Chapter 11 Flashcards
What are the three subfamilies of the family Herpesviridae?
Alphaherpesvirinae
Betaerpesvirinae
Gammaherpesvirinae
How would you classify the speed of replication and killing in the Alphaherpsevirinae subfamily?
rapid
What do latent infections of Alphaherpesvirinae usually involve?
the sensory nerve ganglia
How would you classify the speed of replication and killing in the Betaherpesvirinae subfamily?
slow
Where are Betaherpesvirinae latent infections localized?
in secretory epithelial cells
Where do Gammaherpesvirinae viruses replicate and establish latency?
in lymphocytes
Name 5 key features of all herpesviruses.
- Enveloped
- Produce both acute and latent infecctions
- Clinical signs and pathology extremely variable
- Susceptible to antiviral drugs
What type of virus, genomically, is herpesvirus?
The genome is linear, double-stranded DNA, 125-235kbp
For herpesvirus replication, where does DNA replication and encapsidation occur?
in the nucleus
What are the multisystemic alpha-herpesviruses of veterinary importance?
Equine herpesvirus 1 and 4
Bovine herpesvirus 1 and 5
Marek’s disease virus
Pseudorabies virus
What disease forms do EHV-1 cause?
reproductive, neurological, and/or respiratory disease
What disease form does EHV-3 cause?
equine coital exanthema
What disease forms does EHV-4 cause?
mainly respiratory
What cells does EHV-1 infect?
respiratory epithelial cells, endothelial cells, neuronal cells, and lymphoid cells
What cells does EHV-4 infect?
epithelial cells, neuronal cells
Which equine herpesvirus is most commonly associated with respiratory disease?
EHV-4
Classify respiratory disease caused by EHV-4.
It is an acute upper respiratory infection that is usually self limiting. There is mild to moderate fever and nasal discharge
What animals are susceptible to a lower respiratory infection caused by EHV-4?
neonates, immunocompromised, or naive young animals
Which equine herpesvirus is most commonly associated with abortion?
EHV-1
When does abortion due to EHV-1 usually occur?
During the last four months of gestation, but can occur as early as the 4th month
Note: Equine gestation is approximately 11-12 months
If a foal is born to a mare that has EHV-1 (non-latent), what typically occurs to the foal?
it dies shortly after birth
What important virus characteristics does EHV-1 have that are associated with abortion?
- Replication in endothelial cells and lymphocytes
2. Ability to invade allantochorion resulting in placental and fetal ischemia.
What lesions are typically found on fetuses that were aborted due to EHV-1?
They contain microscopic lesions, which include bronchiolitis, pneumonitis, splenic, and hepatic necrosis, and intranuclear inclusion bodies
What equine herpesvirus causes equine herpes myeloencephalitis?
EHV-1
What premonitory signs do patients with equine herpes myeloencephalitis have?
only fever
What symptoms are associated with equine herpes myeloencephalitis?
neurological dysfunction ranges from mild ataxia and paresis to complete paralysis and recumbency
What is the prognosis of equine herpes myeloencephalitis?
Prognosis is favorable if non-recumbent; recumbent horses frequently develop fatal complications
What distinguishes the hypervirulent strain of EHV-1 from other strains?
The hypervirulent strain of EHV-1 causes high morbidity and case fatality rates, are highly resistant to vaccination, affect horses of all breeds, ages, and vaccine status, and have up to a 10-fold increase in virus replication
How do EHV-1 and EHV-4 enter the horse?
via nasopharyngeal mucous membranes
How does EHV-1 spread systemically?
- The virus spreads to cells underlying lamina propria
- The virus replicates in the regional lymph nodes
3a. Cell-associated viremia - virus is disseminated in CD8+ lymphocytes
3b. Virus disseminated to uterine and CNS vascular endothelium
3c. Virus disseminated to neurons of trigeminal nerve with persistent latent infection of trigeminal ganglino
EHV-1 readily infects endothelial cells. What does this infection result in?
Infection of placental endothelium - abortion
Infection of neuronal endothelium - myelopathy, encephalopathy, myeloencephalopathy
Where do EHV-1 and EHV-4 hibernate (latent phase)?
Mainly in neuronal cells located in the sensory ganglia innervating the nasopharyngeal mucosa
EHV-1 can establish latency in T-lymphocytes
What conditions can reactivate latent EHV-1 and EHV-4 infections?
stress associated with pregnancy, transport, racing, and training
How do reactivated equine herpesvirus infections impact the epidemiology of these viruses?
The reactivated infections are usually inapparent and can be spread to other horses without notice
what does a young horse’s initial infection of equine herpesvirus usually coincide with?
declining maternal antibody
What are the differentials to consider for the respiratory form of EHV-1 or EHV-4?
- Influenza
- Respiratory form of equine viral arteritis
- Rhinovirus
What are the differentials to be considered for the neurological form of EHV-1 or EHV-4?
- Wobblers (cervical stenotic myelopathy)
- Equine degenerative myelitis
- Equine protozoal myeloencephalopathy
- Trauma
- Arboviral encephalidites
How is EHV-1 and EHV-4 diagnosed (tests)?
Viral isolation
Immunohistochemistry
Serology
PCR
What are the shortcomings of vaccine efforts against EHV-1?
- Protection is not complete and is short-lived
- Maternal immune components will interfere with vaccination
- The vaccines generally do not prevent infection, but reduce the severity of clinical disease
What is bovine herpesvirus type 1 (BHV-1) the etiologic agent of?
- Infectious bovine rhinotracheitis (IBR)
- Bovine coital exanthema
- Infectious pustular vulvovaginitis
Why can’t infectious bovine rhinotracheitis (IBV) and infectious pustular vulvovaginitis (IPV) occur concurrently?
Because they do not come from the same strain of BHV-1
What is bovine herpesvirus type 5 (BHV-5) the causative agent of?
neurological disease
What are the five different presentations/disease manifestations of BHV-1?
- Respiratory disease
- Abortion
- Vulvovaginitis and balanoposthitis
- Perinatal mortality
- Keratoconjuntivitis
What is the most economically important disease manifestation of BHV-1?
respiratory disease
What is the portal of entry for BHV-1 and BHV-5?
the nasopharyngeal mucous membranes
If BHV-1 crosses from the mother to the fetus, what happens?
abortion
What differentials should be considered when considering BHV-1?
- Bovine respiratory syncytial virus (BRSV)
- Parainfluenza-3 viurs (PI-3)
- Bovine Viral Diarrhea viurs (BVD)
- Malignant catarrhal fever (MCF)
For both EHV and BHV, when must virus isolation samples be collected?
early
True or False: Unlike EHV, the vaccination for BHV prevents infection.
False: Vaccination does not prevent infection, but will ameliorate clinical disease and/or reduce number of events in an outbreak situation
What causes Marek’s disease?
Gallid Herpesvirus 2
How have clinical signs and the severity of disease associated with infection by Gallid herpesvirus 2 changed (1905-2005)?
The severity of disease has only increased since 1905 - It was orginally chronic and sporadic, but now is acute and aggressive
1905 - Classified as chronic polyneuritis
1915 - Immunosuppression was added to the list of clinical signs
1925 - Visceral lymphoma was added to the list of clinical signs
1975 - Transient paralysis was added to the list of clinical signs
1985 - Acute brain edema and acute rash were added to the list of clinical signs
How many pathotypes of Gallid Herpesvirus 2 are there and what are they called?
4 Mildly virulent (M), Virulent (V), Very virulent (VV), and Very Virulent Plus (VV+)
What are the 4 arbitrary phases of infection of poultry with Marek’s disease virus?
- Early productive-restrictive virus infection causing primarily degenerative changes
- Latent infection
- A second phase of cytolytic, productive-restrictive infection coincident with permanent immunosuppression
- A proliferative phase involving nonproductively infected lymphoid cells
Where does the initial replication of Marek’s disease occur?
in the epithelial cells of the respiratory tract
What differentials should also be considered when considering Marek’s disease?
- Avian leukosis virus
2. Retoci;pendotheliosis virus
What causes pseudorabies?
Suid herpesvirus-1
What is the primary host and reservoir of pseudorabies?
swine
What species can be affected by suid herpesvirus-1?
cattle, dogs, cats, sheep, goats, raccoons, skunks, rodents, and others
Pseudo rabies is _____ to non-swine species.
fatal
True or False: Pseudorabies is reportable.
true
What does stage 5 mean in terms of the PRV eradication program?
PRV free
What does canine herpesvirus-1 cause?
Hemorrhagic disease of pups
What clinical signs are associated with canine herpesvirus 1?
Painful and persistent crying, abdominal pain, depression, and anorexia
How do dogs become infected with canine herpesvirus 1?
Their oronasal epithelium is infected either from the dam’s vagina or other infected dogs
What is the ideal temperature for canine herpesvirus 1 replication?
Between 33-35 C (91.4 - 95 F)
What role does hypothermia play in the pathogenesis of hemorrhagic disease in pups?
Hypothermia can lead to generalized, often fatal disease because:
- Puppies cannot temperature regulate
- Their rectal temperature is lower than adult dogs
- They are unable to mount a fever for protection
- They have suppressed cell-mediated immune responses
What cell type is canine herpesvirus 1 cell associated viremia associated with?
macrophages
What is the significance of Herpesvirus-B for humans?
They can only get it from bites by rhesus or other macaque monkeys and it often leads to fatal encephalitis
What three herpes viruses of veterinary importance are betaherpesviruses?
Porcine herpesvirus-2
Feline herpesvirus 2
Bovine herpesvirus 4
What is the one veterinary disease that is of any real significance in the gammaherpesvirinae subfamily>
Malignant Catarrhal Fever (MCF)
What is MCF caused by?
Viruses that belong to the rhadinovirus genus
The two main viruses that are closely related genetically, that cause indistinguishable diseases are: Alcelaphine herpesvirus type 1 and Ovine herpesvirus 2
Where does Alcelaphine herpesvirus type 1 occur mainly?
in Africa or in zoos or game farms that house the wildebeest
What are the susceptible species of MCF?
cattle, bison, some species of deer, certain other exotic and domestic ruminants
bison and deer are more susceptible than cattle
What are the carrier species of MCF?
Wildebeest and sheep
Do the carrier species of MCF show clinical signs?
no
MCF is often, but not always, ____.
fatal
What differentials should be considered alongside MCF?
- BVD/mucosal disease
- Severe IBR
- Rhinderpest
- FMD
5, Vesicular stomatitis
What signs are associated with pseudorabies virus infection in cats and dogs?
There is usually frenzy associated with intense pruritus, paralysis of the jaws, pharynx, salivation, and howling