1. Foot and Mouth Disease

   1. It is a highly contagious infectious disease of cattle, swine, sheep, goats, deer and other cloven-hoofed animals.
   2. The causative agent is an aphthovirus of the Picornaviridae family.
   3. The virion consists of a single-stranded RNA genome.
   4. Seven types (A, O, C, Asia 1, and South African Territories 1, 2, and 3) have been identified serologically, and multiple subtypes occur within each serotype.
   5. Outbreaks have occurred in every livestock-containing region of the world with the exception of New Zealand and Chile. In addition, the disease is currently enzootic in all continents except Australia, Central America, and North America. However, many countries in Europe do not have foot and mouth disease.
   6. Transmission occurs by insect bites, aerosol and contact.
   7. The incubation period is about 2 to 7 days.
   8. Cattle, sheep, and goats can become carriers. Cattle can harbor the virus for up to 2 to 3 years and sheep for up to 9 months.
   9. Morbidity varies from 50 to 100% but mortality is usually low (less than 5%). However, mortality can be high in young animals as the virus can affect the heart in this age group.
   10. The disease has debilitating effects, including weight loss, decrease in milk production, and loss of draught power, resulting in loss of productivity for a considerable time.
   11. It is the most important disease constraint to international trade in livestock and animal products.
   12. Because of its highly infectious nature and potential for rapid spread, it is a notifiable disease in most countries.
   13. It is not a public health or food safety threat.

1. 1. 14. Clinical signs:
          1. Vesicles and bullae develop at multiple sites and generally on the feet, muzzle and tongue, and are usually preceded by fever. Erosions develop after vesicles and bullae rupture, resulting in excessive salivation and lameness. Severe lesions often occur in areas subjected to trauma or physical stress.
          2. Foot lesions are the most common finding in pigs, while lesions at other sites occur less frequently. Tongue lesions are usually small and less noticeable in pigs than those in cattle.
          3. Generally, the first sign observed in a flock of sheep is lameness. Affected animals become reluctant to walk, anorexic and dull, and may lie away from the others. Affected feet are warm and painful to the touch. Vesicles may be found in the interdigital space.
          4. It is very difficult to make a clinical diagnosis of this disease in sheep. It has been reported, that up to 25% of infected sheep may fail to develop lesions, and an additional 20% may form only one lesion.
      15. Differential diagnoses:
          1. In sheep and goats, the disease is generally mild and can be difficult to distinguish from other common conditions.
          2. In swine, other vesicular diseases including swine vesicular disease, vesicular stomatitis, Seneca Valley virus infection, and vesicular exanthema of swine cause clinical signs similar to those of foot and mouth disease.
      16. Diagnosis:
          1. The diagnosis is based on clinical signs and laboratory tests to determine the serotype of the causal virus.
          2. For laboratory diagnosis, the clinical sample of choice is vesicular epithelium or liquid taken from animals showing early lesions and as much material as possible should be collected (at least 1 g).
          3. The diagnostic test often performed is reverse-transcription PCR, which is a very sensitive test.
          4. The presence of virus can also be demonstrated using antigen ELISA test, which can determine the serotype. This test is preferred for countries with endemic disease. In reference laboratories, sequencing of part of the capsid proteins is often performed to identify the serotype and lineage of the virus strain. 
          5. Virus isolation may also be performed in appropriate cell culture systems. 
      17. In many countries, where disease is endemic or sporadic or there is a risk of its introduction, routine prophylactic vaccination is practiced.

2. Swine Vesicular Disease

   1. Swine vesicular disease is a highly contagious viral disease of pigs, caused by the Enterovirus B virus (Picornaviridae family).
   2. It has been eradicated in Europe with the exception of Italy. The last report in Asia was in China in 1999. It has not been reported in the USA; therefore, state and federal veterinary authorities should be promptly contacted if the disease is suspected or identified in a farm.
   3. The disease is spread primarily by direct contact with infected swine or contaminated environment through mucous membranes or damaged skin barrier. It can also be transmitted by feeding pigs with raw meat products contaminated with the virus.
   4. An infected pig excretes virus from its nose, mouth, urine and feces up to 48 hours before the development of clinical signs.
   5. Clinical signs:
      1. Vesicles and erosions are seen more often on the limbs and around the mouth. On the legs, they typically develop on the coronary bands, interdigital spaces, and pressure points. Affected pigs may be lame. Lesions can less commonly be found on the teats, snout, lips, oral mucosa and tongue.
      2. Systemic signs include a transient and mild fever and decreased appetite. Neurologic signs have been reported but are considered rare.
      3. The incubation period is generally from 2 to 7 days.
      4. Normally, affected pigs recover within 2 to 3 weeks.
      5. Only very few outbreaks have been associated with severe clinical signs.
   6. Differential diagnosis:
      1. The clinical signs of swine vesicular disease are identical to those of foot and mouth disease, vesicular stomatitis, and vesicular exanthema of swine.
   7. Diagnosis:
      1. Clinical signs are similar to other viral diseases. Diagnostic tests typically used to detect viral antigen is ELISA and to detect viral nucleic acid is reverse-transcription PCR.
      2. Various samples can be submitted including lesion material, oral, and nasal swabs. Fecal material can be used to detect subclinical cases via reverse-transcription PCR tests but it is not a good sample for ELISA tests.
      3. Treatment:
         1. There is no specific treatment.

3. Swine Vesicular Exanthema

   1. It is an acute infectious disease of swine caused by a Vesivirus in the Caliciviridae family.
   2. It has not been reported in the USA since 1959; therefore, suspected cases should be reported immediately.
   3. The mortality rates in spontaneous outbreaks are usually less than 5%.
   4. The disease is of importance not only because of the loss of weight of affected animals and abortion in sows, but also because of the difficulty in distinguishing the lesions from the ones of other vesicular diseases.
   5. The disease occurs almost exclusively on premises feeding inadequately treated swill to pigs but, in an outbreak, infection is apparently transmitted by direct contact from pig to pig.
   6. The incubation period is usually between 24 and 96 hours but can be longer.
   7. Clinical signs:
      1. Vesicles and painful erosions on the snout, legs, oral mucosa, coronets, interdigital spaces, and occasionally udder and teats.
      2. Healing occurs within 2 weeks.
   8. Differential diagnosis
      1. Clinical signs are similar to other viral diseases including foot and mouth disease, swine vesicular disease, Seneca Valley virus, and vesicular stomatitis
      2. . The diagnostic tests typically used to confirm a presumptive clinical diagnosis include ELISA assays, reverse-transcription PCR, complement-fixation tests, serum neutralization tests and electron microscopic examination of epithelial tissue samples or tissue cultures.
      3. Treatment:
         1. There is no specific treatment.

References

Belsham GJ, Bøtner A, Lohse L. Foot-and-mouth disease in animals. Merck Manual 2021; https://www.merckvetmanual.com/infectious-diseases/foot-and-mouth-disease/foot-and-mouth-disease-in-animals.

Davies PR. Vesicular exanthema of swine. Merck Manual 2021; https://www.merckvetmanual.com/generalized-conditions/vesicular-exanthema-of-swine/vesicular-exanthema-of-swine.

Donaldson AI, Sellers RF. Foot-and-mouth disease. In: Diseases of sheep. Blackwell Publishing, Iowa, 2007; 282-288.

Grubman MJ, Baxt B. Foot-and-mouth disease. Clin Microbiol Rev 2004; 17: 465-493.

Lin F, Kitching RP. Swine vesicular disease: an overview. Vet J 2000; 160(3): 192-201.

Madin SH, Traum J. Vesicular exanthema of swine. Bacteriol Rev 1955; 19(1): 6.

Scott DW.  Large Animal Dermatology.  In: Viral Diseases.  W.B. Saunders, Philadelphia, 1998; 96 – 119.