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. The present study was carried out in Jazan region in south-west Saudi Arabia to explore the resistance status of Ae. aegypti to pyrethroids and the consequent underlying mechanisms. 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. 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. 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.

Background: Dengue virus (DENV) infection is a global economic and public health concern, particularly in tropical and subtropical countries where it is endemic. Saudi Arabia has seen an increase in DENV infections, especially in the western and southwestern regions. This study aims to investigate the genetic variants of DENV-2 that were circulating during a serious outbreak in Jazan region in 2019. Methods: A total of 482 serum samples collected during 2019 from Jazan region were tested with reverse transcription-polymerase chain reaction (RT-PCR) to detect and classify DENV; positive samples underwent sequencing and bioinformatics analyses. Results: Out of 294 positive samples, type-specific RT-PCR identified 58.8% as DENV-2 but could not identify 41.2%. Based on sequencing and bioinformatics analyses, the samples tested PCR positive in the first round but PCR negative in the second round were found to be imported genetic variant of DENV-2. The identified DENV-2 imported variant showed similarities to DENV-2 sequences reported in Malaysia, Singapore, Korea and China. The results revealed the imported genetic variant of DENV-2 was circulating in Jazan region that was highly prevalent and it was likely a major factor in this outbreak. Conclusions: The emergence of imported DENV variants is a serious challenge for the dengue fever surveillance and control programmes in endemic areas. Therefore, further investigations and continuous surveillance of existing and new viral strains in the region are warranted.

Entomologic investigations were conducted in the Al-Darb, Al-Reath, Al-Aridah, Abuareesh, Al-Ahad, Samttah, Sabyah, Damad and Beash areas by CO₂-baited CDC miniature light traps in the Jazan region. Vectors were identified morphologically, as well as COI gene segment amplification and sequencing. The relative abundance (RA%) and pattern of occurrence (C%) were recorded. The presence of the Rift Valley fever virus (RVFV) in pooled mosquito samples was investigated by reverse transcriptase-polymerase chain reaction (RT-PCR). Culex pipiens (C. pipiens) and Culex tritaeniorhynchus (C. tritaeniorhynchus) were found with RA% values of 96% and 4%, respectively, in the region. Significant variations in vector population densities were observed in different districts. The C. pipiens was found highly abundant in all districts and RA% value (100%) was recorded in the Al-Darb, Al-Reath, Al-Aridah, Samttah and Damad areas, whereas RA% values (93.75%, 93.33%, 92.30% and 91.66%) were noted in Al-Ahad, Sabyah, Abuareesh and Beash districts, respectively. RA% values for C. tritaeniorhynchus were recorded as 8.33%, 7.70%, 6.66% and 6.25% in Beash, Abuareesh, Sabyah and Al-Ahad areas, respectively. The pattern of occurrence for C. pipiens and C. tritaeniorhynchus was recorded as 100% and 44.4% in the region. Phylogenetic analysis of C. pipiens and C. tritaeniorhynchus exhibited a close relationship with mosquitoes from Kenya and Turkey, respectively. All mosquito samples tested by RT-PCR were found negative for RVFV. In summary, the current study assessed the composition, abundance, distribution of different mosquito vectors and presence of RVFV in different areas of the Jazan region. Our data will help risk assessments of RVFV future re-emergence in the region.

Background: Artemisinin-based combination therapy (ACT) is recommended at the initial phase for treatment ofPlasmodium falciparum, to reduce morbidity and mortality in all countries where malaria is endemic. Polymorphism in portions ofP. falciparumgene encoding kelch (K13)-propeller domains is associated with delayed parasite clearance after ACT. Of about 124 different non-synonymous mutations, 46 have been identified in Southeast Asia (SEA), 62 in sub-Saharan Africa (SSA) and 16 in both the regions. This is the first study designed to analyse the prevalence of polymorphism in theP. falciparum k13-propeller domain in the Jazan region of southwest Saudi Arabia, where malaria is endemic.Methods: One-hundred and fortyP. falciparumsamples were collected from Jazan region of southwest Saudi Arabia at three different times: 20 samples in 2011, 40 samples in 2016 and 80 samples in 2020 after the implementation of ACT.Plasmodium falciparum kelch13(k13) gene DNA was extracted, amplified, sequenced, and analysed using a basic local alignment search tool (BLAST).Results: This study obtained 51 non-synonymous (NS) mutations in three time groups, divided as follows: 6 single nucleotide polymorphisms (SNPs) ‘11.8%’ in samples collected in 2011 only, 3 (5.9%) in 2011and 2016, 5 (9.8%) in 2011 and 2020, 5 (9.8%) in 2016 only, 8 (15.7%) in 2016 and 2020, 14 (27.5%) in 2020 and 10 (19.6%) in all the groups. The BLAST revealed that the 2011 isolates were genetically closer to African isolates (53.3%) than Asian ones (46.7%). Interestingly, this proportion changed completely in 2020, to become closer to Asian isolates (81.6%) than to African ones (18.4%).Conclusions: Despite the diversity of the identified mutations in thek13-propeller gene, these data did not report widespread artemisinin-resistant polymorphisms in the Jazan region where these samples were collected. Such a process would be expected to increase frequencies of mutations associated with the resistance of ACT.

Morphological characteristics have been the gold standard method to identify mosquito species. However, morphological identification has many limitations including lack of expertise and damaging of external characters due to improper specimen handling. Therefore, we used the polymerase chain reaction technique (PCR) as an integrated tool to identify Culex mosquito species to establish a more precise and reliable identification system related to their spatial distribution in Jazan region. We identified Culex mosquito species and subspecies using taxonomic keys, and then we used the polymerase chain reaction technique (PCR) as an integrated tool to confirm and refine the list of Culex mosquito species in the region. Phylogenetic trees were constructed for the identified species, and their distinctive clustering was compared with their references species in the GenBank. We identified 7026 adult Culex mosquitoes belonging to 4 species. Culex tritaeniorhynchus was the predominant species (45), followed by Cx. quinquefasciatus (32), then Culex sitiens (20), and Cx. pipiens (3). The most infested areas by Culex in the region were Gizan and Sabya. The PCR achieved 100 success in identifying the four Culex mosquito species. We also report the molecular identification of Cx. quinquefasciatus and Cx. pipiens species for the first time in Jazan region while the molecular identification of Cx. tritaeniorhynchus and Cx. sitiens was reported for the first time in Jazan region and the whole Saudi Arabia. This study utilized for the first time PCR to identify Culex mosquito species in Jazan region. The PCR is a complementary and integrated taxonomy-based identification tool for mosquito species. This integration has the capacity to promote and enhance vector surveillance and control programs, as well as defining the genetic diversity of species in the region.

Nearly half of the world's population are at risk of dengue fever (DF) which is a serious threat to the majority of international public health. Recently, Dengue viruses (DENVs) considered a re-emerging arthropod-borne viral disease that has been growing its transmission in numerous geographic areas across the world, causing dengue-endemic in more than 125 countries globally.