Molecular epidemiology of diarrhoeal virus infection in children in Saudi Arabia.

Abstract

The etiology of viral diarrhoea in children in the Kingdom of Saudi Arabia (KSA) is incompletely characterized. Available data suggest that the causative agents are found at approximately similar frequencies here as elsewhere. However KSA is not a typical country; the lack of rivers and lakes may affect the paths open for virus spread in the Kingdom and the relatively high year-round temperature may limit virus survival in the environment. Sewage is disposed of to sea after treatment, and although virus is found in seawater, exposure via recreational use is limited those living along the coast. Virus is also found in seafood which may aid transmission inland but drinking water is supplied by desalination, a process that would effectively inactivate most viruses. Thus the bulk of viral transmission must be presumably via person to person or food-borne spread inland. Secondly, KSA plays host to many millions of visitors each year who flock to the country from all over the world in a short time period; the Hajj or annual pilgrimage to Makkah. This influx of persons offers opportunity both for the introduction of new strains of viruses and also for person to person transmission in these crowded venues. Consequently, there may be subtle differences in the manner of circulation of these viruses in KSA. This project set out to study the epidemiology of diarrhea viruses in pediatric populations. The study addressed initially rotavirus, enteric adenovirus and astrovirus but was later expanded to include norovirus. Viruses were sought in faecal specimens and characterized for genotype using molecular methods for the first time in KSA. The survey focused on three locations; Jeddah, Makkah and Riyadh. During the Hajj the chief population fluxes are via Jeddah to Makkah. One thousand samples were obtained from children (aged six years or less) presenting with diarrhoea and thus representing community acquired rather than nosocomial infections. Human rotavirus (HRV) group A was detected in 6% (60/ 1000). By RT-PCRG1 was the predominant VP7 genotype (36/58, 62%), followed by the unique G9 (19/58, 33%). The other HRV genotypes found, 02 and 03, were less common at 1.2% (1/58) and 3.4% (2/58), respectively. P-type determination was also performed by RT-PCR and P[8] was clearly the most common (45/56, 80.3%). Overall 01P[8] was the most common, accounting for 60.7% of total samples positive for both genotypes. Rarer types 09P[4] (2/56, 3.57%) and 09P[6] (6/56, 10.7%) were identified for the first time in KSA. Enteric adenovirus (EAdV) was evident in 14/1000 pediatric stool samples (1.4%) by ELISA and all were also positive by RT- PCR. Enteric types 40 and 41 were distinguished using RT- PCR and RFLP; five samples were positive for EAdV-40 and 7 for EAdV-41. One sample showed a mixed infection of both 40 and 41. A single sample was eventually typed as type 31 by Sequencing. Human astrovirus (HAstV) was found in 1.9% (19/1000 samples). All but one was identified as type 8. This was a surprising finding since these infections were not nosocomial but independent, community-acquired cases. The remaining sample could not be amplified. Human caliciviruses are among the most common causes of gastrointestinal and there are no data for these viruses in Saudi Arabia. A smaller panel of 253 stool samples was tested for norovirus by ELISA and 9/253 were found positive (3.5%). Overall, most infections with rotavirus were detected in children of 1 year of age or less (P=0.047), and in children of 3 year of age or less with astrovirus likewise, in adenovirus most of the infections were detected in children of 2 year of age or less with P-Value of= 0.05, and 0.01 respectively. All viruses were distributed equally between males and females. HRV was the most common diarrhoeal virus detected followed by norovirus, although the rotavirus incidence found here was lower than that reported in previous studies. Infections showed a peak shortly after the Hajj during the study period. Novel HRV were found, with the first detection of the emergent G9 serotype and some combinations of G and P types new in KSA. Adenovirus 31 was reported for the first time and we found an unexpectedly high incidence of astrovirus serotype 8