Viruses and GI disease Flashcards
Describe the features of parvoviruses
Icosahedral capsid
No envelope
Small, linear ssDNA genome
Infect and kill actively replicating cells
Persist for long periods in environment
Which parvoviruses are of veterinary importance?
Describe the effect of parvovirus in the villi of the SI
Grow in dividing stem cells in the crypts
Villi tip cells turnover normally but are not replaces as virus kills stem cells
=> stunted villi, malabsorption, maldigestion
Describe Feline infectious enteritis/feline panleukopenia
Faecal-oral transmission
Persists in environment up to a year
Infects lymph nodes of naso and oropharynx => spreads to other tissues
Mainly infects intestinal cells and bone marrow
Kittens most susceptible
Describe the pathogenesis of feline panleukopenia via parvoviruses
Decreased WBC count, killing of lymphoid and myeloid stem cells
High risk of secondary bacterial infection
Describe the pathogenesis of feline infectious enteritis via parvoviruses
Killing of stem cells in crypts
Dehydration due to malabsorption can be fatal
High risk of secondary bacterial infection
Describe the pathogenesis of cerebellar hypoplasia via parvoviruses
Infection in neonatal kittens
Cerebellum controls coordination/balance => wobbly kittens
What are the clinical signs of feline parvovirus?
Pyrexia
Vomiting
Diarrhoea
Dehydration
Shock and sepsis (compromised intestinal mucosa)
High mortality rate
Sudden death
What is the treatment for feline parvovirus?
fluids to support circulation/hydration
antibiotics to reduce sepsis risk
Describe the control of feline parvovirus
Maternally derives antibody wanes after ~8wks
Vaccination ~6wks
Prevent exposure
How can you confirm diagnosis of feline parvovirus?
Faeces contains virus:
- detects virus antigen (ELISA)
- detect virus DNA (PCR)
Detect antibody to virus in blood
Supportive evidence - marked leucopenia/neutropenia
Describe the pathogenesis of canine parvovirus (CPV-2)
Infects actively dividing cells
-Generalised neonatal disease
-Myocarditis in neonatal pups (goes to myocardium rather than cerebellum)
- Bone marrow => leukopenia
- Intestinal villi => enteritis => vomiting and haemorrhagic diarrhoea
- intestinal and mesenteric lymphoid tissues => immunosuppression
Describe heart failure due to myocarditis in canine parvovirus infection
Myocardial necrosis
Inclusion bodies in myocardial cells
Increased Inflammatory cells
Fibrosis
Massive enlargement of heart
Describe features of coronasviruses
+sense ssRNA
Enveloped
Commonly mutate
Survive well in environment and low pH - destroyed by disinfectants
Enteric and respiratory pathogens
What are the important porcine coronaviruses?
TGEV - transmissable gastroenteritis virus
EDV - porcine epidemic diarrhoea virus
PDCoV - porcine delta coronavirus
Describe the pathogenesis of TGEV (transmissible gastroenteritis virus) and EDV (porcine epidemic diarrhoea virus)
Highly contagious
Young pigs
Diarrhoea/vomiting
Rapid dehydration
Describe coronaviruses in cattle
Betacoronaviruses => calf diarrhoea
Scour 4d - 3wks
Dehydration, acidosis, depression, fever
Can cause resp signs
Describe canine coronavirus
Canine enteric CoV
Mild self-limiting diarrhoea
Lethargic and inappetant
Loos feaces +/- mucus and blood
Supportive treatment
Describe feline coronavirus
Most = mild or subclinical enteritis
Some => feline infectious peritonitis
Describe feline infectious peritonitis
Coronavirus replicates in macrophages
Immune complex formation
Vasculitis
=> effusions (Wet FIP) or pyogranulomatous lesions (Dry FIP)
Wet FIP:
- ascites in abdomen => pot belly
- pleural effusion in thorax => dyspnoea
How are coronaviruses controlled?
hygiene
vaccines
removal of infected animals
maintenance of clean herd/housing
Name the pestiviruses of veterinary impotance
Bovine viral diarrhoea
Border disease virus
Classical swine fever
Describe the features of pestiviruses
+ve ssRNA genome
cytoplasmic replication
icosahedral capsid
enveloped
Describe Bovine viral diarrhoea virus
Transplacental transmission
Diarrhoea
Decreased fertility/milk yield
Abortion
Congenital defects
Stunted calves
Immunosuppression
Mucosal disease
Describe mucosal disease as a consequence of bovine viral diarrhoea virus
Only develops in persistent infected animals
Required presence of NCP (non-cytopathic) and CP (cytopathic) virus
CP viruses show marked tropism for GALT
Severe diarrhoea => fatal
Marked mucosal haemorrhage
How is bovine viral diarrhoea virus controlled?
Eliminate persistently infected animals from herd
Maintain closed herd
OR
Maintenance of herd immunity so no naive cattle are infected BVD
Vaccination or deliberate infection
What are the important genera in the family paramyxovirus
Describe the features of paramyxovirus
Large enveloped virus
-ve sense ssRNA
sensitive to heat, detergent, desiccation
cytoplasmic replication
release by budding
What are the notifiable viruses in the genera morbillivirus
Rinderpest virus
Peste despetits ruminants
Canine distemper
Describe rinderpest
High infectious disease of cattle
Respiratory and alimentary tract disease
Very high morbidity and mortality
What are the clinical signs of rinderpest
Nasal and oral discharge
Pyrexia
Oral and nasal erosions and ulcerations
Diarrhoea + mucus, blood and debris
Dehydration => death
Describe pest de petit ruminants
Mucosal erosions and profuse diarrhoea
Describe the pathology of canine distemper
Morbillivirus
Transmitted by direct contact
Virus replicates in upper resp tract
Spreads to tonsils/lymph nodes
Viraemia and systemic spread to epilthelia
What are the clinical signs of canine distemper?
Pyrexia
depression
Ocular and nasal discharge
Cough
Vomiting
Diarrhoea
Hyperkeratosis of nose/pads
Neurological signs if immune response is poor
Describe Newcastle disease
Avian paramyxovirus
Shed in excretions and secretion => aerosols
Mechanical transfer from carcasses
Common in wild birds
Describe the different strains of newcastle disease virus
Ientogenic - mild inapparent infection
Mesogenis - mild resp disease
Neurotropic velogenic - acute, sever, fatal with resp and nervous signs
Viscerotropic velogenic - severe, fatal with haemorrhagic intestinal lesions, resp disease
What are the membrane glycoproteins on viruses and their roles
Fusion/F protein - enables fusion and entry
Haemagglutinin/neuraminidase (HN) - enables virus attachment to cell receptor
Describe the role of F proteins in virulence
synthesised as precursor (F0) and cleaved by host cell proteases to active forms (F1 and F2) - if not cleaved then virus cannot enter
Lentogenic strains - confined to GI and resp tracts where trypsin-like proteases are present
Velogenic strains - can be cleaved in many tissues by different proteases due to altered cleavage site
Describe the control of newcastle disease
Biosecurity
Cull infected animals
Vaccination
