the Leishmania Vector, Phlebotomus papatasi (Diptera: Psychodidae) to Dichlorodiphenyltrichloroethane and Pyrethroids, in Central Iran.

The aim of the present study was to explore resistance markers and possible biochemical resistance mechanisms in the Phlebotomine sand fly Phlebotomus papatasi in Esfahan Province, central Iran. Homogenous resistant strains of sand flies were obtained by exposing P. papatasi collected from Esfahan to a single diagnostic dose of DDT. The adults from the colony were tested with papers impregnated with four pyrethroid insecticides: Permethrin 0.75%, Deltamethrin 0.05%, Cyfluthrin 0.15%, and Lambdacyhalothrin 0.05% to determine levels of cross-resistance. To discover the presence of mutations, a 440 base pair fragment of the voltage gated sodium channel (VGSC) gene was amplified and sequenced in both directions for the susceptible and resistant colonies. We also assayed the amount of four enzymes that play a key role in insecticide detoxification in the resistant colonies. A resistance ratio (RR) of 2.52 folds was achieved during the selection of resistant strains. Sequence analysis revealed no knockdown resistance (kdr) mutations in the VGSC gene. Enzyme activity ratio of the resistant candidate and susceptible colonies were calculated for α-esterases (3.78), ß-esterases (3.72), mixed function oxidases (MFO) (3.21), and glutathione-S-transferases (GST) (1.59). No cross-resistance to the four pyrethroids insecticides was observed in the DDT resistant colony. The absence of kdr mutations in the VGSC gene suggests that alterations in esterase and MFO enzymes are responsible for the resistant of P. papatasi to DDT in central Iran. This information could have significant predictive utility in managing insecticide resistant in this Leishmania vector.

Baseline susceptibility of a wild strain of main vectors of leishmaniasis to WHO-recommended insecticides in southeastern Iran.

BACKGROUND: In Iran, both cutaneous leishmaniases (CL) and visceral leishmaniases (VL) are endemic, recording one of the 10 highest CL prevalence in the world. Parasites are transmitted by the bite of infected Phlebotomus sand fly females. Several sand fly species have been identified as vectors in the studied region of Kerman province. Residual spraying to control adult sand flies, is the only way to decrease the spreading of the diseases but, following control treatment against malaria vectors in endemic areas in Iran, resistance or tolerance to insecticides emerged in some sand fly species. The objective of this study was to survey insecticides susceptibility levels of 3 vector species in wild sand fly populations in different foci of the diseases in Kerman province. Ph. sergenti, and Ph. papatasi respectively vectors of anthroponotic and zoonotic cutaneous leishmaniases and for the first time Ph. alexandri one of the anthroponotic visceral leishmaniases vector were tested against: deltamethrin 0.05%, malathion 5%, dichloro-diphenyl-trichloroethane (DDT) 4%. MATERIALS AND METHODS: In leishmaniases endemic areas species specific sand fly sites were selected in Kerman province, and specimens were collected by manual aspirators at different time intervals during the spring and summer 2019. All the susceptibility tests were performed according to the WHO tube test recommended procedure. RESULTS: Twenty five blood-fed female sand flies from the region's prevalent species were used in each pooled test replicates. All wild specimens died within 60 min of exposure to DDT 4%, malathion 5%, and deltamethrin 0.05%, but the mortality rate for Ph. papatasi exposed to malathion and DDT was 91.6% and 66.6%, respectively. CONCLUSION: According to current study results, Ph. sergenti and Ph. alexandri are highly susceptible to all the evaluated insecticides in the study areas. However, Ph. papatasi was susceptible to deltamethrin (100% mortality), possibly resistant or tolerant to malathion (91.6% mortality), and confirmed to be resistant to DDT (66.6% mortality).

Visceral Leishmaniasis in Southeastern Iran: A Narrative Review.

BACKGROUND: Visceral leishmaniasis (VL) has strong links with poverty, substantial medical and veterinary impacts. This review aimed to focus in studies published during 1994-2016 on VL in southeastern Iran. METHODS: The present review is based on expert knowledge and historical studies published during the past 23 yr (1994-2016) on VL in southeastern Iran. In addition, related literature found in PubMed by using the keywords such as visceral leishmaniasis, kala-azar, and Leishmania infantum are included. RESULTS: Overall, 118 children aged 4.2 yr were detected as infected with human VL (HVL). The majority of the cases were from Orzoieh district (37.1%) in southwest of Kerman Province, followed by Sirjan (15.7%), Jiroft (14.8%), Kahnuj (9.3%) and to lesser extent from other areas. The male to female ratio was 1.7. The three most frequent clinical features were represented by fever (100.0%), anemia (95.0%) and splenomegaly (91.5%). Altogether, 42.0% of the VL cases developed secondary bacterial infections, the overall case-fatality rate was 3.4%, and majorities (88.0%) of the VL patients were undernourished. Overall, 733 dogs and wild canines were examined by different techniques with various seroprevalence ranges. CONCLUSION: In southeastern Iran, VL is endemic in Orzoieh district in Kerman Province. While the dogs are implicated as the main domestic reservoir of VL, wide range of wild canines can serve as a secondary potential reservoir host.