Question:I have owned my 12-year-old light-breed gelding for seven years now in Athens, Greece. He is a bit allergic, with a runny nose and a periodic cough. He also has chronically swollen glands under his jaw and had an episode of hives last spring. For the last two years, after receiving his spring viral vaccinations, he has had three or four rough days. He had colic and was coughing each time. The symptoms passed, but I wonder if this was an allergic reaction to the vaccines and if I should vaccinate him against any viruses. Are any viruses lethal?
Answer: The humid, warm climate of Athens, combined with air pollution, are stressors for equine lungs, and many horses exposed to these conditions exhibit the recurrent airway irritation you describe. Some also develop other signs of immune challenge, such as hives and swollen glands. Your horse does sound like an immune-sensitive individual.
Some viruses, such as rabies, African horse sickness and West Nile virus, can be lethal, but most of the viruses we traditionally vaccinate against, such as influenza and herpesvirus, cause only temporary illness. It may be impossible to determine if your horse's troubles were an allergic response to the vaccine, but it is apparent that your horse is hypersensitive to many things. You may want to try a different brand of vaccine and/or combination of agents.
If your horse's reaction to the vaccine worsens each year, you can be even more sure that it is an allergic response. Whether or not to immunize against a particular disease agent is a decision best made by a local professional who knows the regional risks of disease. Ask your veterinarian if your horse will be more at risk from the immunization shots than from a chance encounter with a random virus.
--Matthew Mackay-Smith, DVM, EQUUS Medical Editor