| Abstract: | Aichi virus has been described as a novel causative agent of gastroenteritis in humans. In this study, we report the seroprevalence distribution of Aichi virus in Tunisia. A panel of 1,000 sera was screened by applying an enzyme-linked immunosorbent assay for immunoglobulin G specific for Aichi virus. A considerable prevalence (92%) of antibody to Aichi virus was found across all age groups. The specific anti-Aichi virus antibodies increased with age, from a high rate (68.8%) in children under 10 years old to about 100% in persons more than 60 years old. We found a statistically significant increase in levels of antibody to Aichi virus according to the age of patients. Immunoglobulin M antibodies were detected among five children. A high frequency of Aichi virus monoinfections in hospitalized children with severe gastroenteritis was previously observed in Tunisia. Aichi virus causes diarrhea with dehydration, fever, and vomiting. This work is the first to establish a correlation between the high seroprevalence of specific Aichi virus antibodies, clinical presentation, and a high frequency of isolation of Aichi virus by genomic characterization in stools of children suffering from gastroenteritis. Our data show the importance and emerging character of Aichi virus in the viral etiology of pediatric gastroenteritis.Viral gastroenteritis is a common illness that affects humans worldwide. Rotavirus, calicivirus, adenovirus, and astrovirus have been established as the most important etiologic agents in these clinical diseases (4). Nevertheless, for many nonbacterial gastroenteritis cases, no etiological agent is diagnosed, and it has been hypothesized that other, viral agents are involved. Among these, Aichi virus (AiV) was first recognized in 1989 as the likely cause of oyster-associated gastroenteritis in a Japanese patient (15). This virus is a new member of the family Picornaviridae and is classified in a new genus, Kobuvirus (9, 15). The detection of AiV in stool samples collected from nonbacterial-gastroenteritis outbreaks due to oyster consumption was documented in Asia (14, 16, 19) and in Europe (1, 7). Moreover, this virus was recently identified in oysters implicated in a gastroenteritis outbreak in France (6). The detection of AiV strains has also been reported in fecal specimens from children suffering from gastrointestinal symptoms in several studies in Asian countries (8, 17, 20), in Brazil (7), and in France (1). However, a low incidence (0.9 to 3.1%) of AiV strains was observed in all these surveys in sporadic, as well as epidemic, gastroenteritis. On the other hand, several seroprevalence studies of antibodies to AiV have been conducted in Japan (16), Germany (7), and France (5) showing a high level of seroprevalence (80 to 95%) in adults, which supports widespread exposure to AiV, at least during childhood, and proves that the virus is quite prevalent.In Tunisia, we previously reported the epidemiology and genomic characterization of AiV strains circulating in the pediatric Tunisian population over more than 4 years (12). In this previous prospective survey, contrary to the data in the literature, we showed that AiV was the third most frequently detected agent, after rotavirus and norovirus, in children with sporadic gastroenteritis symptoms. In addition, we observed a high incidence of monoinfections and a relatively high frequency of hospitalizations due to AiV infections, indicating the role of AiV as a causative agent of pediatric diarrhea in our country. Moreover, we previously analyzed sewage and shellfish samples for the presence of AiV from January 2003 to April 2007 (unpublished data), and we performed a comparative analysis of environmental AiV strains with those from clinical cases detected in the same period. AiV was the second most frequent pathogen in sewage, after rotavirus, and a correlation between environmental and human strains was observed. These previous data suggest that AiV plays an important role in pediatric gastroenteritis and environmental contamination in Tunisia.Pursuing our research on AiV epidemiology, in this paper, we report the first seroepidemiological survey of antibodies to AiV in the Tunisian population. One thousand randomly chosen sera from Tunisian individuals were analyzed by an enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G (IgG) specific to AiV. We performed a statistical analysis of IgG antibody levels according to age, and we also looked for AiV-specific immunoglobulin M (IgM) antibodies. We combined the serologic results with clinical and virological data in order to better understand the epidemiology and the role of AiV as a pathogenic agent implicated in gastroenteritis. |
