"No hoof, no horse" is a familiar saying, but "no lungs, no horse" is equally true. Respiratory infections are the most common infectious diseases of horses. The acute infection in horses can sideline your horse anywhere from a week to a month. Worse yet, complications can have even more serious and long-lasting effects for your horse.
The symptoms of respiratory-tract infection are hard to miss, and are the same for horses as they are for you. These include:
• Runny nose/nasal discharge-clear to yellow or white
• Often runny eyes or eye inflammation
• Cough-from dry to very moist
• Depression/lethargy (seems sick)
• Poor appetite (both from feeling ill and throat pain)
• Changes in breathing pattern (normal respiratory rate is 6 to 8 breaths per minute)
Respiratory Tract Invaders
There are several primary causes of respiratory tract infections. Identifying what's at the root of the horse's problem will make it faster and easier to get him into recovery and minimize the chance of any lasting damage. Here are some of the immediate considerations.
Bacteria: Strangles is the most well known bacterial respiratory tract infection. It usually remains confined to the upper portions of the respiratory tract (throat and local lymph nodes), but can sometimes also involve the lungs. At least 10% of strangles cases will end up with chronic infections in the guttural pouches.
A wide variety of bacteria can infect the lungs and cause pneumonia. In otherwise healthy adults, this usually occurs after the lung has been irritated by a virus infection, or in horses with weak lungs because of chronic allergic disease. Heavy exercise and shipping are also risk factors for developing bacterial pneumonia (and viral infections), because they cause a temporary weakening of the immune system. Both foals and aged horses, which have weaker immune systems, may be more susceptible to bacterial invasion of the lungs.
- Differentiating the cause of a respiratory infection (viral, bacterial, fungal, parasitic) will make it easier to treat.
- Look for symptoms like those you'd see in a human: lethargy, runny nose, cough, fever, and loss of appetite.
- Separate your sick horse from the rest of the herd as soon as you notice symptoms.
- Keep an eye on other horses that have been exposed to the sick horse.
- Avoid treating your horse with human cough and cold remedies.
- Talk to your veterinarian about vaccinating your horse against several common causes of equine respiratory infections.
Viral: Myxoviruses cause the most uniformly severe viral infection in horses-influenza. As in people, influenza typically causes higher fevers and more lung damage, and has many potential complications. Horses are also usually sick for much longer with influenza virus than other viruses. Two to four weeks is not uncommon, sometimes even longer.
While flu takes the honors for severity, herpes virus in the form of rhinopneumonitis wins hands-down for how widespread it is. Once infected, the virus remains with the horse for life. Foals and aged horses are the most likely to have symptoms, which range from a slight snotty nose to a cold-like illness with fever and cough.
Once the immune system gets on top of the infection, the antibody response forces the virus to retreat to inside white blood cells in the lymphatic system. It avoids complete destruction by constantly mutating, but this mechanism also keeps the immune system constantly activated and on its trail.
Eventually, the horse and low levels of the herpes virus come to coexist-although stress or another infection may temporarily weaken the control the immune system has over it. When this happens, the horse may again show symptoms of respiratory disease or, at the least, will begin to shed the virus, exposing other horses to the disease even if he is not showing symptoms himself. Herpes virus can also invade other organs.