Foot-and-Mouth Disease (FMD) is a highly contagious viral disease that primarily affects cloven-hoofed animals like cattle, swine, sheep, goats and deer. While it does not generally pose serious health risks to adult animals, the disease can cause pain, illness and loss in productivity. However, the biggest concern with FMD is its potential to severely impact the livestock industry and international trade. Well-developed vaccination strategies have proven effective in preventing and controlling outbreaks of FMD across the world.
What is Foot-and-Mouth Disease?
Foot-and-mouth disease virus (FMDV) belongs to the Aphthovirus genus of the family Picornaviridae. There are seven distinct serotypes of FMDV which means that infection with one serotype does not provide protection against another. FMDV is highly contagious and can spread rapidly between susceptible animals through direct contact and airborne transmission via aerosols from infected animals. The disease mainly causes blisters or vesicles (blister-like swelling) in the mouth and on the feet of infected animals which gives rise to the name of the disease.
While adult animals usually recover from the disease itself, FMD has serious production impacts via decreased milk and meat yields. It can also lead to abortion in pregnant animals. Mortality rates are typically low except in young animals. This viral disease is endemic in parts of Asia, Africa, and South America where vaccination is not regularly practiced. However, many parts of the world including the European Union, Australia, New Zealand, North America and some others are FMD-free following vaccination programs and strict import regulations.
Vaccination Strategies for FMD Control
Vaccines play a central role in preventing FMD outbreaks. Several vaccine types are available and national control programs are tailored based on epidemiological factors. Broadly, vaccination strategies fall under the following categories:
- Emergency Vaccination: Used during outbreaks to quickly vaccinate susceptible animals and curb further spread of infection. It aims to establish a buffer zone around infected areas.
- Protective Vaccination: In non-infected regions, animals are routinely vaccinated to prevent incursion of the disease. Revaccination at regular intervals is required to maintain protective immunity levels.
- Preventive Vaccination: Practiced in endemic regions to reduce disease incidence and transmission. Combining vaccination with other measures like movement control helps contain the virus.
- Eradication Vaccination: Once an outbreak is controlled, this helps eliminate the last foci of infection and establish country-wide freedom from disease. Surveillance is critical along with quarantine measures.
FMD Vaccine Types
The most widely used Foot and Mouth Disease Vaccine vaccines today are inactivated or chemically-treated vaccines prepared from infected live-animal tissues in cell culture. These provide good protection and have advantages like:
- Safety: Highly purified and inactivated - cannot cause disease in vaccinated animals.
- Efficacy: Elicit both innate and adaptive immune responses for quality protection. Can be tailored to provide coverage against multiple serotypes.
- Thermostability: Certain new-generation vaccines have enhanced stability at higher temperatures facilitating transportation and storage in tropical climates without refrigeration.
- Rapid Response: Large quantities can be rapidly manufactured within weeks to respond effectively to outbreak emergencies.
Apart from conventional vaccines, newer technologies like DNA vaccines, adenovirus-vectored and synthetic peptide-based FMD vaccines are being evaluated for their potential to overcome some present limitations and support disease eradication programs. However, more validation of their efficacy and safety under field conditions will be required.
Vaccination Challenges and Recommendations
While vaccines are very effective, obstacles remain in managing FMD globally due to factors like:
- Antigenic Difference: Vaccines must be updated each season to match circulating field virus strains for continued high protection. Surveillance allows this.
- Poor Livestock Infrastructure: In developing nations, delivering multi-dose vaccination schedules to scattered villages can be challenging requiring innovative approaches.
- Cost Considerations: Recurrent vaccination programs demand substantial funding which may not always be available.
- Cross-Border Trade Risks: Movement of animals and animal products across borders where vaccination status can vary, requires strict import-export controls to prevent re-entry of the virus.
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