Molecular epidemiology of norovirus in symptomatic and asymptomatic population in Burkina Faso

Poster (2012, September)

Background Noroviruses (NoV), belonging to the family Caliciviridae, are now recognized as the leading cause of gastroenteritis outbreaks worldwide, and represent an important cause of sporadic ... [more ▼]

Background Noroviruses (NoV), belonging to the family Caliciviridae, are now recognized as the leading cause of gastroenteritis outbreaks worldwide, and represent an important cause of sporadic gastroenteritis in both children and adults. Many studies describe NoV epidemiology. However, few data are available about the NoV strains circulating in most of African countries, in particular in Burkina Faso. The population of Burkina Faso is characterized by the young age of its habitants, and most are living in rural environment. Objectives The purpose of this epidemiological study was to determine the prevalence of NoV in Bobo Dioulasso (Southern part of Burkina Faso) by molecular diagnosis methods in patients presenting or not gastroenteritis symptoms, to quantify the excreted viral load, and to genotype the circulating strains. Methods Patients with and without gastro-intestinal disorders were selected in several Health Care Centres of Bobo Dioulasso. Clinical and epidemiological data, as well as stool samples, were collected during 8 weeks through March to April 2011. Viral genomic RNA was automatically extracted with a Maxwell® (Promega) instrument. Molecular detection of genogroups (G) I, II and IV NoV in stool samples was performed by a home-made real-time RT-PCR targeting the ORF1-ORF2 polymerase junction region. For each positive sample, viral load was estimated by using standard curves (successive dilutions of recombinant GI and GII plasmids). Molecular characterization was performed on the detected strains, using both polymerase and capsid regions. Results NoV were detected in 21.6% of the 453 collected stool samples, with a distribution of 21.0% and 23.1% in the samples from the 319 symptomatic (SP) and the 134 asymptomatic patients (AP) respectively. Genogroup distribution was 7.2% for GI, 10.7% for GII and 3.1% for both GI and GII among SP’s samples, and was 11.2% for GI, 10.4% for GII and 1.5% for both GI and GII among AP’s samples. Average viral load values were higher for GI NoV in SP than in AP (p=0.02), when they were higher for GII NoV in AP than in SP (p=0.04). Phylogenic analysis showed a high degree of genotypical diversity in both groups of patients. One recombinant strain GII.7/GII.6 was also detected, to our knowledge, for the first time. Conclusion Even if a true pathogenic role of NoV could not be showed from the study design, it allowed to precise the molecular epidemiology of NoV strains prevalent in a representative country of the East African region. It also showed that asymptomatic patients could play an important role as a NoV “reservoir”. Despite the fact that GII strains, and more precisely those belonging to GII.4 genotype, are nowadays highly reported worldwide, the surprising proportion of NoV GI detected in this study suggests that GI and GII strains should be excreted in equal proportion in the environment. The origin of this epidemiologic difference, even if partially explained by the difference in immunity and genetic sensitivity of the population, is still to be solved. [less ▲]

A Review of Known and Hypothetical Transmission Routes for Noroviruses

in Food and Environmental Virology (2012), 4(4), 131-152

Human noroviruses (NoVs) are considered a worldwide leading cause of acute non-bacterial gastroenteritis. Due to a combination of prolonged shedding of high virus levels in feces, virus particle shedding ... [more ▼]

Human noroviruses (NoVs) are considered a worldwide leading cause of acute non-bacterial gastroenteritis. Due to a combination of prolonged shedding of high virus levels in feces, virus particle shedding during asymptomatic infections, and a high environmental persistence, NoVs are easily transmitted pathogens. Norovirus (NoV) outbreaks have often been reported and tend to affect a lot of people. NoV is spread via feces and vomit, but this NoV spread can occur through several transmission routes. While person-to-person transmission is without a doubt the dominant transmission route, human infective NoV outbreaks are often initiated by contaminated food or water. Zoonotic transmission of NoV has been investigated, but has thus far not been demonstrated. The presented review aims to give an overview of these NoV transmission routes. Regarding NoV person-to-person transmission, the NoV GII. 4 genotype is discussed in the current review as it has been very successful for several decades but reasons for its success have only recently been suggested. Both pre-harvest and post-harvest contamination of food products can lead to NoV food borne illness. Pre-harvest contamination of food products mainly occurs via contact with polluted irrigation water in case of fresh produce or with contaminated harvesting water in case of bivalve molluscan shellfish. On the other hand, an infected food handler is considered as a major cause of post-harvest contamination of food products. Both transmission routes are reviewed by a summary of described NoV food borne outbreaks between 2000 and 2010. A third NoV transmission route occurs via water and the spread of NoV via river water, ground water, and surface water is reviewed. Finally, although zoonotic transmission remains hypothetical, a summary on the bovine and porcine NoV presence observed in animals is given and the presence of human infective NoV in animals is discussed. © 2012 Springer Science+Business Media New York. [less ▲]

Complete genome sequence of a novel bovine norovirus: Evidence for slow genetic evolution in genogroup III genotype 2 noroviruses

in Journal of Virology (2012), 86(22), 12449-12450

A new genogroup III genotype 2 bovine norovirus, B309/2003/BE, was entirely sequenced and genetically compared to the original Newbury2/1976/UK strain and to Dumfries/1994/UK, detected in 1976 and 1994 ... [more ▼]

A new genogroup III genotype 2 bovine norovirus, B309/2003/BE, was entirely sequenced and genetically compared to the original Newbury2/1976/UK strain and to Dumfries/1994/UK, detected in 1976 and 1994, respectively. Interestingly, except in welldefined coding regions (N-terminal protein, 3A-like protease, hypervariable region of the capsid protein, and C-terminal part of the minor structural protein), very low genetic differences were noted between the entire genomes of these three strains along a 30-year-long period. It allowed some hypotheses of hotspots of genetic evolution through a low genetic evolution background in genotype 2 genogroup III bovine noroviruses. © 2012, American Society for Microbiology. [less ▲]

Les Norovirus : grands coupables méconnus de gastro-entérites

in Revue de la Médecine Générale [=RMG] (2011), (285), 316-321

Recently, noroviruses emer- ged worldwide as a main and frequent cause of sporadic and epidemic gastroenteritis. The symptomatology they cause is usually benign. Their real impact lies on Public Health ... [more ▼]

Recently, noroviruses emer- ged worldwide as a main and frequent cause of sporadic and epidemic gastroenteritis. The symptomatology they cause is usually benign. Their real impact lies on Public Health and Food Safety levels. [less ▲]

Experimental evidence of recombination in murine noroviruses

in Journal of General Virology (The) (2010)

Molecular detection of kobuviruses and recombinant noroviruses in cattle in continental Europe

in Archives of Virology (2009), 154

Spécificité et diversité virales : implications en médecine vétérinaire

in Bulletin des Groupements Techniques Vétérinaires (2008), hors série

Noroviruses and sapoviruses in pigs in Belgium.

in Archives of Virology (2008), 153(10), 1927-31

Porcine noroviruses and sapoviruses belong to the family Caliciviridae and are rarely reported in European countries. In this study, swine stools from a region representative of northern Europe were ... [more ▼]

Porcine noroviruses and sapoviruses belong to the family Caliciviridae and are rarely reported in European countries. In this study, swine stools from a region representative of northern Europe were screened for these viruses by RT-PCR. Both porcine noroviruses and sapoviruses were detected, showing their circulation in this region. The porcine norovirus strains were genetically related to genotype 19 strains in the genogroup II of the genus Norovirus. The porcine sapovirus strains were genetically related to the porcine enteric calicivirus Cowden reference strain and to newly described porcine strains in the genus Sapovirus. [less ▲]

Detection and quantification of human and bovine novoviruses by a TaqMan RT-PCR assay with a control for inhibition.

in Molecular and Cellular Probes (2008), 22

Noroviruses are single-stranded RNA viruses belonging to the family Caliciviridae. They are a major cause of epidemic and sporadic gastroenteritis in humans and calves. Reverse transcription-polymerase ... [more ▼]

Noroviruses are single-stranded RNA viruses belonging to the family Caliciviridae. They are a major cause of epidemic and sporadic gastroenteritis in humans and calves. Reverse transcription-polymerase chain reaction (RT-PCR) has become the ‘‘gold standard’’ for detection of noroviruses in faecal and environmental samples. However, false negative results due to co-concentration of RT-PCR inhibitors are a continuous concern. A TaqMan real-time RT-PCR assay making use of a foreign internal RNA control and a RNA standard was developed. Very interestingly, this method is capable of detecting human noroviruses belonging to genogroups I and II, and bovine noroviruses belonging to genogroup III. Inhibitors were removed efficiently by 1/10 dilution of the sample or addition of bovine serum albumin to the RT-PCR mix. This assay was validated with human and bovine stool samples previously tested for norovirus by conventional RT-PCR. The ability to detect norovirus in stool samples that were negative by conventional RT-PCR assay demonstrate the higher sensitivity of the TaqMan assay compared to the conventional RT-PCR assay. This real-time RT-PCR assay allows the detection of both human and bovine noroviruses, avoids false negative results and is able to quantify the level of norovirus contamination. [less ▲]

Animal noroviruses.

in Veterinary Journal (2008), 178(1), 32-45

Among enteric caliciviruses, noroviruses belong to the genus Norovirus, one of the four accepted genera in the family Caliciviridae. These single-stranded, positive-sense RNA viruses are highly variable ... [more ▼]

Among enteric caliciviruses, noroviruses belong to the genus Norovirus, one of the four accepted genera in the family Caliciviridae. These single-stranded, positive-sense RNA viruses are highly variable both genetically and antigenically. Several animal enteric caliciviruses that are morphologically indistinguishable and genetically closely related to human noroviruses have been identified. The first bovine enteric noroviruses were described in Great Britain and are known as Newbury Agent 2. At least three genetic clusters of porcine noroviruses join together within genogroup II noroviruses. Human noroviruses are the most important cause of acute gastroenteritis illness in people of all ages. In the USA, they are associated with approximately 30-50% of all food-borne outbreaks. Until now, noroviruses have not been associated with gastroenteritis outbreaks in immunocompetent animals. Neither bovine nor porcine noroviruses can replicate in cell culture, although human norovirus can grow in a complex 3D culture system. However, the recently discovered murine noroviruses can replicate in cell culture and are therefore used as model viruses to study human noroviruses. This review focusses on virus classification, virion structure, pathogenesis, epidemiology, immune response and diagnosis of animal noroviruses in comparison with human noroviruses. The classification of animal enteric caliciviruses within the Norovirus genus raises the question of whether transmission from an animal reservoir to humans could occur. Answering this question is important in determining the risk of cross-species infections affecting the epidemiology and evolution of these viruses and so complicating the control of human norovirus infections. [less ▲]