57. Transmissible gastroenteritis of swine.

Question 1

Virus size and shape?

Answer 1

TRANSMISSIBLE GASTROENTERITIS OF SWINE.

CORONAVIRIDAE FAMILY

• 60-220nm diameter; ~20nm x 10nm projections (crown - corona); spherical shape
• Enveloped (less susceptible to acidic environment)
• +ssRNA genome (26-32kb)
• 4-5 structural proteins (S, E, N, M)
• Frequently mutations ʹ Recombination
• Good antigens

Question 2

History, occurence epidemiology?

Answer 2

Occurrence

• Doyle and Hutchings: 1946 USA, 1956 Japan, 1957 England, everywhere except tropical regions
• Seasonal (Nov-April) during farrowing
• PRCoV: 1984 Belgium

Epidemiology

• Alphacoronavirus 1
• Uniform serologically
• Isolation on porcine spleen and thyroid tissue
• CP: weak
• Dog, fox and mouse can shed virus and will be seropositive but there is no disease
• OIE-listed
• Incubation: 1-2 days ➝ detectable in intestines and lungs for months

TGE

• Epizootic

• During winter in susceptible herds
• Rapid spread
• Severe signs, high mortality

• Enzootic

• Where it is already present
• High piglet production
• Frequent introduction of animals
• Slowly progressing
• Around weaning
• Mortality: < 10%

Question 3

Pathogenesis?

Answer 3

Pathogenesis

1. Viral intake: oronasal route
2. Virus replication: epithelial cells of lungs or intestines (jejunum)
   - Replication on top of entire villi, villus atrophy, immature cells replace epithelium
   - Decreased lactose digestion, increase osmotic pressure
   - Na/K transport broken, electrolyte imbalance
3. Viraemia
4. It can get into milk but not foetus
5. Virus shedding for 2 weeks
6. Cause of death ➝ dehydration, metabolic acidosis, hyperkalaemia consequence of heart failure

Question 4

Clinical signs?

Answer 4

Clinical signs

• Susceptible herd
• Rapid spread
• All age groups, but age dependent clinical signs!
• Vomiting, diarrhoea: yellowish, watery, characteristic odour, loss of appetite
• Newborn up to 10 days -> 100% mortality (Vomiting diarrhoea)
• 2-3 week-old -> 20 % mortality
• Older / adults -> absent mild/clinical signs inappetance weight loss watery diarrhoea
• Endemic herd: Slow spread; Clinical signs in piglets of susceptible sows or weaned pigs (colostral immuntity!)

Question 5

Pathology?

Answer 5

Pathology

• Atypical
• Dehydrated piglets, dilated stomach and intestines,
• full of undigested milk
• Mucosa inflammation(fundus), foamy, yellowish, undigested bowel content
• Villous atrophy of intestinal mucosa

Question 6

Diagnosis and DD?

Answer 6

Diagnosis

• Clinical signs, pathology, histology + IF
• PCR, VN
• Virus isolation: STC, thyroid cells, blind passages
• ELISA (Mab), iIF

DD:

1. E. coli,
2. Rotavirus,
3. Adenovirus,
4. PEDV

Question 7

Treatment and protection?

Answer 7

Treatment

• < 2 week-old: beyond recovery /
• After: heating, fluid and electrolyte replacement
• Administering of milk or milk substitute
• Protection against secondary infections
• OIE-listed

Protection

• Colostral immunity, IgAs
• PRCV (Oralvaccination with live attenuated vaccines)