Coronaviridae Flashcards
Severe acute respiratory syndrome
SARS
- new, emerging coronavirus
- economic loss
- affected 29 countries
Properties of coronaviruses
Linear, positive sense ssRNA
- 75-160 nm diameter
- envelope with large, widely spaced, club shaped peplomers
- replicates in cytoplasm and virions released by exocytosis
What are the 4 structural proteins of coronaviruses?
- peplomer glycoprotein S (E2)
- transmembrane glycoprotein M (E1)
- nucleocapsid phosphorprotein N
- some viruses have peplomers with hemagglutinin plus acetylesterase activities, HE (E3)
All coronaviruses contain an ______
Envelope
Antigenic group 1
Mammalian
- human coronavirus (229E), common cold
- transmissible gastroenteritis virus of swine: gastroenteritis
- feline infectious peritonitis virus: peritonitis, pneumonia, meningoencephalitis, panophthalmitis, wasting
- canine coronavirus: enteritis
Due to coronaviruses share antigenicity?
No, do not cross protect
- due to high chance of mutation and lack of proofreading ability
Antigenic group 2
Mammalian
- human coronavirus OC43: common cold
- mouse hepatitis virus: hepatitis, encephalomyelitis, enteritis
- bovine coronavirus: gastroenteritis
- porcine hemagglutinating encephalomyelitis virus: vomiting, wasting, and encephalomyelitis
Antigenic group 3
Avian
- infectious bronchitis virus of chickens: tracheobronchitis, nephritis
Antigenic group 4
Avian
- bluecomb disease virus of turkeys: enteritis
Coronaviruses have been associated with infections of the ______ and _____ tracts
Respiratory and enteric tracts
- CNS disease in monkeys, rats, rabbits, other species
Every chicken is vaccinated against _______
Infectious bronchitis virus
- does not completely prevent disease as outbreaks still occur due to viral mutation and selection pressure from constant vaccination (only due to live vaccine)
Transmissible gastroenteritis of swine (TGE)
Occurs in winter months
- characterized by vomiting and profuse diarrhea
- causes high mortality in piglets
- efficacy of vaccines is limited
Clinical features of TGE
Occurs at farrowing time, incubation time 1-3 days
- infected piglets show vomiting, watery diarrhea and rapid loss of weight
- piglets <7 days old die within 2-7 days –> > 3 weeks old live, but are weak
TGE in growing, finishing, and adult swine
Show inappetence, diarrhea, or unnoticed
- sows infected late in pregnancy may develop fever but rarely abort
Diagnosis of TGE
- immunofluorescence
- virus isolation
- rising antibody titers in paired sera from sows with affected litters or from pigs that have recovered from the disease
- electron microscopy-negative stain
TGE causes ______ in piglets
Sudden death
- vomiting and diarrhea
Vaccinate sows with ________
Attenuated vaccine 3 weeks before farrowing in order to provide piglets with high levels of protective Ab in the colostrum
- respiratory variant can interfere with the serodiagnosis
Transfer of natural passive immunity
- cow, swine, horse: 3 maternal placental layers, and 3 fetal layers = postnatal transfer
- sheep, goat: 2 or 3 maternal placental layers, 3 fetal layers = postnatal transfer
- dog, cat: 1 maternal layer, 2 or 3 fetal layers = IgG cross of placenta, and postnatal transfer
- mouse, rat: 0 maternal layers, 3 fetal layers = prenatal and postnatal transfer
Feline infectious peritonitis
Affects cats of all ages, over 90% have antibody against FIP
- incidence of clinical disease is lower <10%
- subclinical infections are common
FIP occurs in association with ______
Retroviruses (feline leukemia, feline immunodeficiency, feline syncytial virus, parvovirus (feline panleukopenia))
- feline coronavirus that causes diarrhea may be a variant of FIP
Coronavirus is likely to ______
Mutate
- interference between respiratory and intestinal coronavirus
Clinical signs of FIP
- depressed, may have a fever
- classic wet form: abdominal distention
- only a proportion of clinically diseased cats develop peritonitis
- pleuritis results in dyspnea
- neurologic and ocular disease may occur
Diagnosis
- virus isolation: peritoneal exudates, blood
- detection of antibody: only works if antibody titer is high
- hypergammaglobulinemia
Epidemiology and control of FIP
Spread via aerosol
- seropositive cats develop more progressive form of disease than seronegative
- vaccines are available (not effective)
- control depends on segregation of infected cats
Canine coronavirus diarrhea
Causes mild gastroenteritis
- occurs in association with canine parvovirus infection = more severe diarrhea
- commonly infects pups
CCV serology
Closely related to transmissible TGEV, but CCV does not infect pigs
- TGEV: produces a subclinical infection in dogs
CCV diagnosis
Virus isolation, EM
- inactivated vaccine is available
What serves as a model system for coronavirus infection?
Mouse Hepatitis Virus
Mouse Hepatitis Virus
Causes: hepatitis, encephalomyelitis, enteritis, nephritis
- high mortality in neonatal mice
- weanlings can sustain subclinical infections
Type and severity of MHV is dependent on:
Strain of the virus and the age/strain of the mouse
Porcine Hemagglutinating Encephalomyelitis Virus
Occurs in piglets <2 weeks old
- anorexia, hyperesthesia, muscle tremors, paddling of legs, vomiting = emaciation and death
- diarrhea is not common!
- high mortality in young piglets
PHEV is similar to _________
Porcine polioencephalomyelitis
- caused by picornavirus
- requires differentiation based on viral particles
PHEV pathogenesis
Infection via URT and pharynx –> spreads to brain via peripheral nerves
PHEV diagnosis
Virus isolation in primary cultures of porcine cells and detection of the virus by HA
- no vaccines available
Bovine coronavirus diarrhea
Affects the vili of the small intestine and the large intestine
- diarrhea occurs in 1 week old calves (similar to rotavirus)
- affects glucose and lactose metabolism
Is villous atrophy more severe with rotavirus or coronavirus?
Coronavirus
Infectious bronchitis virus
More than 20 serotypes –> no cross protection
IBV - respiratory manifestations
- wet eyes
- gasping
- coughing and sneezing
- tracheal rales
- nasal discharge
IBV - nonrespiratory manifestations
- decreased egg production
- misshapen eggs
- nephritis/nephrosis (not common in US)
How does IBV affect the poultry industry?
- increased mortality, condemnation at processing, downgrading of carcasses
- decreased production
- slowing of the line speed during inspection
IBV prevention
- biosecurity
- management (ex: use more hygenic nipple drinkers)
- vaccination
- monitoring immunity
- equipment
Bluecomb disease
Affects turkeys of all ages –> most severe in 1-6 week old poults
- loss of appetite, chirping, diarrhea
- skin of head and neck become cyanosed
- enteritis
Bluecomb disease vaccine
Inactivated vaccine is available –> not effective
Porcine coronavirus
CV777 - Porcine Epidemic Diarrhea
- acute diarrhea in swine of all ages
- is not related to 4 groups of coronaviruses antigenically
- 50% mortality rate
- adults are subclinical
- no vaccine!
