Rotaviruses of Animals and Humans

Named because of their wheel-like appearance examined by electron microscopy (rota is Latin for wheel) rotaviruses have become established as causes of severe acute diarrhea in the young of many mammalian and avian species worldwide. Rotavirus disease is age-dependent. For example, in mice and rabbits, diarrhea infections occur only during the first two weeks of life. Rotaviruses are classified into groups A to G based on the differencies in the group-specific inner-capsid protien, VP6. The the majority of human and mammalian infections are due to group A viruses. Group A viruses are further classified into serotypes by antigenic differences on VP4 protein. Groups B and C have been identified infrequently in humans. Many studies have provided evidence for interspecies rotavirus transmission (pigs and cattle, pigs and horses, pigs and humans).4

Group A rotavirus occurs worldwide. It is the leading cause of severe diarrhea among infants and chidren. Group B rotavirus is responsible predominantly for adult diarrhea disease ad is called adult diarrhea rotavirus or ADRV. Group C rotavirus has been associated with with rare cases of diarrhea in children in many countries.7 Rotaviruses are stable within a pH range 3 to 7 and are resistant to iodophor, quarternary ammonium, chlorine and hypochlorite (bleach) disinfectants. Ethanol, phenols, and formalin can inactivate the virus.



Transmission and Replication

Rotaviruses are transmitted from one individual to another by fecal-oral route or by aerosol. Rotaviruses replicate in the cytoplasm of enterocytes lining the small intestine causing cell death. Profuse watery diarrhea results from a combination of mechanisms including loss of enterocytes responsible for absorption and digestion, and activation of the enteric nervous system. During the acute phase of rotavirus infection viral particle can be found in the liver, spleen, pancreas, thymus, and kidneys. However, it is not clear if the virus is replicating at these sites.1

Ingestion of viable rotavirus particles can infect humans. Rotaviruses survive well in air, and limited studies in animals have shown that entry of rotaviruses through the nose can lead to gastroenteritis.6

The disease is worst in young animals and can rapidly lead to fatal acidosis, dehydration, and hypovolemic shock. Animals that die from rotavirus enteritis are dehydrated and have very liquid intestinal contents. Diarrhea is fluid and yellow/white. Ingestion of colostrum with high titers of rotavirus-neutralizing antibody provides temporary immunity against disease in newborn animals.5

Equine Rotavirus

Equine rotaviruses only affects foals, but not cattle or humans. Considering the large concentrations of virus shed into the environment, as well as the ability of the virus to remain viable for as long as 9 months, the potential for an outbreak after the first clinical case is real. Adult horses are not clinically affected during outbreaks of foal diarrhea.2

Waterborne Rotavirus Outbreaks

Rotaviruses have been implicated in at least 9 documented waterborne outbreaks. Rotaviruses are commonly present in human waste waters, so the conditions for waterborne rotavirus outbreaks are likely in place whenever human sewage contaminates drinking water. U.S. study of groundwater contamination by viruses found that 13.8% sites tested positive for rotavirus. Like other enteroviruses, they are removed by conventional water treatment processes and inactivated by chlorination, although not as effectively as enteric bacteria.3

References

  1. Desk Encyclopedia of Human and Medical Virology. Brian W. J. Mahy, Marc H. V. van Regenmortel
  2. Equine infectious diseases. Debra C. Sellon, Maureen T. Long
  3. Safe drinking water: lessons from recent outbreaks in affluent nations. Steve E. Hrudey, Elizabeth J. Hrudey
  4. Diseases of swine. Barbara E. Straw, David J. Taylor
  5. Veterinary microbiology. Dwight C. Hirsh, Nigel James Maclachlan, Richard L. Walker, Richard L. Walker (DVM.)
  6. Viruses, parasites, pathogens, and HACCP. Yiu H. Hui, K. D. Murrell, Peggy S. Stanfield, Syed A. Sattar, Wai-Kit Nip
  7. Waterborne Pathogens: Review for the Drinking-Water Industry. Emmanuelle Guillot, Jean-Fran├žois Loret





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