Infectious Diseases
Infectious and contagious diseases
Contagious diseases such as Strangles and diarrhoea can cause severe illness in horses, requiring intensive care and management. At the RVC, we have a purpose-built, dedicated Isolation Unit that allows us to treat horses with potentially contagious diseases, whilst at the same time preventing spread of the disease to other horses. Horses housed in the Isolation Unit receive round-the-clock monitoring and intensive care, and also have access to state of the art diagnostics.
Strangles, and diarrhoea, are two of the most frequent reasons that horses will need to be housed in isolation units.
Strangles
Strangles is a contagious disease of horses caused by a bacteria called Streptococcus equi (S equi). Horses acquire the infection from other horses, who may or may not be showing signs of the disease. Horses with Strangles typically have a fever, nasal discharge and swollen lymph nodes. (picture) The lymph nodes may form abscesses, which can then burst and drain purulent material (‘pus’). Most horses with Strangles will recover uneventfully, but in about 20% of horses complications will occur. In fact, the name ‘Strangles’ comes from one of these complications – the lymph nodes which surround the larynx and pharynx (the throat) may become so enlarged that the block flow of air, hence the horse sounds like it is being ‘strangled’. In these cases, a tracheotomy, or ‘trach tube’ where a temporary hole is made into the trachea (the windpipe) is necessary to allow the horse to breathe. (picture) Horses with a trach tube in place require close monitoring to ensure that the airway remains open; at the RVC, we can provide this level of care to horses.
Most horses with Strangles will no longer be contagious after a few weeks following resolution of clinical signs. However, in some horses, the bacteria can ‘hide’ in the guttural pouches, which are paired air filled sacs that lie on either side and above the larynx.(diagram) Identifying these so called 'carrier horses' is an important part of investigating a disease outbreak, to make sure that the yard or farm is clear of the disease. In some horses, abscesses which form on the floor of these sacs burst and discharge pus. The pus can then solidify, to form chondroids, and it is these horses that can continue to pass on the bacteria to other horses, without showing any signs of disease. Identifying these horses can only be done by using endoscopy to visualise within the guttural pouch, and then obtaining samples of the pus or chondroids to confirm the presence of the bacteria. If chondroids are identified, they need to be removed. A specialised ‘basket’ is passed via the endoscope and the chondoids removed one by one. (picture)
The HBLB has developed guidelines to help with managing horses with Strangles. It is available to download from their website: HBLB Codes of Practice.
Diarrhoea
Although mild diarrhoea is often associated with a change of feed or a stressful episode, severe diarrhoea can be a life threatening disease in foals and horses. These are often our most critically ill patients, and require intensive care and treatment. Some of the causes of diarrhoea, such as Salmonella ( a bacteria) can be passed from horse to horse, and also from horse to person, so it is essential that these horses are housed in Isolation to prevent transmission of disease. Horses with diarrhoea can rapidly become severely dehydrated (in some cases they may lose as much as 100 litres of diarrhoea in a day), and will typically need to be put on intravenous (IV) fluids (a ‘drip’) to replace the fluid they are losing. They can also lose a lot of electrolytes in the diarrhoea, which need to be replaced in the fluids; this requires careful and frequent blood sampling to ensure the correct supplementation is being given; our on-site clinical laboratory allows us to run samples 24 hours a day, 7 days a week, ensuring horses are given optimal care and treatment. Many horses with diarrhoea are depressed and off their feed. We pay significant attention to the diet of these horses; we have many different feed types to ‘tempt’ them to eat, and can offer them small meals around the clock. Because nutrition plays a very important part of recovery from any severe illness, we are very pro-active with inappetent horses, especially foals that have very small reserves of energy to draw on if they do not eat. We have the ability to ‘tube feed’ horses, or, if this is not possible, to provide ‘parenteral nutrition’ – that is, nutrition via the vein. This requires checking of blood sugar levels several times a day, as well as monitoring electrolyte levels daily. All of this can be performed in the horses who are housed in the Isolation Unit.