Coronaviridae & Arteriviridae Flashcards
(34 cards)
1
Q
Describe Coronaviridae…
A
- Largest genomes of RNA viruses
- Linear +ve sense ssRNA
- non-segmented genome
- Envelopes
- Replicate in cytoplasm
- Bud from ER
- Exit cell by exocytosis
- Moderately fragile
- Don’t grow well in culture
- Use EM for diagnosis
2
Q
What makes coronaviridae moderately fragile?
A
- Survive 1-2 days at room temperature
- Destroyed by lipid solvents and extremes of pH
- Naked RNA can be infectious
3
Q
What are some diseases caused by coronaviruses?
A
- Feline infectious peritonitis (FIP)
- Transmissible gastroenteritis (TGE)
- Pig vomiting and wasting disease
- Pig epidemic diarrhoea
- Chicken Infectious bronchitis
- Calf, puppy, kitten, foal diarrhoea
- Human common colds
- SARS
4
Q
What are some coronaviridae fundamentals?
A
- Most cause mild disease in adults but more severe disease in newborns
- except: FIP, TGE and SARS
- Most mammalian coronaviruses have a tropism for endodermal cells: liver, kidney, intestinal or respiratory epithelium
- Most species have only one serotype
- Serological cross- reactivity occurs between mammalian coronaviruses of different species
5
Q
Describe Feline infectious peritonitis (FIP)/ Feline enteric coronavirus (FCV)…
A
- Peritonitis
- Pleuritis
- Neurological signs
- Ocular lesions
- Can get wet or dry effusive FIP
- Faecal-oral transmission
- Widespread in all cat populations
- FCV seropositivity is high but FIP is uncommon consequence of infection (only 1-5% develop this)
- Persists in intestinal tract and continues to replicates at low levels for months
6
Q
How can FECV (feline enteric coronavirus) mutate into FIPV (feline infectious peritonitis virus)?
A
- Spontaneous mutations
- Recombination with other coronaviruses
7
Q
Describe the epizootiology of FCV’s…
A
- Each cat develops and harbours is own distinct quasispecies
- Evidence is mounting that FIPV’s are mutants of FECV arising in each FECV infected animal
8
Q
What cell does FECV have a tropism for?
A
Intestinal epithelial cells
9
Q
What cell does FIPV have a tropism for?
A
Macrophages
10
Q
How do you diagnose FIP?
A
Use a combination of findings
- History
- Physical Exam: ultrasound
- Clinical Pathology: Fluid analysis, serum biochemistry / CBC
- Histopathology
11
Q
How do you control FIPV?
A
- Minimise immunosuppression due to stress/ other infections
- Eliminate FCoV from the cat’s environment (disinfectants etc.)
- Vaccination - difficult because of the ‘antibody-mediated enhancement of disease’
12
Q
What are the three important Porcine Coronaviruses exotic to NZ?
A
- Transmissible Gastroenteritis (TGE)
- Haemagglutination Encephalomyelitis (Vomiting & Wasting disease, V & WD)
- Epidemic Diarrhoea
13
Q
Describe Transmissible Gastroenteritis (TGE)…
A
- Outbreak of vomiting and diarrhoea
- Especially in winter
- Incubation period of 1-2 days
- Signs persist for 3-5 days
- Animals of all ages affected
- High mortality in piglets due to dehydration
- High morbidity , low mortality in animals over 5 wks
- May cause stunting, agalactia or subclin infection
- Carriers can excrete virus for 3-4 months
14
Q
Describe Bovine Coronavirus…
A
- In NZ
- Causes diarrhoea in young calves
- Diarrhoea lasts 4-5 days
- Diagnosed by EM, Cell culture with trypsin or calf diarrhoea faecal Ag ELISA
- Checks for rota and coronaviruses and E.coli
- Zoonotic
15
Q
Describe Infectious bronchitis in chickens…
A
- Gasping disease of chickens
- In NZ
- Explosive outbreaks of entire flock
- Can establish persistent infection in young birds
- Can be shed in faeces
- Diagnosed by flock serology; HI, virus isolation, , ID by ELISA or AGID
- Controlled by Modified live virus vaccination
16
Q
Describe Canine Coronavirus…
A
- Present in NZ
- Diarrhoea in young animals
- Usually lasts 2-3 days
- Affected animals are less ill than with parvo and don’t become leucopenic
- Diagnosis by EM, serology, faecal Ag detection
- Vaccines are available
17
Q
Describe Arteriviridae…
A
- Small (45-70nm) diameter
- Enveloped
- Icosahedral
- RNA genome
- Highly species specific
- Infection outcome can range from asymptomatic to abortion to lethal hemorrhagic fever
- Often establish persistent infections
- Macrophages are primary target cells
18
Q
What are some examples of arteriviridae…
A
- Porcine Reproductive and Respiratory syndrome virus (PRRS)
- Equine Arteritis Virus (EAV)
- Lactate dehydrogenase- elevating virus in mice
- Simian haemorrhagic fever virus in monkeys
- Wobbly Possum disease virus
19
Q
Describe Equine arteritis virus (EAV)…
A
- Asymptomatic
- Influenza like illness in adults
- Interstitial pneumonia in young foals
- Abortions in pregnant mares
20
Q
Describe EAV pathogenesis…
A
Vasculitis due to virus associated vascular injury
21
Q
Describe EAV abortions…
A
Foetuses are usually partially autolysed and are often devoid of any gross lesions
22
Q
How is EAV transmitted?
A
Respiratory route
- Aerosols from respiratory tract, aborted material etc.
- Fomites
- Close contact is necessary
Venereal Route
- Infected stallions can shed virus in semen for months- years without clinical signs
- Very efficient route of dissemination
23
Q
Describe the epizootiology of EAV…
A
Need to ID shedder stallions!
- Positive serology = suspicious (seropositive stallion is not necessarily a shedder)
- Confirmation of virus in semen by virus isolation or PCR
- Breeding stallion with seronegative mares and checking for seroconversion of mares 4 weeks later
- Teasers can be a potential source of the virus
24
Q
How do you diagnose EAV?
A
Based on clinical signs
- but remember there are other DDx e.g. EHV, lepto etc.
Laboratory Diagnosis
- Virus Isolation
- Ag detection
- RT-PCR
- Serology: Virus Neutralisation test is gold standard, ELISA
25
Describe EAV prevention/ management...
More important in breeding facilities
- Segregate pregnant mares
- ID carrier stallions
- Breed carrier stallions only to seropositive mares
- Semen test for AI
- Vaccination (prevents disease not infection)
26
When should horses be vaccinated for EAV?
- Colts before puberty to prevent infection establishment
- Mares before insemination by shedder stallions or AI
- Seronegative stallions to prevent infection
27
Describe Porcine reproductive and respiratory syndrome (PRRS) virus...
- Late term abortions increases the number of stillborn foetuses
- Premature weak piglets often die in respiratory distress
- Piglets also get: muscle tremours, eyelid oedema, conjunctivitis and/ or fever and splayed leg
- Reproductive disease occurs when sows are infected in the 3rd trimester of pregnancy
- - they have normal litters after
28
What is respiratory PRRS characterised by?
- Difficulty breathing
- Eyelid oedema
- Sneezing
- Pyrexia
- Stunted growth
- Poor food conversion
29
What clinical signs are seen in sows with PRRS?
- Inappetance
- Lethargy
- Fever
- Respiratory distress
- Oestrus delay
- Early return to oestrus
- Abortion
- Early farrowing
- Birth of mummified dead, weak piglets
30
What clinical signs are seen in boars with PRRS?
- Lethargy
- Depression
- Reduction of ejaculate volume
31
What clinical signs are seen in suckling piglets with PRRS?
- Respiratory embarrassment
- Delayed development
- Depression
- Palpebral oedema
- Sneezing
- Conjunctivitis
- Rough hair coat
- High mortality
32
What clinical signs are seen in weaners and growing piglets with PRRS?
- Respiratory distress
- Secondary viral and bacterial infections
- Skin changes; blue ears
- Reduced growth rate
- Splay-legged piglets
33
How is PRRS controlled?
- Negative herd: biosecurity + testing to prevent new intro
- Removal of positive animals
- Management strategies to limit spread
- Maintenance of protective immunity by vaccination and simultaneous deliberate exposure to the virus
34
Describe wobbly possum disease virus...
- Inappetance
- Behaviour changes
- Neurological deficits
- Death
- Genomic sequence most closely related to arteriviruses
