Parvoviruses & Circoviruses Flashcards
What type of nucleic acid do both parvoviruses and circoviruses have?
ssDNA
Describe the fundamentals of parvovirus?
- Icosahedral
- Non-enveloped
- Linear ssDNA genome
- Replication involves ds-DNA intermediate
- Replication occurs in the nucleus
- Virions are released by cell lysis
- Most haemagglutinate RBCs
- Very resistant in environment
- Require actively dividing cells for optimal replication
- Recovered animals are solidly immune
- Virulence lost following repeated in vitre passages
Describe parvoviruses environmental resistance…
- Can withstand exposure from pH3 to pH 9
- Can be at 60C for 1 hour
- Withstands solvents
- PerO2, bleach and glutaraldehyde are the best disinfectants
Describe the pathogenesis of Parvoviruses…
- Infection by ingestion or aerosol
- Primary replication in pharyngeal lymphoid tissue (some pass directly into SI)
- Viraemia
- Localisation in actively dividing cells that have receptor for the virus
- There are larger numbers and varieties of rapidly dividing cells in young animals
Foetus: affects various tissues
Neonate: affects cerebellum, myocardium and adult tissues
Adult: affects intestine, lymphoid tissues and bone marrow (panleukopenia)
What are some common features of parvoviral infections?
- Mainly in young animals
- Found everywhere - exposure at an early age
- Little antigenic variability within subtypes
- Each virus has a relatively narrow host range
- Acute infection is followed by shedding of the virus, some may cause persistent infection
- Rapid (3-5days) development of strong immune response
- lifelong immunity in survivors
- Can get up to 22 weeks of maternal derived immunity
What can be used to detect parvovirus in faeces?
Haemagglutination
- HAI is commonly used to measure anti-parvoviral antibody titres in a patients serum
Describe Feline Panleukopenia…
- All Felidae members are susceptible
- Incubation period 2-10 days
- Profound leukopenia (decr WBCs)
What are the clinical signs of Feline panleukopenia infection?
- Fever - can lead to death
- Second fever 3-4 dpi
- vomiting
- Inappetence, profuse bloody diarrhoea
- Dehydration can lead to death
- Infection around birth: cerebellar hypoplasia
- Virus excreted via most routes for 2-6dpi
- may be shed in faeces for up to 25 days
What are the 3 main clinical presentations of Feline Panleukopenia?
- Acute death
- Diarrhoea
- Cerebellar Hypoplasia
How is feline panleukopenia prevented?
Live attenuated vaccine!
- Don’t give to pregnant queens
What are the two types of canine parvo?
CPV-1: avirulent minute virus of canines
CPV-2:
- panleukopenia/ enteritis
- generalised neonatal disease
- myocarditis
How long is it before a dog/ puppy recovers from parvo?
Recovers or dies in 4-7 days
- virus shedding stops about a week after recovery
- If survivors have extensive damage to gut epithelium then there will be chronic malabsorption and protein loosing enteropathy
Describe the pathogenesis of canine parvovirus…
- Infection through the oropharyngeal route
- Primary replication in nasopharyngeal lymphoid tissue
- Secondary spread through viraemia
- Infection of SI crypt cells
- must happen by systemic spread
- Shortened flattened villi: diarrhoea
- Secondary bacterial infections through damaged epithelium
- Infection of lymphoid cells: leukopenia
What are the most common signs of CPV infection?
- Lethargy
- Vomiting
- Diarrhoea
- Leukopenia
- Neutropenia
- Fever
How do you detect CPV infection in a live animal?
- Detection of faecal antigen or viral DNA
- ELISA, virus isolation, PCR etc
- HAI
- Vaccination with live attenuated virus may cause false positives up to 2 weeks post vax\
How do you detect CPV infection in a Post Mortem?
- Histological lesions
- Fat on frozen tissue sections or immunohistochemistry
Describe Porcine Parvovirus disease..
It is the most important cause of infectious reproductive failure in pigs
What are some clinical signs of infection with porcine parvo?
- Stillbirth
- Mummification
- EED
- Infertility
- Respiratory Disease
- Vesicular disease
- Low fertility in boars
Describe the pathogenesis of Porcine parvo…
Sow is infected orally
- Either infects foetus or placenta
- -If placenta infected then sow likely to abort
Infection of Foetus
Day 15: foetus resorbed - sow can return to service
Day 45: Severely affected foetus likey to die = mummies, partial still births and neonatal death
Day 90: Immunocompetent foetus, likely to survive
- normal piglet with antibody at birth
How do you control porcine parvovirus?
- Vaccinate gilts
- Maternal antibody interferes with immunisation for up to 6 months - some gilts cn become infected in first pregnancy
- Virus may be shed in semen
What are some other types of parvovirus?
- Rodent Parvo
- Mink Enteritis
- Aleutian disease of mink
What are some diseases caused by circoviruses?
- Beak and feather disease virus
- Chicken anaemia virus
- Porcine circovirus type 2 (post weaning multisystemic wasting syndrome associated)
Describe the family circoviridae…
- 17-22nm
- Icosahedral
- Non-enveloped
- Resistant in the environment
- Circular ss-DNA
- Replicate in cell nucleus in replicating cells
- Very diverse
- Tend to cause immunosupression
What are some porcine circovirus 2 associated diseases (PCVAD)?
- Porcine multisystemic wasting syndrome (PMWS)
- Porcine dermatitis and nephropathy syndrome (PDNS)
- Pneumonia as part of Porcine Respiratory Disease Complex (PRDC)
- PCV-2 associated enteritis
- PCV-2 associated reproductive failure
Describe Post-weaning Multisystemic wasting syndrome (PMWS)…
- Affects pigs 4-16 weeks old (15-50Kg)
- Targets multiple organ systems
- In acute outbreaks: 4-10% pigs affected, of which 70-80% die
What are the clinical signs of PMWS?
- Ill-thrift
- Listlessness
- Coughing
- High fever
- Dyspnoea
- Lymphadenopathy
- Diarrhoea
- GI ulcers
- Jaundice
- Striking skin lesions
May be accompanied with dermatitis and severe kidney damage (PDNS)
What is the role of PCV-2 in PMWS?
It is the main, but not the sole agent
Other factors may be important:
- Environmental
- Concurrent
- Different strains of PCV-2?
- Genetic predisposition?
Describe Psittacine beak and feather disease…
- Wide spread in Australian Wild cockatoos and other psittacines
- Caused by a typical circovirus which attacks beak, feathers and immune system = Immunodeficiency
- Affects mostly young birds
- Spread by feather dust, faeces and other secretions
How do you diagnose Psittacine beak and feather disease?
Characteristic Clinical Features
- Fragile feathers or with thickened outer feather sheath
- Powder-down feathers often affected first
- Decreased powder = dull feathers
- Shiny, overgrown or broken beaks
- Feather and or beak lesions
- Slowly progressive disease
- Mucoid or green diarrhoea in acutely affected birds
- HAI on powder down feathers to detect anti-viral ABS and ID affected flocks
- PCR
Describe Chicken Anaemia Virus…
- Acute, immunosuppressive disease of young chickens
- Chickens only
- Transmitted through fomites or eggs
- Live vaccine available
What are the clinical signs of Chicken Anaemia Virus?
- Anorexia
- Lethargy
- Depression
- Atrophy or hyperplasia of lymphoid organs
- Cutaneous or intramuscular haemorrhages
- 10% mortality
More severe in co-infection with other viruses
Chicks susceptible up to 1 week of age
