Dengue fever (DF) is endemic to Makkah and Jeddah, the Kingdom of Saudi Arabia (KSA). However, until recently, the circulation of dengue virus (DENV) in Aedes mosquitoes in these areas was unknown. Serological surveillance of DENV in Ae aegypti is a powerful tool for early detection of dengue outbreaks and essential for developing effective control strategies. Therefore, this research aimed to examine a sample of adult Ae aegypti mosquitoes from Makkah, KSA, to detect DENV. In total, 1295 Ae aegypti mosquitoes were collected from the field from target areas of Makkah with a high incidence and prevalence of DF. The samples were divided into 259 coded pools (five mosquitoes in each) and preserved in 1.5 mL plastic tubes. The tubes were labeled, capped, and stored at−86°C until use. RT-PCR was used to detect DENV in the samples. All positive pools were confirmed by RT-PCR. The RT-PCR products were analyzed by gel electrophoresis (1.5% agarose in Tris-acetate EDTA buffer), stained with ethidium bromide, and visualized. DENV was isolated from six female Ae Aegypti collected from six pools (out of 259 pools). No other viruses were detected. Only five of the nine target localities had positive pools. Samples from the remaining four localities yielded negative results. Four DENV-positive mosquitoes were collected at the aquatic stages, and two were collected at the adult stage. These results show the circulation of DENV in adult mosquitoes and offspring, indicating vertical transmission of DENV. In conclusion, this study found that, in Makkah, DENV is circulating in dengue vectors with a high significance rate, suggesting the possibility of a dengue outbreak in the future; therefore, a sensitive surveillance system is vital to predict the outbreak and for early intervention and control.
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 a new genetic variant of DENV-2. The newly identified DENV-2 variant showed similarities to DENV-2 sequences reported in Malaysia, Singapore, Korea and China. The results revealed a new genetic variant of DENV-2 was circulating in Jazan region that was highly prevalent and drove the serious regional outbreak in 2019. Conclusions: The emergence of new 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.
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