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Infectious Diseases 2 > Coronaviridae & Arteriviridae > Flashcards

Coronaviridae & Arteriviridae Flashcards

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
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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
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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
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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
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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
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6
Q

How can FECV (feline enteric coronavirus) mutate into FIPV (feline infectious peritonitis virus)?

A
  • Spontaneous mutations

- Recombination with other coronaviruses

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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
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8
Q

What cell does FECV have a tropism for?

A

Intestinal epithelial cells

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9
Q

What cell does FIPV have a tropism for?

A

Macrophages

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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
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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’
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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
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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
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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
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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
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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
Q

Describe EAV prevention/ management…

A

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
Q

When should horses be vaccinated for EAV?

A
  • Colts before puberty to prevent infection establishment
  • Mares before insemination by shedder stallions or AI
  • Seronegative stallions to prevent infection
27
Q

Describe Porcine reproductive and respiratory syndrome (PRRS) virus…

A
  • 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
Q

What is respiratory PRRS characterised by?

A
  • Difficulty breathing
  • Eyelid oedema
  • Sneezing
  • Pyrexia
  • Stunted growth
  • Poor food conversion
29
Q

What clinical signs are seen in sows with PRRS?

A
  • Inappetance
  • Lethargy
  • Fever
  • Respiratory distress
  • Oestrus delay
  • Early return to oestrus
  • Abortion
  • Early farrowing
  • Birth of mummified dead, weak piglets
30
Q

What clinical signs are seen in boars with PRRS?

A
  • Lethargy
  • Depression
  • Reduction of ejaculate volume
31
Q

What clinical signs are seen in suckling piglets with PRRS?

A
  • Respiratory embarrassment
  • Delayed development
  • Depression
  • Palpebral oedema
  • Sneezing
  • Conjunctivitis
  • Rough hair coat
  • High mortality
32
Q

What clinical signs are seen in weaners and growing piglets with PRRS?

A
  • Respiratory distress
  • Secondary viral and bacterial infections
  • Skin changes; blue ears
  • Reduced growth rate
  • Splay-legged piglets
33
Q

How is PRRS controlled?

A
  • 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
Q

Describe wobbly possum disease virus…

A
  • Inappetance
  • Behaviour changes
  • Neurological deficits
  • Death
  • Genomic sequence most closely related to arteriviruses

Infectious Diseases 2 (9 decks)

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