Lecture 31: Role of the Equine Practitioner in Infectious Disease Outbreaks

what are regulatory diseases?

• diseases reportable by law to state or federal animal health authorities

• includes foreign animal diseases and infectious diseases that are internationally reportable to WOAH

• other contagious or infectious diseases that have an existing control or eradication program

• diseases that threaten the national flock or herd either by their clinical features or their impact on international trade

all federally reported diseases are also

state reportable

just because a disease is reportable does not mean

it is actionable by the state

equine herpes myeloencephalopathy (EHM)

• respiratory, reproductive and/or neurological signs

• spread by airborne/respiratory route (direct contact)

• most horses are exposed to the virus early in life → fever/resp signs only

• supportive care, antivirals

• death often by euthanasia

• EHV-1 vaccine is labeled for prevention of respiratory form of the disease only!

neurological clinical signs from encephalitis may include

ataxia, paresis of hind limbs, urine retention/incontinence, bladder atony, penis extension, recumbency, poor tail and anal tone, lethargy, and/or coma

what is the concern with EHM?

• neurological disease with respiratory spread

• reportable disease in many states but actionable or not will vary

• highly contagious

• difficult to control/mitigate

• non-clinical shedders and recrudescence of the disease in adult horses

• outbreaks tend to cause panic in the equine industry

in every case of EHM, the attending veterinarian is the

first responder

what is the goal in EHM outbreak response?

the index case is the only case

how do you accomplish the index case of EHM being the only case?

• isolation of clinical cases

• implement enhanced biosecurity

• monitoring of exposed horses

what is step 1 of EHM outbreak?

evaluate the premises and isolate clinical cases → use PPE as soon as you arrive on site

what is step 2 of EHM outbreak?

perform exam, collect diagnostic samples, start treatment

treatment for EHM

• symptomatic treatment for fever, neuro signs

• supportive care

• anti-virals may benefit these cases, especially early in disease

• new intervention strategies → equine amnion therapy

what is step 3 of EHM outbreak?

establish enhanced biosecurity protocols

isolation area objectives

• eliminate contact with other horses

• limit the amount of shared airspace

• limit exposure to insects and rodents

• isolation area should be downwind of general population

• limit human access to only designated personnel

• designated equipment

• barriers and signage should indicate area quarantined

• PPE and footbaths should be used at the entrance/exit of the area

what is step 4 of EHM outbreak?

determine who is exposed and start temperature monitoring → 101.5 degrees F is above a fever

direct contact for EHM

horses, livestock, dogs, humans

indirect contact for EHM

hands, clothing, equipment, communal areas, shared airspace

what is step 5 to EHM outbreak?

submit samples and report the suspect case → call state vet

what will meet confirmed case definition for EHM?

EHV-1 PCR positive on either nasal swab or the whole blood with compatible neurological signs

true or false: both strains of EHV-1 can cause large outbreaks and the response is the same.

true

what is step 6 of EHM outbreak?

EHM confirmed → report to state vet and owner/barn manager

cleaning and disinfecting for EHM

• step 1 → remove loose organic material

• step 2 → wash with detergent and rinse thoroughly

• step 3 → allow to dry

• step 4 → apply disinfectant

disinfectants

• follow manufacturer recommendations and label instructions

• bleach and alcohol are inactivated by organic matter

• environments with organic material → phenolics, accelerated hydrogen peroxide products

EHM outbreak source

• sometimes can’t confirm the source of EHM outbreak

• some histories are clear

what should a lab be screening with to make sure they are catching EHV strain types?

glycoprotein B gene PCR