Sarcoids are local lesions similar to warts. It is the most frequent benign (non-cancerous) cutaneous tumor (35% to 90%) present on equine animals. It is caused by the cow papillomavirus, which grows on horses, ponies, donkeys and zebras aged from 1 to 7 years old, which have been in contact with, or in proximity to this virus. However, stable horses can also be infected. Indeed, other reasons, such as genetic factors can occur, causing some breeds to suffer more than others. Quarter Horses are twice as likely to contract a tumor than Thoroughbreds. Moreover, Geldings tend to develop sarcoids at higher rates than stallions or mares, due to the castration traumatism.
Sarcoids can occur in a spontaneous way or following wounds, scars, bites or stings, which can favor its apparition. The young horse would be subject to develop a unique tumor which multiplies with its age.
Even if this equine disease does not represent a danger for the life of the animal, the painless but esthetic consequences can lead to an incapacity to use the horse, due to the frequent localization at the passage of the cinch or the bridle, which can provoke an irritation. Generally, sarcoids are located on the limbs at 50%, and 32% on the head and the neck.
The diagnosis comprises primarily observation, and a histopathology and biopsy.
We count 5 types of sarcoids:
Occult: flat, observed on hairless, scabby and squamous parts, thicker and ultra-pigmented skin.
Verrucous: similar to a large wart.
Fibroblastic: exuberant fleshy masses, often due to a wound or another type of sarcoid, due to a traumatism.
Nodular: Delimited and firm subcutaneous swelling.
Mixt: intermediary stage between two other kinds of sarcoids presented before.
Many therapeutic ways exist to counter this recurring problem: surgery, immunotherapy, chemotherapy, radiotherapy, cryotherapy ect. Nevertheless, because of its recurrence of almost 50%, this tumor remains a real problem for the veterinary surgeon.
However, one treatment has proven to be efficient in this recurrence struggle: the electrochemotherapy, a therapy highlighted by the retrospective study of the Professor Tamzali from the Veterinary School of Toulouse (EVJ, 2011), and one of the Professor Tozon from the Veterinary School of Ljubljana (Veterinary Record, 2016). Professor Tamzali treated 194 sarcoids: 15 occults, 80 verrucous, 30 nodular, 35 fibroblastic and 34 of mixt way on 48 equids with an efficacy rate of 99.5% per tumor on 4 years without recurrence. As for the Professor Tozon, she treated 70 sarcoids: 5 verrucous, 2 nodular, 25 fibroblastic and 9 mixt on 32 equids with an efficacy rate of 92.3%.
This therapy, conducted under general anesthesia, is a combination of chemotherapy (injection of anti-cancerous products) with the application of short, intense electrical impulsions on the entire lesion. The electrical field increases the temporary permeability of the cells and multiplies by 70 the penetration rate and the accumulation of the cytotoxic drug (Cisplatine) inside the targeted cells. According to the size and the infiltration of the tumor, one to four sessions are required with an interval of four weeks. No secondary effect has been observed. Muscular contractions without consequences can occur during the electrical impulsions.
The other treatments are:
Here is a comparison of electrochemotherapy and medical treatments available:
|Electrochemotherapy||- Simple and quick technique|
- No training needed
- No recurrence at 4 years
- No secondary effects
|- General anesthesia necessary at each session (2.8 +/- 1.3 per tumor and 3.6 +/- 2.1 per animal)|
|Surgery||- Inexpensive||- Recurrence at 6 months|
- Impossible on eyelid or penis
- Frequent bleeding
|Cryosurgery||- Rate of success: 80%|
- Horses can be treated standing under sedation
|- Impossible on cheeks and close to joints|
- Long recovery
- Recurrence rate of 91% in periorbital region
- Difficult to conduct
- Requires expertise
|Laser therapy||- Recurrence rate between 29% and 38%|
- Less edema, pain and hyper-granulation
|- Long recovery|
- Expensive equipment
- Training required
|Radiotherapy||- Satisfactory results||- Very expensive|
- Restrictive legislation on radioactive substances
- Training required
|Ligature||- No anesthesia needed|
- Good results
|- Only nodular and fibroblastic sarcoids|
- Risk of infection
- Possible tumor growth
- Frequent recurrence
|Phototherapy||- Excellent cosmetic results||- Tumors still present|
- Easy to set up
- High rate of success on periocular sarcoids
- 20% to 60% of success on other sarcoids
|- Variable results|
- Possible severe inflammatory reactions
- Possible anaphylactic shock which can lead to the death of the animal
|Local chemotherapy||- Little recurrence||- Regulated utilization|
Most veterinarians who deal with sarcoids say that they are frustrated by their incapacity to definitively treat sarcoids. However, those who have tested electrochemotherapy recommend it over any other technique, like at the Clinique de Grosbois and the Clinique Vétérinaire Equine d’Argonay