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Transmissible Gastro-Enteritis (TGE)

See also chapter 8.

(551) TGE is an economically-damaging highly-infectious disease of pigs that is enzootic in most pig rearing countries of the world. Thus, for the majority of readers it is not an exotic disease but is enzootic and a serious risk to your herd.

Should you be concerned about TGE?

A few countries are thought to be free of it, which is why it is mentioned briefly here. They are Australia, New Zealand, Ireland and Denmark.

Australia and New Zealand are so remote from sources of infection and have such strict import controls that they are most unlikely to be contaminated.

Ireland and Denmark are more at risk. If you are involved in pig farming in either you should be aware of TGE because it is enzootic in the UK and mainland Europe. Both Ireland and Denmark have strong pig industry (producers and slaughterers) associations which take every legitimate precaution to keep TGE out but since it is commonly spread by flocks of starlings and on pig lorries and their drivers' feet, it might get in. (It did get into Ireland once several years ago but fortunately did not spread). The proximity of Denmark to Germany suggests that Denmark is at most risk but the prevalence of antibodies to porcine respiratory coronavirus (PRCV), which is antigenically closely similar to TGE, in Denmark probably reduces this risk. PRCV is not present in Ireland.

Importance of TGE

If your herd is fully susceptible to TGE and it becomes infected up to 100% of piglets under 2 weeks of age will die. Many older sucking pigs and some weaned pigs will also die. A proportion of recently bred sows will return to service. As a rule of thumb you can predict that the number of young pigs that die will be >1.5 times the number of breeding females in the herd. The precise number depends on the actions you take and the concurrent diseases present in your herd.

If the herd is farrow to finish you will suffer a substantial loss of revenue and negative cash flow for 4-5 weeks about 4-5 months after the outbreak and another one 4-5 months later.

Clinical signs

When TGE first enters the herd it causes acute diarrhoea in all age groups including sows. In piglets and young weaned pigs the faeces are very liquid, brightly coloured (grey, yellow, green and faun), gassy, shooting out as if from a hose-pipe and smelling strongly (typical of this disease).

Young piglets also vomit bright green or yellow vomitus. Baby piglets die in a few days.

Diagnosis

In an acute severe outbreak in a breeding herd or a farrow-to-finish herd the clinical picture provides a strong presumptive diagnosis. A main feature, which differentiates it from other diarrhoeas is that all age groups are affected. Mild outbreaks of TGE may be difficult to distinguish from PED on clinical grounds. Also TGE in grower-finisher herds may be confused with other conditions. To confirm the diagnosis, samples have to be sent without delay to a laboratory. The best samples are freshly dead or dying piglets. In grower/finishers send the youngest. Also send paired blood samples from early in the outbreak and again ten days later.

The best test, which will give an answer in a matter of hours, is to freeze the ileum (last part of the small intestine), section it for histology and carry out fluorescent antibody tests (FATs) on the sections. ELISAs may also be available in some more sophisticated laboratories. Polymerase chain reaction (PCR) tests would be possible but are probably not available. The blood samples can be subjected to serum neutralisation tests to detect rising antibody titres. Unfortunately these results take at least 2 weeks.

Treatment

  • See chapter 8.
Management control and prevention
  • The most important precautions are careful loading of pig lorries and keeping out visitors, starlings and other birds such as seagulls.
  • Vaccination - There is only one main serotype of TGE and theoretically it should be possible to produce an effective vaccine but because of the type of immunity involved most commercially available vaccines are not very effective

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