Background and history

These viruses are widespread both in pig populations and most other mammals and there are a number of different types or groups.

Group A is probably the common pig one, but B, C and E also occur. However the frequency with which different ones occur is unknown and from a practical view point it is probably academic.

Rotaviruses are ubiquitous and they are present in most if not all pig herds with virtually a 100% sero-conversion in adult stock. A further epidemiological feature is their persistence outside the pig, where they are resistant to environmental changes and many disinfectants. Maternal antibodies persist for 3-6 weeks after which pigs become susceptible to infection but exposure does not necessarily result in disease. It is estimated that only 10-15% of diarrhoeas in pigs are initiated by a primary rotavirus infection.

The fact that the virus persists in the environment accounts for widespread infection and therefore a constant risk of disease.

Clinical signs

Sows

• Transient diarrhoea.

Piglets

• Watery profuse diarrhoea in younger animals.
• Villus atrophy is a consistent feature with dehydration, malabsorption and wasting.
• Diarrhoea usually persists for 3-4 days.
• Pigs look hollow in the abdomen and become dehydrated.
• The eyes are sunken.
• The skin around the rectum is wet.

Weaners and growers

In a mature herd:

• A watery profuse diarrhoea appears after piglets are 7 to 10 days of age. It becomes progressively less important with age.
• However if pathogenic strains of E. coli are present severe disease can occur with heavy mortality.
• Villus atrophy is a consistent feature which results in malabsorption.
• Dehydration.
• Diarrhoea usually lasts 3-4 days.
• Pigs look hollow.
• Eyes are sunken.
• Skin around the rectum is wet.

The role of rotaviruses in the post-weaned pig is probably less important although they are often identified when acute E. coli diarrhoea occurs in the first 7-10 days after weaning.

Diagnosis

Whenever there is a diarrhoea problem in pigs from 10 to 40 days of age rotavirus infection either as primary agents or secondary must be considered. Laboratory examinations are required by electron microscopy and ELISA tests. Try the litmus test by soaking scour in litmus paper, E. coli infections turn blue, virus infections red.

Causes

• Poor house hygiene.
• Permanently populated houses. Adopt all-in, all-out.
• Movement of pigs.
• Temperature fluctuations.
• Contaminated boots and clothing.

Prevention

• Reduce the levels of virus in the environment by all-in all-out procedures and effective disinfection. Leave the house empty for 2 to 4 days before pigs are moved in.
• Disinfect with peroxygen based disinfectants such as Virkon S or chlorine based ones.
• Reduce the spread of virus between infected and non infected pigs. Use foot dips and clean clothing and wash hands after handling sick pigs.
• Apply control procedures outlined for coliform infections.
• If a persistent problem is diagnosed in sucking pigs expose sows to piglet scour by collecting it in wet saw dust, or mix the faeces in waters. Feed the contaminated material via the watering systems or into troughs two to three times weekly. Carry this out in weeks four and three before farrowing.
• Modified live vaccines are available in some countries.
• In the weaned pig adopt all-in all-out procedures with cleaning and disinfection in first stage flat decks. Pay particular attention to environmental stress and temperature fluctuations.

Treatment

• There are no specific treatments for rotavirus infections.
• Provide antibiotic therapy either by injection, by mouth or in the drinking water, to control secondary infections such as E. coli.
• Apralan, amoxycillin, neomycin, framycetin and enrofloxacin could be used.
• Provide dextrose/glycine electrolytes to counteract dehydration.
• Provide dry warm and comfortable lying areas.