THOUGH the terms contagious and infectious are often used interchangeably they aren’t technically the same. Infectious disease is caused by agents such as bacteria, viruses and parasites; most are contagious – in that they spread directly between animals (including human-animals). Tetanus is an example of an infectious disease that isn’t contagious.

Important industry

We have a hugely important equine breeding industry, rightly lauded at home and abroad for the quality of horse we produce.

Infectious disease greatly increases production costs; mares may not conceive or hold to term; feed costs may be unduly high; and foals may not thrive sufficiently to shine in these competitive times – at sales or at athletic events.

Key considerations in disease control

  • Knowledge and where to seek good advice. Industry Codes of Practice provide detailed information on infectious disease of use to both Sports and TB breeders. Teagasc and Horse Sport Ireland run educational programmes. Equine veterinarians have the required expertise and are obliged to remain up-to-date.
  • Biosecurity: do not allow random contact between your breeding stock and other equines: a pony home from a day out or the stud farm’s teaser might be a real threat to your broodmare herd’s health. Isolate and disinfect. What did you bring home from the sales today - on or in the horse(s) you bought? Shared horse transport with anyone?
  • Hygiene - keep foaling boxes scrupulously clean and foal outdoors if weather permits. Treat foals’ navels with iodine again and again and again! Wash a mare’s perineum after foaling, a stallion’s sheath after mating.
  • Vaccination and other preventive medicines like plasma. Antibiotics have a role in specific instances to treat bacteria only: they have no effect against viral disease.
  • Don’t exclude donkeys, mules or ponies from your healthcare plans – most equids are capable of carrying most equine infectious diseases.
  • Don’t use medicines (be they antibiotics, de-wormers or other) as a crutch to replace good husbandry practices.
  • Keep stock in robust good health: the best defence mechanism we all possess is our own immune system.
  • Ensure that foals get good colostrum early enough. Do not go back to bed until a newborn is standing and sucking strongly. Consider supplementing foals born of maiden mares, mares recently bought-in and mares that have run milk before foaling.
  • Reduce stocking rates and keep pastures clean. Horses are inefficient and patchy grazers – cattle, sheep, pasture vacuums and paddock sweepers can mop up any mess.
  • Periodically test dung samples for worm egg counts to detect worm burdens, to make a specific diagnosis, and then decide on treatment.
  • Test your mares for venereal disease before breeding and send them only to stallion farms whose sires are similarly tested and who insist on such tests.
  • Consider AI if the breed society rules and your choice of stallion allows.

    • Specific parasitic diseases

    Strongyloides are gut parasites and this one is clever enough to find its way into mother’s milk. Foals can be safely treated with the white worm drenches from about three weeks of age.

    Strongyles come as either the large or the small redworms. Some migrate through the lung, blood vessels and the liver: colic is a frequent complication. Sometimes huge numbers emerge from their winter hibernation in the gut wall, all at the same time, with disastrous consequences including life-threatening diarrhoea. Sadly, growing resistance to both the white worm drenches and to the ivermectin drug group has been identified, thus, from June 1st 2022 these drugs will become Prescription Only Medicines meaning you must involve your vet to procure them.

    Ascarids can grow over a foot long and block foals’ intestines with fatal consequences. Eggs on pasture are highly resistant to the temperate Irish climate so these parasites are found pretty much everywhere our horses graze. Treatment is generally as per strongyloides and strongyles.

    Bots spend most of the year as flies on the wing. They are only found in the larval stage in horses’ stomachs during winter. The ivermectins, as above, should deal with them, but only during the mid-winter months.

    Tapeworms like to congregate at a particularly narrow spot in the intestinal tract so it seems sensible to move them on every now and then. The ivermectins don’t kill these, but manufacturers often produce combination products these days.

    Specific bacterial diseases - tetanus

    Tetanus is a clostridial disease like anthrax, blackleg and pulpy kidney; spores survive all weathers in soil and then develop in deep tissues where air is excluded. It’s not directly transferable from horse to horse, the danger is from puncture wounds, foot abscesses/gravel/drops, navel infections in the foal and surgical procedures like Caslick’s.

    Sadly it is often fatal in horses though it is readily prevented by vaccination – so this should be a no-brainer. Horses are vaccinated using two doses four to six weeks apart followed by annual or even two yearly booster doses. Foals are protected for their first few months by administering the booster dose to an already vaccinated mare in the final two months of pregnancy AND making sure that the foal receives a good supply of colostrum early – the first is of no value without the second.

    Treat navels with iodine. An alternative, much relied on, but temporary passive measure is for vets to administer tetanus antitoxin (TAT) to horses when at real risk of infection. Remember that this is no substitute for vaccination – which is active, long-lasting protection against tetanus for the future.