Prevention of bacterial respiratory infections, such as Strangles, bacterial pneumonia and pleuropneumonia (travel sickness or shipping disease), is very important.

Otherwise longterm damage to the lungs and loss of performance potential can result, or even death.


Strangles is a bacterial infection of the upper respiratory system caused by colonization of the bacteria Streptococcus equi in the throat area and lymph nodes behind and under the jaw.

Outbreaks are most likely to occur on studs, agistment and boarding stables when horses carrying the infection are introduced. Nasal discharge from infected horses spread the disease to other horses via feed or pasture, and flies and birds can transfer it from feeder to feeder over a relatively wide area.

In the first 3 – 7 days signs of infection include depression, loss of appetite, elevated temperature above 39°C, heat, pain and swelling of the lymph nodes under the jaw. After 7 – 10 days the lymph nodes may burst open to release yellow, smelly pus. Open draining abscesses and nasal discharges actively spread the infection.

Infected horses should be isolated and strict feed and environmental hygiene practiced to contain the spread of infection. Consult your vet for advice on therapy, as the stage of infection is critical to long term recovery.

Treatment with antibiotics is strictly targeted in the first 4 – 7 day period. Vaccination is available. It does not guarantee protection against the virus but can limit the duration and severity of the disease. Vaccination of non-infected horses may be worthwhile to restrict the spread. Again, consult your vet for advice.

Bacterial pneumonia

Bacterial pneumonia often follows viral infections or other stressful events such as racing, transport, overcrowding or anaesthesia, which lower the natural lung defense mechanisms. Bacteria are carried into the damaged airways and air sacs on dust inhaled from feed, bedding or working surfaces. A wide range of common bacteria has the potential to develop infection and cause pneumonia.

Common signs include a raised temperature, increased rate and difficulty of breathing, discoloured nasal discharge, and respiratory distress with wheezing and coughing during light exercise. In severe cases, the horse becomes lethargic and loses gum colour due to poor oxygen uptake. Diagnosis is a job for your vet using tracheal swabs or BAL lung wash, with appropriate cell counts and sensitivity tests.

Severe infection can cause long term scarring of the lungs and loss of performance potential. Treatment with injectable, oral or nebulised antibiotics and the use of bronchodilators in the feed or via an Equine Aeromask system will aid in clearance of accumulated secretions. Measures to reduce dust in feed and bedding, and feeding at ground level to encourage lung drainage is recommended. Consult your vet for advice.

Pleuropneumonia or 'travel sickness'/'shipping disease'

Horses that have raced or been subjected to strenuous exercise immediately prior to long distance traveling are particularly prone to developing pleuropneumonia, which if not recognized and treated early, is invariably debilitating and may be fatal.

Low-grade viral infection, breathing contaminated air in poorly ventilated transports and the stress of travel appear to be the main underlying causes. Travel stress includes noise, cramped spaces, high speed driving, swaying of trailers and inadequate rest stops. The risk of travel sickness is increased if horses are unable to put their heads down (‘short tying’) to drain normal respiratory secretions.

Transporting horses that are suffering from underlying viral disease, or are tired and dehydrated after racing or competition increases the risk. Dusty feed and hay containing bacterial germs and moulds, and breathing in dust from roads, results in inhaled contamination, which overloads the lungs’ defense system. Unfortunately, many modern ‘streamlined’ floats and horse transports are often poorly ventilated.

Early signs include depression, fever, loss of appetite and rapid, shallow breathing. These early signs may be confused with colic, as horses resist moving, stand with the front legs apart, and paw at the ground. As the condition worsens, the horse may turn to look at its painful chest. Immediate veterinary advice should be obtained. Unfortunately, once pleuropneumonia worsens, it is difficult to treat, and can result in death within 3 – 5 days.

Prevention of pleuropneumonia

  • Always ensure horses are cooled down, and given a drink before long distance travel, and delay travel overnight for very tired, dehydrated or stressed horses if a very long trip is planned
  • Ensure sufficient ventilation to keep air flowing without causing chills
  • Provide dampened feed or pellets to reduce dust and airborne contamination, and locate feeders below chest bar height
  • Do not tie the head too short so the horse can put its head down
  • Avoid transporting horses suffering from respiratory disease
  • Ensure the trailer is in good condition and level on the tow bar, drive steadily and smoothly
  • Stop every 3 – 4 hours and open the trailer doors. If possible, unload and allow the horse(s) to walk, or preferably graze or feed with the head down for at least 15 – 20 minutes. Provide access to drinking water and dose with a rehydration drink such as Recharge over the tongue to replace electrolytes and stimulate drinking.
  • If a horse has competed or raced hard, give it a day off after a long trip. Place dampened feed at floor level or let it graze in a grassy, green paddock for a few hours to encourage drainage of the respiratory system
  • After travelling a horse over a long distance, keep a careful watch for loss of appetite, depression, fever and obvious discomfort fir the first few days. Seek veterinary advice if the temperature is elevated (over 38.5°C).