Our sun-worshipping pets can suffer from commonest cancer

SUNSCREEN: The best protection is shade and keeping pets in it during the hottest part of the day.
SUNSCREEN: The best protection is shade and keeping pets in it during the hottest part of the day.

Most Australians are familiar with the Cancer Council's excellent public health campaign reminding us to slip on a shirt, slop on some sunscreen, slap on a hat and, more recently, seek shade and slide on some sunglasses before venturing out in the sun.

Like us, dogs and cats can develop skin cancers due to skin damage from sun exposure. To some degree, fur acts as a protective layer from the sun's harmful rays so animals that develop skin cancer often do so on parts not protected by a thick layer of fur, including the nose, ears, and the belly or groin area.

The most common type of skin cancer seen in companion animals in Australia is squamous cell carcinoma, named after the cells in the top layer of skin where this cancer is found.

Squamous cell carcinomas, or SCCs, often begin as a discrete area of red, inflamed or even ulcerated skin, sometimes with crusting or scabbing. As they grow they become quite painful. If left untreated, they can cause large, disfiguring lesions.

The most dramatic SCCs I see are typically in cats with SCCs on the nose. Not only do they damage the tissue, but severe SCCs here impact a cat's sense of smell and appetite.

Lighter coloured cats, particularly white cats or those with pink ears and noses, are more prone to these. SCCs can also occur on the toes or nail beds, leading to severe pain, lameness and reluctance to walk.

Just like people, there are occasional dogs who are extreme sunbakers. Owners will report that these dogs lie on their backs with their bellies exposed to the sun. This behaviour should be discouraged, as it increases the risk of skin cancer.

Diagnosis of any type of skin cancer is usually made by surgical biopsy. A range of treatments are available including surgery, radiotherapy and chemotherapy. The earlier skin cancer is detected, the better the outcome.

Studies have shown that ozone depletion and global warming have already increased the rate of skin cancers in people. We know what we need to do to protect ourselves, and we should consider taking similar measures with companion animals.

My colleague, veterinary dermatologist Beth McDonald, advises that 15 minutes in the sun is enough to cause damage to non-pigmented skin in a dog or cat.

According to Dr McDonald, the best thing we can do is ensure that animals are indoors when the UV index is high (usually between 10am and 3pm).

And when she says indoors, she means indoors and out of the sun.

I know plenty of animals who are sun-seekers, looking for that patch of direct sunlight coming right through the window. It is important that animals absorb UVB rays from the sun so they can produce vitamin D, but they don't need to be baking in full sunlight to achieve that.

In addition to minimising exposure to high levels of UV radiation, there are other steps you can take to protect your pet.

  • Ensure that all animals have access to shade all day (and that sunbaking animals are prevented from doing so especially from 10am to 3pm);
  • If your dog must go out when the UV index is high, consider a "sun suit" such as those made in Australia by Bromelli www.bromellidogs.com.au;
  • Custom-made hats, nose-guards and goggles are available online. They need to be fitted carefully. Animals may need to be conditioned to wear these;
  • If your companion animal develops a suspicious skin lesion, or has a scab that keeps reforming at the same site, make an appointment to see your veterinarian.

Sunscreen needs to be reapplied at regular intervals, and is readily licked off by animals when it is applied around the nose or muzzle. If ingested in large amounts, zinc-based sunscreens can be toxic. Sunscreen can be used in small amounts for limited periods of sun exposure.

Dr McDonald discourages use of spray-on sunscreens, so ask your vet about the most appropriate sunscreen for your pet.

Dr Anne Quain BVSc (Hons), MANZCVS (Animal Welfare), Dip ECAWBM (AWSEL) is a lecturer at the Sydney School of Veterinary Science and a practising veterinarian.