A020 - VESICULAR STOMATITIS

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A020 - VESICULAR STOMATITIS

Nature of the disease
Vesicular stomatitis (VS) is a viral disease caused by a Vesiculovirus of the Rhabdovirus family which occurs in the western hemisphere. It affects livestock and humans and is responsible for significant economic loss as well as being important in the differential diagnosis of FMD.

Two different antigenic types of virus are distinguished: Indiana and New Jersey

Classification
OIE List A disease
Susceptible species
Clinical disease occurs in cattle, horses and pigs. Sheep and goats are relatively resistant.

Many American wildlife species are susceptible including bats, rodents and birds. 
Humans can become infected with VS, resulting in an influenza-like disease.

Distribution
VS is found in the Americas having been reported from southern Canada to northern Argentina. The disease is endemic in Central America, Venezuela, Colombia and Ecuador. It was not reported from United States since 1998.
Clinical signs 
After a short incubation period animals show symptoms that are clinically not distinguishable from foot and mouth disease:
  • Vesicles may be seen on the tongue, lips, gums, coronary bands, interdigital skin or teats.
  • Fever,
  • Excess salivation and lip smacking,
  • Difficulty eating, anorexia and loss of condition,
  • Lameness in some cases
  • Drop in milk yield in dairy cattle

The vesicles may not be readily apparent unless animals are examined closely. They rupture readily producing ulcers which tend to heal rapidly unless secondary infections occur.
 Mortality is low. Many infections are sub-clinical.

In humans the disease resembles influenza. Sometimes vesicles may be present on the mouth and the hands. Diarrhoea and vomiting can occur.

Post-mortem findings 
Gross lesions are restricted to the vesicles described above. Secondary infection are frequent.
Differential diagnosis 
Specimens required for diagnosis 
Any vesicular disease in cattle or pigs should be regarded as possible FMD until proven otherwise.

Recent or concurrent disease in other species (cattle, sheep, goats, horses etc) should also be investigated.

Specimens should be sent to laboratory in emergency and with adequate biohazard containment.

Laboratory procedures include:

  • Identification of the virus by ELISA, Complement Fixation Test and PCR using vesicular fluid and vesicular epithelium in sterile tubes with buffered tryptose broth with phenol red (pH 7.6). samples should be kept at 4°C and shipped within 24 hours or frozen if buffered tryptose is not available. Throat swabs can be sent but there are of less quality than vesicular fluid and epithelium.
  • Serology based ELISA, Competition ELISA, Virus Neutralisation or Complement Fixation Test using paired and convalescent serological samples.
Transmission   
Most of the epidemiology of VS is unclear. The virus is relatively resistant in the environment, specially at low temperatures. Infection is thought to spread to and between animals by:
  • Direct contact between infected domestic or wild animals (e.g. deer, rodents, frogs) and susceptible livestock
  • Mechanically by flies feeding on infected secretions
  • Mechanically on equipment (milking material, water and feed troughs)
  • Biting insects like sandflies (Phlebotomus spp.) or mosquitoes (Aedes spp.),

The virus enters through damaged skin or mucosa. Aerosols are thought to be unimportant.
It has been found in milk but does not survive pasteurisation.
Transmission via semen is considered possible but transmission via embryos is considered unlikely.
Humans are primarily infected via the respiratory tract, conjunctiva and through skin abrasions

Risk of introduction   
Most likely route of entry is with infected livestock, or on contaminated equipment. Provided the usual quarantine precautions are taken, the risk would appear to be low. The virus could be theoretically introduced with insects or by infected people.
Control / vaccines  
There is no commercial vaccines for vesicular stomatitis virus although some vaccines have been experimentally developed.

Control is based on elimination of infected animals, disinfections of premises and control of arthropods vectors.

References
  • GEERING WA, FORMAN AJ, NUNN MJ, Exotic Diseases of Animals, Aust Gov Publishing Service, Canberra, 1995, p. 265-271
  • MORGAN-CAPNER P, BRYDEN AS (1998),Vesicular Stomatitis In Zoonoses, ed by SR PALMER, Lord SOULSEY and D.I.H. SIMPSON, Oxford University Press, Bath Press, Avon, 1998, p.321-323
  • Office International des Epizooties, 2002
  • Vesicular Stomatitis, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p 495-496
  • Vesicular Stomatitis, In Veterinary Medicine, Saunders, Eight ed, 1997, London p. 976-978