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transmissible gastroenteritis and porcine respiratory coronovirus infection

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transmissible gastroenteritis and porcine respiratory coronovirus infection

Summary

  • Last modified
  • 09 November 2017
  • Datasheet Type(s)
  • Animal Disease
  • Preferred Scientific Name
  • transmissible gastroenteritis and porcine respiratory coronovirus infection
  • Overview
  • Transmissible gastroenteritis (TGE) is a disease confined to pigs, which was first seen in the USA in the 1940s (Doyle and Hutch...

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Pictures

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PictureTitleCaptionCopyright
Litter of TGE affected piglets.
TitleSymptoms
CaptionLitter of TGE affected piglets.
CopyrightVeterinary Laboratories Agency (VLA)
Litter of TGE affected piglets.
SymptomsLitter of TGE affected piglets.Veterinary Laboratories Agency (VLA)
TGE affected piglet; weak, dehydrated and  with pink discolouration of skin.
TitleSymptoms
CaptionTGE affected piglet; weak, dehydrated and with pink discolouration of skin.
CopyrightVeterinary Laboratories Agency (VLA)
TGE affected piglet; weak, dehydrated and  with pink discolouration of skin.
SymptomsTGE affected piglet; weak, dehydrated and with pink discolouration of skin.Veterinary Laboratories Agency (VLA)
Transluscent intestine of TGE affected piglet.
TitlePathology
CaptionTransluscent intestine of TGE affected piglet.
CopyrightVeterinary Laboratories Agency (VLA)
Transluscent intestine of TGE affected piglet.
PathologyTransluscent intestine of TGE affected piglet.Veterinary Laboratories Agency (VLA)
Villous atrophy of small intestine.
TitlePathology
CaptionVillous atrophy of small intestine.
CopyrightVeterinary Laboratories Agency (VLA)
Villous atrophy of small intestine.
PathologyVillous atrophy of small intestine.Veterinary Laboratories Agency (VLA)
One of the only other agents to cause syncytia in addition to PCV2 is porcine respiratory coronavirus, and this is a section from 1987 when the UK first experienced the condition. Nearly all lungs are positive using immunohistochemistry.
TitleHistological section of lung with syncytium
CaptionOne of the only other agents to cause syncytia in addition to PCV2 is porcine respiratory coronavirus, and this is a section from 1987 when the UK first experienced the condition. Nearly all lungs are positive using immunohistochemistry.
CopyrightStan H. Done
One of the only other agents to cause syncytia in addition to PCV2 is porcine respiratory coronavirus, and this is a section from 1987 when the UK first experienced the condition. Nearly all lungs are positive using immunohistochemistry.
Histological section of lung with syncytiumOne of the only other agents to cause syncytia in addition to PCV2 is porcine respiratory coronavirus, and this is a section from 1987 when the UK first experienced the condition. Nearly all lungs are positive using immunohistochemistry.Stan H. Done

Identity

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Preferred Scientific Name

  • transmissible gastroenteritis and porcine respiratory coronovirus infection

International Common Names

  • English: enzootic TGE; porcine respiratory coronavirus, tge-like virus; porcine respiratory coronovirus infection; transmissible gastroenteritis; transmissible gastroenteritis in pigs, tge; transmissible gastroenteritis of pigs

English acronym

  • TGE

Overview

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Transmissible gastroenteritis (TGE) is a disease confined to pigs, which was first seen in the USA in the 1940s (Doyle and Hutchings, 1946). It has since been seen in most swine producing areas of the world. The causative agent is a coronavirus, an enveloped positive strand RNA virus similar to coronaviruses affecting other domestic animals, including dogs and cats, with which it cross-reacts in a variety of serological tests. TGE can be a significant cause of economic loss in breeding herds, primarily because of the very high piglet mortality, although it is of less importance in rearing and finishing herds. The main clinical features (Pritchard, 1982) are watery diarrhoea, vomiting and loss of appetite affecting all ages of pigs. Sucking piglets are the most severely affected group. When a naïve herd is first infected, the mortality in piglets aged less than two weeks can reach 100% primarily due to dehydration. There is no specific treatment and vaccines, although commercially available in some countries, are currently of limited value. The disease is usually seasonal, with outbreaks occurring mainly in the winter months in temperate climates. In some countries, such as the UK, large-scale epidemics have tended to occur at fairly regular intervals of a few years. However, this situation has changed since the widespread emergence, in the mid 1980s, of a closely related, but non-enteropathogenic and clinically inconsequential, porcine respiratory coronavirus (PRCV) (Pensaert et al., 1986) which has coincided with the declining incidence of TGE in the European pig population. In recent field studies, Pritchard et al. (1999) noted clinically silent seroconversion to TGEV in a number of herds in the UK and raised the possibility of further changes in the TGEV or PRCV genomes. The literature on TGE and PRCV was recently reviewed by Saif and Wesley (1999).

This disease is on the list of diseases notifiable to the World Organisation for Animal Health (OIE). The distribution section contains data from OIE's WAHID database on disease occurrence. Please see the AHPC library for further information on this disease from OIE, including the International Animal Health Code and the Manual of Standards for Diagnostic Tests and Vaccines. Also see the website: www.oie.int.

Hosts/Species Affected

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The pig is the maintenance host. However, the virus is closely related to feline and canine coronaviruses and may be able to replicate subclinically in dogs, cats and foxes (Bohl, 1989). Birds may act as mechanical vectors but have not been shown to replicate the virus (Pilchard, 1965).

Distribution

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TGE is widely recognized throughout the pig-keeping world although it is absent from Australasia and a few other countries. The distribution of PRCV is less certain, since infection with this virus causes mild or inapparent illness and tests for its presence are often not carried out or reported. However, it is believed to have a very widespread distribution.

For current information on disease incidence, see OIE's WAHID Interface.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

AfghanistanNo information availableOIE, 2009
ArmeniaDisease not reportedOIE, 2009
AzerbaijanDisease not reportedOIE, 2009
BahrainDisease never reportedOIE, 2009
BangladeshDisease never reportedOIE, 2009
BhutanNo information availableOIE, 2009
Brunei DarussalamDisease not reportedOIE Handistatus, 2005
CambodiaNo information availableOIE, 2009
ChinaRestricted distributionNULLAnon, 1997; OIE, 2009
-Hong KongDisease never reportedOIE, 2009
Georgia (Republic of)Disease never reportedOIE Handistatus, 2005
IndiaDisease never reportedOIE, 2009
IndonesiaDisease not reportedOIE, 2009
IranDisease never reportedOIE, 2009
IraqDisease never reportedOIE, 2009
IsraelAbsent, reported but not confirmedOIE, 2009
JapanPresentNULLKamogawa et al., 1996; Anon, 1997; OIE, 2009
JordanNo information availableOIE, 2009
KazakhstanDisease not reportedOIE, 2009
Korea, DPRDisease not reportedOIE Handistatus, 2005
Korea, Republic ofDisease not reported20070820Anon, 1997; Chae et al., 1998; Chae et al., 2000; OIE, 2009
KuwaitDisease never reportedOIE, 2009
KyrgyzstanDisease not reportedOIE, 2009
LaosDisease not reportedOIE, 2009
LebanonDisease not reported1998Anon, 1997; OIE, 2009
MalaysiaDisease not reportedOIE, 2009
-Peninsular MalaysiaDisease not reportedOIE Handistatus, 2005
-SabahDisease never reportedOIE Handistatus, 2005
-SarawakCAB Abstracts data miningOIE Handistatus, 2005
MongoliaNo information availableOIE, 2009
MyanmarDisease not reported2001Anon, 1997; OIE, 2009
NepalNo information availableOIE, 2009
OmanDisease never reportedOIE, 2009
PakistanNo information availableOIE, 2009
PhilippinesDisease never reportedOIE, 2009
QatarNo information availableOIE, 2009
Russian Federation
-Russia (Asia)PresentRukhadze et al., 1993
Saudi ArabiaDisease never reportedOIE, 2009
SingaporeDisease not reportedOIE, 2009
Sri LankaDisease never reportedOIE, 2009
SyriaDisease not reportedOIE, 2009
TaiwanLast reported2003OIE Handistatus, 2005
TajikistanDisease not reportedOIE, 2009
ThailandNo information availableOIE, 2009
TurkeyNo information availableOIE, 2009
TurkmenistanDisease not reportedOIE Handistatus, 2005
United Arab EmiratesNo information availableOIE, 2009
UzbekistanDisease not reportedOIE Handistatus, 2005
VietnamDisease never reportedOIE, 2009
YemenNo information availableOIE, 2009

Africa

AlgeriaDisease not reportedOIE, 2009
AngolaNo information availableOIE, 2009
BeninNo information availableOIE, 2009
BotswanaDisease never reportedOIE, 2009
Burkina FasoNo information availableOIE, 2009
BurundiNo information availableOIE Handistatus, 2005
CameroonNo information availableOIE Handistatus, 2005
Cape VerdeNo information availableOIE Handistatus, 2005
Central African RepublicDisease not reportedOIE Handistatus, 2005
ChadNo information availableOIE, 2009
CongoNo information availableOIE, 2009
Congo Democratic RepublicDisease not reportedOIE Handistatus, 2005
Côte d'IvoireDisease not reportedOIE Handistatus, 2005
DjiboutiDisease never reportedOIE, 2009
EgyptNo information availableNULLAnon, 1997; OIE, 2009
EritreaNo information availableOIE, 2009
EthiopiaNo information availableOIE, 2009
GabonNo information availableOIE, 2009
GambiaNo information availableOIE, 2009
GhanaNo information availableOIE, 2009
GuineaNo information availableOIE, 2009
Guinea-BissauNo information availableOIE, 2009
KenyaNo information availableOIE, 2009
LesothoDisease not reportedOIE, 2009
LibyaDisease never reportedOIE Handistatus, 2005
MadagascarDisease never reportedOIE, 2009
MalawiNo information availableOIE, 2009
MaliNo information availableOIE, 2009
MauritiusDisease not reportedOIE, 2009
MoroccoNo information availableOIE, 2009
MozambiqueDisease never reportedOIE, 2009
NamibiaDisease not reportedOIE, 2009
NigeriaNo information availableOIE, 2009
RéunionNo information availableOIE Handistatus, 2005
RwandaNo information availableOIE, 2009
Sao Tome and PrincipeDisease not reportedOIE Handistatus, 2005
SenegalNo information availableOIE, 2009
SeychellesNo information availableOIE Handistatus, 2005
SomaliaNo information availableOIE Handistatus, 2005
South AfricaDisease never reportedNULLWilliams et al., 1994; OIE, 2009
SudanDisease never reportedOIE, 2009
SwazilandDisease never reportedOIE, 2009
TanzaniaNo information availableOIE, 2009
TogoNo information availableOIE, 2009
TunisiaDisease not reportedOIE, 2009
UgandaNo information availableOIE, 2009
ZambiaNo information availableNULLStafford et al., 1992; OIE, 2009
ZimbabweDisease never reportedOIE, 2009

North America

BermudaDisease not reportedOIE Handistatus, 2005
CanadaPresentNULLAnon, 1997; OIE, 2009
-OntarioPresentWilson et al., 1999
GreenlandDisease never reportedOIE, 2009
MexicoPresentNULLAnon, 1997; OIE, 2009
USAPresentNULLAnon, 1997; OIE, 2009
-IowaPresentWesley et al., 1997

Central America and Caribbean

BarbadosDisease not reportedOIE Handistatus, 2005
BelizeDisease never reportedOIE, 2009
British Virgin IslandsDisease never reportedOIE Handistatus, 2005
Cayman IslandsDisease not reportedOIE Handistatus, 2005
Costa RicaNo information availableOIE, 2009
CubaPresentOIE, 2009
CuraçaoDisease not reportedOIE Handistatus, 2005
DominicaDisease not reportedOIE Handistatus, 2005
Dominican RepublicDisease never reportedOIE, 2009
El SalvadorDisease never reportedOIE, 2009
GuadeloupeNo information availableOIE, 2009
GuatemalaDisease never reportedOIE, 2009
HaitiDisease never reportedOIE, 2009
HondurasNo information availableOIE, 2009
JamaicaDisease never reportedOIE, 2009
MartiniqueDisease not reportedOIE, 2009
NicaraguaDisease never reportedOIE, 2009
PanamaNo information availableOIE, 2009
Saint Kitts and NevisNo information availableOIE Handistatus, 2005
Saint Vincent and the GrenadinesDisease never reportedOIE Handistatus, 2005
Trinidad and TobagoDisease never reportedOIE Handistatus, 2005

South America

ArgentinaDisease never reportedOIE, 2009
BoliviaNo information availableNULLAnon, 1997; OIE, 2009
BrazilDisease not reportedOIE, 2009
ChileDisease never reportedOIE, 2009
ColombiaDisease not reportedOIE, 2009
EcuadorDisease never reportedOIE, 2009
Falkland IslandsDisease never reportedOIE Handistatus, 2005
French GuianaDisease never reportedOIE, 2009
GuyanaDisease not reportedAnon, 1997; OIE Handistatus, 2005
ParaguayDisease never reportedOIE Handistatus, 2005
PeruDisease never reportedOIE, 2009
UruguayDisease never reportedOIE, 2009
VenezuelaNo information availableOIE, 2009

Europe

AlbaniaNo information availableOIE, 2009
AndorraNo information availableOIE Handistatus, 2005
AustriaNo information availableNULLAnon, 1997; OIE, 2009
BelarusPresentNULLAnon, 1997; OIE, 2009
BelgiumDisease not reported2004Pensaert et al., 1986; Pensaert et al., 1993; Reeth and Pensaert, 1994; Anon, 1997; OIE, 2009
Bosnia-HercegovinaDisease not reportedOIE Handistatus, 2005
BulgariaDisease not reported1997Anon, 1997; OIE, 2009
CroatiaDisease not reportedOIE, 2009
CyprusDisease not reported200707Anon, 1997; OIE, 2009
Czech RepublicDisease not reported1998Anon, 1997; OIE, 2009
DenmarkDisease never reportedOIE, 2009
EstoniaDisease not reportedOIE, 2009
FinlandDisease not reportedOIE, 2009
FranceNo information availableNULLAnon, 1997; OIE, 2009
GermanyDisease not reported200804Anon, 1997; OIE, 2009
GreeceDisease not reportedOIE, 2009
HungaryDisease not reportedOIE, 2009
IcelandDisease never reportedOIE, 2009
IrelandDisease not reportedOIE, 2009
Isle of Man (UK)Disease never reportedOIE Handistatus, 2005
ItalyNo information availableOIE, 2009
JerseyDisease never reportedOIE Handistatus, 2005
LatviaDisease not reportedOIE, 2009
LiechtensteinDisease not reportedOIE, 2009
LithuaniaDisease not reportedOIE, 2009
LuxembourgDisease not reportedOIE, 2009
MacedoniaNo information availableOIE, 2009
MaltaDisease not reportedOIE, 2009
MoldovaDisease not reportedOIE Handistatus, 2005
MontenegroDisease not reportedOIE, 2009
NetherlandsDisease not reportedOIE, 2009
NorwayDisease never reportedOIE, 2009
PolandDisease not reported1997Anon, 1997; OIE, 2009
PortugalDisease not reportedOIE, 2009
RomaniaDisease not reported2004Anon, 1997; OIE, 2009
Russian FederationDisease not reportedOIE, 2009
-Russia (Europe)PresentRukhadze et al., 1993
SerbiaNo information availableOIE, 2009
SlovakiaPresentOIE, 2009
SloveniaDisease not reportedOIE, 2009
SpainNo information availableNULLCubero et al., 1993; Anon, 1997; OIE, 2009
SwedenDisease never reportedOIE, 2009
SwitzerlandDisease not reported1995Bereiter et al., 1988; Anon, 1997; OIE, 2009
UKDisease not reported2001Pritchard, 1982; Brown and Paton, 1991; Anon, 1997; OIE, 2009
-Northern IrelandDisease never reportedOIE Handistatus, 2005
UkraineDisease not reported2004Anon, 1997; OIE, 2009
Yugoslavia (former)No information availableOIE Handistatus, 2005
Yugoslavia (Serbia and Montenegro)Disease not reportedOIE Handistatus, 2005

Oceania

AustraliaDisease never reportedNULLMulland et al., 1994; OIE, 2009
French PolynesiaDisease never reportedOIE, 2009
New CaledoniaDisease never reportedOIE, 2009
New ZealandDisease never reportedOIE, 2009
SamoaDisease never reportedOIE Handistatus, 2005
VanuatuDisease never reportedOIE Handistatus, 2005
Wallis and Futuna IslandsNo information availableOIE Handistatus, 2005

Pathology

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TGE is characterised by marked dehydration in baby piglets associated with villous atrophy of the small intestine with thinning and translucency of the gut wall and very watery, foul smelling flocculent, greenish-yellow intestinal contents. Undigested milk clots are usually present in the stomach. Gastritis is occasionally seen, particularly in enzootic TGE where secondary colibacillosis can be a complicating feature. Urate crystals are often prominent in the kidney pelvis of affected baby piglets. Uncomplicated cases of PRCV are characterised only by a mild interstitial pneumonia.

Diagnosis

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Acute outbreaks of enzootic TGE are usually fairly characteristic because of the large number of pigs of different age groups affected, often simultaneously. The main differential diagnosis is porcine epidemic diarrhoea (PED). This is caused by a serologically unrelated coronavirus and produces a clinically very similar disease, although not usually as severe. Enzootic TGE in an endemically infected herd is much less characteristic and can be difficult to diagnose clinically. It needs to be differentiated from other causes of pre and post weaning diarrhoea, including enteric colibacillosis, rotavirus infection or coccidiosis. TGE outbreaks confined to finishing units may be confused clinically with other causes of high morbidity diarrhoea such as swine dysentery or salmonellosis, although blood and mucus are absent from the faeces in uncomplicated TGE outbreaks.

Laboratory diagnosis of TGE is based on the demonstration of virus, viral antigens, nucleic acids or virus-specific antibodies (Paton et al., 1996). For virus detection, samples should preferably be collected from neonates in the early stages of disease. Samples of faeces or ligated lengths of small intestine are suitable for virus detection which can be by means of electron microscopy, virus isolation, antigen capture ELISA, fluorescent antibody tests (FAT) on cryostat sections and RT-PCR. The virus is labile, and therefore samples must be kept cool and transported to the laboratory without delay. Where possible, portions of small intestine should be snap frozen on solid carbon dioxide, immediately after collection. A practical approach is to screen samples by electron microscopy, ELISA or FAT and to confirm positive results by virus isolation or RT-PCR. Immunocytochemistry on formalin fixed small intestine is also possible. Virus neutralisation tests or various ELISAs can be used for serological diagnosis. Antibodies develop within 10 days of infection and persist for many months.

Diagnosis of PRCV is rarely attempted in relation to clinical disease outbreaks since the agent is considered to be of minimal pathogenic significance on its own. The main importance of PRCV is that it complicates the laboratory diagnosis of TGE. PRCV can be detected in respiratory tissues by virus isolation, IFAT, RT-PCR and immunohistochemistry on formalin fixed sections. The virus is present at only low levels, if at all, in the gastrointestinal tract. PRCV and TGEV can be differentiated by means of monoclonal antibodies and genetic analysis. Serologically, the two viruses fully cross-neutralise one another rendering the serum neutralisation test of limited value other than for general disease screening. Differentiation is only possible by means of competitive ELISAs using monoclonal antibodies specific for TGEV.

List of Symptoms/Signs

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SignLife StagesType
Digestive Signs / Anorexia, loss or decreased appetite, not nursing, off feed Pigs:Weaner,Pigs:Growing-finishing pig,Pigs:Gilt,Pigs:Sow,Pigs:Boar Diagnosis
Digestive Signs / Diarrhoea Pigs:All Stages Diagnosis
Digestive Signs / Unusual or foul odor, stools, faeces Pigs:All Stages Diagnosis
Digestive Signs / Vomiting or regurgitation, emesis Pigs:All Stages Diagnosis
General Signs / Dehydration Pigs:Piglet,Pigs:Weaner,Pigs:Growing-finishing pig Diagnosis
General Signs / Fever, pyrexia, hyperthermia Sign
General Signs / Fever, pyrexia, hyperthermia Sign
General Signs / Hypothermia, low temperature Pigs:Piglet Sign
General Signs / Inability to stand, downer, prostration Sign
General Signs / Lack of growth or weight gain, retarded, stunted growth Pigs:Piglet,Pigs:Weaner,Pigs:Growing-finishing pig Diagnosis
General Signs / Polydipsia, excessive fluid consumption, excessive thirst Pigs:Piglet Sign
General Signs / Reluctant to move, refusal to move Sign
General Signs / Tenesmus, straining, dyschezia Sign
General Signs / Trembling, shivering, fasciculations, chilling Pigs:Piglet Sign
General Signs / Underweight, poor condition, thin, emaciated, unthriftiness, ill thrift Pigs:Piglet,Pigs:Weaner,Pigs:Growing-finishing pig Sign
General Signs / Weight loss Pigs:Piglet,Pigs:Weaner,Pigs:Growing-finishing pig Diagnosis
Nervous Signs / Coma, stupor Sign
Nervous Signs / Dullness, depression, lethargy, depressed, lethargic, listless Pigs:All Stages Sign
Reproductive Signs / Agalactia, decreased, absent milk production Pigs:Sow Sign
Respiratory Signs / Coughing, coughs Sign
Respiratory Signs / Dyspnea, difficult, open mouth breathing, grunt, gasping Sign
Respiratory Signs / Increased respiratory rate, polypnea, tachypnea, hyperpnea Pigs:All Stages Sign
Skin / Integumentary Signs / Matted or dirty hair Pigs:Piglet,Pigs:Weaner Sign
Skin / Integumentary Signs / Rough hair coat, dull, standing on end Sign

Disease Course

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In a fully susceptible herd the disease usually presents as an explosive, high morbidity outbreak affecting all ages of pigs. Losses continue in unweaned piglets until sows develop lactogenic immunity, which protects sucking piglets in the face of further virus challenge. TGE is clinically much more severe in neonates and mortality is highest in this age group. Acute onset watery diarrhoea and occasional vomiting lead to rapid dehydration, weight loss, and death. Older animals also develop watery diarrhoea and may vomit, but recover after a few days illness. Lactating sows can become agalactic which exacerbates the losses in their piglets. Reproductive failure is not a specific feature. The length of the epizootic phase in breeding herds varies from 2 or 3 weeks to several months, depending mainly on the size of herd, the farrowing programme, rate of spread of infection, development of immunity and whether any naïve breeding stock are added.

In larger, continuously farrowing, herds, particularly those with over 500 sows, the disease often persists in a clinically milder enzootic form. The main features of enzootic TGE (Pritchard, 1987) are mild diarrhoea in unweaned piglets from about 6 days of age and in recently weaned pigs. In some herds, enzootic TGE remains virtually subclinical for long periods although there may be short-lived episodes of overt clinical recrudescence, particularly in purchased breeding replacements and their litters.

In the 1980s, a new variant of TGE, termed porcine respiratory coronavirus (PRCV) (Pensaert et al., 1986) appeared in Europe. This is a deletion mutant of TGE with an altered tissue tropism, which replicates in the respiratory rather than the enteric tract (Cox et al., 1990). Infection is mainly subclinical. Unlike TGE, PRCV spreads via respiratory aerosols and has become widespread in Europe and elsewhere. Although the emergence of PRCV complicated the laboratory diagnosis of TGE it appears to have led to the reduced prevalence of TGE seen in Western Europe. It is assumed that pigs recovered from infection with PRCV are at least partially protected against TGEV infection, although this has proved difficult to demonstrate experimentally.

Epidemiology

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TGEV spreads within and between farms primarily by infected faeces. The incubation period is short (12-72 hours). Virus is shed in the faeces for about 2 weeks after clinical recovery, although there remains some debate about whether pigs may excrete viable virus for longer periods. The virus is heat and light labile. In temperate climates, it survives much better in the winter, which partly accounts for its mainly seasonal occurrence. As well as direct pig to pig contact, virus may be disseminated via faecally contaminated equipment or by birds, particularly starlings, acting as mechanical vectors. In countries where epizootic outbreaks have occurred periodically, the virus is probably maintained in large endemically infected breeding herds (Pritchard 1987) or in large continuous throughput finishing units. In contrast to TGE, PRCV spreads aerogenically. In large herds, the infection is rarely self-limiting and consequently in pig dense regions, there is a high seroprevalence of PRCV infection.

Impact: Economic

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Outbreaks of TGE in naïve breeding herds almost invariably result in severe, albeit usually short-lived, economic losses. In 56 epizootic outbreaks investigated in the UK by Pritchard (1982) piglet deaths averaged 1.3 times the total number of sows in the herd (about 6% of the annual piglet production). This has led some countries to make the disease notifiable, whilst it is in the B list of the Office International des Epizooties (OIE). In fattening units, anorexia and diarrhoea cause a reduction in feed conversion efficiency and can extend the finishing period by about 2 weeks.

Disease Treatment

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No specific treatment is available. Although heavy losses are inevitable in unweaned piglets during the early stages of an outbreak, fluid replacement therapy helps mitigate dehydration and prevents some deaths. Good husbandry and nursing, especially warmth, are beneficial. Early weaning or cross suckling onto immune sows can sometimes be worthwhile (Pritchard, 1982).

Prevention and Control

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The International control of TGE relies on preventing trade in carrier pigs, by health certification and serological testing either side of a period of quarantine. The likelihood of introducing TGEV into a herd can be reduced by good biosecurity. This includes avoidance of visitors and vehicles, bird proofing (where feasible), purchasing pigs from a small number of reputable sources and quarantining them on arrival. Maintaining freedom from PRCV is difficult and demands an isolated location away from other pigs. TGE vaccines are available in some countries, such as the USA, but their efficacy is rather limited because it is difficult to elicit the necessary local mucosal (IgA) immunity using killed vaccines or attenuated live vaccines (Saif and Jackwood, 1990).

Once TGE enters a herd it is beneficial to try and infect all the pigs in the herd as soon as possible in order to generate immunity and ultimately bring the outbreak to an end. This can be achieved by spreading diarrhoeic faeces or viscera, adding it to feed and/or mixing unaffected and affected groups of pigs. Spreading infection to pregnant sows and purchased breeding stock is popularly termed 'feedback'. In particular, deliberately infecting pregnant sows or gilts with at least 2 weeks left before farrowing should ensure they have protective IgA antibodies in their colostrum and milk by the time their piglets are born. However, this method of live TGE inoculation has the risk of spreading other infections such as leptospirosis, classical swine fever. In some countries a permit is needed before infected material can be fed to healthy animals, for example, 'feedback' may come under regulations controlling swill (garbage) feeding to pigs. Conversely, in an attempt to reduce the otherwise inevitably high baby piglet mortality, simultaneous efforts can be made to isolate pregnant sows with less than 2 weeks before farrowing, and farrowing houses containing baby piglets less than about 3 weeks old. However, these attempts at isolation are usually very difficult to achieve in practice. An 'all-in, all-out' policy, with good cleansing and disinfection, will help to prevent disease perpetuation amongst growing and fattening pigs.

References

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Bereiter M; Hasler J; Keller H, 1988. Transmissible gastroenteritis (TGE) in Switzerland: antibody persistence after infection and seroepidemiological studies on the importance of the TGE virus as cause of diarrhoea. Schweizer Archiv für Tierheilkunde, 130(5):237-248; 31 ref.

Bohl EH; Pensaert MB, 1989. Transmissible gastroenteritis virus. 1. (Classical enteric variant). 2. (Respiratory variant). Virus infections of porcines., 139-153, 154-165; many ref.

Brown IH; Paton DJ, 1991. Serological studies of transmissible gastroenteritis in Great Britain, using a competitive ELISA. Veterinary Record, 128(21):500-503; 17 ref.

Chae C; Kim O; Min K; Choi C; Kim J; Cho W, 2000. Seroprevalence of porcine respiratory coronavirus in selected Korean pigs. Preventive Veterinary Medicine, 46:293-296.

Chae C; Kwon D; Kim O; Min K; Cheon DS; Choi C; Kim B; Suh J, 1998. Diarrhoea in nursing piglets associated with coccidiosis: prevalence, microscopic lesions and coexisting microorganisms. Veterinary Record, 143(15):417-420; 21 ref.

Cox E; Hooyberghs J; Pensaert MB, 1990. Sites of replication of a porcine respiratory coronavirus related to transmissible gastroenteritis virus. Research in Veterinary Science, 48(2):165-169; 16 ref.

Cubero MJ; León L; Contreras A; Astorga R; Lanza I; Garcia A, 1993. Transmissible gastroenteritis in pigs in south east Spain: prevalence and factors associated with infection. Veterinary Record, 132(10):238-241; 37 ref.

Doyle LP; Hutchings LM, 1946. A transmissible gastroenteritis of pigs. Journal of the American Veterinary Medical Association, 108:257-259.

FAO, 1997. Animal Health Yearbook 1996. FAO Animal Production and Health Series No 36.

Kamogawa O; Tomita Y; Kaneko M; Yamada S; Kubo M; Shimizu M, 1996. Isolation of porcine respiratory coronavirus from pigs affected with porcine reproductive and respiratory syndrome. Journal of Veterinary Medical Science, 58(4):385-388; 23 ref.

Mulland BP; Davies GT; Cutler RS, 1994. Simulation of the economic impact of transmissible gastroenteritis on commercial pig production in Australia. Australian Veterinary Journal, 71:151-154.

OIE Handistatus, 2002. World Animal Health Publication and Handistatus II (dataset for 2001). Paris, France: Office International des Epizooties.

OIE Handistatus, 2003. World Animal Health Publication and Handistatus II (dataset for 2002). Paris, France: Office International des Epizooties.

OIE Handistatus, 2004. World Animal Health Publication and Handistatus II (data set for 2003). Paris, France: Office International des Epizooties.

OIE Handistatus, 2005. World Animal Health Publication and Handistatus II (data set for 2004). Paris, France: Office International des Epizooties.

OIE, 2009. World Animal Health Information Database - Version: 1.4. World Animal Health Information Database. Paris, France: World Organisation for Animal Health. http://www.oie.int

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