Respiratory infections whether caused by viruses or bacteria and sometimes mycoplasma are more common in younger horses, especially less than 4 years of age. Winter can actually be a good time for horses and bad time for people. For people, the reason we get more viral infections (colds, flu), and to a lesser extent bacterial respiratory infections, in Winter is because we spend more time with other people in enclosed spaces i.e. we have more close contact with more people than in Summer. For horses, the risk is when they are leaving the yard and going to mix with other horses. So the risk for horses with respect to infectious disease may actually be less in Winter and greater in the competition season.
There is also respiratory disease caused by irritants. Here we think of things like cold air, which is why you should not work horses with long term respiratory disease such as equine asthma syndrome (RAO, also known as COPD, Heaves, and IAD) hard on very cold mornings. Horses are also sensitive to common environmental pollutants such as PM10 (from car exhausts), SO2 (sulphur dioxide), NO2 (nitrogen dioxide) and ozone. If you do have a horse that’s prone to respiratory disease or has been diagnosed with any form of equine asthma then it’s worth monitoring the pollution and air quality and either not exercising or at least avoiding exercise at canter and gallop on low air quality days.
Allergic respiratory disease tends to occur in older horses and we don’t tend to see chronic respiratory diseases like equine asthma and SPAOPD (Summer Pasture Associated Obstructive Pulmonary Disease – essentially like RAO but horses are better inside as they develop allergy to primarily outdoor allergens such as pollen) developing until 6-7 years of age. With allergic respiratory disease this can be a risk all year round. More time in the stable in Winter and increased hay intake can increase exposure to moulds, forage mites and bacterial endotoxin – all potent respiratory allergens and especially for horses with equine asthma which usually show less symptoms out than stabled – the opposite to SPAOPD affected horses. During Spring, Summer and Autumn even when out horses can be susceptible to exposure to pollen and moulds. Again, older horses with equine asthma in particular can be worse at certain times of the year when turned out as they may be sensitive to both moulds which grow on trees, crops and shrubs and pollens.
SIGNS OF RESPIRATORY DISEASE IN HORSES
◦ Nasal Discharge at rest and or after exercise (of any colour and down one or both nostrils)
◦ Increased respiratory rate
◦ Increased respiratory effort
◦ Flaring of the nostrils
◦ Respiratory noise at rest or during exercise
◦ Poor recovery after exercise
◦ Generally lower performance than expected
If horses cough they almost certainly have respiratory disease (even if you only hear the odd cough). But horses do not cough regularly. Studies have shown that horses may cough once and then 3 hours later cough 6 times, then 12 hours later cough twice, etc. They do not cough regularly like people. So unless you fit a video camera or put a microphone in the stable or spend 24h with your horse you won’t know how much he coughs.
If your horse is NOT COUGHING, that unfortunately does not necessarily mean he is healthy and DOES NOT have respiratory disease. The only way to be sure your horse does not have respiratory disease is to have them scoped. How do we know this? There are a number of studies which have invited owners of “healthy” non-coughing horses to be ‘scoped.
Spring is a time when it is very common for horses to start to show respiratory symptoms such as cough or nasal discharge. Although this is often associated with horses being ridden more and or worked harder (which increases the deposition of allergens and irritants in the lungs) this is not the main reason. The main reason is that whilst pollen and mould levels are very low over Winter (November to February), things start to pick up for both Pollen and moulds in February/March and this is often triggered as you might expect by the odd warm early Spring day. February-March starts to see Hazel, Yew, Elm and Alder and to a lesser extent Willow, Poplar, Ash and Birch all producing pollen. Grass pollens don’t really come in until May-June-July.
If your horse is stabled overnight or most of the time, make sure you provide them with good air quality – steamed hay, sealed floor (e.g. ComfortStall from Haygain) and minimal low dust bedding (e.g. large woodchip). Keep windows and ventilation grills open at all times – you can always add more rugs. If your horse lives out and is being fed hay, then its still worth steaming to reduce inhalation of dust, pollen, bacteria and moulds.