Sarna sarcóptica em cães: sinais, tratamento e prevenção

What causes it

The mite is called Sarcoptes scabiei var. canis. It is about 0.3 mm long, too small to see without a microscope. Female mites dig tunnels in the top layer of the skin and lay their eggs there. The young mites grow into adults in about two to three weeks, and the whole life cycle happens on the dog.

Much of the itch comes from the dog's allergic reaction to the mites and their droppings. This is why a dog can scratch hard even when only a few mites are present, and why scratching can start before the skin looks very bad.

Sarcoptic mange is a different condition from demodectic mange. Demodex mites live in small numbers on the skin of most healthy dogs and do not pass to people. Sarcoptic mites spread easily to other dogs and can cause a short-lived rash in people.

Como se transmite

Most dogs catch mange through direct contact with an infested dog. Mites can also pass on shared bedding, blankets, towels, brushes, and clipper blades. Kennels, shelters, grooming salons, dog parks, and homes with many dogs are common places for it to spread.

Foxes and other wild members of the dog family can carry the mite and pass it to dogs. Sarcoptic mange is common throughout Europe, and in some areas many red foxes have it. Dogs that roam or live near foxes have a higher risk.

Away from a dog, the mites do not live long. In cool, damp places some can survive for up to two or three weeks, so bedding and sleeping areas can pass them on for a while.

Signs usually appear anywhere from about 10 days to 8 weeks after contact. During that time a dog can carry mites and pass them to other dogs before it starts to itch.

Sinais a observar

The first sign is usually sudden, intense itching that does not settle. The rash often starts on the edges of the ears, the elbows, the hocks (the ankle joints of the back legs), the belly, and the chest. Without treatment it can spread over the whole body.

• Constant scratching, chewing, and rubbing against furniture or the ground
• Small red bumps that turn into crusts
• Crusty, scaly edges on the ear flaps
• Hair loss, often first on the ears, elbows, legs, and belly
• Red, raw, or bleeding skin from scratching
• Thick, darkened skin in long-standing cases
• Oozing or smelly sores, which can mean a secondary skin infection
• Weight loss, weakness, and swollen lymph nodes in severe cases

Many dogs with sarcoptic mange kick a back leg in a scratching motion when the edge of the ear flap is gently rubbed. Vets see this ear reflex as a strong hint. It does not confirm mange by itself, so the vet will still want to check further.

When to call the vet

Mange is rarely an emergency in the first days. It does get worse without treatment, and long-standing cases take longer to heal. Book a vet visit soon if your dog is itching hard, has crusty ears or elbows, or if more than one pet or person in the home is itchy.

Contact a vet the same day if your dog stops eating, seems weak and dull, is losing weight, has open wounds from scratching, or has sores that are oozing, smelly, or spreading fast. These can be signs of severe mange or a skin infection that needs prompt care.

How vets diagnose it

The vet will ask when the itching started and whether your dog has been around other dogs, a shelter, or foxes. They will look at where the rash is and may check the ear reflex.

The usual test is a skin scraping. The vet gently scrapes several areas of affected skin and looks at the material under a microscope for mites or eggs. Finding mites confirms the diagnosis. Not finding them does not rule it out, because scrapings miss the mites in many dogs that truly have mange.

A blood test for antibodies to the mite is available in some places. Many vets start treatment based on the signs and the history. If the dog clearly improves on treatment against mites, that supports the diagnosis.

How it is treated

Sarcoptic mange is treated with prescription antiparasitic medicine that kills the mites. Several modern options are given by mouth or applied to the skin, and many work well after one or a few doses. Your vet will choose the medicine and schedule based on your dog's age, weight, breed, and health.

Some herding breeds, such as collies, can carry a gene change that makes certain antiparasitic medicines dangerous for them. For any dog, it is safest to use only the medicine your vet prescribes. Products made for farm animals or other pets can harm dogs, and home remedies can irritate damaged skin and delay proper treatment.

Your vet may also recommend medicated baths to soften and remove crusts, antibiotics if the skin is infected, and sometimes a short course of medicine to calm itching and inflammation in the first days.

All dogs in the home usually need treatment at the same time, even those that are not itching. Dogs can carry mites for weeks before they show signs, and one untreated dog can pass mites back to the others. It is best to keep the affected dog apart from other dogs until your vet says it is no longer contagious.

Most dogs start to itch less within about two weeks. The skin and coat usually take six to eight weeks to recover fully. It is recommended to finish the full course even if your dog looks better, and to go to any recheck your vet suggests.

At home, wash bedding, blankets, and soft toys in hot water and dry them on a hot setting. Clean brushes, collars, and harnesses, and vacuum the places where your dog lies. Throwing out old bedding is sometimes simpler. The medicine clears the mites from the dog, and cleaning helps stop them from coming back.

Spread to people and other pets

People who handle or cuddle an infested dog can develop an itchy rash of small red bumps, often on the forearms, belly, chest, or thighs, where their skin touched the dog. Several family members may itch at the same time. The dog mite cannot reproduce on human skin, so the rash is temporary. It usually fades within a few weeks once the dog is treated and contact with the mites stops.

If you have an itchy rash, see your doctor and mention that your dog has mange. Wash your hands after handling your dog during treatment, and keep the dog off your bed until your vet gives the all clear.

Other dogs in the home are at high risk and should be checked and treated as your vet advises. Cats are rarely affected by this mite. If any other pet in the home starts to itch, ask your vet to look at it.

Prevention and newly adopted dogs

Ask your vet whether your dog's regular flea and tick preventive also protects against sarcoptic mites. Several modern products do. It also helps to keep your dog away from foxes and from dogs with obvious skin disease, and to avoid sharing bedding or brushes with dogs you do not know.

Dogs that live on the street meet many other dogs and sometimes foxes, and shelters and kennels put many dogs in a shared space. Both settings help mange spread. At Paw Squadron, the first stops after every rescue are the vet and a bath, with a checkup, deworming, and treatment against fleas and other parasites. Before adoption, every animal gets a checkup, treatment, vaccinations, and a microchip.

Any dog can pick up mites, and signs can take weeks to appear, so it helps to know what to look for. In the first weeks after adoption, watch for new itching, crusty ear edges, or hair loss on the elbows and legs. If you see them, call your vet and keep the new dog apart from other dogs until it has been checked. If you already have dogs at home, a vet visit before they share beds is a sensible step.

You can find more guides on skin care and parasites in PawPedia, and dogs looking for homes on the Adoptions page.