CORONAVIRUSES

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Causative Agent(s)

Transmissible Gastroenteritis Virus (TGEV), Porcine Respiratory Coronavirus (PRCV), Porcine Epidemic Diarrhoea Virus (PEDV), Porcine Hemagglutinating Encephalomyelitis Virus (HEV).

These four swine coronaviruses have been identified as causing disease in pigs.

Clinical Presentation and Epidemiology

In pigs, Corona viruses affect a variety of organs, including the gastrointestinal and respiratory tracts, the peripheral and central nervous systems (CNS), and the mammary glands.

The disease is characterized by vomiting, severe diarrhoea, and high mortality affecting pigs of all ages.

Although swine of all ages are susceptible to TGEV infection, mortality in pigs that are five weeks of age and above is generally low. Porcine Respiratory Coronavirus (PRCV).

PRCV is a TGEV variant that infects the respiratory tract.

The clinical signs of Epidemic Transmissible Gastroenteritis high morbidity and mortality in pigs under two weeks of age, vomiting and profuse watery, yellowish diarrhoea, dehydration, rapid loss of weight. In finishing pigs and in sows the clinical signs observed include inappetence, diarrhoea, and vomiting. Infection generally spreads rapidly, most pigs becoming infected in 2– 3 days especially during cold weather.

The signs of Endemic Transmissible Gastroenteritis are milder n sero-negative pigs of the same age. Mortality is generally low, especially when pigs are kept warm.

The signs of Porcine Respiratory Coronavirus are anorexia coughing, dyspnoea, abdominal breathing, and depression.

Diagnostic Considerations

The samples required for diagnosis are nasal swabs, lung homogenates, faeces, intestinal contents.

The laboratory tests that are used to diagnose the disease are immunofluorescence, immunohistochemistry, direct fluorescent antibody test, enzyme-linked immunosorbent assay (ELISA) in cell culture and Real-time reverse transcription-polymerase chain reaction (RT-PCR). Where facilities are available, electron microscopy is used. Immune electron microscopy (IEM) has advantages over conventional EM by being more sensitive.

Management and Treatment

There are no antiviral drugs for corona viruses.

The only available treatment for TGE is to administer multivitamins, and fluids containing electrolytes.

Provision of a warm draft-free, dry environment and provide water or nutrient solutions freely to TGEV-infected pigs.

Treat for secondary bacterial infection with antibacterial agents such as Oxytetracycline L.A. 20mg/kg b.w., single dose IM.