Rotaviruses

Antigenicity

• 5 distinct antigenic groups: A to E
• A is the most commonly seen and studied
• A is further subdivided to G and P types

Hosts

• RVs are thought to be mostly species specific, but some transmission between species occurs
• Group A is present in all mammals
• Groups B and C are common in pigs but not fully understood

Pathogenesis

• Strains vary in virulence but are always confined to the gut
• Incubation: 1-4 days
• Target tissue: small intestine enteroycte
  • Infected enterocytes are shed, villi shorten, and become covered with immature cuboidal epithelium
  • As such, absorption is compromised
• Results in white scour
• NO viremia: confined to GIT
• Associated symptoms:
  • Weight loss
  • Depression
  • Dehydration
• Can be fatal if unchecked

Epidemiology

• Occurs in neonates of most species, although the role of RVs in lamb and foal diarrhoea is less certain
• NOT associated with diarrhoea in dogs and cats
• Group A RVs are endemic in domestic animals worldwide
• Orofecal transmission, highly infectious
• Excreted in feces as maternal antibody wanes (calves: 2 weeks, piglets: post-weaning)

Diagnosis

• On feces:
  • ELISA and Latex agglutination
• On sera:
  • Rising antibody titres are not particularly helpful as most animals show high Ab levels from passive immunity

Control

• Ensure maternal antibody transfer through the reception of colostrum
• Hygiene and management strategies: all-in/all-out, isolation of sick animals, etc.
• Fluid therapy where necessary
• Dam vaccine:
  • Boost and prolong Ab secretion during suckling
  • Primarily for beef suckler herds as dairy calves receive batch milk after 24 hours

Vilous atrophy in Enteritis

• Affects young foals and calves.

Pathology

Gross

• small intestine distended with yellow fluid.

Histopathology

• Loss of villus epithelium
  • Replacement with cuboidal or squamous cells
• Villus atrophy.
• Relatively mild inflammation.
• Coronavirus in young calves results in similar pathological changes.