Infectious and Misc Respiratory Diseases 1

Question 1

How can equine respiratory viruses be spread?

Answer 1

-Horse to horse transmission
-contact with excretions
-Recrudescence of latent infections

Question 2

What is the pathology of viral respiratory infections?

Answer 2

Virus attaches to respiratory epithelium, enters epithelial cells and uses the cell to replicate, its released from epithelial cells, killing cells, its shed in 48 hours, damages the epithelium and mucociliary clearance mechanism, spread systemically, epithelium take month or more to recover

Question 3

What immune response is created to viral infections?

Answer 3

Innate - secrete soluble factors into mucus(complement and cytokines)

Humoral Response - upper IgA and lower IgG

Cell Mediated - viral antigens presented locally by dendritic cells, replication inhibited by NK and cytotoxic T cell

Question 4

Who is commonly effected by equine respiratory viruses and what are the signs?

Answer 4

Young horses

Acute signs: high fever, malaise, cough, nasal discharge, lymph node swelling and tenderness, limb and ventral edema

Chronics: Decreased performance, chronic discharge, chronic pharyngitis, cough

Question 5

What are some syndromes that are secondary to viral infection?

Answer 5

Bacterial infection, lower airway hyper-reactivity and inflammation, pericarditis, vasculitis, purpura

Question 6

On clinical pathology what is suggestive of viral respiratory infection?

Answer 6

CBC: mild, normocytic, normochromic anemia, leukopenia with mild lymphopenia, mild to modearte neutrophilia, monocytosis, fibrinogne

Chem: elevated CK, AST and LDH

Question 7

How do you treat equine viral infections?

Answer 7

Treat the symptoms
-Fever and malaise - NSAID (flunixin or phenylbutazone)
-Cough - Bronchodilator or nebulizer (Clenbuterol, saline)
-Nasal Discharge - Clean
-Dehydration (oral or IV Fluids)
-Neurologic Signs - Antiviral - acyclovir or Oseltamivir or corticosteroids - dexamethasone, prednisolone inhaled
-Laminitis prevention - ice boot, NSAID
-Concurrent bacterial infection/pleuritis - broad spectrum

Question 8

How do you monitor viral infecitons?

Answer 8

Temp, resp rate, pleural pain, monitor fluid intake, fecal consistency, soak feed, feed softer, clean environment, rest 3-week past resolution fever and other signs

Question 9

What are some good biosecurity measures to prevent the spread on farm?

Answer 9

Isolate, dedicated clothing, footwear and tolls, monitor, remove and isolate more horses, submit samples PCR for diagnosis, no off-farm movement

Question 10

How can you prevent equine viral respiratory disease?

Answer 10

Vaccination - stimulate cell mediated and antibody response
MLV, Killed, Antiviral

Question 11

What are some diagnostic tests that can be used to detect viruses?

Answer 11

Equine Respiratory Panel - swab, lavage, TTW BAL
Viral Isolation - swab (best)
Viral Titers - serum

Question 12

What are some common causes of equine respiratory disease?

Answer 12

Equine Influenzas (RNA)
Equine Herpes Virus 1 and 4 (DNA)
Equine Arteritis (RNA)

Question 13

What are some less common causes of infectious ERD?

Answer 13

Equine Rhinovirus (foal >3-4wk)
Equine Adenovirus (foals)
Equine Herpes Virus 2 (weanling)
Equine Herpes 5 (Multinodular pulmonary fibrosis

Question 14

What are some rare causes of ERD?

Answer 14

African Horse Sickness
Hendra Virus

Question 15

What are some viral characteristics of Equine Influenza?

Answer 15

Most common URT virus horse
RNA and Fragile
Orthomyxoviridae
Type A - classified on hemagglutinin and Neuroaminidase
-Can experience Antigenic drift or shift

Question 16

What are the 2 types of Equine Influenza?

Answer 16

H7N7 and H3N8 (more common and worse disease)

Question 17

How do you prevent equine influenza?

Answer 17

Vaccination - ML, Inactivated, canary pox vectored
-Intranasal is option that’s effective
- Foals: 9-11 months
-Young Performance - e2-4m
-Adult pleasure - e6-12m
-Pregnant Mare - 8 wk. prior to foaling

-Isolate new horses 3 weeks
-Sick animals need to isolate and change and do last
-Recuperating horses in clean environment

Question 18

What are some characteristics of Equine Herpes 1 and 4?

Answer 18

DNA
Herpesviridae, alphaerpesvirinae
-most infected by 2yr
Vertical transmission
Incubate 2-10 days
-Latent n resp lymphoreticular system and trigeminal ganglia
-Steroid make it shed
-Can become a carrier

Question 19

What are the 5 syndromes that Herpes causes?

Answer 19

-Upper respiratory tract infection - most common presentation

-Late Term Abortion - 5 month in, minimal autolysis, high viral load in placenta and fetus, several mares (storm)

-Pulmonary Vasculotropic Infection - herpes1, acute and severe fever, resp, fatal, pulmonary edema second to vasculitis

-Neonatal Foal Death - cant nurse, interstitial pneumonia, poor prognosis

-Myeloencephalopathy - cauda equina syndrome, xanthochronic, point mutation

-Neuropathic = mutation EHV1 - no vaccine for this part

Question 20

What does treatment and monitoring look like for EHV?

Answer 20

Same as Equine influenzas
Prevent with vaccine (Inactivated, ML, mono or bivalent)

-Vaccine 1 at 6 months, 2 doses 3-4 week intervals and third 8-12 weeks
-Then every 4-6 months
- Broodmare: 5,7-,9- and 11-month gestation (Prevent abortion)

Question 21

What are some characteristics of Equine Viral Arteritis?

Answer 21

RNA
Arteriviridae
Abortion and Respiratory
Worldwide
Standardbred and Warmblood
Pathogenesis: aerosolized, contact infected horse, veneral
-Cells affected: viremia, replication, macrophage, endothelium, mesothelium

Question 22

What are the clinical signs of EVA?

Answer 22

Respiratory infection mild or subclinical
-Conjunctivitis, edema periorbital region, edema mid-ventrum, limbs, prepuce, scrotum and mammary gland
-Young foals fatal interstitial pneumonia
-Abortion 3-10months, mare has resp sign, fetus autolyzed
-Persistent Infection - testosterone can affect (stallion has in accessory sex gland)

Question 23

What is treatment and prevention for EVA?

Answer 23

Like other virus
Vaccination:
MLV, under certain circumstance
-Breeding colt 6-12m
-Seronegative mare - before breeding to carrier stallion, isolate 21-day post breed still shed
Once vaccinated =seropositive

Question 24

What are some additional viruses?

Answer 24

Equine Rhinitis - young, older shed, incubate 3-8 d, wide host

Adenovirus - foals

Equine Herpes 2 - B - URT, Ocular disease, pneumonia, 2-3m old

Equine Herpes 5- multinodular interstitial disease

Exotic Virus: African Horse Sickness and Hendra Virus

Question 25

What tests can you use to ID each Virus?

Answer 25

Equine Influenzas - Elisa, Viral isolation, PCR< Serology

Herpes - Viral isolation, PCR, Flourescent AB, Serology

Viral Arteritis - Viral isolation, PRC< Serology