Viral Diseases Flashcards
What animals can be infected by canine distemper virus? Where is it frequently seen?
carnivores —> dogs are reservoirs
breeding and shelter environments
How is CDV transmitted? How long are hosts contagious?
oronasal exposure to virus-contaminated respiratory secretions, vomit, feces, urine, and environmental fomites
up to 3 months
What is the initial step to the pathogenesis of CDV? What happens next? What happens when the host recovers?
- infects macrophages and monocytes in the upper respiratory tract and spreads to the stomach, bowels, spleen, liver, BM, lymphatics, and eventually the eyes, skin, and CNS where it persists
- infects epithelial tissues throughout the body and shed from everywhere until the resolution of respiratory signs
no longer spreads, even if neurologic signs develop
What does the effect of CDV depend on?
immune response
- good response = do not get ill, clears infection
- mild response = will get clinical disease and likely get better, can persist and develop CNS signs
- no response = severe disease and death likely
can cause immunosuppression —> concurrent infections common
What dogs are likely to suffer from severe illness from CDV?
puppies
What is the first week of CDV illness like?
hard to differentiate from other infectious upper respiratory disease
- vomiting, severe diarrhea
- fever, dehydration
- lymphopenia
- lethargy, anorexia
- conjunctivitis
- respiratory signs, viral pneumonia nad secondary bacterial pneumonia
What is the most common symptom of clinically ill patients with CDV? Where does it most commonly progress to? What does this result in?
respiratory signs
- ocular epithelium: photophobia, anterior uveitis, chorioretinitis, permanent hyperreflective retinal lesions
- renal and bladder epithelium
How is the skin most commonly affected by CDV?
- pustular rashes
- hyperkeratosis and hardening of the paw pads
How are teeth affected by CDV?
permanent denal enamel hypoplasia of adult teeth prior to eruption in puppies
- gives a clue of previous infection
What additional sign is can be seen in young large breed dogs infected with CDV?
metaphyseal osteosclerosis of long bone, not usually associated with lameness
When can CNS signs appear in patients infected by CDV?
any point in their life —> progressive, affects prognosis
- during infection
- 1-3 weeks after recovery
- can develop in dogs that never had symptoms
What CNS sign is strongly suggestive of CDV? What other signs are seen?
myoclonus - spastic twitching of temporal or appendicular muscles
- seizures
- ataxia
- hypermetria
- paraparesis or tetraparesis
- severe cervial pain
- puppies infected in utero or as neonates can develop CNS signs within the first 4-6 weeks of life
How is CDV diagnosed? What is able to be seen within 1-2 weeks of infection? Why is it difficult?
- clinical signs
- known poor vaccination history
- lymphopenia, thrombocytopenia, hypoalbuminemia, hypoglobulinemia
- radiographs show pneumonia
intranuclear and intracytoplasmic viral inclusions in monocytes, lymphocytes, neutrophils, or erythrocytes
neurologic disease seen can be difficult to narrow down to CDV without history or evidence of systemic signs
What are the 3 major ways to diagnose CDV?
- serology - not helpful at the peracute stage, 4x increase in serum IgG titer over 2-3 week period or IgM levels indicative of a current infection
- cytology - IN and IC inclusion bodies found in cells on stained peripheral blood smears or conjunctival swabs/scrapings
- PCR - any fluid or tissue, may not differentiate vaccine vs actual infection
What is treatment for distemper like?
SUPPORTIVE
- fluids
- antibiotics if there is secondary bacterial bronchopneumonia —> broad-spectrum for several weeks
- seizure control
myoclonus has no known effective treatment, prognosis with neurologic disease is guarded to poor
How is CDV prevented?
VACCINATION
- at least 3 vaccines every 3-4 weeks between the ages of 6-16 weeks of age with the last booster given at 16 weeks
- an extra administration of a dose at 18-20 weeks recommended if dogs are in high-risk environments
- next dose given in a year, then q 3 weeks
How is CDV prevented?
- susceptible to most routine hospital disinfectants
- isolate dogs with GI or respiratory signs to avoid aerosolization
CDV manifestations:
How is canine parvovirus transmitted? Why is it so easily spread?
fecal-oral and fomites
- shed in huge amounts in stool for 2 weeks after initial exposure
- resistant to many disinfectants, allowing for long persistence in the environment
(recovered dogs don’t transmit infection)
What breeds are more susceptible to developing parvovirus? When can they begin to become infected?
BLACK AND TAN - Rottweilers, Pit Bulls, Dobermans, English Springer Spaniel, German Shepherds
12-14 weeks, once maternal antibodies wane
What do puppies infected in utero with CPV typically develop? Why is this rarely seen?
myocarditis
- most bitches are vaccinated and confer maternal antibodies to their pups
- pups with myocarditis will rarely survive long enough to see signs of it
What is an especially rare manifestation of CPV?
erythematous cutaneous lesions (erythema multiforme)
What cells does CPV-2 target? What can exacerbate signs?
rapidly dividing cells - thymus, bone marrow, spleen, crypt cells of the gut epithelium
STRESS: weaning, concurrent infections, GI parasites, overcrowding, poor nutrition, age
What is the pathogenesis of CPV? How do most patients initially present?
viral destruction of intestinal crypt cells cause villus collapse, diarrhea, vomiting, intestinal bleeding, and bacterial invasion
depression, hyporexia, vomiting typically without diarrhea at first
What is characteristic of CPV infection? What secondary effect is common?
- severe hemorrhagic diarrhea with fetid odor developing 24-48 hours following initial infection
- vomiting prominent enough to mimic FB obstruction or cause esophagitis
intestinal protein loss = hypoproteinemia
How can CPV affect the bone marrow?
damages BM progenitor cells or BM necrosis —> transient or prolonged neutropenia = increased susceptibility to serious infections, especially with GIT translocation
(neutropenia also caused by demand for neutrophils in the GIT)
What is indicative of serious GIT translocation seen with CPV? What most commonly causes death?
- hypoglycemic due to endotoxic shock from G - bacteria
- skin necrosis
- polyarthritis, diskospondylitits
- intussusception
septicemia, endotoxemia, and shock