by About the disease
FMD is endemic in parts of Asia, Africa, and South America. The virus is easily transmitted through direct contact between infected and susceptible animals or indirectly via people, vehicles, equipment, air, aerosols and fomites carrying the virus. All cloven-hooted animals like cattle, sheep, goats, pigs, deer are susceptible to the disease. But cattle are the most affected. Once infected, the animal suffers from blister-like lesions in and around the mouth as well as between the hoofs. This causes pain and lameness restricting movement and feeding. High fever, reduced milk production are other symptoms. Though mortality is low, morbidity can reach 100% in susceptible populations. Recovery takes 2-6 weeks but the virus may remain in some recovered animals and under favorable conditions get transmitted to other susceptible hosts.
Economic impact of FMD
FMD outbreaks have huge economic consequences due to reduced productivity and international trade restrictions. Milk yield drops by 40-60% in infected dairy cattle. Draft animals show reduced work capacity affecting agricultural activities. In meat producing animals, weight loss occurs due to lameness and inappetence. Depending on husbandry systems and species affected, a single FMD outbreak can cause direct production losses up to USD $120 million annually for a small country. Countries free from Foot and Mouth Disease Vaccine lose markets worth billions as importing countries ban livestock and their products from affected regions. During the 2001 FMD outbreak in UK, over 6 million animals were slaughtered at a cost of over £8 billion and losses of over £5 billion to rural economy. Thus, controlling and preventing FMD has economic significance at national and international levels.
Foot and Mouth Disease Vaccines
Broadly two types of vaccines are available – chemically inactivated/alum precipitated vaccines and live, attenuated vaccines. Chemically inactivated vaccines employ chemically treated (inactivated) strains of the virus thus rendering them non-infectious but retaining essential antigenic properties to induce protective immunity. These are considered very safe as there is no risk of virus replication or spread. However, their efficacy is limited to 4-6 months requiring booster doses. Also, they cannot differentiate infected from vaccinated animals.
Live vaccines employ carefully attenuated (weakened) strains of Foot and Mouth Disease Vaccine virus that have lost virulence but retained immunogenicity. They replicate in vaccinated animals providing long lived protection of 12-24 months or more with a single dose. Since they replicate locally, they also stimulate mucosal immunity crucial for preventing virus transmission. Newer marker vaccines incorporate specific cell markers or DNA sequences that help distinguish vaccinated from infected animals using laboratory tests.
Status of vaccination in different regions
In FMD free regions like EU countries, USA, Australia and New Zealand stamping out is practiced without vaccination to maintain disease-free status. Rapid culling of infected and in-contact animals is done to eradicate the virus.
In endemic regions of Africa and parts of Asia, emergency ring vaccination combined with movement control remains the primary strategy to curb outbreaks. Live vaccines play a key role due to their ability to block virus transmission from livestock keeping communities where re-introduction is common. Countries like India follow a strategized vaccination program along with zoning and movement control.
South America has extensive FMD vaccination programs using inactivated vaccines every 4-6 months with additional emergency vaccination during outbreaks in Brazil, Argentina, Uruguay etc. However, regular re-introductions occur from wildlife reservoirs in the region posing a continuous challenge.
Vaccination strategies for control
Based on epidemiology, livestock demography and resources, countries plan customized FMD control strategies using vaccines. Emergency ring/mass vaccination quickly builds herd immunity around outbreak sites. It may be combined with culling in severe situations.
Routine/strategic vaccination involves annual/biannual immunization of high risk populations and areas near international borders or trade routes preventing introduction and spread. Vaccine choice considers duration of protection, differentiation of infected from vaccinated, genetic/antigenic match with prevalent strains etc.
Newer approaches include marker vaccines, vaccination zoning, vaccination assisted stamping out helping facilitate disease control and trade. Continuous research to develop economically feasible thermostable, polyvalent and differentiating vaccines adapting to field conditions will strengthen global efforts against this economically devastating disease.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
