Kate Southorn explains more about how you can protect your horses from contagious respiratory diseases.
We have all been there, a new horse arrives on the yard and within 2 weeks it is coughing and has a snotty nose and a high temperature.
Invariably if they are in internal stables or on a large yard, there is contact with many other horses either directly or via yard staff or equipment. They may have been turned out with another set or horses, so the “in-contact” group covers most of the yard.
Even on a yard with stringent isolation of new horses, there is a risk of picking up infections when out competing, particularly where you are stabling at events.
Challenges of Contagious Respiratory Infections
Contagious respiratory infections in horses are a major concern for vets and horse owners alike. One of the main challenges is managing lots of owners, who may be using different veterinary surgeons as a yard group and diagnosing the cause of the infection. The key to managing disease outbreaks is individual horse owners and yard staff working as a team to control the spread of infection.
There are 2 main causes: bacteria (eg. Streptococcus Equi Equi, “strangles”) and viruses (e.g. Equine Influenza, Equine Herpes Virus 1 and 4). Testing for infection involves taking nasopharyngeal swabs (3 are required at 1 weekly intervals as Strangles bacteria are notoriously difficult to detect), a guttural pouch wash via endoscopy or blood tests checking for an immune response (serology). The body needs time to develop an immune response, so 2 samples are taken with a 2-week gap between them and horses are often only positive on the second sample. This means that in this scenario, it would take a minimum of 2 weeks for vets to be able to confirm that the cause of the problem is NOT strangles, however positive result at any point would suggest that it is. Sadly, there is no short cut to excluding Strangles in this scenario.
The serology blood test may be positive in horses that have been previously exposed to strangles and those that have been vaccinated against it. Neither the vaccine nor previous infection or a positive serology will protect the horse from a new strangles infection. We expect those horses to show reduced illness when infected but they can still be infected and become long term infectious as a result of the current outbreak. In these horses the blood test will NOT help us decide if they have an infection this time, so swab or lavage are the only options. Horses that show a positive response on serology may or may not be persistently infected and require further testing to confirm the absence of active and potentially contagious Strangles disease. In these cases we recommend a guttural pouch lavage, as this is the common site for persistent infection.
So How Can You Protect Yourself From Contagious Infections?
Whilst vaccination is highly effective at reducing the spread and severity of respiratory diseases in the community of horses as a whole, they do not prevent infection in individuals but will reduce morbidity (severity of signs of disease) this applies to influenza, EHV and strangles vaccines. Hygienic management practices at home and whilst competing are the most effective strategy. Blood testing new horses before they enter the yard can be helpful, however as it takes 2 weeks for a horse to become positive after infection, it is not a good alternative to proper isolation procedures. Ideally new horses should be isolated for 4 weeks, as the incubation period for most respiratory infections is 3 weeks. Horses should not share stables, buckets, bridles and hay nets, unless they are disinfected between animals. When travelling and at shows avoid giving lifts to horses from other yards and take your own buckets, forage and water supplies. Do not used shared troughs, bacteria persist for long periods in damp, dark places. Avoid direct contact with other horses and their handlers or letting your horse graze in communal areas. Fresh bedding should be used in temporary stabling and surfaces such as door tops/windows should be wiped with disinfectant wipes. Most disinfectants and hand sanitisers will kill strangles bacteria, so remember cleanliness is still the most effective way of preventing infections.