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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • RNA viral disease (Vesiculovirus, Rhabdoviridae) that primarily affects horses, cattle, and swine and occasionally sheep, goats, camelids, and wildlife
  • 2 primary serotypes (New Jersey and Indiana)
  • Epidemic or only a few animals
  • Clinically indistinguishable from foot-and-mouth disease in ruminants and swine
  • Transmission via arthropod vectors, aerosol or contact exposure to saliva or fluid from ruptured vesicles
  • Incubation period is typically 2–8 days
  • Suspected cases reportable in many other countries, including the USA

Signalment!!navigator!!

Any age, sex, or breed of susceptible species.

Signs!!navigator!!

  • Vesicles or ulcers (includes mucocutaneous junction)—oral cavity (most common), nares, coronary bands, mammary glands, or external genitalia
  • Transient fever
  • Ptyalism
  • Anorexia
  • Weight loss
  • Coronitis resulting in lameness and/or hoof wall deformation/laminitis/hoof wall sloughing
  • Epistaxis
  • Nasal edema, laryngitis, or pharyngitis
  • Drop in milk production

Causes and Risk Factors!!navigator!!

  • Virus spread via insect vectors (black flies, sand flies, and Culicoides spp.), mechanical transmission, and movement of animals
  • Moving streams/creeks

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • NSAID toxicosis
  • Candidiasis
  • Blister beetle (cantharidin) toxicosis
  • Organophosphate paste dewormers (i.e. trichlorfon, dichlorvos)
  • Plant awn stomatitis ulcerations
  • Equine coital exanthema (equine herpesvirus 3)
  • Autoimmune diseases, such as bullous pemphigoid or paraneoplastic bullous stomatitis
  • Uremia
  • Mechanical trauma or chemical contact

CBC/Biochemistry/Urinalysis!!navigator!!

  • Often within normal limits
  • Stress leukogram may be present
  • Electrolyte abnormalities and hemoconcentration secondary to dysphagia or anorexia

Other Laboratory Tests!!navigator!!

  • Significant antibody levels via complement fixation, VN, and/or ELISA (capture ELISA for immunoglobulin M or competitive ELISA) tests in the presence of active lesions (ELISA and VN maintain antibody titers many years after exposure)
  • Virus isolation or real-time reverse transcriptase polymerase chain reaction performed on vesicular fluid, epithelial tissue, or direct swabs from recently ruptured vesicles

Diagnostic Procedures!!navigator!!

Cytologic and histopathologic examination of lesions may be useful in differentiating VS from other diseases.

Pathologic Findings!!navigator!!

Biopsy of acute lesions reveals nonspecific neutrophilic dermatitis, edema, epidermal necrosis, and reticular degeneration.

Treatment ⬆ ⬇

TREATMENT

Supportive care. Softened feeds may decrease cachexia due to anorexia. Cleanse lesions with mild antiseptics to avoid secondary bacterial infections. IV fluids in older animals to maintain hydration.

Medications ⬆ ⬇

MEDICATIONS

Oral or IV NSAIDs may be indicated to control painful lesions. Studies suggest recombinant equine interferon-β1 given at a dose of 0.3–1.0 μg/kg IM every 2 days may be useful as a prophylactic treatment for animals at high risk, or animals showing the initial signs of the disease.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Expected Course and Prognosis!!navigator!!

  • Self-limiting; lesions often heal within 2 weeks
  • Months may be required for complete regression, especially in the case of an immunocompromised or metabolically deranged animal
  • Scarring or depigmentation may occur
  • Prognosis is excellent for recovery unless laminitis or secondary bacterial infections are present
  • Immunity hypothesized to be short lived
  • Reinfection during subsequent outbreaks is observed
  • No cross-strain immunity

Epidemiology/Prevention!!navigator!!

  • High morbidity and low mortality
  • Endemic in northern South America, Central America, and Mexico
  • Sporadic outbreaks occur in southwestern USA
  • Highly contagious for the first few days after rupture of the vesicles
  • Quarantine for at least 14 days from the onset of lesions in the last affected animal on the premises
  • Disinfect facilities and fomites with chlorine, iodine, or a quaternary ammonium compound
  • Institute insect control measures
  • No commercially available vaccine in the USA

Complications!!navigator!!

  • Secondary bacterial infections
  • Laminitis
  • Dehydration and weight loss secondary to anorexia

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Zoonotic Potential!!navigator!!

  • Humans have rarely contracted VS (influenza-like illness) when handling infected animals and under laboratory conditions. Wear protective measures (gloves, eyewear, and frequent handwashing)
  • OIE removed VS from its list of internationally reportable animal diseases in 2015
  • Still reportable in the USA; regulatory quarantine action is required on premises

Pregnancy/Fertility/Breeding!!navigator!!

No known effects on pregnancy are documented.

Abbreviations!!navigator!!

  • ELISA = enzyme-linked immunosorbent assay
  • NSAID = nonsteroidal anti-inflammatory drug
  • OIE = Office International des Épizooties/World Organisation for Animal Health
  • VN = virus neutralization
  • VS = vesicular stomatitis

Suggested Reading ⬆ ⬇

Kim L, Morley P, McCluskey B, et al. Oral vesicular lesions in horses without evidence of vesicular stomatitis virus infection. J Am Vet Med Assoc 2000;216(9):1399–1404.

Author(s) ⬆

Author: Angela M. Pelzel-McCluskey

Consulting Editor: Ashley G. Boyle

Acknowledgment: The author and editor acknowledge the prior contribution of Kerry E. Beckman.