Habronemiasis

Veterinary advice should be sought before applying any treatment or vaccine.

Habronemiasis

Granular Dermatitis, Jack Sores, Bursati, Swamp Cancer

Habronemiasis is a parasitic skin condition that most frequently affects horses living in the southeastern region of the United States. The disease can manifest in two different forms:
  • Conjunctiva habronemiasis
  • Cutaneous habronemiasis
It is caused by a skin tissue reaction to the larvae of the equine stomach worms (Habronema majus, H. muscae and Draschia megastoma) once deposited into recent wounds and other moist areas of the horses' body, such as the prepuce, penis periocular tissues, or distal limbs. Flies serve as the intermediate host that transmit the larvae to horses, specifically house flies (Musca domestica), face flies (M. autumnalis), and stable flies (Stomoxys calcitrans).

Some horses appear to have an increased susceptibility to habronemiasis, and often have recurring episodes each year. Clinical signs of disease are characterized by the development of pink or reddish-brown, fleshy or greasy-looking sores which occasionally ulcerate, and contain small, calcified, rice-like yellow material. This yellow material are actually the worm larvae.

Sites on the horse that are most frequently affected by habronemiasis are areas of previous wounds, lower legs (specifically between coronet band and fetlock), belly, sheath, face, and eyes. Habronemiasis occurs seasonally, as it coincides with when flies are most abundant, which is usually late spring through to early fall.

Symptoms

Pink, or reddish-brown, fleshy or greasy-looking sores
Nonhealing skin lesions
Yellow calcified, rice-like material
Large ulcerative granulomatous lesions

Diagnosis

  • History
  • Clinical signs
  • Physical exam
  • Cytology
  • Biopsy analysis

Treatment


TreatmentDetails
Topical and/or systemic steroid therapy
Ivermectin dewormingAdminister one full dose by mouth
Fly control measures
SurgeryMay be required in severe cases to remove build up of granular tissue

Prevention

  • Dressing horses in fly control gear (fly mask and/or fly sheet)
  • Regularly deworm
  • Regularly remove manure from areas where horses are kept
  • Practice proper waste management
  • Adding sodium bisulfate to stalls (~2.5 to 5 lbs/100 sq ft of stall space)
  • Parasitic wasps
  • Ultraviolet light traps placed near barn entrances and 1 to 2 m from the floor
  • Sticky resin fly papers "ribbons" (placed at 0.25cm inch of fly strip for every 28.32 square meters of barn floor)
  • Stabling horses during peak fly activity
  • Properly and promptly addressing any open wounds found on the horse.

Scientific Research References

Good Overviews

Risk Factors

  • Large fly populations
  • Recent wound

Seasonality

WinterSpringSummerAutumn