Transmissible Gastroenteritis Virus

Also known as: TGEV — TGE — Epidemic Diarrhoea

Introduction

TGEV is an enteric coronavirus, of which there is only one serotype. It is now rare in Europe, due to a respiratory coronavirus variant which is now prevalent and is thought to provide immunity to TGEV.

Pigs are particularly susceptible to a number of specific enteric viruses, especially coronaviruses. These may produces outbreaks on a whole farm basis in all ages of pigs. TGEV produces an explosive diarrhoeic disease, which spreads through the farm rapidly. There is a malabsorptive diarrhoea, which affects neonates and can be fatal depending on age and immune status of the piglet. In very young pigs, the virus can reach 100% mortality, whereas in pigs over 5 weeks of age it is rarely fatal.

There is severe villus stunting present in the intestines, which is similar in pathological appearance to rotavirus. The lamina propria is congested and oedemetous. These changes are in contrast to coliform infections, which show much more normal villi. Many gram-negative bacteria can be seen adhering to the villi wall if a gram stain is used and this can contribute to the disease. Secondary bacterial infection make clinical signs more severe.

The virus is highly contagious and is spread by orofaecal transmission. The infection can occur in two forms, firstly, epizootic, where an explosive infection occurs following introduction to a non-immune herd. Enzootic infection occurs when a herd is persistently affected.

Immune sows provide passive immunity but piglets will suffer mild symptoms post-weaning.

Signalment

Pigs only. It can affect other species but is not a disease problem in these. All ages are susceptible but younger pigs are more severely affected. In pigs less than 2 weeks of age the disease is usually fatal. In pigs older than around 5 weeks, pigs will usually recover.

Clinical Signs

Signs include very severe malabsorptive diarrhoea, depression, lethargy, weakness, dehydration and death.

Diagnosis

Diagnosis is best performed by fluorescent microscopy on small intestinal sections.

Treatment and Control

In an epizootic outbreak, where immune sows are not present in the herd, it is important to separate sows that are due to farrow down within two weeks immediately from the rest of the herd if this is not already the case. Then, the herd should be immunised by exposing them to infected stock. Disease will only be mild in older pigs, so immunising them in this way reduces the risk of the fatal form of the disease in piglets.

There is no effective vaccine.

References

Cowart, R.P. and Casteel, S.W. (2001) An Outline of Swine diseases: a handbook, Wiley-Blackwell

Jackson, G.G. and Cockcroft, P.D. (2007) Handbook of Pig Medicine, Saunders Elsevier

Straw, B.E. and Taylor, D.J. (2006) Disease of Swine, Wiley-Blackwell