Torovirus and Diarrhea in Children

ABSTRACT & COMMENTARY

Synopsis: Torovirus antigen was absent from the stools of control children, but was found in those of 27% of children less than 18 years of age in a Brazilian slum who had diarrhea. It was usually detected, however, in the presence of other known enteric pathogens.

Source: Koopmans MPG, et al. Association of torovirus with acute and persistent diarrhea in children. Pediatr Infect Dis J 1997;16:504-507.

Koopmans and associates performed a case control study examining the possible etiologic role of toroviruses as a cause of human gastroenteritis. This was done in the context of an ongoing prospective evaluation of diarrhea in an urban slum in Brazil.

The study population comprised 33 children with acute diarrhea, 41 with persistent diarrhea, and 17 control children. All were less than 18 months of age. Torovirus antigen was detected in stool by ELISA in nine (27%) children with acute diarrhea, 11 (27%) with persistent diarrhea, but in no controls (P = 0.02). Torovirus-like particles were detected on electron microscopy of coded stool samples of four of five ELISA-positive samples and one of five ELISA-negative samples.

Despite screening for a wide variety of known enteric pathogens, the only individual potential pathogen significantly associated with acute diarrhea was torovirus, which was also associated with persistent diarrhea. There was also a statistically significant correlation (P = 0.04) between detection of enteroaggregative Escherichia coli by aggregative adherence probe and the presence of persistent diarrhea, and statistical significance was approached (P = 0.08) with detection of Cryptosporidium. Despite its frequent detection, however, Torovirus was present as a sole potential pathogen in only one each of the children with acute and persistent diarrhea.

COMMENT BY STAN DERESINSKI, MD, FACP

Toroviruses are enveloped RNA viruses that have been assigned to the Coronoviridae, and are known causes of diarrhea in both cattle and horses. Particles consistent with toroviruses have frequently been detected in the stools of humans with diarrhea, but this method of identification is uncertain. Furthermore, even assuming that the particles detected were toroviruses, their role as an etiologic pathogen in human diarrhea has remained largely unexamined.

The authors of this article are very careful to not indicate that they believe they have demonstrated an etiologic role for toroviruses in causing diarrhea in these children. This care is demonstrated by the title of the article, which, appropriately, indicates that they have only demonstrated an association and not necessarily a role in pathogenesis. They point out some of the unusual results of their study as well. Thus, no virus has previously been associated with persistent, as distinct from acute diarrhea, and none has accounted for such a high prevalence of detection in children with diarrhea in the absence of an outbreak. Finally, torovirus was almost always associated with another enteric pathogen in this study, further muddying the water.

Thus, the role of torovirus in causing diarrhea in humans remains unproven, but the data reported by these investigators are tantalizing.