Piroplasmosis in Horses by a Vet – 2025 Babesiosis Awareness & Biosecurity Guide 🧬🐴

By Dr Duncan Houston, BVSc

Introduction

Piroplasmosis, also known as equine babesiosis, is a tick-borne disease caused by Babesia—a protozoan parasite that infects red blood cells. Historically considered rare in the U.S., this disease is now a growing concern due to increased international horse transport and regional tick populations. In 2025, awareness, prevention, and testing are more important than ever, especially in high-risk states like Texas and Florida.

What Causes Piroplasmosis? 🧬

• Caused by two main protozoans: Babesia caballi and Theileria equi
• Invade and destroy red blood cells, leading to anemia and systemic illness
• Transmitted by tick bites and contaminated instruments or needles

Symptoms to Watch For ⚠️

• Fever
• Anemia (pale gums)
• Lethargy or malaise (horses just “not looking right”)
• Yellow-tinged eyes or gums (jaundice)
• Dark red or brown urine
• Decreased appetite, weakness, or colic signs

Carrier Horses – Silent Spreaders 🔄

• Some infected horses show no signs but remain lifelong carriers
• Even clinically normal horses can transmit the parasite via:
  • Tick bites
  • Reused needles or shared dental/surgical equipment

Transmission Routes 🚫🦟💉

• Ticks: Most common and natural method of infection
• Contaminated needles: Using the same syringe on more than one horse
• Shared dental tools or tattoo equipment that hasn’t been properly sterilized

Diagnostic Testing 🧪

• Serology: Detects antibodies to Babesia or Theileria
• PCR: Detects parasite DNA in blood
• Repeat testing is sometimes needed due to test limitations

Regulatory Considerations 📋

• Horses testing positive are banned from entry into the U.S., Canada, Australia, Japan, and the U.K.
• Positive horses may be quarantined or euthanized depending on jurisdiction
• Export or import protocols often require clearance testing

Treatment & Prognosis 💊

• Treatment may reduce symptoms but rarely eliminates the parasite completely
• Imidocarb dipropionate is used—but has side effects and may not clear all infections
• Even treated horses may still carry and spread the organism

Prevention in 2025 ✅

1. Use Only Sterile Needles & Syringes 💉

• Always use a new sterile needle for each horse
• Use a clean syringe and needle when drawing from multi-dose vials
• Never reuse tattoo, dental, or surgical tools without complete disinfection

2. Tick Control Measures 🪰

• Apply equine-approved tick repellents regularly
• Clear brush and weeds from pastures
• Inspect horses daily, especially legs, ears, and under tails

3. Isolate and Test New Horses 🧪

• Quarantine all incoming horses for 21+ days
• Test for piroplasmosis before integrating into your herd

Case Example: Imported Carrier Horse

1. Four horses imported from Mexico to Florida were tested on arrival
2. Two tested positive for Theileria equi despite appearing healthy
3. Due to regulatory risk, they were permanently quarantined
4. Others in the shipment tested negative and were cleared after quarantine

FAQs About Piroplasmosis

Q: Can a positive horse be cured?

A: Treatment may reduce symptoms but often does not clear infection. Positive horses may remain infectious for life.

Q: How do I protect my horses?

A: Tick control, sterilization, and testing new arrivals are your best tools.

Q: Can I sell or show a horse with piroplasmosis?

A: Not in most cases—regulations vary, but positive horses are often restricted from travel and competition.

Conclusion

Piroplasmosis remains a rare but dangerous disease in U.S. horses—especially in southern states and international imports. Since many infected horses appear healthy yet still transmit the disease, preventing exposure is critical. In 2025, good hygiene, strict needle protocol, tick control, and biosecurity can help you avoid this challenging blood-borne parasite.

Concerned about testing, travel rules, or exposure risk? Visit AskAVet.com or our app 📱 to speak with Dr Duncan Houston and our equine infectious disease team. 🩺🐴