Papillomavirus Disease in the horse


Edmund Hainisch presented this veterinary webinar from the University of Vienna Veterinary School. Having spent some years training in the UK the webinar was delivered, not surprisingly, in flawless English and maintained interest throughout.

He began by outlining the basic biology of the papillomaviruses. They are highly species specific and infect the basal layer of the epidermis. For this to happen wounds are necessary. Virus replication produces a tumour.  In humans there are some 200 viruses of this type. In the skin they produce warts, papillomatosis/carcinoma in the upper respiratory tract and head and neck cancers. Genitally they can be divided into low risk (genital warts, chondylomata) and high risk cervical carcinoma.

In non-human animals there are 112 papillomaviruses affecting 54 species.  Of interest to veterinarians those affecting horses, cattle, dogs, cats, rabbits and even reptiles.

Papillomata in the Horse

Juvenile Warts (ecPV 1).  ec  comes from the Latin-equus cabellus

These are seen in young animals, are self-limiting, spread epidemically, are multiple and affect the face and muzzle in particular. Autoimmunity normally occurs within a few weeks to months. Usually no treatment is necessary.  Differentiation from sarcoids is via appearance and site of lesions and the fact that they are usually multiple. Excellent clinical pictures were shown


Lesions were shown from an outbreak in a group of 25 cases investigated by the presenter.  All were BP 1 and 2 and were diagnosed by identification of the virus in skin and in peripheral blood mononuclear cells.  Treatment is difficult. Cisplatin cream has been tried

Equine Sarcoid (BPV 1 and 2)

Sarcoid affect all equids and is the most common skin tumour. Affects between 1 and 12 % of horses and is a tumour of young horses between 3 and 12 years of age with a peak at 7 years.  These are difficult to treat as there is a high recurrence rate following attempted treatment.

They tend to be found in thin skin with few hairs, in places where flies like to land-on the head, neck, around the eyes and ventral aspect and at sites of injury following rubbing, for example. The virus spreads in the environment and transmission can be from grooming each other and from tack, saddles etc. Insects can also  transmit it.  The virus affects the epidermis resulting in the development of a fibroblastic tumour at the site.

There are 6 forms: – occult, verrucose, nodular, fibroblastic, mixed sarcoid (hyperplastic, verrucose) and malevolent. Very clear illustrations of each of these types were featured. Malevolent types carry the worst prognosis.

Diagnosis relies of finding all the lesions, at typical sites, of typical appearance and of a typical age. Excisional biopsy with good margins and /or PCR testing is definitive. Edmund cautioned the use of wedge biopsy or fine needle aspiration as this may facilitate spread. He also advised against the injudicious use of the word ‘wart’ as these are extremely uncommon (with the exception of the juvenile warts already discussed.) If they are not juvenile warts they are likely to be sarcoids. PCR testing is available at the University of Vienna* and Edmund is happy to advise on sampling, and illustrations are also available in the webinar. There is a turnaround time of 5 days and a cost of 30 euros.

  • Edmund Hainisch
  • RGO Lab
  • Equine Clinic
  • Vet Uni Vien
  • Veterinarplatz 1
  • 1210 Vien
  • Austria

Treatment should be prompt (no waiting), tailored to the sarcoid, the horse and its owner A variety of approaches is possible. Don’t underestimate the disease and don’t give up too soon.

Treatments discussed comprised surgical excision (always with adjunct therapy), CO2 laser, electrical cautery, banding, cryotherapy, and hyperthermia.

Adjunct therapy mentioned included cisplatin, 5-FU ointment, mitomycin, AWE-Ludes (Liverpool sarcoid cream), acyclovir and mistletoe extract.

A few centres offer Brachytherapy with Ir192 irradiation, which appears to offer the best results.

Other less commonly used therapies discussed included imiquimod, BCG vaccine, therapeutic vaccination and auto implantation. The success of the latter two is debatable but ‘worth a try in hopeless cases’.

Prevention was discussed. Hygiene measures to limit spread are important concentrating on tack, grooming equipment and saddles for example.  Turning out with older horsres(less likely to be infected) was also suggested and finally vaccination is actively under research at the Vienna school and preliminary results are very promising, although there is some way to go before this is licensed.

Genital squamous cell carcinoma (ec PV2)

This is the most common genital tumour of the horse representing 50-85% of the total. Tends to occur in older horses and geldings. In these penile squamous cell carcinoma is the commonest problem. The various lesions, plaque like, cauliflower were well illustrated. Metastasis is seen in 12-17%. This occurs to local inguinal lymph nodes, but also rarely elsewhere including the lungs. Similar cauliflower and ulcerative lesions may be seen on the female genitalia.

Diagnosis is based on examination under sedation (ACP helps relaxing the penis facilitating examination ), palpation, rectal examination, endoscopy, chest X-ray and excisional biopsy.

Therapy may be surgical or the use of local ointments such as mitomycin, or 5 FU

Preventative measures include regular examinations of the penis, regular sheath cleaning and in the future vaccination.

Reviewers Comments

This was the last (of 6) in the MSD sponsored equine veterinary webinars. All have been excellent. Edmund Hainisch clearly presented this webinar with extensive use of first class illustrations throughout, which are a must see. It will be of interest to colleagues that regularly treat horses, dermatologists interested in comparative dermatology, and essential viewing for those, residents for example, contemplating examinations in dermatology.


Leave a Reply

Your email address will not be published. Required fields are marked *