Foot-and-Mouth Disease (FMD)

Foot-and-mouth disease (FMD) is a highly contagious viral disease that affects artiodactyls, including cattle, pigs, sheep, and goats. The disease is prevalent in Asia, Africa, the Middle East, and South America, seriously endangering the healthy development of animal husbandry and the foreign trade of related animal products. Given this, OIE has listed it as a class A infectious disease. BioVenic, as a leading animal diagnostics company, can help customers solve problems related to FMD.

Cause and Effects

FMD is caused by the foot-and-mouth disease virus (FMDV), a member of the Picornaviridae family and the Aphthovirus genus. The diameter of FMDV virus particles is 20-25 nm, spherical, without an envelope, and it is the smallest one among RNA viruses.

FMDV is known for its high mutation rate, and there are seven serotypes of O, A, C, SAT1, SAT2, SAT3, and Asia-1 and dozens of subtypes. There is no cross-immunity between different serotypes, which poses a challenge to the effective control and prevention of FMD.

Fig.1 Virion structure of FMDV.^1,2

The impact of FMDV is far-reaching, affecting individual farms and entire countries. The disease causes severe economic losses due to reduced productivity, loss of export markets, and trade embargoes imposed on affected regions.

Epidemiology

• Source of Infection: The source of infection of FMD is generally sick animals and stealth-infected animals, and the virus content in the blister fluid is relatively high.
• Transmission Routes: FMD spreads through direct contact with infected animals, exposure to contaminated materials, and respiratory droplets.

Fig.2 The speed of FMDV transmission is related to the number of infected animals.^3,4

• Susceptible Animals: Under natural conditions, FMDV can infect a variety of animals. Artiodactyla animals have the highest susceptibility, and the order of susceptibility is cattle, pigs, sheep, and camels.
• Epidemic Characteristics: It is often epidemic or pandemic, has a certain periodicity, and has the characteristics of rapid and long-distance transmission.

Public Health Risk

FMD poses minimal risk to human health. In rare cases, humans can become infected with the virus, usually resulting in a mild illness with flu-like symptoms. The main concern with FMD is its impact on livestock, food security, and the economy.

Pathogenesis

Upon infection, FMDV replicates in the epithelial cells of the mouth, nose, and other susceptible areas. The virus causes damage to the epithelial lining, leading to the formation of vesicles. These vesicles rupture, releasing viral particles and further spreading the infection. The immune response plays a critical role in the pathogenesis of FMD, as both innate and adaptive immune mechanisms contribute to disease progression and recovery.

Signs and Symptoms

The severity of symptoms depends on the type of virus strain, the amount of exposure, and the infected animal's age, species, and immunity. In susceptible animals, the incidence can reach 100%. The mortality rate of adult animals is generally low, ranging from 1% to 5%; the mortality rate of calves, lambs, and piglets is relatively high, reaching 20% or higher.

Typical clinical symptoms include the formation of blisters and plaques on the oral mucosa, lower extremities, and breasts. Bursting blisters can cause lameness and reluctance to move. Blisters usually heal within 7 days, but open blisters are prone to secondary bacterial infections.

Other common symptoms include fever, depression, salivation, loss of appetite, weight loss, stunted growth, and decreased milk production, which persist even after recovery.

Fig.3 Characteristic symptoms of pigs infected with foot-and-mouth disease.^5,6

Diagnosis of FMD

Virus isolation and identification is a traditional diagnostic method, and BioVenic usually develops immunodiagnostics and molecular diagnostics solutions for its customers, such as RT-PCR, and ELISA.

• RT-PCR: Real-time RT-PCR can sensitively detect the FMDV genome in suspicious samples.
• ELISA: ELISA is the preferred laboratory diagnostic technique. It can not only detect FMDV antigen but also identify the serotype of the virus.

Treatment

There is no specific treatment for FMD in animals. Supportive care measures may be permitted in countries where FMD is endemic, including,

• Provide soft feed to ease eating.
• Foot baths to relieve lameness.
• To prevent secondary bacterial infections, maintain good hygiene practices.

Prevention and Control

• Before the animals enter the field, the livestock house is fully and strictly disinfected. After the animals enter the field, do a good job of sanitation and disinfection.
• When introducing species, strict quarantine must be carried out to avoid the introduction of breeds or young animals with FMDV.
• In areas without FMD, once FMD-infected animals are found, report the outbreak immediately. In addition to culling sick animals and treating them harmlessly, livestock houses, drinking water, feed, venues, and contaminated items are also strictly disinfected.
• Compulsory immunization strategies are implemented in FMD-endemic areas. In areas without FMD, once an outbreak of FMD occurs, vaccination may be considered to limit the spread of the disease. BioVenic can research vaccines with good safety and high immunity for customers.
• Strengthen feeding management, scientifically feed animals, and improve the disease resistance of susceptible animals such as pigs, cattle, and sheep.

BioVenic is committed to contributing to the control and prevention of foot-and-mouth disease. We help customers develop innovative diagnostic solutions, including rapid, accurate testing methods, reagents, and kits. We also help veterinary researchers develop effective vaccines that provide broad protection against different strains of foot-and-mouth disease. If you would like more information, please feel free to contact us.

References

1. Kotecha, Abhay, et al. "Rules of engagement between αvβ6 integrin and foot-and-mouth disease virus." Nature communications8.1 (2017): 15408.
2. Image retrieved from Figure 1 "Apo and holo αvβ6-FMDV complexes." Kotecha, Abhay, et al., 2017, used under [CC BY 4.0], the image title was changed to "Virion structure of FMDV."
3. Arzt, Jonathan, et al. "Quantitative impacts of incubation phase transmission of foot-and-mouth disease virus."Scientific reports9.1 (2019): 2707.
4. Image retrieved from Figure 2 "Experimental design, FMDV transmission study." Arzt, Jonathan, et al., 2019, used under [CC BY 4.0], the image title was changed to " Fig. 2 The speed of FMDV transmission is related to the number of infected animals."
5. Stenfeldt, Carolina, et al. "The pathogenesis of foot-and-mouth disease in pigs."Frontiers in veterinary science 3 (2016): 41.
6. Image retrieved from Figure 1 "Progression of foot lesions in pig infected with FMDV A24 Cruzeiro at 2 (A) and 24 (B) days after intraoropharyngeal inoculation." Stenfeldt, Carolina, et al., 2016, used under [CC BY 4.0], the image title was changed to "Characteristic symptoms of pigs infected with foot-and-mouth disease."