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Avoid allergic reactions

With only the rare occurrence of allergic reactions in cattle they are not mentioned much in the literature. However, today’s modern producers give more in the way of vaccines and antimicrobials. With longer-acting products that are only approved subcutaneously or intramuscularly and not intravenously the risk level is elevated. The carrier or base in the products also can cause allergic reactions so you never know when one will arise. The treatment is very effective if given in time so I thought this was an ideal time to raise the whole issue of allergic reactions in the cattle sector.

Most allergic reactions come about from the administration of products such as vaccines or antibiotics. It is clearly marked on all labels by pharmaceutical companies that these products can rarely cause allergic (anaphylactic) reactions and to administer epinephrine. Less commonly an allergen can be inhaled or taken in orally. The reaction may be local such as can happen with a bee sting where the surrounding tissue becomes very swollen. In the cattle industry we are more concerned with the full-blown reaction where eventually the lungs can fill with fluid resulting in pulmonary edema and death.

Generally speaking severe reactions happen within 15 to 20 minutes of the insult. Clinical signs might include uneasiness, and increased respiration. The most noticeable signs, can be swollen, puffy eyelids and copious amounts of salivation. Bloat and staggering often follow and can progress to collapse from the lack of oxygen, the animal turns blue and dies.

It is a good routine to take a quick look at cattle after processing once they have settled, to observe anything abnormal. When castrating cattle with a knife and covering with penicillin we always observe the pen for two things, excessive bleeding and any telltale signs of an allergic reaction.

It has been my experience with antibiotics that if you get one reaction there may be several. There can be a genetic susceptibility in a herd to a specific allergen so if you inject a number of animals and you get one reaction watch very closely for others. Mark down the animal affected especially if it is a breeding animal as it could reoccur next time and that product needs to be avoided on that animal for sure.

Treatment kits should always contain a bottle of epinephrine, the universal antidote for allergic reactions. If you never need to use it that is a good thing. The bottle will often get covered in dust and expire, so check once in a while and replace it as necessary. It will be way too late to go to the neighbours or rush to the veterinary clinic to purchase a bottle. Having a bottle on hand could prove to be a very worthwhile investment and it is not an expensive product. Allergic reactions happen fast. Even if the bottle you have has expired it can still be used in a pinch. The efficacy may be decreased and you may need to use more to get the desired results. The one good thing about allergic reactions is you know right away if the treatment is working.

The dosage of epinephrine is generally one cc per 100 pounds given subcutaneously or intramuscularly (the product comes in the strength of one mg per ml). One may want to hurry  up the process by giving it intravenously but that can cause heart fibrillation. If given this way it should be diluted to a 10 per cent solution with saline and at only one-quarter of the normal dose. I personally don’t recommend it. If the animal is having difficulty breathing it is fractious so it is better to give it quicker by the other routes described on the label. I have a tendency to split the dose in two and give one subcutaneously and the other intramuscularly.  Clinical signs will begin to decrease within minutes. You are not done yet. Often the treatment needs to be repeated several times as the epinephrine wears off so keep the animal under close observation until it has completely recovered. Wait at least an hour after the last treatment before being fully confident the allergic response will not return.

Corticosteroids such as dexamethasone may also be prescribed for longer coverage or a diuretic to remove excess lung fluid. Do all this in consultation with your veterinarian. It is good if he/she is aware of any allergic reactions as several steps may be taken. Often if a product is involved the pharmaceutical manufacturer wants to know about it and check the product. You may be advised not to use the product if there is thought to be a genetic susceptibility. Record the animal to avoid using the same product on it in the future. If several animals are involved that product may need to be avoided completely.

Individual reactions can occur with some products if they are not approved for intravenous usage and you happen to hit a small arteriole when injecting. The likelihood of this happening has been dramatically reduced since most products are now approved for use subcutaneously. If a subcutaneous injection is given properly it is almost impossible to hit a big enough vein or artery to cause a problem. With intramuscular products like daily penicillin it is a good precaution to first place the needle and then attach the syringe with the product. If blood comes bubbling out of the needle it is best to pull it out and place it in another location. I always tell farmers I could induce an allergic reaction every time by giving penicillin intravenously.

Our management practices have reduced many individual allergic reactions. Pharmaceutical companies also monitor which carriers and immune stimulators cause reactions and try to develop equally effective but less reactive ones. Hopefully you will never have an allergic reaction on your farm. But if you do you will want to have epinephrine on hand. It is cheap insurance and when needed can definitely save several lives. Make sure and keep the expiry date in mind and replace it when necessary.

Before you face a life-or-death situation I want you all to go out to your treatment kits and make sure they are stocked with a bottle of epinephrine!

About the author


Roy Lewis is an Alberta-based veterinarian specializing in large-animal practice. He is also a part-time technical services vet for Merck Animal Health.



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