Livestock Vaccine
1. What is Foot and Mouth Disease (FMD)?
FMD is a highly contagious viral disease affecting cloven-hooved animals, including cattle, swine, sheep, and goats. It also affects wildlife like deer and antelope; notably, the African buffalo can carry the virus without showing symptoms.
In non-vaccinated populations, the morbidity rate can reach 100%. While rarely fatal in adults, it causes extreme suffering and can be lethal to young animals.
2. What causes FMD?
The disease is caused by an aphthovirus from the Picornaviridae family. There are seven immunologically distinct types: A, O, C, SAT1, SAT2, SAT3, and Asia1. Because there are many genotypes within these types, vaccines must be specifically matched to the circulating field strain to be effective.
3. What are the clinical signs?
Signs vary by species and age, but the hallmark symptom is the appearance of vesicles (blisters).
- Location: Muzzle, tongue, lips, mouth, between toes, and on teats.
- Behavioral signs: Extreme lameness (due to ruptured blisters on feet), hypersalivation (drooling), and reluctance to eat.
- Production loss: Fever, depression, rapid weight loss, and a severe drop in milk production.
4. How is FMD transmitted?
The virus is found in all excretions (saliva, milk, semen, etc.). It spreads via:
- Direct Contact: Introducing infected animals to a healthy herd.
- Fomites: Contaminated vehicles, clothing, footwear, or equipment.
- Ingestion: Feeding raw or improperly cooked infected animal products (swill feeding).
- Aerosol: The virus can travel through air currents over long distances.
- Laboratory/Manufacturing: Accidental release or production errors in live-virus vaccines.
5. Where is FMD found globally?
FMD is endemic in much of Africa, the Middle East, and Asia (including India). Most of Latin America uses zoning to maintain FMD-free status. Currently, North America, Western Europe, Australia, New Zealand, and Indonesia are recognized as FMD-free.
6. Why is FMD considered such a serious problem?
While not a major public health risk (human infection is rare and mild), FMD is an economic catastrophe. An outbreak triggers an immediate closure of export markets for meat, dairy, and wool.
Note: The 2001 UK outbreak showed that tourism and rural communities can take over a decade to recover. In Australia, a major outbreak is estimated to cost the economy between $8 billion and $13 billion.
7. Does an FMD vaccine exist, and how does it work?
Yes. Health authorities recommend inactivated virus vaccines. These are chemically treated so they cannot reproduce. Modern “highly purified” vaccines are preferred because they allow veterinarians to differentiate between infected and vaccinated animals (DIVA strategy).
8. What is the recommended vaccination schedule?
For cattle, the standard protocol is:
- Primary Dose: 4 months of age.
- Booster Dose: 1 month after the first injection.
- Revaccination: Every 6–12 months, depending on local regulations and the local viral challenge.
9. How safe are these vaccines?
FMD vaccines are highly regulated. Although virulent virus is used in manufacturing, the final product is strictly controlled to ensure the virus is completely inactivated. Field tests are conducted to ensure efficacy and monitor for any adverse reactions before public authorization.
10. Why might a vaccination program fail?
Success depends on “herd immunity.” Several factors can lead to “breakthrough” infections:
- Coverage: Less than 90% of the herd being vaccinated.
- Viral Load: A heavy “viral challenge” from nearby infected farms can overwhelm a vaccinated animal’s immunity.
- Incubation: The short 48-hour incubation period makes post-exposure vaccination difficult.
- Animal Health: Parasites, immunosuppression (from drugs like Corticosteroids), or poor nutrition can weaken the immune response.
Pro-Tip: Always deworm animals 1–2 weeks before vaccination to ensure a strong immune response.
11. How should the vaccine be stored?
FMD vaccines are temperature-sensitive. They must be stored in a cold chain between 2°C and 8°C (35°F – 46°F). Freezing the vaccine will destroy its effectiveness.
12. Which strains are currently recommended?
The OIE (World Organisation for Animal Health) recommends strains based on global matching studies. Current global strains include O1 Manisa, A22 Iraq, and Asia1 Shamir. However, using local isolates is often crucial for inducing the best protection against regional outbreaks.