Cause: Sarcoptes Scabiei
Sarcoptic mange or ‘fox mange’ is caused by the highly infectious parasite ‘Sarcopties Scabiei’. The mite has a wide host range affecting most commonly puppies and dogs but can also be transmitted to cats, rabbits, foxes and even humans. Signs typically associated with the condition include a severe itch and alopecia possibly leading to self –trauma. Given its debilitating effects if left unrecognized, seeking veterinary attention is always advisable, with prompt treatment easily curing the condition.
Lifecycle of Sarcoptes
The mites usually spend all there time on the host with the lifecycle being complete in 2-3weeks.
The female mite burrows through the skin creating a tunnel in the superficial layers. On its way it feeds from the liquid that oozes from this damaged skin. The eggs are deposited in these tunnels. After 3-5 days the eggs hatch and the six legged larvae crawl to the surface. In turn these larvae then migrate superficially to create areas where they can moult becoming nymphs and then adults. After this process is complete the adult male emerges to seek a female and the cycle is repeated over and over.
Because of its rapid ability to multiple a single mite is enough to produce an infection that can cover the whole body.
Clinical signs of affected animals
Symptoms classically shown by infected dogs are typically severe, intense itch and widespread alopecia. Mites can attack healthy skin of dogs of any age and breed. Areas affected are characteristic of the parasite and include the margins of the ears, the elbows, hocks, abdomen and chest. Dogs may show signs in all or one of these body parts.
Red papules or pustules can develop along with yellow crusts. This can lead to very inflamed skin that is dry and painful. Omportantly the signs are non-seasonal helping to distinguish it from other conditions. Atopy, an allergy to environmental allergens is commonly confused with it.
Unfortunately, self –trauma can occur due to the severity of the underlying condition. In cases where animals are left untreated the whole skin surface can be involved with dogs becoming weak and emaciated.
Diagnosis of canine scabies
Confirmatory diagnosis is achieved by seeking veterinary attention. Diagnosis can be very frustrating both for the veterinarian involved and the owner. Superficial skin scrapes are performed to identify the mite or any eggs. Unfortunately these microscopic mites can be difficult to demonstrate and are only recognized in around 20% of cases. This means that whilst the presence of a single mite is diagnostic, failure to identify a mite does not rule out the condition.
Pustules can be squeezed to release pus with the pus analysed under a microscope to determine the presence of any mites.
Recently a blood test called an ‘ELISA’ has been produced to identify sarcoptes infected dogs. As no test is full proof the major drawback with it being animals with concurrent house dust mite allergies will cross react, falsely demonstrating positive to the test. Due to this it is not widely used in the field.
Affected animal can show a positive ‘pedal -pinnal reflex’. Due to the intensity of itch, rubbing the ear margin between the thumb and forefinger induces the dog to scratch with its back leg. Therefore diagnosis is usually based on a combination of history, clinical signs and response to treatment.
Treatment of Scabies
Successful treatment is based on isolation of any infected animals, treatment of those infected and any animals in- contact. This mite is highly contagious and rapidly spread.
There are several treatments available for the condition. One method possible is an organophosphate dip ‘Amitraz’. Long haired dogs are advised to be clipped and bathed with a benzoyl peroxide shampoo first. These dips are very effective when used correctly. When scabicidal dips are used the entire dog must be treated. Treatment failure occurs if it is not applied carefully to the face and ears. It is very important that the instructions given with the product are followed exactly for success and also because it can be toxic to humans. The product should be made to the correct concentration and ideally the dogs should be dipped outside on a warm day to avoid hypothermia. This treatment is not recommended in Chihuahuas or diabetic animals. One side effect uncommonly reported is a sedative like effect. In this case veterinary attention should be sought and the treatment discontinued. To be successful the dip should be repeated as according to veterinary guidelines. Some cases of resistance have been reported.
Other current medications available are ‘spot-ons’. These include ‘Advocate’ and ‘Stronghold’. These preparations have the advantage of their easy application with the drug been stored in a vial that is applied to the back of the neck. Your veterinary surgeon may consider this the better option if for example the skin is very painful and application of a dip may be traumatic. Again multiple applications are required.
Another off license treatment is Ivermectin. Because it is off label this tends to be reserved in cases that are not suitable for the previously mentioned treatments or where these have been used and are unsuccessful. This drug should be applied with caution in collies or Shetland sheep dogs or in any animals that are sensitive to Ivermectin. It should also be avoided in heart-worm positive animals.
Less favourably used is a product called milbemycin. This may be effective at certain dosages given by mouth when prescribed by your veterinarian.
As well as treating affected animals it is prudent to treat any in-contact animals to prevent reinfection as they may be asymptomatic carriers. Because of the hypersensitivity reaction involved it may take 4-6wks for the itchiness to resolve. Sarcoptes mites usually die quickly in the environment however survival of up to 3wks has been reported so thorough cleaning of the environment and bedding is not to be forgotten.
In addition, to temporarily relieve discomfort, corticosteroids or anti-histamines may be prescribed along with antibiotics if any infection is present on the skin.
Prevention of mange
Sarcoptes Scabiei is able to survive for a short term in the environment. This means that your dog doesn’t have to come into direct contact with an infected individual to get the mite. The mite can also be caught from foxes so one way to reduce the risk is to avoid contact with other dogs or foxes. Also avoid segregation in places where these animals may have been.
Zoonotic potential
Sarcoptes can be spread to humans uncommonly. The condition is self limiting. It is always advisable that you consult a doctor should you have any skin complaints following diagnosis of an infected dog.
