cdv Flashcards
Genus and family of CDV? genome type? enveloped?
genus Morbilivirus family Paramyxoviridae negative ss-RNA enveloped
How does CDV induce immune-mediated cytolysis?
how does CDV infect lymphoid tissues?
CDV binds SLAM (signaling lymphocyte activation molecule = membrane glycoprotein on lymphoid tissues) * selectively binds via H and F proteins
How does CDV cause immune suppression?
- virally induced cytolysis 2. P gene expression of virulence proteins V and C –> inhibits interferon and cytokine responses of lymphoid cells
what is the mechanism by which acute CDV infection infiltrates the CNS?
upregulation of SLAM in immune cells infiltrating the CNS –> amplifies viral replication in the brain
T/F: CDV isolates are serologically homogeneous?
T
what are CDV isolates Snyder hill, A75/17, and R252 known for?
highly virulent and neurotrophic Snyder hill - polioencephalomyelitis A75/17 and R252 - cause demyelination
properties of CDV proteins coded by the ___ and ____ genes affect viral persistence and the ability to cause CNS disease
N and M genes
T/F: CDV is a “hardy” virus
False - susceptible to UV light, heat/drying - susceptible to chloroform, dilute formalin, phenol, and quaternary ammonium disinfectants
- survives longer in colder temps
Main species/groups susceptible to CDV (8)?
bears/pandas Canidae (wild k9 species, raccoon) Mustelidae (ferret, mink, otter, badger) Skunks Procyonidae (Cotai, Kinkajou, raccoon) Viverridae (binturona, foosa, linsang, civet) Herpestidae (mongoose, meerkat) Felidae (large species)
T/F: with passing years, the host range of CDV appears to have widened?
True - interspecies transmissions, viral recombination events have occured
Molecular changes in the ____ gene may be responsible for the spread of CDV to nondog hosts in the wild
hemagglutinin gene
How is CDV shed?
spread most commonly by aerosol or droplet exposure can be isolated from most other body tissues and secretions including urine
For how long after infection can CDV be excreted?
up to 90 days
T/F: based on the results of serosurveys, the infection rate for CDV is considered to be higher than the disease rate?
True - reflects a certain degree of natural and vaccine-induced immunity in the general dog population
T/F: most dogs that become infected with CDV do not clear the virus completely.
False - most dogs clear the virus completey, some may harbor virus in their CNS.
The prevalence rate of spontaneous distemper in cosmopolitan dogs is greatest between ____ and ____ mos of age
3-6 mos of age - correlates with the loss of maternal-derived antibodies in puppies after weaning
Basic steps of CDV infection?
- CDV enters the resp tract via aerosols –> local lymphoid tissues (ex/ tonsils)2. primary viral replication occurs in lymphoid tissues. 3. primary replication sites –> macrophages w/CDV enter lymphatics –> heart –> bloodstream (mononuclear cell-associated viremia) 4. virus enters the CNS via cerebral circulation –> perivascular spaces of blood vessels -OR- enters CNS via choroid plexus and eventually the CSF. 5. Dogs with poor immunity undergo spread to many tissues (skin, glands, GI/resp/urogenital epithelium) –> dramatic and severe clinical signs
how can CDV cause seizures?
CDV can travel from the nasal passage through the cribiform plate and anterograde via the olfactory nerve to the olfactory bulb and CNS –> localizes primarily to the piriform lobes of the cerebral cortex
How long post-infection does CDV infect the CNS?
8-9 days post infection
by day _____ post-infection, animals with adequate CDV antibody titers and cell-mediated cytotoxicity clear the virus from most tissues and show no clinical signs of illness
by day 14 post-infection, animals with adequate CDV antibody titers and cell-mediated cytotoxicity clear the virus from most tissues and show no clinical signs of illness
in which tissues can CDV persist for extended periods of time?
uveal tissues neurons integument (footpads)
uveal tissues neurons integument (footpads)
direct viral replication –> multifocal lesions in gray/white matter –> leads to polioencephalomalacia
The outcome of CNS infection from CDV depends on the appearance of circulating _____ antibodies to the ____ glycoprotein
The outcome of CNS infection from CDV depends on the appearance of circulating IgG antibodies to the H glycoprotein
what are the two main routes by which CDV enters the CNA?
- hematogenous - virus w/in lymphoid cells enters the brain via fine blood vessels and deposits in perivascular virchow-robin spaces 2. neural - anterograde through olfactory neurons
dogs with CNS CDV may develop polioencephalomalacia of the _____ and _____ lobes
piriform and temporal lobes (rhiencephalic structures)
Acute CDV encephalitis is characterized by _______
direct viral replication and injury neuronal infection/necrosis –> gray matter lesions
what changes are seen in microglial cells in patients infected with CDV?
- upregulated MHC II - enhanced secretion of ROS - upregulation of proinflammatory cytokines
How does acute CDV cause demyelination? chronic?
CDV infection leads to metabolic dysfunction of oligodendroglial cells –> down regulation of myelin gene expression –> demyelination
chronic - CD8+ lymphocytes attack oligodendroglial cells that are expressing CDV antigen
How do acute CDV encephalitis and chronic subacute CDV encephalitis differ?
acute: minimal perivascular cuffing/inflammatory response
chronic: upregulation of inflammatory response –> perivascular cuffing. CD8+ lymphocytes predominate –> destroy oligodentroglial cells through “innocent bystander” mech –> further demyelination
inclusion body polioencephalitis is a variant form of CDV encephalitis that should be suspected when?
- after vaccination 2. in dogs with sudden onset of only neurologic manifestations of distemper
what clinical signs caused by distemper are rarely associated with neurologic disease?
vesicular and pustular dermatitis
** dogs developing nasal and digital hyperkeratosis usually have various neurologic complications
T/F: CDV can be transmitted transplacental? T/F: CDV can cause abortion/stillbirth?
True/true
What abnormalities are seen on MRI in patients with CDV? what does this correspond to histopathologically?
hyperintense foci and loss of contrast between gray and white matter was found in the T2WI in the brain –> corresponds to demyelination
How can CDV IgG in CSF be used to diagnose active infection?
Compare CDV IgG (CSF):CDV IgF (serum) to similar ratio for another virus (CPV, CAV)
in dogs clinically affected with CDV immunofluorescence is usually performed on cytologic smears prepared from what swabs? (4)
conjunctival, tonsillar, genital or respiratory epithelium
what is a drawback to PCR testing for CDV?
false positive - positive results have been found in naturally or experimentally exposed dogs
what are the pros of CDV PCR testing?
high sensitivity can distinguish between virulent and vaccine viral strains
dog that dies of CDV has: neuronal and myelin degeneration/primary demyelination without significant perivascular inflammation - was this an acute or chronic infection?
acute
where are the predilection sites for CDV in the CNS? (5)
1) lateral cerebellar peduncles 2) dorsolateral medulla 3) deep cerebellar white matter optic 4) nerves/tracts 5) spinal cord
Older/immunocompetent dogs tend to develop CDV leukoencephalomyelitis with a predominance of lesions in the?
caudal brainstem and spinal cord –> signs of ataxia and vestibular involvement
lesions of vaccine-induced distemper are typically?
in which cells can CDV inclusions most commonly be found?
epithelial cells of mucous membranes reticulum cells (?) leukocytes glia neurons
T/F: vaccination with inactivated canine distemper whole virus vaccines produce sufficient immunity to prevent infection after challenge exposure?
False - vaccinated dogs will show a less severe disease than unvaccinated controls however
what two membrane glycoproteins does CDV have?
H (attachment) F (fusion)
