Bovine papillomavirus (BPV)
Also known as
Bovine papillomaviruses (BPV) are a group of DNA viruses that are common in cattle. Infection with these viruses causes warts (papillomas and fibropapillomas) of the skin (including on the teats and udder of cows) and alimentary (digestive) tract, and more rarely cancers of the alimentary tract and urinary bladder. They also cause the skin tumors (equine sarcoid) in horses and donkeys.
Warts are unsightly skin growths, transmitted by these viruses from one animal to another. Once they become established in a herd of cattle they can be difficult to completely eliminate. Even though affected animals develop immunity and may never have warts again, warts may be continually spread to younger animals in the herd.
The warts are often spread to calves by direct contact from infected cows or older animals. The virus can be spread by direct and indirect contact and may become a continual problem in a herd, due to the long incubation period. After exposure, it can be about 2 months before the warts show up in a susceptible animal. The virus is host specific, meaning that it only affects cattle.
Warts may suddenly appear in several animals at once, such as a group of weanlings or yearlings that were exposed earlier. Warts often crop out in places where the skin was broken, allowing the virus to enter deeper layers of skin. They may develop in ears after tagging, or any other area of the body where the skin has been punctured or scraped.
Warts are most common in calves and yearlings since they have not yet developed immunity to the virus. The growths often appear quickly, and grow swiftly into a rough-looking or smooth shaped mass. They may be small and rounded or become very large. A large warty mass inside the ear may make it so heavy that the ear droops down.
There are several types of warts--including growths shaped like cauliflower, others like small horny bumps, and some that are more smooth and flat. Warts may appear on head, neck and shoulders, in the mouth or vagina, on the teats, vulva or penis.
Warts caused by one type of the virus have a cauliflower-like appearance and can become as large as a fist. These are most common on the head, neck and shoulders, but may also occur in other locations. Another type has a nodular appearance. Warta are unsightly but most of them do not cause problems except in show animals.
In some cases, however, large warts may bleed, or lead to secondary infections. Warts on a cow’s teats can cause mastitis and interfere with suckling and milking. Fibropapillomas can be a problem if the occur in the genital area, causing pain and sometimes loss of reproductive function, or interfere with calving.
Warts on a bull’s penis may interfere with breeding. Immunosuppressed animals may develop extensive growths in the upper gastrointestinal tract, which can cause difficulties with eating and breathing.
The virus is in highest numbers at the outer surface of the wart; this is why warts on the skin can spread so readily on an animal or to other animals by direct or indirect contact. If an infected animal rubs the wart on a fence or feed bunk, the virus may be picked up by any animal that comes in contact with that object.
Warts on an affected animal often spread rapidly from the area in which they started, such as in an ear, or around the mouth or neck, or along the shoulders or brisket, or on the teats and udder.
Then, almost as quickly as they appeared, the warts dry up and fall off, or shrink up and disappear--once the animal has had time to develop antibodies against the virus and build immune defense against it.
The best treatment for warts is time. They always disappear, though in some animals it may take several months to a year.
- Skin growths that appear suddenly and grow larger;
- Some growths are rough while others are smooth or nodular.
The virus can be transmitted from one animal to another by instruments that puncture the skin (such as tagging or tattooing tools, needles) and by biting flies such as horn flies, horse flies and stable flies that feed on one animal and then another.
A healthy animal in good condition will build immune defense and generally never get warts again. This is why warts are mainly just a problem in young animals or in the occasional adult that has not yet encountered the virus.
To prevent transmission of warts to other animals in the herd, isolate affected individuals when you first notice the wart. Otherwise other cattle will develop warts, since the virus affects any exposed animal that has no immunity. Isolating the infected animal is no guarantee of preventing spread of warts, however.
Due to the long incubation period, that animal may have already infected others by the time you notice the warts.
Commercial vaccines against warts are sometimes used but don’t always work because there are several types of wart virus. An autogenous vaccine (created from something within the animal’s own body) is more effective. It can be made by your veterinarian from a piece of the warty tissue.
This stimulates the body to mount a defense against that particular virus and get rid of the warts more quickly, and can also be used to protect susceptible animals that might come into contact with the infected one.
This vaccine can be given to other cattle in the herd (following directions from your vet for dosage, administration and frequency) to protect them from the same type of warts.
If warts are a problem for an animal, such as around the mouth or nostrils (interfering with breathing or eating), or on the teats (interfering with milking), or on a young bull’s penis, they can be surgically removed by your veterinarian.
With skin growths, this usually means cutting them off with a sterilized knife or surgical scissors, or tying them off with thread. If removed during their early growing stages, however, warts may be stimulated to re-grow. It is safest to remove them after they are past their peak of development.
In later stages, their disappearance can be hastened by carefully pulling, twisting or snipping off one of the warts, crushing a small one, or removing part of a large mass of warty tissue.
Disrupting the wart in this manner puts the virus into contact with the bloodstream if the area bleeds a little, which tends to encourage the animal’s immune system to create antibodies and fight the warts--to get rid of them quicker. It’s best to remove or disrupt warts only when they’re starting to regress.
Do not use iodine or any other caustic type of disinfectant on warts. These treatments are effective for ringworm (caused by a fungus) but not for the wart virus, and may be harmful to the animal. Iodine burns the skin and may create more sore areas.
The simplest treatment is time, leaving the warts alone to disappear on their own--unless the growths must be eliminated more quickly for health reasons. In that case, consult with your vet about removing them or trying an autogenous vaccine.