Virology 1 - Companion Animal Flashcards
Infection vs disease
Best diagnostic test varies based on question asked
Organism ID without lesions
Infection
Organism ID + lesion
Disease (clinical or sub clin)
Organism ID + lesion + clinical signs
Clinical disease
Serology
Gives history (antibody) of exposure but nothing on current disease status
- thus why we dont often vaccinate for high problem viruses
Neurotrophic viruses
RABIES on differential list for ALL species
Neurotrophic viruses in dogs
Canine distemper virus
Canine herpes virus ( encephalitis in puppies <6wks)
Neurotrophic viruses in cats
Feline infectious peritonitis virus
Feline immunodecifiency virus
Feline leukemia virus (myelitis)
Feline panleukopenia virus (cerebellar hypoplasia)
neurotrophic viruses in horses
Equine herpes virus 1* risk base vaccine
West Nile virus
Equine togavirus (EEE, WEE, VEE)
Equine infectious anemia virus (rarely neurotrophic)
Ataxia localization
Cerebellum
Seizure localization
Cerebrum
Canine distemper virus
Paramyxovirus
Highly contagious
Infects dogs but multiple wildlife species
Infects many cell types
Affects many systems
Produces intracytoplasmic & intranuclear inclusion bodies
3-6 months of age when maternal antibodies decline
Cell types infected by distemper
Epithelial, lymphoid, oligodendroglial cells
Systems affected by distemper
Skin, respiratory, gastrointestinal, urinary tracts, brain
Lesions produced by distemper
Intra cytoplasmic and intranuclear inclusion bodies
Distemper pathogenesis
Virus travels to CNS by infected lymphocytes, monocytes & platelets
Spreads to CSF
Lesions in brain include inflammation & demyelination
Progression of demyelination
Lymphoplasmacytic perivascular cuffing
Demyelination may progress to necrosis & infiltration by gitter cells
Clinical signs for distemper
Acute disease with recovery = lifelong immunity or neurological disease & death
Leukopenia
Diarrhea, vomiting
Conjunctivitis, nasal discharge
Coughing
Hardening of nose & footpads
Diagnosing distemper
PCR or virus isolation
White matter vacuolization (from demyelination)
Intranuclear inclusions are found in cerebellum (found everywhere)
Rabies virus
Rhabdovirus
Infects nervous system of ALL mammals/humans
Infection is invariably fatal
Endemic of all continents except Australia & Antarctica
How rabies population is maintained
Maintained & passed in wildlife
Urban rabies in dogs = 95% of all human cases
Sylvatic rabies is maintained in raccoons, skunks, bats, foxes
Transmission of rabies
Contact of salvia from infected animal
Incubation period depends on location of bite, size, immune status & strain (up to 6 months)
Clinical course of rabies
Clinical course is short, once onset only last a few days to a few weeks
Clinical signs range from excitation to depression
Definitive diagnosis is only available post-mortem
Rabies pathogenesis
Virus passes to axon terminals of motor neurons & sensory axon terminals
Virus moves by retrograde a o plastic flow to neurons in the CNS
Eosinophilic intracytoplasmic inclusions (Negri bodies) in neurons
Cells with inclusion bodies for rabies
Neuronal cells
Differentiating between CDV & Rabies
Age of onset
Course of neurological signs
Presence of other clinical signs
Progression of disease
Laboratory diagnosis
FIP
Feline infectious peritonitis AKA feline coronavirus replicated in interstitial epithelium
Enteritis in young kittens is possible
FIP mechanism
Has a tropism for macrophages
Infection is invariably fatal
PCR is available but wont differentiate between FCoV and FIP
FIP disease
Disease is sporadic & common in large cat populations
Cats <1 year are most susceptible
Virus is shed in feces
Transmission is ingestion /inhalation
Age, immune status, genetics of host, virulence of strain play a role
Dry form of FIP
Associated w moderate cell-mediated immunity
Considered a chronic form
Pyogranulomatous vasculitis in all organs including eye & brain
Clinical signs depend on organs most severely affected
Wet form of FIP
Associated with weak cell-mediated immunity
Accumulation of fluid in the abdomen, thorax and lateral ventricles
Fibrinous pleuritis, peritonitis, pericarditis
Cats present w breathing difficulties or distended abdomen
Immune complex disease
Feature of FIP meaning:
If animals has immunity it will survive even if they get sick
If they lack immunity or have poor immunity, prognosis is worse
Feline immunodeficiency virus
Lentivirus (retrovirus)
1.5-3% of healthy cats in US are infected
Transmitted via bites (^^ in free range male cats)
Can be transmitted transplacental or in milk
FIV pathogenesis
Virus is picked up from bite wound by dendritic cells & carried to lymph nodes
Virus infects T lymphocytes & replicates
Spreads to other lymph nodes (fever, non specific neuro)
Could present clinically normal or immunodeficient
Clinical disease of FIV
Recurrent infection of skin, eyes, respiratory tract, urinary bladder
persistent fever, gingivitis, stomatitis
Meningoencephalitis or encephalitis w seizures or behavioral changes
Diagnose by ELISA (for antibody) or PCR (viral RNA)
Differentiating between rabies, FIP & FIV
Age of onset
Course of neurologic signs
Presence of other clinical signs
Progression of disease
Lab diagnosis - FIV snap test
Equine herpes virus 1
Alphaherpesvirinae
3 strains - EHV1 D752, N752, H752
D752 - respiratory /reproductive/neurologic
N752 - respiratory & reproductive only
Equine herpes myeloencephalopathy
Typically with D752 strain
Commonly follows outbreak of respiratory disease or abortion on farm
Neurologic form is reportable
diagnosing /signs of EHM
Vasculitis, necrosis, hemorrhage of SC/brain
PCR on nasal swaps = shed when neurologic
PCR can differentiate between D and N but not H
Arthropod borne viruses
Flavaivirus
- West Nile virus
Togaviridae
- eastern/western encephalitis
- Venezuelan equine encephalitis
West Nile virus
Flavivirus
Mosquito borne
Infects horses, humans, birds
Transmission cycle is between birds/mosquitos
Main signs are primarily neurologic
EEE
Eastern equine encephalitis
Togovirus (alphavirus)
Mosquito borne, incubation period is 4-10 days
EEE mechanism
Virus travels to lymph node & replicates in macrophages & neutrophils
Death occurs 3-4 days after onset of neurologic sings
Mortality rate is 70-90%
WEE
Western equine encephalitis
Alphavirus - seen west of Mississippi
Milder than EEE, mortality 15-20% rate
Mosquito borne
Diagnosing WEE
Arboviral encephalitides by IgM ELISA on serum, PCR or IHC on brain /spinal cord
Killed vaccines are available(core)
Differentiating among all EQ viruses
Course of neurologic signs
Presence of other clinical signs
Time of year
Presence of similar disease in other animals
Laboratory diagnosis
Core vaccines for horses
Core vaccines for cats
Core vaccines for dogs
