Spatiotemporal Distribution of Malaria in the Kingdom of Saudi Arabia.

BACKGROUND: Malaria is a significant public health concern in the Kingdom of Saudi Arabia (KSA). This study aimed to investigate the spatiotemporal distribution of malaria in the KSA between 2017 and 2021. METHODS: A spatial analysis was conducted using data for malaria cases stratified by Plasmodium species reported by the Ministry of Health for the period 2017-2021. Covariate data such as environmental, socioeconomic, and demographic factors were assembled from different publicly available sources. RESULTS: A total of 13,852 cases were reported from 20 regions in the KSA during the study period. The study indicated a decline in the overall number of reported cases from 2715 in 2017 to 2616 in 2021, primarily driven by a decrease in Plasmodium falciparum infections. However, the number of Plasmodium vivax cases increased in 2021. Southern regions of the KSA remained at higher risk due to imported cases from neighboring Yemen. Socioeconomic and demographic factors, such as access to healthcare and education, were found to affect malaria transmission. Environmental factors, such as temperature and rainfall, were also identified as determinants of malaria risk. CONCLUSIONS: This study showed significant spatial variation in malaria cases in the KSA that was related to underlying socioeconomic status and environmental factors. The findings of this study highlight the need for continued efforts to control and eliminate malaria in the KSA, particularly in regions with higher risk of malaria.

The emergence of an imported variant of dengue virus serotype 2 in the Jazan region, southwestern Saudi Arabia.

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.

Molecular analysis of knockdown resistance (kdr) mutations in the voltage-gated sodium channel gene of Aedes aegypti populations from Saudi Arabia.

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.

DNA Barcoding of Potential Mosquito Disease Vectors (Diptera, Culicidae) in Jazan Region, Saudi Arabia.

The conventional morphological characterization of mosquito species remains heavily used for species identification in Jazan, Saudi Arabia. It requires substantial expertise and time, as well as having difficulty in confirming identity of morphologically similar species. Therefore, to establish a reliable and accurate identification system that can be applied to understanding spatial distribution of local mosquito species from the Jazan region, DNA barcoding was explored as an integrated tool for mosquito species identification. In this study, 44 adult mosquito specimens were analyzed, which contain 16 species belong to three genera of potential mosquito disease vectors (Aedes, Anopheles, and Culex). The specimens were collected from the Jazan region located in southwest Saudi Arabia. These included old and preserved mosquito voucher specimens. In addition, we assessed the genetic distance based on the generated mitochondrial partial COI DNA barcodes to detect cryptic diversity across these taxa. Nine mosquito species belonging to three genera were successfully barcoded and submitted to GenBank, namely: Aedes aegypti, Aedes caspius, Aedes vexans, Aedes vittatus, Anopheles arabiensis, Culex pipiens, Culex quinquefasciatus, Culex sitiens, and Culex tritaeniorhynchus. Of these nine species, Aedes vexans, Aedes vittatus, Culex sitiens, and Culex tritaeniorhynchus were registered in GenBank for the first time from Saudi Arabia. The DNA barcodes generated a 100% match to known barcodes of these mosquito species, that also matched with the morphological identification. Ae. vexans was found to be either a case of cryptic species (subspecies) or a new species from the region. However, more research has to be conducted to prove the latter. This study directly contributes to the development of a molecular reference library of mosquito species from the Jazan region and Saudi Arabia. The library is essential for confirmation of species in support of existing mosquito surveillance and control programmes.

Kelch 13-propeller polymorphisms in Plasmodium falciparum from Jazan region, southwest Saudi Arabia.

BACKGROUND: Artemisinin-based combination therapy (ACT) is recommended at the initial phase for treatment of Plasmodium falciparum, to reduce morbidity and mortality in all countries where malaria is endemic. Polymorphism in portions of P. falciparum gene 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 the P. falciparum k13-propeller domain in the Jazan region of southwest Saudi Arabia, where malaria is endemic. METHODS: One-hundred and forty P. falciparum samples 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 the k13-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.

Role of climatic factors in the incidence of dengue in Port Sudan City, Sudan.

BACKGROUND: Dengue fever outbreaks have occurred in Port Sudan City, Sudan, during the last 2 decades. Climatic factors may play a role in dengue incidence. AIMS: This study aimed at discribing the relationship between climatic factors and dengue fever incidence in Port Sudan during 2008-2013. METHODS: This ecological study entailed secondary data analysis of dengue fever cases and climate information to explore which climatic factors predict the incidence of dengue fever. The Wilcoxon rank sum test and multiple linear regression examined the association between number of dengue fever cases and climatic factors during lag times of 1-6 months. RESULTS: Relative humidity and maximum and minimum temperatures were correlated with dengue incidence in Port Sudan at different time intervals during 2008-2010. Precipitation and relative humidity were correlated with dengue fever during 2011-2013. However, 3-5-month lagged relative humidity was the strongest explanatory variable for the incidence of dengue. CONCLUSION: Dengue transmission appears sensitive to climatic variability. Elucidating the role of climatic factors in dengue fever helps in risk assessment and prevention of epidemics.

Knockdown resistance mutations contributing to pyrethroid resistance in Aedes aegypti population, Saudi Arabia.

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 south-west 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.