Coronaviruses

1. LECTURE #10
Coronavirus

2. LECTURE #10
Genra
• Coronavirus: Dozen of pathogens of
mammals and birds
• Torovirus: Contains two viruses of
– Berne virus:Isolated from a horse with diarrhea
– Breda virus:Isolated from neonatal calves with
diarrhea.

3. LECTURE #10
• Coronavirus can be subdivided into three cluster groups on the
genetic and serologic properties
• Group 1 :
– Transmissible gastroenteritis virus,
– Porcine respiratory coronavirus,
– Porcine epidemic diarrhea virus
– Canine coronavirus,
– Feline infectious peritonitis virus.
• Group 2:
– Mouse hepatitis virus,
– Porcine hemagglutinating encephalomyelitis virus
– Canine respiratory coronavirus.
– Turkey blue comb disease virus
• Group 3 :
– Avian infectious bronchitis virus,

4. LECTURE #10
Structure
• Enveloped, 80–220 nm in size,pleomorphic
• Coronaviruses :Spherical
• Toroviruses: Disc, kidney or Rod shaped .
 Large club-shaped spikes
(peplomers)
 Helical nucleocapsid.
Some coronaviruses have a
second fringe of shorter spikes
(hemagglutin)

5. LECTURE #10
Genome
Single molecule of linear positive-sense, single-stranded
RNA,
Size: 27.6–31 kb in size for coronaviruses
25–30 kb for toroviruses,
The largest known non-segmented RNA viral genomes.
The genomic RNA is 5’-capped and 3’- polyadenylated.

6. LECTURE #10
Coronavirus Replication
Nested Transcription: Nidovirales
Nested set are generated by a leader-primed mechanism of
discontinuous transcription

7. LECTURE #10
Swine transmissible gastroenteritis
virus (TGEV)
• Most important viral disease of young piglets,
highly contagious, short incubation period
• An exclusive small intestine disease, affecting
the mature epithelial cells of the villi
• Natural host, swine only; temperature-sensitive,

8. LECTURE #10
CORONAVIRIDAE: TGEV
• Acquisition: Inhalation or ingestion, large amounts
of TGEV in the feces and the respiratory
secretions
• Fecal shedding: important means of spreading
among piglets in farrowing and nursery facilities
• Signs: severe diarrhea, vomiting, dehydration,
occasionally high mortality if infected in first few
wks of ages
• Varied in different ages of pigs

9. LECTURE #10
CORONAVIRIDAE: TGEV
• Young piglets: short incubation, vomiting,
watery-yellowish diarrhea, severe
dehydration, rapid weight loss, coma and
high mortality (100% in some litters)
– Death due to dehydration, acidosis and
shock
– Feces containing undigested milk, strong
offensive odor, but lack red color (no
vascular system involvement)

10. LECTURE #10
CORONAVIRIDAE: TGEV
• Older pigs: milder signs with much lower
morbidity and mortality and a more
protracted course
• Sows: low grade fever, vomiting, and
diarrhea—much milder signs and sometime
without notice
– Isolation of TGEV from the lungs of
slaughter pigs without clinical signs

11. LECTURE #10
CORONAVIRIDAE: TGEV
• Pathology Mechanism:
• Replicates in the tip of mature epithelial
cells of small intestinal villi
• Inhibition of the absorptive and secretive
functions of the small intestine--diarrhea
• Destroy intestinal epithelium, but no effect
on the Lieberkühn cells at the base of the
intestinal villi

12. LECTURE #10
CORONAVIRIDAE: TGEV
• Gross Pathology:
• Extremely thin intestinal walls, transparent,
undigested milk-curds in the distended small
intestines
• Important observation: white color diarrhea
containing undigested milk
• Villous atrophy: loss of villi in the duodenum,
jejunum and to a lesser extent in the ileum

13. LECTURE #10
CORONAVIRIDAE: TGEV
EM: normal small intestinal villi
EM: shortened, somewhat blunted small
intestinal villi infected with attenuated TGEV
EM: Loss of villi in small intestine due
to infection with virulent TGEV

14. LECTURE #10
CORONAVIRIDAE: TGEV Diagnosis
• Presumptive diagnosis: epidemiology, signs, and
gross lesion
• Definitive diagnosis: FA (epithelial cells of villi), or
EM (feces)
• Differential diagnosis: TGE and rotavirus diarrhea
– TGE clinical signs, morbidity and mortality rate,;
TGE--seasonal, rotavirus--year-around
– Others: colibacillosis (villi not affected),
clostridial enteritis and coccidiosis

15. LECTURE #10
CORONAVIRIDAE: TGEV
• Prevention and Control:
• Vaccinating sows to sensitize IgA-producing B-
lymphocytes and produce IgA into colostrum
• Lactogenic immunity: IgA and IgG in
colostrums, early and continuous suckling
(important for protection of newborns)!!!
• IgA vs IgG: IgG cannot resist digestion by
enzymes in the GI
• Active immunization of piglets?
immunologically immature newborns
• Practicing good hygiene in the farrowing
facilities !

16. LECTURE #10
Porcine epidemic Diarrhoea
• Caused by the porcine epidemic diarrhoea virus that leads
to severe gastrointestinal disease in pigs.
• It is closely related to transmissible gastroenteritis virus in
pigs but spread slowely
• Piglets are most susceptible to the disease, as are young
adults during periods of stress.
• Transmission :Fecal-oral route.
• Symptoms:Watery diarrhoea, pyrexia, anorexia and lethargy
• Diagnosis :FAT, ELISA can detect antigen or antibodies.
• Prevention: Dehydration management, Biosafety measure

17. LECTURE #10
Bovine coronavirus enteritis
• Infection causes 'calf enteritis‘
• It can also cause 'winter dysentery' in adult
cattle.
• It can infect both domestic and wild ruminants
and has a worldwide distribution.
• Transmission is horizontal, via fecal-oral or
respiratory routes.

18. LECTURE #10
Diagnosis
• Symptoms:
• Calves:one week and three months mostly
affected. Gastrointestinal signs include
profuse diarrhoea, dehydration, anorexia.
Respiratory sign includes purulent nasal
discharge.
• Adult:normally subclinical, but winter
dysentery affects cattle over the winter
months
• Test: ELISA, EM, FAT

19. LECTURE #10
Feline infectious peritonitis
• Feline infectious peritonitis (FIP) is usually fatal, aberrant
immune response to infection with feline coronavirus
(Immunopathology).
• The virus is a mutation of feline enteric coronavirus (FECV).
Virus undergoes a systemic phase after infecting peritonium.
• There are two main forms of FIP: effusive (wet) and non-effusive
(dry)
• Effusive FIP:Accumulation of fluid within the abdomen or chest,
which can cause breathing difficulties. Anorexia, fever, weight
loss, jaundice, and diarrhea.
• Dry FIP : lack of appetite, fever, jaundice, diarrhea, and weight
loss, but there will not be an accumulation of fluid.

20. LECTURE #10
Turkey Bluecomb disease
• Transmission is horizontal via the faeces, and
can be direct or indirectly spread by fomites.
• Symptoms: Diarrhoea, anorexia and lethargy.
Most of the birds in a group are usually
affected and their overall appearance is of
darkened skin and ruffled feathers.
• Diagnosis: FAT, ELISA, PCR etc

21. LECTURE #10
Canine coronavirus
• Enteritis: Highly contagious intestinal disease
worldwide in dogs
• The virus invades and replicates in the villi of
the small intestine. Intestinal disease may be related
to virus induced apoptosis of cells of the epithelial
mucosa of the small intestine.
• The disease is highly contagious through fecal oral
transmission.
• Second type of canine coronavirus has been shown
to cause respiratory disease in dogs Known as canine
respiratory coronavirus