What Veterinarians Should Know About FMD Vaccination Strategies

Vaccination remains one of the most discussed and complex aspects of foot-and-mouth disease (FMD) control. While vaccines can significantly reduce disease spread and decrease losses during outbreaks, vaccination alone does not completely eliminate infection risk. For practicing veterinarians, understanding both the strengths and limitations of FMD vaccination is essential for making informed field-level decisions and guiding producers effectively. 

FMD vaccination strategies must balance disease control, surveillance, animal movement considerations, and long-term herd management¹. 

How Conventional FMD Vaccines Work 

Most conventional FMD vaccines are based on adjuvanted inactivated virus preparations¹. These vaccines are designed to stimulate protective antibody responses against circulating viral strains. 

One important challenge is that FMD virus exists in multiple serotypes: 

• O 

• A 

• C 

• Asia-1 

• SAT-1 

• SAT-2 

• SAT-3 

Immunity against one serotype does not provide reliable protection against another¹. This means vaccine matching becomes critically important during vaccination planning. 

The viral capsid, especially the VP1 protein, plays a major role in determining antigenicity and vaccine effectiveness¹. 

Vaccination Does Not Fully Prevent Infection 

One of the most practical realities veterinarians should understand is that vaccination does not completely prevent upper respiratory tract infection. 

Vaccinated animals may still: 

• Become infected 

• Develop subclinical infection 

• Carry virus in the upper respiratory tract 

• Progress to persistent infection² 

In many cases, vaccinated cattle may appear clinically normal while harboring infection. This creates important surveillance challenges during outbreak management. 

Vaccination primarily reduces: 

• Clinical severity 

• Virus shedding 

• Transmission risk¹ 

but it does not guarantee sterilizing immunity. 

Understanding the Carrier State in Vaccinated Animals 

Persistent infection remains one of the most debated challenges associated with FMD control. 

Approximately half of infected cattle may become carriers after recovery^3,4,5. Vaccinated animals exposed to virus may also enter a carrier state without developing obvious disease signs². 

This has important implications because: 

• Carrier animals complicate surveillance 

• Trade restrictions may continue 

• Monitoring programs become more intensive 

• Long-term control strategies become more difficult 

Routine oral swabs are insufficient for diagnosing persistent infection. Specialized probang sampling is required¹. 

DIVA Strategy: A Practical Surveillance Tool 

Modern purified vaccines attempt to remove non-structural proteins (NSPs) from vaccine formulations¹. 

This supports the DIVA (Differentiating Infected from Vaccinated Animals) approach, which helps veterinarians distinguish animals that have been vaccinated from those that have been naturally infected with FMD virus. 

Practical interpretation includes: 

• Antibodies against structural proteins may indicate vaccination 

• Antibodies against NSPs suggest previous infection⁴ 

However, this system is not perfect and depends heavily on vaccine quality⁴. 

For veterinarians involved in outbreak surveillance, understanding DIVA interpretation is extremely important during post-vaccination monitoring. 

Why Vaccine Matching Matters 

FMD virus evolves continuously through mutation and recombination^6,7,8. 

Because of this: 

• Poorly matched vaccines may provide inadequate protection 

• Epidemiological surveillance becomes critical 

• Vaccine selection must consider circulating strains 

Veterinarians should recognize that vaccine effectiveness depends not only on vaccination itself but also on how closely vaccine strains match field viruses. 

Future Directions in FMD Vaccination 

Research continues to explore newer vaccine platforms, including: 

• Virus-like particles 

• Recombinant vaccines 

• Vectored vaccines⁹ 

These approaches aim to: 

• Improve immune protection 

• Enhance safety 

• Reduce manufacturing risks 

• Improve differentiation between infected and vaccinated animals 

At present, conventional inactivated vaccines remain the primary tool for FMD vaccination programs. 

Practical Takeaways for Field Veterinarians 

When advising producers, veterinarians should remember: 

• Vaccination reduces disease impact but does not eliminate infection risk 

• Vaccinated animals still require surveillance 

• Biosecurity remains essential even in vaccinated herds 

• Vaccine handling and administration quality matter 

• Rapid detection remains critical despite vaccination 

Vaccination should always be viewed as one component of a larger disease-control strategy. 

Conclusion 

FMD vaccination is a powerful disease-control tool, but it comes with important practical limitations that veterinarians must understand clearly. While vaccines reduce clinical disease and transmission, they do not completely prevent infection or persistent carrier states. 

Successful vaccination programs depend on proper vaccine matching, strong surveillance, biosecurity, and continuous monitoring. For practicing veterinarians, combining vaccination knowledge with practical outbreak management remains essential for effective FMD control. 

References 

1. Arzt J, Sanderson MW, Stenfeldt C. Foot-and-mouth disease. Veterinary Clinics of North America: Food Animal Practice. 2024 Jul 1;40(2):191-203. https://www.sciencedirect.com/science/article/am/pii/S0749072024000033 

2. Stenfeldt C, Eschbaumer M, Rekant SI, Pacheco JM, Smoliga GR, Hartwig EJ, Rodriguez LL, Arzt J. The foot-and-mouth disease carrier state divergence in cattle. Journal of virology. 2016 Jul 15;90(14):6344-64. https://journals.asm.org/doi/pdf/10.1128/jvi.00388-16 

3. Stenfeldt C, Arzt J. The carrier conundrum; a review of recent advances and persistent gaps regarding the carrier state of foot-and-mouth disease virus. Pathogens. 2020 Feb 28;9(3):167. https://www.mdpi.com/2076-0817/9/3/167 

4. Bertram MR, Yadav S, Stenfeldt C, Delgado A, Arzt J. Extinction dynamics of the foot-and-mouth disease virus carrier state under natural conditions. Frontiers in Veterinary Science. 2020 May 20;7:276. https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2020.00276/pdf 

5. Hayer SS, Ranjan R, Biswal JK, Subramaniam S, Mohapatra JK, Sharma GK, Rout M, Dash BB, Das B, Prusty BR, Sharma AK. Quantitative characteristics of the foot‐and‐mouth disease carrier state under natural conditions in India. Transboundary and emerging diseases. 2018 Feb;65(1):253-60. https://www.academia.edu/download/52151567/Hayer_et_al-2017-Carrier_Extinction_India.pdf 

6. Brito B, Pauszek SJ, Hartwig EJ, Smoliga GR, Vu LT, Dong PV, Stenfeldt C, Rodriguez LL, King DP, Knowles NJ, Bachanek-Bankowska K. A traditional evolutionary history of foot-and-mouth disease viruses in Southeast Asia challenged by analyses of non-structural protein coding sequences. Scientific Reports. 2018 Apr 24;8(1):6472. https://www.nature.com/articles/s41598-018-24870-6.pdf 

7. Bachanek-Bankowska K, Di Nardo A, Wadsworth J, Mioulet V, Pezzoni G, Grazioli S, Brocchi E, Kafle SC, Hettiarachchi R, Kumarawadu PL, Eldaghayes IM. Reconstructing the evolutionary history of pandemic foot-and-mouth disease viruses: the impact of recombination within the emerging O/ME-SA/Ind-2001 lineage. Scientific Reports. 2018 Oct 2;8(1):14693. https://www.nature.com/articles/s41598-018-32693-8.pdf 

8. Fish I, Stenfeldt C, Spinard E, Medina GN, Azzinaro PA, Bertram MR, Holinka L, Smoliga GR, Hartwig EJ, de Los Santos T, Arzt J. Foot-and-mouth disease virus interserotypic recombination in superinfected carrier cattle. Pathogens. 2022 Jun 3;11(6):644. https://www.mdpi.com/2076-0817/11/6/644 

9. Diaz-San Segundo F, Medina GN, Stenfeldt C, Arzt J, de Los Santos T. Foot-and-mouth disease vaccines. Veterinary microbiology. 2017 Jul 1;206:102-12. https://www.sciencedirect.com/science/article/am/pii/S0378113516308033