The present study was designed to provide information on the susceptibility status of the adult and larvae of Aedes aegypti mosquitoes in Jazan region of Saudi Arabia. Bioassay tests were performed on adults and larvae by using WHO recommended concentrations and test kits. Adults of Ae. aegypti mosquitoes were exposed to test papers impregnated with Lambda-cyhalothrin (0.05%), Cyfluthrin (0.15%), Deltamethrin (0.05%), Permethrin (0.75%), Fenitrothion (1%), Bendiocarb (0.1%) and DDT (4%) insecticides. Ae. aegypti mosquitoes were found to be susceptible only to Cyfluthrin; (mortality rate was 100 %), whereas variable resistances were observed from the rest of the other insecticides tested (mortality rates ranged between 93.6 and 17%).

Background: Dengue is endemic in Saudi Arabia especially in Jeddah, Makkah, Asir, and Jazan areas where pyrethroids are widely used to control the vector, Aedes aegypti. Resistance of Ae. aegypti to pyrethroid insecticides has been reported from most of these areas. Aims: The present study was carried out in Jazan region in southwest Saudi Arabia to explore the resistance status of Ae. aegypti to pyrethroids and the consequent underlying mechanisms. Methods: Three pyrethroids (permethrin, lambda-cyhalothrin, and cyfluthrin) were used to investigate the resistance status of Ae. aegypti adults following World Health Organization (WHO) standard methods: PCR and sequencing techniques were used to detect the S989P, V1016G and F1534C kdr mutations. Results: Ae. aegypti populations were susceptible to cyfluthrin and having a possibility of resistance to permethrin while resistant to lambda-cyhalothrin. Three potential kdr mutations were detected for the first time in Ae. aegypti population, F1534C, V106G, and S989P. It was found that F1534C often co-exists with V1016G and this haplotype was strongly associated with permethrin and lambda-cyhalothrin resistance. On the other hand, S989P mutation was detected as RR in 18.8% with a low-frequency rate (R) of 18.8%, and in 55.5% as R with 58.3% frequency rate in permethrin and lambda-cyhalothrin-resistant female mosquitoes, respectively. Conclusions: Early detection of resistance alleles should be considered the essential tool for the successful implementation of insecticide resistance management strategies by providing early warning of insect resistance.

Dengue fever is considered to be the most important mosquito-borne disease and considered as endemic disease in Jazan region, Saudi Arabia. The present study aimed to analyze the prevailing dengue virus serotypes for the fi rst time in the region. Serum samples of 220 suspected dengue cases were collected throughout 2016 and tested by one step Reverse Transcription Polymerase Chain Reaction (RT-PCR) with a set of specifi c primers for detection of four dengue virus serotypes followed by sequencing the PCR products to confi rm the results. Out of the 220 serum samples, 124 were found positive for dengue infection (56.4%). Three dengue virus serotypes were detected; DEN-1, DEN-2 and DEN-3. DEN-2 is the most common and predominant type in the region rating 83.9% (104/124), followed by DEN-1 8.9% (11/124), and then DEN-3 7.2% (9/124). The high seroprevalence of dengue virus infections in Jazan region indicates its endemicity. The present study highlights the importance of tracking the spread of dengue virus types and its implication for analyzing changes in dengue endemicity in specifi ed areas over time. Complete genome sequencing is required for the three detected dengue virus serotypes circulating in the region (DEN-1, DEN-2, and DEN-3) to serve as references for any future epidemiological researches and/or outbreaks.

Background The Aedes aegypti mosquito is the primary vector for dengue, chikungunya, yellow fever and Zika viruses worldwide. The first record of Ae. aegypti in southwestern Saudi Arabia was in 1956. However, the first outbreak and cases of dengue fever were reported in 1994, and cases have increased in recent years. Vector control for Ae. aegypti mainly uses pyrethroid insecticides in outdoor and indoor space spraying. The constant use of pyrethroids has exerted intense selection pressure for developing target-site mutations in the voltage-gated sodium channel (vgsc) gene in Ae. Aegypti against pyrethroids—mutations that have led to knockdown resistance (kdr). Methods Aedes aegypti field populations from five regions (Jazan, Sahil, Makkah, Jeddah and Madinah) of southwestern Saudi Arabia were genotyped for known kdr mutations in domains IIS6 and IIIS6 of the vgsc gene using polymerase chain reaction (PCR) amplification and sequencing. We estimated the frequency of kdr mutations and genotypes from Saudi Arabia as well as from other countries, Thailand, Myanmar (Southeast Asia) and Uganda (East Africa). We constructed haplotype networks to infer the evolutionary relationships of these gene regions. Results The three known kdr mutations, S989P, V1016G (IIS6) and F1534C (IIIS6), were detected in all five regions of Saudi Arabia. Interestingly, the triple homozygous wild genotype was reported for the first time in two individuals from the highlands of the Jazan region and one from the Al-Quoz, Sahil region. Overall, nine genotypes comprising four haplotypes were observed in southwestern Saudi Arabia. The median-joining haplotype networks of eight populations from Saudi Arabia, Southeast Asia and East Africa for both the IIS6 and IIIS6 domains revealed that haplotype diversity was highest in Uganda and in the Jazan and Sahil regions of Saudi Arabia, whereas haplotype diversity was low in the Jeddah, Makkah and Madinah regions. Median-joining haplotype networks of both domains indicated selection acting on the kdr-mutation containing haplotypes in Saudi Arabia. Conclusions The presence of wild type haplotypes without any of the three kdr mutations, i.e. that are fully susceptible, in Saudi Arabia indicates that further consideration should be given to insecticide resistance management strategies that could restore pyrethroid sensitivity to the populations of Ae. aegypti in Saudi Arabia as part of an integrative vector control strategy. Graphical Abstract