When to Contact a Vet: Red Flags and Safety Reminders

Your Veterinarian Is Your Partner

Throughout this site, we consistently recommend consulting a licensed veterinarian for any health decisions regarding your horse. This article takes that guidance further by identifying specific situations and warning signs that should prompt an immediate or urgent call to your vet.

Critical reminder: This article does not replace veterinary advice. When in doubt, always err on the side of caution and contact your veterinarian.

Before Deworming: When to Consult First

Contact your veterinarian before administering any dewormer if:

• Your horse has not been dewormed recently and may have a heavy parasite burden. Rapid die-off of large numbers of parasites can sometimes cause serious complications.
• Your horse is a foal or young horse (under 1 year). Young horses have different parasite concerns and sensitivities.
• Your horse is pregnant or lactating. While many dewormers are labeled as safe during pregnancy, your vet should confirm the timing and product choice.
• Your horse has a history of adverse reactions to deworming products.
• Your horse is currently ill or debilitated. Deworming a sick horse could add additional stress to an already compromised system.
• Your horse is on other medications. Drug interactions, while uncommon with most dewormers, should be evaluated by a professional.
• You are unsure which product to use. Your vet can recommend the most appropriate active ingredient based on fecal testing.

After Deworming: Signs of Adverse Reactions

While most horses tolerate deworming products well, adverse reactions can occur. Contact your veterinarian if your horse shows any of the following signs after deworming:

Digestive Disturbances

• Colic symptoms: Pawing, rolling, looking at the flank, refusing to eat, or lying down more than usual. Any signs of colic should be treated as urgent.
• Diarrhea or loose stool: While mild digestive changes can occasionally occur, persistent or severe diarrhea warrants a call to your vet.
• Complete loss of appetite lasting more than 12–24 hours.
• Excessive drooling or difficulty swallowing after paste administration.

Allergic or Hypersensitivity Reactions

• Swelling around the face, muzzle, or body
• Hives or skin reactions
• Difficulty breathing — this is an emergency
• Excessive sweating without exercise or high temperatures

Behavioral Changes

• Lethargy or depression beyond normal post-treatment quietness
• Unusual agitation or restlessness
• Signs of pain (grinding teeth, tense posture, elevated heart rate)

Other Concerning Signs

• Fever (normal equine rectal temperature is approximately 99°F–101°F / 37.2°C–38.3°C)
• Swelling at the throat or injection site (if injectable products were used by a veterinarian)
• Neurological signs such as incoordination, head pressing, or abnormal behavior — seek emergency veterinary care immediately

Emergency Situations

The following situations require immediate veterinary attention (do not wait):

1. Signs of severe colic — violent rolling, sweating, elevated heart rate, refusing to stand
2. Difficulty breathing — labored breathing, flared nostrils, or abnormal respiratory sounds
3. Collapse or inability to stand
4. Severe swelling especially around the head and throat
5. Neurological symptoms — staggering, disorientation, head pressing against walls or objects
6. Profuse or bloody diarrhea

Parasite-Related Red Flags (Unrelated to Recent Deworming)

Sometimes, signs of a parasite problem require veterinary attention regardless of when the horse was last dewormed:

• Unexplained weight loss despite adequate feeding
• Poor coat condition — dull, rough, or patchy hair
• Pot-bellied appearance (particularly in young horses)
• Chronic mild colic or recurring digestive issues
• Visible worms in manure — while sometimes normal after deworming, seeing worms in a horse that has not been recently treated suggests a significant burden
• Rubbing the tail excessively, which can indicate pinworms
• Failure to thrive in young, growing horses

Fecal Egg Count Follow-Up

Your veterinarian may recommend follow-up fecal egg counts after deworming to verify that the treatment was effective. If a follow-up FEC shows that parasite egg counts have not decreased significantly:

• The parasites may be resistant to the active ingredient used
• The correct amount may not have been administered (if the horse spit out paste, for example)
• The product may have been compromised (expired, improperly stored)

Your veterinarian can evaluate the situation and recommend next steps, which may include a different active ingredient or modified approach.

Building a Relationship With Your Vet

Establishing a good working relationship with an equine veterinarian benefits your horse's long-term health:

• Schedule annual wellness exams that include parasite management discussions
• Keep records of which products you have used and when
• Communicate openly about your horse's health history and any concerns
• Follow through on recommended fecal testing and treatment protocols
• Ask questions — a good veterinarian welcomes informed, engaged horse owners

Sources and References

• American Association of Equine Practitioners (AAEP): Horse Owner Resources
• Merck Veterinary Manual: Overview of Gastrointestinal Parasites of Horses
• AAEP: When to Call the Vet

---

This article is for educational purposes only. It does not constitute veterinary advice. Always consult a licensed veterinarian for guidance specific to your horse.