Vesicular Disease: A persistent cause of Foreign Animal Disease investigation

In recent years, there has been an increase in the presence of vesicular lesions noted on swine, and consequently foreign animal disease investigations (Kasari, 2016). Vesicular diseases are a group of similar diseases in swine that produce a fever with vesicles (a fluid filled blister on the skin) that progresses to erosions (ulcers on the skin) that can occur on/near the mouth, snout, muzzle, teats and feet. Vesicular diseases that affect swine include, foot and mouth disease (FMD), senecavirus A, vesicular stomatitis (VS), vesicular exanthema of swine and swine vesicular disease. Any evidence of vesicular disease in swine must be investigated by a Foreign Animal Disease Diagnostician (FADD) – these are individuals who are state/federal employees that are specially trained to investigate suspect and confirmed FAD cases. Each suspect vesicular disease case must be thoroughly investigated as it closely resembles the clinical signs of FMD, a foreign animal disease (FAD). Foreign animal diseases, especially FMD, can have devastating animal health and economic impacts on the agriculture and food animal industry. Since FMD poses a threat to the United States, any lesions that present like blisters must be investigated by state/federal animal health officials through a foreign animal disease investigation to protect animal health and the agriculture industry.

Updated: 03/2023


This article will:

  • define vesicular disease
  • discuss causes for vesicular disease in swine
  • explain the response by producers, veterinarians and animal health officials
  • describe control and prevention strategies

What is vesicular disease?

A vesicular disease is a disease that usually produces a fever and fluid filled vesicles (blisters) that are normally present over the mouth, snout, and feet. Blisters easily rupture and are usually noticed as ulcers on the snout and hooves since pigs use their snout so frequently (Figures 1-4). In swine, there are a few common causes of vesicular disease; FMD, senecavirus A, vesicular stomatitis (VS), vesicular exanthema of swine and swine vesicular disease. There is no way to distinguish between these diseases based on clinical signs alone, so diagnostic testing on any vesicles must be done to rule out any disease that poses a threat to the United States (Kasari, 2016).

Foot and Mouth Disease (FMD)

FMD is a highly contagious viral disease of wild and domestic cloven hooved animals (Swine Disease Manual, FMD, 2018). The disease can affect swine, cattle, small ruminants and deer. FMD is known to spread large distances through the air and by indirect and direct contact. Clinical signs associated with FMD include a fever and blisters on the snout, nose, tongue, lips and coronary band of the feet (Swine Disease Manual, FMD, 2018). Due to these lesions, other clinical signs can be seen: such as, lethargy, decreased appetite or going off of feed. FMD does not carry a high death rate, but it does cause disease in many animals due to blisters in areas that are frequently used by pigs, like the snout and feet. Control of FMD is of major importance and can have a huge economic impact. If FMD were to ever enter the US, all animal movement would be stopped, any animals that are infected or near infected animals would be euthanized, international trading of pork and pork products would cease. No animals would be able to be imported or exported until the US is considered free of the disease. These actions would cause a loss of billions of dollars to producers and the entire agricultural industry. In countries where there is always widespread disease present, FMD vaccines are used to try to manage and eliminate the disease. FMD vaccines are not currently permitted in the United States.

Senecavirus A

Senecavirus A is a viral disease that presents similarly to FMD. Senecavirus A is spread from pig to pig and through their respiratory secretions. The signs of senecavirus A are very similar to

FMD and include fever, erosions, ulcers and blisters on the snout, mouth and feet (Senecavirus A CSFPH, 2017). Senecavirus A has been found in both commercial market and show pigs (Buckley, et al., 2022). It has been reported that senecavirus A may be linked to stressful events, such as shipping/transportation. Stress seems to accelerate the appearance of blisters (Buckley, et al., 2022). Neonates are reported to have an acute disease, while sows/gilts have the more classic lesions of disease (Rademacher et al., 2015). In recent years, senecavirus A cases in swine production have increased, prompting FAD investigations by state/federal animal health officials with each reported case (Rademacher et al., 2015). To test for senecavirus A, the best samples to take are fluid from blisters or swabs from any ulcers, this is only done by a FADD. Samples are then sent to a specific federal veterinary diagnostic laboratory for testing. There is currently no vaccine for senecavirus A, but work is being done to develop one for future use. The best way to prevent or control an outbreak of senecavirus A is to implement strict biosecurity protocols.

Vesicular Stomatitis (VS), Vesicular Exanthema of Swine, and Swine Vesicular Disease

Vesicular Stomatitis (VS), vesicular exanthema of swine and swine vesicular disease are all viruses that create vesicular lesions on the snout, mouth and feet. Compared to FMD and senecavirus A, these diseases are uncommon in the U.S. and rarely seen in production today (Swine disease manual, Vesicular Stomatitis and Vesicular Exanthema of Swine, 2018). Although these diseases are not common in the U.S., it is still a possibility they could cause a disease outbreak.

Response to Vesicular Disease

The response to vesicular disease involves communication and participation from multiple entities. Those entities include the producer, veterinarians, state animal health officials, and federal animal health officials. The first step in recognizing vesicular disease falls to the producer and employees that see the animals on a daily basis. If any blisters or ulcerations are noticed around the mouth, nose or feet, your veterinarian needs to be contacted (Animal Health Emergency Management, USDA APHIS, 2022). Your veterinarian should examine the animals and if vesicular lesions are noted, they will call the state veterinarian. A state/federal animal health official, specially trained as a Foreign Animal Disease Diagnostician (FADD), will be sent out to the farm to assess the animals. If they determine that the pigs have vesicular lesions, they will sample the lesions and send them to the USDA to determine if FMD is the cause of the lesion (Kasari, 2016).

If FMD is the cause, state and federal animal health officials will issue quarantines for the farm and farms around it. There will be no movement of animals, animal products or equipment to and from the premise. Then the stamping out/culling of affected and in-contact animals would go into effect to control the spread of disease. The last step is to thoroughly disinfect and clean the farm so that when new animals are allowed into the facility they do not contract the disease (Kasari, 2016).

If FMD or another FAD is not the cause, the producer has the option to determine the cause with their veterinarian but a response involving state/federal animal health officials would not occur.

Control and Prevention of Vesicular Disease

The best prevention strategy for vesicular diseases in swine is to have strict biosecurity protocols. There is a vaccine for FMD, but the use of it is a decision that is made among state and federal entities in the face of an outbreak (Animal Health Emergency Management, USDA APHIS, 2022) and it is not currently an option in the United States.


Vesicular diseases of swine produce fever and fluid filled blisters that are normally present over the mouth, snout, and feet. The most concerning vesicular disease is FMD, since it can have a devastating effect on the entire agricultural industry. Recently, there has been an increase in the presence of senecavirus A on swine farms, prompting FAD investigations. If vesicular lesions are noticed by producers/employees on a farm, a veterinarian needs to be contacted to determine if vesicular disease is present. If it is, then more animal health officials get involved to conduct a FAD investigation to hopefully rule out or prevent further spread of FMD.

Images of Vesicular Lesions

Figures 1-4. These are a few pictures of what vesicular lesions may look like. Immediately notify you veterinarian if these are noticed.

References and Citations

“Animal Health Emergency Management.” USDA APHIS | Animal Health Emergency

Management, 25 Oct. 2022,

Buckley, Alexandra C., and Kelly M. Lager. “Senecavirus A: Frequently Asked Questions.”

Journal of Swine Health and Production, 1 May 2022,

CFSPH. Senecavirus A – CFSPH. CFSPH Iowa State University College of Veterinary Medicine , 2017,

Kasari , Ellen M. “USDA Response to Senecavirus A.” 19 Dec. 2022.

Iowa State University College of Veterinary Medicine. “Foot-and-Mouth Disease (FMD).”

Swine Disease Manual: Index of Diseases,

Rademacher, Chris, et al. “Senecavirus a.” Iowa State University, 2015,

Recommendations from the Senecavirus a Working Group to Reduce Disruptions to Commerce

in the Pork Industry. 12 Oct. 2017,

United States, Congress, Iowa Department of Agriculture and Land Stewardship. Foreign

Animal Disease Investigation: Producer Guidance, Iowa Department of Agriculture and

Land Stewardship, pp. 1–1.

“Vesicular Stomatitis.” Iowa State University College of Veterinary Medicine,

“Vesicular Exanthema of Swine (San Miguel Sea Lion Viral Disease).” Iowa State University

College of Veterinary Medicine,