Understanding shipping fever

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You are here: Home / Articles / Horse care

Karen Coumbe MRCVS

26 April, 2004

Most owners ensure that their horses are protected for a journey by bandaging limbs, supplying haynets, making sure they are safely tied up and checking that the lorry is roadworthy. Yet few think about the potential danger to the horse's lungs, which is probably the most crucial point.

Transporting horses for long distances is recognised as an important contributing factor in the development of respiratory disease, which can be a major, and potentially fatal, problem. Shipping fever (pleuropneumonia), is essentially a combined infection involving the lungs (pneumonia) and the pleural cavity (pleuritis).

There is minimal danger involved in a short trip to a local show, but increasingly large numbers of animals are now transported worldwide. Competition horses, family cobs and ponies are being flown across continents, while lorry loads regularly go back and forth between the UK and Europe. There are also animals doing lengthy domestic journeys.

The risk of the horse suffering from shipping fever increases with the duration of transport, but the length of the journey is not the only contributing factor.

Horses are trickle feeders and need to nibble continuously. When travelling they will consume less hay and water, so on a lengthy journey they run a risk of becoming dehydrated. Dehydration will impair lung defence mechanisms that normally help to clear infectious material.

If ventilation is inadequate, the horse may also be exposed to a higher concentration of irritants or allergens from the hay and bedding. In addition, ammonia from urine acts as an irritant to the airways, as do temperature extremes and overcrowding.

One of the biggest problems is that by being tied-up for the duration of the journey, the horse is stuck in an unnatural, head-high posture. Unable to put their head down, this will affect the clearance of mucus from the airways and cause bacteria to spread to the lower airways, causing infection.

The stress of travel also contributes to disease. Cortisol, the hormone produced by the body under stress, decreases immunity and the ability to combat infection, making the horse more susceptible to the bugs heading into the lungs.

Preventing problems

It may help to drain mucus from the airways by encouraging horses to lower their heads occasionally during travel, for example by feeding them titbits at floor level. This is one reason why it is important to ensure that the horses have rest breaks and are unloaded and allowed to move.

The air quality when travelling by road can be improved by good ventilation, but this is not so simple on a plane, where windows cannot be opened or dirty bedding easily offloaded. It will help to use a low-dust bedding material such as paper or cardboard on rubber matting and feed well-soaked hay or haylage.

It is important to ensure that horses are fit for the journey and do not have any ongoing respiratory problems. It is also advisable to check their temperatures before they travel. Consider delaying the trip if they have a high temperature before they start, as they could already be incubating an infection.

Warning signs

Signs of shipping fever include:

Lethargy, depression and loss of appetite
Cough
A nasal discharge, which may smell foul
A high temperature
If the pneumonia is severe, it is very painful for horses to breathe, so they take shallow breaths
The chest may be so sore that they do not want to move, pass dung or lie down. This can be mistaken for laminitis, colic or other illness

Diagnosis relies on the clinical signs, especially if recent travelling is reported, with an ultrasound scan used to detect fluid in the chest. If significant amounts of fluid are found, this may need to be drained and analysed to ensure appropriate treatment is prescribed.

Chest drains may be inserted and washing through sterile saline (pleural lavage) may help remove infection. Occasionally, the chest has to be opened to drain abscesses.

The likelihood of any affected horse returning to normal function depends on the severity of the disease. Survival rates range from 30% to more than 90%, and the chance of a full recovery is improved with early diagnosis and prompt and aggressive therapy. Any case is likely to need lengthy antibiotic therapy.

Other causes

While the majority of cases are associated with the stress of long-distance transport, pleuropneumonia can also occur:

After strenuous exercise, particularly in racehorses
After general anaesthesia and surgery
After infections such as strangles
As a follow on from inhalation pneumonia due to choke or other problems such as an inhaled foreign body
After a chest wound such as a broken rib or penetrating injury

This article was published in full in Horse & Hound (15 April 04). To purchase a back issue contact (tel: 020 8532 3628).