Detection and genotyping of group A rotaviruses isolated from sewage samples in Monastir, Tunisia between April 2007 and April 2010

AIMS

To ascertain the viral load, the distribution of G and P types of group A rotaviruses (RV-A) in sewage samples and to compare strains in clinical, animal and environmental samples.

METHODS AND RESULTS

During our study from April 2007 to April 2010, 518 samples of raw and treated sewage were collected from two biological sewage treatment plants (STPs) located in the Monastir region, Tunisia. RV-A was detected by real-time RT-PCR in 375 (72·4%) sewage samples. According to the quantification results of RV-A, it appears that the viral load in raw and treated sewage of the two STPs was quite similar (P = 0·735). The genotyping of RV-A strains detected in sewage samples showed a great diversity with 10 G types and 8 P types. Most of them were described as common in humans, but we also detected genotypes commonly found in animals. All the genotypes detected in two previous studies performed in our laboratory on clinical and bovine samples were also found in environmental samples. However, some genotypes commonly found in animal were only found in sewage samples.

CONCLUSION

The comparison of environmental, clinical and animal data suggests that STPs may convey not only human sewage but also animal wastes, both of them contaminated with numerous RV-A strains which are not efficiently eliminated by the sewage treatment process and may spread to surface waters.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work demonstrates the potential release of human and animal RV-A into water sources, representing a public health risk, by inducing gastroenteritis in population, but also by increasing the risk of zoonotic transmission and formation of reassortant viruses which could get a higher infectious potential. Our findings also suggest that monitoring of sewage may provide an additional tool to determine the epidemiology of RV-A circulating in a given community.

Relationship between GII.3 norovirus infections and blood group antigens in young children in Tunisia

Noroviruses (NoVs) constitute a major cause of gastroenteritis in Tunisia. One hundred and fourteen matched saliva and stool samples were collected from children (n = 114) suffering from acute gastroenteritis at the hospital of Monastir during the winter season 2011-2012. For 98 of 114 children, blood samples were collected for secretor genotyping. NoVs were associated with 36.8% (n = 42/114) of the gastroenteritis cases. The GII.3 genotype was the most common (69% of all NoVs). For patients who were phenotyped (n = 114) for human blood group antigens (HBGAs), the secretor and non-secretor phenotypes represented 79% and 21%, respectively. Of the NoV infections, 83% were detected in all ABO groups. Five GII.3 isolates, one GII.1 isolate and one GII.7 isolate were detected in Lewis-positive non-secretors, confirmed by genotyping of the FUT2 gene. Even though our data showed that GII.3 NoVs could infect non-secretors, no binding was observed with saliva and GII.3 baculovirus-expressed virus-like particles from the same symptomatic non-secretor individual. This suggests that other factors might also participate in NoV attachment in children and newborns.

Detection and molecular characterization of enteric viruses in environmental samples in Monastir, Tunisia between January 2003 and April 2007

AIMS

A prospective study was performed to characterize the main human enteric viruses able to persist in sewage samples and in shellfish tissues, and to establish the correlation between environmental strains and viral infantile diarrhoea observed in the same area during the same period.

METHODS AND RESULTS

A total of 250 sewage (raw and treated) and 60 shellfish samples were collected between January 2003 and April 2007 in Monastir region, Tunisia. Group A rotavirus (RVA) was detected in 80 (32%) sewage samples, norovirus (NoV) in 11 (4·4%) and enteric adenovirus (AdV) in 1 (0·4%). Among 60 shellfish samples collected near sewage effluents, one was contaminated by NoV (1·6%).

CONCLUSION

Our data represent the first documentation in Tunisia, combining gastroenteritis viruses circulating in the environment and in clinical isolates. We observed a correlation between environmental strains and those found in children suffering from gastroenteritis during the same period study. This suggests the existence of a relationship between water contamination and paediatric diarrhoea.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our results address the potential health risks associated with transmission of human enteric viruses through water-related environmental routes. The research findings will aid in elucidating the molecular epidemiology and circulation of enteric viruses in Tunisia and in Africa, where data are rare.