Equine Infectious Disease Prevention Programs

Question 1

Vaccine efficacy depends on what?

Answer 1

the type of vaccine and route of administration

Question 2

When should you being vaccines for foals and how many do they typically require?

Answer 2

6 mo of age; 3 vaxs

Question 3

What are the core vaccines for equines?

Answer 3

• Tetanus
• Encephalitis
  
  • EEE, WEE, West Nile Virus
• Rabies

Question 4

What is tetanus? What are the clinical signs of this disease? How is it treated and how can it be prevented?

Answer 4

• Neuro dz caused by Clostridium tetani, present in intestines, manure, soil, spores enter thru wounds, umbilicus
• C/S: stiff gait, facial mm spasm, third eyelid prolapse, sawhorse stance, excessive response to external stimuli, recumbency
• Tx: sedatives, mm relaxants, tetanus antitoxin, penicillin or metronidazole
• Prev: all horses should be vaccinated - tetanus toxoid vax, booster if open wound/sx procedure >6 mo since vax, begin @ 6 mo of age if foal recived colostrum from vaxed mare

Question 5

What are the 4 arboviruses and what is their lifecycle?

Answer 5

• Alphavirus: EEE, WEE, VEE
• Flavivirus: WNV
• Lifecycle: mosquitos and birds (crows) = reservoir, dead-end hosts = horses and humans

Question 6

What are the clinical signs of West Nile Virus?

Answer 6

• fever
• mm fasciculations
• weakness/ataxia
• flaccid paralysis
• changes in mentation
• CN deficits

Question 7

What are clinical signs of Eastern Equine Enchephalomyelitis?

Answer 7

• neuro signs 5d after exposure
• death 2-3d later
• low grade fever first
  
  • viremia for 2d
• fever (up to 106)
  
  • during viral proliferation
• behavior change: irritable, somnolent, self-mutilation, hyperesthesia, hyperexcitable, decr food/water consumption
• dementia: head-pressing, leaning against wall, compulsive walking, blindness –> seizures

Question 8

What time of year do most EEE outbreaks occur vs. WNV outbreaks?

Answer 8

• EEE: April-Sept
• WNV: June-Dec

Question 9

What is the differene between the viral targets and mortality rates of EEE and WNV?

Answer 9

• EEE:
  
  • Mortality: 75-95%
  • Targets cerebral cortex
• WNV:
  
  • Mortality: 30-33%
  • Targets mid-hind brain/spinal cord

Question 10

What are the vaccination protocols for EEE and WNV?

Answer 10

• EEE: in FL, booster EEE/WEE every 4-6 mo, booster 1 mo prior to peak mosquito season
• WNV: vax dependent
  
  • Fort Dodge/BI: 2x per year
  • Merial - 1x per year
  • Intervet Prevenil - 1x per year
• Vax broodmares 30-60d prior to foaling
• Foals: begin vax series @ 3-4 mo (3 vaxs!)

Question 11

What is the most common reservoir of rabies? What are the clinical signs of this disease? What is the vaccine protocol for rabies?

Answer 11

• Raccoons
• C/S: can look like anything - incubation = 2-9 wks, dumb form, ascending paralysis, furious form
• Vax protocol: annual Killed vax IM
  
  • Foals: begin at 6 mo

Question 12

What are the risk-based vaccines for equines?

Answer 12

• Influenza
• Equine Herpesvirus (Rhinopneumonitis)
• Strangles

Question 13

Describe the pathogenesis of equine influenza. What are the clinical signs for this disease, and what is the vaccination protocol for this?

Answer 13

• susceptible population <3 yrs, incubation period 1-3d, stressful conditions/travel
• C/S: high fever (1-5d), cough (sev wks), nasal d/c, lethargy, depression, reduced appetite, mm soreness
  
  • rest is ESSENTIAL following infxn
• Vax protocol: vax q 6-12 mo–> decr viral shedding (inactivated IM, MLV IN, canarypox vector IM)
  
  • Broodmares - give IM vax in last 30d of pregnancy
  • Foals @ 6 mo

Question 14

Describe EHV 1 and 4

Answer 14

• EHV 1: abortion (7-9 mo of gestation), neonatal death, neuro dz, resp dz
  
  • fever and nasal d/c prior to neuro dz
• EHV 4: resp dz
• also known as rhinopneumonitis, C/S nearly identical to influenza
• incubation time 2-10d, shed virus for 2-3 wks, most common in weanling and yearling
• transmitted via resp route, contaminated equipment and stress can cause recrudescence

Question 15

How is EHV prevented?

Answer 15

• vaccination decr shedding of virus and severity of C/S
• foals and weanlings - start b/t 4-6 mo
• yearlings - q 6 mo
• broodmares - booster at 5, 7, 9 mo of pregnancy to prevent abortion (usually occurs @ 7-9 mo)
• vax 30 d prior to foaling w/ EHV 1+4 for colostral immunity

Question 16

Describe EHV neuro disease

Answer 16

• considered directly contagious!
• “neurotropic” strain of virus has high mortality
• vax does not prevent dz (maybe MLV does?)

Question 17

How do you control EHV outbreaks?

Answer 17

• isolate all new arrivals for 21 d
• disinfect transport vans
• isolate horses w/ fever
• keep aborted material away from herd
  
  • isolate mare

Question 18

Describe Strangles. What are the clinical signs?

Answer 18

• caused by Strep equi equi
  
  • reportable dz in Florida
• C/S: fever, l.n. enlargement + abscessation, purulent nasal d/c, resp distress d/t retropharyngeal l.n. enlargement

Question 19

How is Strangles transmitted? And what is the incubation period like?

Answer 19

• Transmission: ingestion or inhalation of infected discharge
  
  • horse-horse contact or fomites (handlers), highly contagious
  • high morbidity, low mortality
• Incubation: 3-14d, isolate horses w/ a fever ASAP, shed bacteria starting at 1-2d after onset of pyrexia

Question 20

How do you confirm a diagnosis of Strangles?

Answer 20

• Nasal/pharyngeal culture = gold standard
• PCR - nasal swab or nasal flush/guttural pouch
  
  • 3 negative PCRs needed to be released from quarantine
• Serology for SeM protein
  
  • helpful for confirming purpura/bastard strangles, repeat in 7-14d if weak (+)

Question 21

How long are horses infected with Strangles infectious?

Answer 21

• at least 4 wks after C/S resolve
• guttural pouch is clear
  
  • after guttural pouch samples are neg

Question 22

Describe hygiene procedures needed for a Strangles outbreak.

Answer 22

• protective clothing
• gloves, booties
• foot baths
• disinfect stables/transport vehicles
• rest pastures - 4 wks

Question 23

When should Strangles vaccines be administered?

Answer 23

• previously affected farms
• farms with young stock
• sale/show stables

Question 24

Describe the various types of Strangles vaccines

Answer 24

• M-protein based given IM
  
  • Strepguard
  • Strepvaxll
• need to booster 1-2x yr
  
  • can cause abscesses at injxn site
  • start vax at 4-6 mo
• Intranasal: Pinnacle (3 inital vaxs), IN may be more effective, can also call abscesses, start vax at 6-9 mo

Question 25

What are potential risks of the Strangles vaccine?

Answer 25

* Immune-mediated purpura hemorrhagica * Mild form of the dz * Abscess formation * **No vaccination in the face of dz!**

Question 26

What are some examples of regionally used vaccines?

Answer 26

* Botulism- KY, PA-broodmares * Potomac Horse Fever * Equine Viral Arteritis (EVA) * Rotavirus: endemic farms

Question 27

Describe botulism

Answer 27

* toxicoinfectious botulism * "Shaker foal syndrome" * forage poisoning * _toxin blocks transmission of impulses in nerves_ - weakness, dysphagia, death "flaccid paralysis" * **most horses affected by types B and C** * endemic area: KY, mid-Atlantic seaboard states

Question 28

Describe the botulism vaccine protocol

Answer 28

* Equine vaccine available: * BotVaxB (Neogen) - type B toxoid * **No cross-protection and type C toxoid not approved for use in horses** * Vax rx pregnant mares in endemic areas, to prevent dz in foals - give last trimester

Question 29

Describe Potomac River Horse Fever and the vaccine protocol for it

Answer 29

* Neorickettsia risticii * endemic to eastern US and CA * seasonal: July-Sept * Transmission thru trematode parasites of fresh water snails - horses eat caddis flies * C/S: severe diarrhea and fever, laminitis * Tx: oxytetracycline, supportive care * Vax: **questionable** b/c field evidence is lacking -lack of seroconversion, 2 doses 3-4 wks apart

Question 30

Describe Equine Viral Arteritis and the vaccine protocol for this.

Answer 30

* abortion is main concern * transmission: resp/semen * Dx: EVA titers and virus isolation * Vax: used to control EVA outbreaks, to prevent transmission from carrier stallions * seroconversion caused by vax may interfere w/ requirements for export of semen or stallions * MLV: stallions and open mares * colts 6-12 mo, seronegative mares if bred to infected stallion

Question 31

Describe Rotavirus and how to treat and prevent it

Answer 31

* most common cause of infectious diarrhea in foals * C/S: profuse watery diarrhea, fever, lethargy * **highly contagious** * Tx: supportive care * Prev: vaccination of pregnant mares before foaling in endemic herds may provide some protection

Question 32

What is Lepto associated with?

Answer 32

* recurrent uveitis, kidney infections, abortion

Question 33

What vaccine has colic side effects following its official use?

Answer 33

* Corynebacterium pseudotuberculosis

Question 34

Describe Equine Infectious Anemia, how it's diagnosed

Answer 34

* retrovirus transmitted by biting flies or blood contaminated needles * **Reportable in all states** * Acute: fever, depression, petechiation * Chronic: icterus, anemia, dependent edema * Dx: "Coggins" test (AGID) or ELISA * need neg test q 6-12 mo

Question 35

Describe piroplasmosis

Answer 35

* Theileria equi (formerly Babesia equi) * Babesia caballi * Transmission: tick-borne dz (Dermacentor), mechanical vector transmission * US considered non-endemic * C/S: * Chronic - weak, decr appetite * Acute - fever, anemia, jaundice, hemoglobinuria * Dx: cELISA