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Herd immunity

The current pandemic has led to a broader understanding of the importance of herd immunity, but is herd immunity also a concern for our horses and how exactly do we go about creating it?

What is herd immunity?

Herd immunity occurs when a significant portion of the herd has been vaccinated against, or developed immunity to, a particular contagious condition. It allows for individuals who have not developed immunity yet to have a measure of protection against the contagious disease.

Why is herd immunity important?

Herd immunity minimises the spread of some contagious diseases, such as equine influenza. If the majority of horses are vaccinated against/immune to these contagious diseases, there will be a reduction in the circulation of these diseases in the population. This is because if only a low number of animals are susceptible to an illness spread of the disease is much less likely to occur. This reduces the chance of an outbreak.

It is, however, worth noting that this is only the case for diseases that pass from person to person or animal to animal. For other diseases like tetanus and AHS, vaccination of one or more horses in the herd has no effect on the susceptibility of the unvaccinated animal. This is because the spread is not from animal to animal but rather through an independent vector – a bacterium in the case of tetanus, and a midge in the case of AHS.

Take home message

Herd immunity is something that is worth discussing with your vet or yard owner, especially if you are considering moving a young horse to a new yard or situation. However, ultimately you need to get your horse vaccinated against all relevant diseases to ensure optimal protection against these potentially life-threatening conditions.