Lecture 7: Canine 2 Flashcards
What is the viral family and characteristics of canine distemper virus
Family: Paramyxoviridae
* (-)ssRNA, 1 serotype
What are the populations that can be infected by canine distemper virus
Epidemiology
* Affects a wide range of animals including Canindae and Felidae
* Unvaccinated domestic/feral dog = primary reservoir for infecting wildlife
What iss the pathogenesis of canine distemper virus? What is the route of transmission? Location of replication? Target cells?
- Multiply in lymphoid tissue, lamina propria, Kupffer cells
- Transmit via aerosol
- Target cells: lymphocytes, ameloblasts, keratinocytes, nerve cells
What are the clinical signs of canine distemper virus
- If adequate host immune system = subclinical (virus may enter CNS)
o Most (50-70%) - If inadequate host immune system = no or low Ig response = mild dz or severe multisystemic disease = virus cleared/remain in lungs or persist in tissue
o 30% all cases result in neurologic dz
What are features of clinical dz of canine distemper virus
- Biphasic fever curve: 3-4d and again at 14-15d
- Acute: conjunctivitis, fever, anorexia, vomit, diarrhea
- Chronic: ataxia, tremor, myoclonus, seizure, moribund
- CNS effects: demyelinating encephalitis, axonal injury, plasmocytic or lymphocytic infiltrates
- GI + Resp + Cutaneous effects = multisystemic dz
o Most recover from resp and GI signs - Enamel hypoplasia: in young (<6mo), destroy ameloblasts
- Hard Pad dz: hyperkeratosis of foot pads/nasal planum
What is observed when looking at canine distemper virus affected tissue via histology
- Inclusion bodies in cytoplasm
- Perivascular cuffing
- Demyelination of white matter
How to diagnose canine distemper virus
- rtPCR, serological assays (IgM confirms infection), pathology/histo (IF/IHC)
o can’t distinguish vx and infected - must submit 2 serum samples – 1 in clinical phase and another 2 weeks after
What are the features of the vaccines used to control canine distemper virrus
- attenuated modified virus vaccine – long lasting immunity
o contraindicated in immunosuppressed, pregnant or non canine - Recombinant canarypox vectored vaccine
o Protect against dz not infection
o For ferrets/zoo animals
o Effective against canarypox and canine distemper - Inactivated vaccine
o Protect against dz not infection
What is the global distribution of rabies? What animals does it affect?
- Birds/amphibians/reptiles = resistant, all mammals get (rrodents = rare)
- Only absent in New Zealand
What are the sources of rabies in Canada and AB
- Source in CA: bats/skunk/racoon/fox
- Source in AB: bats < skunk < cat
What are 3 characteristics of the rabies virus
- (-)ssRNA, enveloped
- Family = Rhabdoviridae
- Genus = Lyssavirus
How is rabies transmitted
- Canine and wildlife reservoirs transmit between
o Reservoirs can infect non-reservoir domestic and livestock animals and people - Transmit via skin damage/mucus membrane/aerosol
o Clinical signs not required for virus shedding
What is the pathogenesis of rabies infection?
- Retrograde transport in neurons to CNS
- Incubation: day to months
o Time to CNS infection depends on how far the wound is from the CNS (100mm/day)
What are the clinical consequences of rabies? How does it differ between species?
Clinically: 100% mortality
* Once virus in CNS
* Furious form (aggressive behaviour): cats
* Paralytic form (paralysis): horse, cattle, bats
* Dogs get both types
What is the histology you would see as a result of rabies virus infection
Histo
* Non-suppurative encephalomyelitis
* Ganglioneuritis/glial nodules (babes nodules)
* Intracytoplasmic inclusions (Negri bodies)
How to diagnose rabies virus infection
Dx:
* If suspect = quarantine
* Dx done by CFIA
* Use fresh brain tissue as sample – use direct fluorescein antibody test on cerebellum/medulla oblongata
How is rabies virus controlled in domestic and wild populations? What are some limitations of control in wild populations?
Vx:
* Modified live virus/recombinant/inactivated for dogs/cats/ferret/horse/cow/sheep (IM)
* Vaccinia-rabies glycoprotein recombinant vaccine or adenovirus type 5 vector expressing rabies glycoprotein = wildlife (oral vx)
o Limited control over dose or what animals will eat or it may be removed from environment
Control:
* WHO guidelines (control movement and quarantine/mass immunization/control stray population/surveillance and testing of affected animals)
* Rabies vaccine = core
What are 3 primary pathogen viruses causing canine enteritis
Canine Enteritis (Rotavirus/coronavirus/parvovirus)
What are the features of the canine parvovirus
Family; parvoviridae
* ssDNA, non enveloped
* CPV2 affect dogs but 2a and b can now replicate in cats
* CPV1 = non pathogenic
What are some risk factors for canine parvovirus
Risk factors
* Canids – predisposed in rottweiler/Staffordshire bull terrier/Doberman/GSD/Alaskan sled dogs
* Young/unvaccinated
How is canine parvovirus transmitted
Transmit: fecal-oral/fomite – very stable (susceptible to bleach >10min)
What are the clinical sign of canine parvovirus and how do they change based on age
Clinically:
* Lymphopenia
* Enteritis
* Neonatal myocarditis
* In utero: to fetus – cause myocarditis = suddeen deahth or congestive heart fail and death
* Neonate (<8wk) – myocarditis and sudden death OR generalized dz and death (10d old)
* Post natal (>8wk) – affect LN/tonsil/pharynx and cause viremia = lymphoid deficiency and immunodeficiency OR enteritis resulting in recovery or death
o If the viremia targets the liver/lung/kidney = minimal pathology
* Older dogs = asymptomatic
* Dehydration/bloody diarrhea/small intestine dilation and lumen hemorrhage
What is a main difference between canine parvovirus and rota/corona virus causing canine enteritis
canine parvo causes bloody diarrhea because it targets crypt enterocytes
What is the pathogenesis of canine parvovirus
Pathogenesis
* Target: crypt enterocytes
* Sloughing of GI epithelium = exposing blood vessels = hemorrhagic diarrhea
How is canine parvovirus diagnosed
Dx:
* Electron microscopy – but low sensitivity (require lots of viral particles per gram of feces) – can do for any viral dz
* Immunochromatography test: antigen-antibody reaction
o Can do in clinic but vaccine can induce (+) rxn
o Negative result doesn’t actually mean they are not infected
* PCR
How is canine parvovirus prevented?
Prevention
* Vaccines – live attenuated and inactivated
* >1:40 Ig titre test = protective (use hemagglutinin inhibition test – should still be effective after a serial dilution to 1:40)
What to consider when thinking about the vaccine schedule of canine parvovirus
- Maternal Ig half life = 9-10 d
o Vaccination during this time will prevent seroconversion
o Vaccinate from 9-16/20 wks, 2-3wks apart to ensure immunity with high titre vx
What are the viral features of canine coronavirus
Family: coronaviridae
* (+)ssRNA, enveloped
* 2 types: CCoV1 and 2
* Alphacoronavirus
Infection with canine distemper virus
A All infected dogs show clinical manifestations
B Requires direct contact with infected dog
C Can occur in dogs and horses
D Is restricted to the central nervous system
E May affect tigers
E
Rabies
A Is transmitted through mites and lice
B Is a preventable disease of the central nervous system
C Is a non-preventable disease of the immune system
D Has been eradicated from most parts of the world
E Is commonly transmitted via reuse of needles in the
livestock industry
B
Canine parvovirus infection may NOT lead to
A Myocarditis
B Lymphoid depletion
C Enteritis
D Cerebellar aplasia
E Sudden deaths
D
How the canine parvovirus-2 emerged and evolved implicating
diseases in both canines and felines? (3 marks).
Canine parvovirus 2 emerged from canine parvovirus 1. There are further mutations to canine parvovirsu 2 that have created subtypes that can affect felines
For the control of canine parvovirus -2 infection, vaccination is
started at 9 weeks of the age and then, multiple boosters are
given 2-3 weeks apart until 16-20 weeks. What is the rationale
for this vaccination schedule? (2 marks)
Maternal antibodies protective for 9 days after
What are the clinical signs of canine coronavirus
Clinically
* Pantropic coronavirus: affect lung/spleen/liver/kidney/brain
* Fever/lethargy/hemorrhagic diarrhea/lymphopenia/death
* Spontaneous recovery (8-10d)
* Orange/malodourous/watery feces
* No fever or leukopenia
* Puppies >6mo can live
How is canine coronavirus transmitted? Incubation time? Shedding time?
Transmission
* Contagious via fecal oral
* Incubation = 1-3d
* Shed for 6-9d but up to 6mo post infection
What is the pathogenesis of canine corona virus?
Pathogenesis
* Target: mature enterocytes
o Tip of epithelium replaced by non functional epithelium = reduce secretory and absorption function = accumulation of nutrients (disaccharide..) in lumen which increases osmotic pressure = secretory diarrhea
How to diagnose canine coronavirus
Dx:
* Electron microscopy, immunochromatography, RTPCR
How to prevent canine coronavirus
- Enteric coronavirus vaccine doesn’t prevent against respiratory form
