Aichi Virus in Sewage and Surface Water, the Netherlands

Willemijn J. Lodder

, Saskia A. Rutjes, Katsuhisa Takumi, and Ana Maria de Roda Husman

Author affiliations: National Institute of Public Health and the Environment (RIVM), Bilthoven, the Netherlands (W.J. Lodder, S.A. Rutjes, K. Takumi, A.M. de Roda Husman); Utrecht University, Utrecht, the Netherlands (A.M. de Roda Husman).

Abstract

Detection of Aichi virus in humans was initially reported in Japan in 1989. To establish a timeline for the prevalence of Aichi virus infection among humans in the Netherlands, we conducted molecular analysis of archival water samples from 1987–2000 and 2009–2012. Aichi virus RNA was detected in 100% (8/8) of sewage samples and 100% (7/7) of surface water samples collected during 1987–2000 and 100% (8/8) of sewage samples and 71% (5/7) of surface water samples collected during 2009–2012. Several genotype A and B Aichi virus lineages were observed over the 25-year period studied, but the time course of viral genetic diversity showed recent expansion of the genotype B population over genotype A. Our results show that Aichi virus has been circulating among the human population in the Netherlands since before its initial detection in humans was reported and that genotype B now predominates in this country.

Gastroenteritis is a common waterborne disease in humans of all ages worldwide. Children and the elderly are most severely affected, especially in low-income countries (1). A number of viral etiologic agents, such as picornaviruses, caliciviruses, rotaviruses, human adenoviruses, and astroviruses, have been identified in the past few decades. However, a diagnostic gap remains in samples for which no causative agent is determined. It has been suggested that other picornaviruses may be involved (2).
Aichi viruses (species Aichivirus, genus Kobuvirus, family Picornaviridae) are small, nonenveloped viruses with a single-stranded, positive-sense RNA genome. Aichi virus in humans was reported in 1989 in Japan from a sample collected during an oyster-associated gastroenteritis outbreak (3); the complete nucleotide sequence of an Aichi virus was described in 1998 (4). Clinical signs and symptoms of Aichi virus infection include diarrhea, abdominal pain, nausea, vomiting, and fever, reflecting gastroenteritis (3,5). Aichi virus has been found at low incidence in patients with gastroenteritis in several regions around the world, including South America (6), Asia (7,8), Europe (6,9–12), and Africa (13). Serologic studies indicate that up to 90% of the human population has been exposed to Aichi viruses by the age of 40 years (14). However, the epidemiology of gastroenteritis caused by Aichi virus is, to a large extent, unknown.
Aichi viruses have mainly been detected by PCR targeting the 3CD junction of the virus genome (15). The 3CD junction region has been described as conserved, and the viral protein (VP) 1 region is more genetically diverse (4,6,9,16). VP1 sequence typing is standard for the classification of picornaviruses (17), but analysis of the 3CD region has been used to divide Aichi viruses into 3 genotypes: A, B, and C (9,15).
Aichi viruses excreted with human feces contaminate surface waters directly or after discharge of treated or untreated sewage (18). Humans could be exposed to these viruses in surface waters used for the production of drinking water (after insufficient treatment) or for recreational purposes and after consumption of raw shellfish cultivated in contaminated surface waters. One indication that Aichi viruses may be transmitted by the fecal–oral route is the detection of these viruses in sewage samples in Tunisia (19), in surface waters in Venezuela (20), and in sewage and river waters in Japan (21). Some of these studies demonstrated a high Aichi virus prevalence in water samples. Viruses in sewage are thought to reflect the viruses circulating in the human population, originating from asymptomatic and symptomatic persons (22). Hence, environmental surveillance studies are extremely useful to determine the circulation of viruses in the human population (22,23) and to obtain sequence information of the circulating strains.
To establish a timeline for the emergence of Aichi viruses among the human population in the Netherlands, archival sewage and surface waters sampled over a >25-year period were subjected to molecular analysis targeting VP1 and the 3C region of the Aichi virus genome. The detected viruses were typed by sequence analysis to determine genetic variability. These environmental Aichi virus strains were subsequently compared with strains previously isolated from clinical materials and environmental samples worldwide. The possible emergence of the Aichi virus infections in humans was inferred by analyzing the population dynamics of these Aichi viruses.