Respiratory Infections Part 1 (test 2)

Question 1

What is an important characteristic of Herpesviruses?

Answer 1

They usually are persistent infections with bouts of LATENCY

Question 2

Name three Subfamilies of herpesviruses

Answer 2

alphaherpesvirinae
betaherpesvirinae
gammaherpesvirinae

Question 3

What are three characteristics of alphherpesvirinae subfamily?

Answer 3

• replicate and kill cell cells rapidly
• latency usually in neurons
• most pathogens in this group

Question 4

What are three characteristics of betaherpesvirinae subfamily?

Answer 4

• replicate slowly
• cause cell enlargement (cytomegaly)
• Latency often in secretory epithelium
• most NON-pathogenic in normal hosts

Question 5

What are three characteristics of Gammaherpesvirnae subfamily?

Answer 5

• infect lymphoctyes, establish latency
• complex disease patterns leading to lymphoid dysregulation, proliferation, neoplasia
• disease in NON-adapted hosts

Question 6

What are 6 general propterties of all herpesviruses?

Answer 6

1. Enveloped virus (easily inactivated in the environment)
   
   • transmission generally requires CLOSE contact (access to mucosal epithelial surfaces, short distance aerosols)
2. Viral infection leads to a persistent (LIFE-long) infection
3. infections include BOTH active replication and latency/reactivation
   
   • virus replication and shedding associated with clinical disease
   • Latency responsible for persistence
   • reactivation often in response to STRESS
4. Clinical Signs and pathology extremely variable
   
   • may be localized or systemic infections
   • can see disease in multiple organ systems
   • pathology can range from acute necrosis/inflammation to neoplasia
5. Susceptible to antiviral drugs, may be treated (ACYCLOVIR-lessen the severity of the disease and decrease viral shedding)
6. Structure and replication of viral genome
   
   • relatively large and complex genome
   • dsDNA
   • Has genes for viral replication, modulation of cell cycle, modulation of host immune responses
   • replication occurs in the NUCLEUS (EOsinophilic intranuclear inclusion bodies)

Question 7

Alphaherpesvirinae Subfamily viruses usually begin as what clinical presentation?

Answer 7

RESPIRATORY-and then spreads to other organ systems

Question 8

What are the 3 main EQUINE alphaherpesviruses?

Answer 8

EHV-1
EHV-3
EHV-4

Question 9

EHV-1 causes what kind of disease?

Answer 9

Respiratory disease, abortion and perinatal mortality, CNS

Question 10

EHV-3 causes what kind of disease?

Answer 10

Equine coital exanthema (localized genital infection)

Question 11

EHV-4 causes what kind of disease?

Answer 11

Equine Rhinopneumonitis virus (mainly respiratory, neronal)

Question 12

What are EHV-4 clinical signs?

Answer 12

Localized upper respiratory infection (rhinopneumonitis)

• nonspecific: depression, anorexia, FEVER
• regional lymphadenopathy, nasal discharge, coughing
• mild to moderate, self-limiting, full recovery
• secondary bacterial pneumonia

Question 13

What is the Main EHV pathogenesis?

Answer 13

Initially localized infections of respiratory tract that enter via nasopharyngeal respiratory epithelium

• lytic infection of epithelial cells in the URT
• clinical signs associated with ulceration, exudate and inflammation

Question 14

What is a secondary infection with EHV?

Answer 14

opportunistic bacteria can colonize ulcerated areas-nasal discharge changes to mucopurulent
-sometimes damage can lead to bacterial colonization in the lungs. aka pneumonia.

Question 15

What tissue does EHV-1 and 4 set up shop to cause latency?

Answer 15

They target neurons of sensory ganglia innervating nasopharyngeal mucosa.

EHV-1 may establish latency in T cells

Question 16

What can cause reactivation of latent viruses?

Answer 16

Stress, pregnancy, shipping, training or racing

Question 17

What are differentials with upper respiratory infection?

Answer 17

EHV, Equine Influenza, EVA, Rhino-infections

Question 18

How do you diagnose EHV?

Answer 18

Culture or PCR (need appropriate samples)

• timing-need sample early
• sample correct tissues
  
  • NASOPHARYNGEAL SWAB

Serology

• viral neutralization with A/C paired serum-recent infection
• New Elisa that can discriminate between EHV-1 & 4

Question 19

How do you control EHV?

Answer 19

Minimize stress and VACCINATE!

Question 20

Systemic effects of EHV include what?

Answer 20

Extra-respiratory spread associated with lymphocyte tropism

- virus accesses underlying lamina propria, lymphocytes
- replication in regional lymph nodes
- dissemination in CD8+ lymphocytes
- Virus disseminates to endothelium in target tissues (uterus-ABORTION, CNS-NEUROLOGIC DISEASE) (EHV-1)