Thursday, 30 April 2020

Scratching the surface of skin disease

When itchy pets scratch a lot it can be painful and upsetting for them as well as distressing for their owners. All pets will scratch to relieve themselves of a temporary annoyance such as debris caught in the coat or an insect climbing on the skin. Some pets simply enjoy a good scratch without there being any cause for concern.

Itching becomes a problem when a pet scratches to such an extent that it causes damage to the skin. They will often chew and lick at the irritation too.

There can be many causes of skin problems in our pets. Some animals suffer from a combination of causes that can make diagnosis and treatment more challenging.

Here is an overview of the most common conditions;

1. Parasites

a) Fleas are the most common cause of itching in pets.
One of the first questions the vet will ask is whether your pet is regularly treated for fleas and will look through your pet's coat for evidence of these parasites. Fleas are visible as small brown parasites moving through the coat. Often flea dirt will be noted before fleas themselves. 
Fleas can be controlled by regular use of effective products prescribed by your vet. 
Some animals develop allergies to fleas; see section 'allergies'.

b) Mites; There are several types of mites that can affect our pets but those listed below are most commonly encountered;

  • The Sarcoptes scabiei canis mite causes sarcoptic mange  which is a very uncomfortable skin disease seen in dogs. These mites will burrow into the outer layer of the skin causing intense itching and irritation. The skin becomes  inflamed with excessive scale and crusting and starts to lose  hair. The intense itch often leads to further injury through  excessive scratching. The most commonly affected areas are the face, ears, muzzle, hocks, elbows and chest, but the  disease can extend over the entire body.

Sarcoptes scabiei mite
(microscopic view)

The mite is  contagious and is primarily spread through direct contact with  an infected animal. The mite also affects foxes who can indirectly spread the mite to dogs via the environment, as the mite can survive off of the host for a number of days.
If Sarcoptes is suspected, the vet will take some skin scrape samples to examine under the microscope. The presence of a mite or their eggs on a slide confirms a positive diagnosis, but a negative skin scraping does not rule out sarcoptic mange. Because these mites burrow deep into the skin and an animal only needs to be infected by a few to show significant symptoms, a skin scrape does not always pick up the mites. In these cases, a presumptive diagnosis may therefore be made, based on clinical signs.
Cats rarely get sarcoptic mange, however if they do the most common form is notoedric mange caused by the mite Notoedres cati.

Sarcoptes mites can be transferred to humans, but because humans are not a natural host for the mite the condition tends to be short lived. (Consult your doctor for advice should you be concerned). 

  • The Demodex Canis mite is confined to dogs. These mites usually live in small numbers deep in the hair  follicles without causing any problems. In some cases the mite can take over, leading to a condition called  Demodicosis or Demodectic mange.
    This is typically  seen in puppies and young dogs less than two years  old  due to their growing/immature immune systems. It  can also occur in older dogs who have a weakened  immune system caused by illness. The  most common  symptoms are patchy hair loss around the  face and forelimbs, (localised) or generalised hair loss, skin redness and crusting. Demodex mites are transmitted to puppies from their mother during the first few days of life.

    Demodex mites
    (microscopic view)

Since the mite is found on virtually all dogs, exposure of a normal dog to one with demodectic mange is not dangerous. 
Your vet will take skin scrapes samples to be examined under the microscope. The finding of larger than normal numbers of Demodex mites in skin scrapings confirms the diagnosis.

Demodex Canis mites are host specific meaning they only live on dogs and aren't transferred to humans and cats. Humans and cats each  carry their own species of Demodex but are less likely to encounter problems. 

  • Ear mite; or 'Otodectes Cynotis' can affect pets of all ages but  are more often found in puppies and kittens. They affect the ear canals causing the pet to shake its head or scratch at their ears. A dark brown waxy material can build up in the ears. Ear mites are extremely contagious and can be passed to other pets in the household ( but not humans!).

A microscopic view of
Otodectes Cynotis

Though ear mites are extremely small, they are not so small that they cannot be spotted by the naked eye. Using an otoscope (instrument for inspecting the ear), the vet will look closely at the inside of the ear to see if there are any tiny dots moving around. A sample may be taken and looked at under a microscope to allow the mites to be identified. 
  • Cheyletiella mite; or 'walking dandruff' are most commonly encountered on rabbits and guinea pigs but can affect dogs and cats too. Though humans are not a natural host for this parasite, the mite can live on people for a while. The mites cause irritation and a characteristic dandruff type flaking of the skin.

A microscopic view of Cheyletiella

Cheyletiella mites tend to be larger than most mites, but can still be quite difficult to find.

They don’t burrow under skin but hide within the keratin coat of the skin’s epidermis or outermost layers. Moving skin flakes (walking dandruff) may or may not be visible to the naked eye. Samples of dandruff caught on sticky tape can be examined for the presence of mites or their eggs.

  • Seasonal harvest mites ('Trombiculodis') is a small orange mite most commonly encountered in the late summer. It can cause intensely itchy reactions on your pet and is often found in small crevices, such as between the toes or in the folds of the ears. They often cluster together so on inspection, orange dots are visible on the pet's skin.

Harvest mites between a dog's toes

Although parasites can be troublesome, the good news is that they can be controlled and cured! We have a variety of medications that are highly effective.

2. Allergic skin disease

Allergies (or hypersensitivity) among our pets are extremely common and may be evident as rubbing around the face and ears, or constant ear infections. You may see them chewing and licking their paws or generally scratching all over or rubbing themselves against furniture or along the floor ( Dogs). The skin is prone to infection.

In cats, itchiness is again a sign and they begin to over-groom as they lick and bite at the irritation. This results in damage to the hair and the appearance of bald patches - often over their thighs, back or tummy. They can develop a red and crusty rash commonly seen around the head, neck and base of the tail. 

  • Flea allergic dermatitis - This is an allergic reaction to a flea bite and is the most common cause of allergy in both dogs and cats. The animal is actually allergic to the flea saliva and doesn't need to have many fleas to suffer a reaction to them. The associated itching and inflammation can lead to excessive scratching and chewing at the skin which damages it and leads to secondary bacterial or fungal infections.
Routine, effective flea control is essential to treating flea allergy dermatitis.

  • Atopy (atopic dermatitis) - Environmental allergens are inhaled or absorbed across the skin barrier and trigger an allergic reaction in the skin. Causes of allergies generally fall into two categories, seasonal and non-seasonal. The seasonal allergies tend to flare up at certain times of the year, whereas the non-seasonal allergies are a continual year round problem.

Common allergens include pollen (from flowers, weeds, grasses and trees), mould spores, house dust/ house dust mites and hair dander from other animals, but there can be a long list of potential triggers. 
Dogs are more prone to atopy than cats.

Typically symptoms of atopy develop between the age of six months - three years of age but we do see it in animals that are older too. Any breed of dog may be affected but some are more prone to developing it than others. Some breeds most commonly affected include terriers; especially West Highland White Terriers and Staffordshire Bull Terriers, Labrador Retrievers, Golden Retrievers and German Shepherds. It is common for pets with atopic dermatitis to develop ear infections and secondary bacterial and yeast infections.

There is no single specific test to diagnose atopic dermatitis. Essentially, it is a clinical diagnosis based on history, physical examination,  ruling out other pruritic (itchy) skin diseases and response to treatment. Our vets may recommend tests such as skin cytology  (to look for bacteria or yeast), skin scraping (for mite identification), or cultures (for fungal causes).If allergens are suspected, the vet may discuss serum testing (blood testing) and/or intra-dermal (skin) testing that can determine what the animal is allergic too.

Management options: 

Depending on the severity of your pet's symptoms and the length of the specific allergy season,  one or more of the following treatments will probably be required;
  • Anti-inflammatory therapy. Treatment with anti-inflammatory drugs such as corticosteroids, or with antihistamines, will quickly block the allergic reaction in most cases. Essential fatty acids can improve the response to steroids and antihistamines in some cases. 
  • Immune modulators (dogs). This type of medication changes the way the skin reacts to allergens leaving it less reactive and itchy. It makes the skin less sensitive so that it doesn't get itchy in the first place. 
  • A non-drug treatment with high efficacy and safety is available for dogs in the form of an injection.  It can be used in conjunction with any other treatment but in many dogs it will probably be the only treatment needed. It is a biological medication (a protein, not a chemical) that works like a dog's own immune system to block the signals that trigger itch. Injections are usually given every four weeks.
  • Immunotherapy. If either intradermal skin testing or blood testing for atopy has been performed and specific allergens have been identified, immunotherapy may be recommended. This involves administering an allergy vaccine by injection to desensitise your pet to the allergen .Allergy vaccine therapy is typically life-long once started.
There are other things that may be added into long-term treatment of atopic dogs in addition to one of the main treatments.

1. Avoidance of allergens – such as avoiding dusty areas or country walks at certain times of the year ( but this is not easy! Also pets can be allergic to multiple allergens!)
2. Shampooing to wash allergens from the skin and to keep the skin hydrated and free from scurf. The vet will recommend the best shampoo to use to suit your pet's needs. 
3. It is always essential to prevent secondary bacterial infections (pyoderma) and yeast infections (Malassezia) with medicated shampoos and tablets prescribed by your vet.
4.Local treatment using other drugs e.g. in ears or on feet when these areas are particularly problematic for an individual.
5. A nutritional supplement of essential fatty acids ( EFAs)  to support the skin cells and help to maintain coat health. 

All sufferers and their symptoms are unique, and there is no one treatment that fits all. Your vet can talk through the options tailored specifically to your pet. 

Atopic dermatitis is an incurable condition but it can be successfully managed. The aim of treatment is to control symptoms and make the pet comfortable. Regular visits to the surgery are often required so that the vet can monitor your pet's progress and ensure that they are receiving the right treatments in relation to your pet's symptoms.

  • Adverse Food Reaction. Animals can develop reactions to particular proteins in food, although anything and everything can cause a reaction. The reaction triggers an adverse response of the immune system to an ingested molecule found in a food source. This immune system reaction often takes months or even years to occur before your pet begins to show signs of a food allergyTo develop a food allergy, an animal must have had prior exposure to the protein so it may be a food that the animal has been on for years. Apart from itchy skin, a small proportion of pets may also show signs relating to the gut, such as vomiting, diarrhoea or an increased frequency of defaecation.

The ideal test to diagnose or rule out a food allergy is a strict food elimination diet. Feeding a dog or a cat with a food sensitivity a new diet containing solely new ingredients (or novel proteins), can eliminate this over-exaggerated response by the immune system and alleviate signs of the food allergy. There are special hypoallergenic prescription diets available that contain hydrolysed protein - this is where the protein has been broken up into pieces too small for the body's immune system to recognise. The diet needs to be fed solely for at least 8 weeks to see an  improvement.

Food intolerance is an abnormal response to an ingredient but it does not involve the immune system. The symptoms however can be very similar to those of a food allergy.

3. Infections

  • Bacterial skin infection
Pyoderma is more common in dogs but cats can also be affected. They can be simple or complex infections. Simple infections are ones that occur following a one-time or simple event, e.g flea infestation or scratch to the skin surface. Complex infections are usually secondary to underlying skin conditions such as allergies, parasites, hormonal conditions or diseases that compromise the immune system. The skin is weakened and bacteria that naturally reside in the skin minding their own business, multiply, resulting in infection

Skin fold pyoderma is an infection of the surface layers of the skin. It occurs where two layers of skin fold over one another, creating a warm, moist environment with poor air  ventilation,  where bacteria can flourish. This condition is more common in breeds of dogs that have loose skin and prominent skin folds such as bulldogs, boxers, spaniels & pugs.

Signs of pyodema include red irritated areas of skin, crusting of the skin, moistness, discharging spots and an unpleasant smell. 
Treatment involves regular, frequent use of a topical wash or cream prescribed by the vet. Antibiotic therapy may also be required. 
It is important to keep these areas as clean and dry as possible to prevent recurring problems (the vet will demonstrate how to do this). 

Moist dermatitis, also known as 'hot spots' is seen most commonly in dogs. They can appear suddenly, usually as a result of the animal scratching, biting or licking at an irritation. The sore area can increase in size in a short space of time - a small, red area of skin can quickly become a large, raw oozing lesion. It is important to bring your pet in to see the vet as soon as possible so that treatment can be started. Moist dermatitis is usually triggered by an underlying skin problem.

  • Yeast infection
Yeast is commonly found on the skin of dogs and cats, particularly in the ear canal, between the toes and around the anus. They have a mutually beneficial relationship with the bacteria found upon the skin surface. The yeast organisms are opportunistic; this means they take advantage to grow and infect the skin when the conditions are right. When the number of yeast multiply, inflammation of the skin occurs. This tends to happen more often in dogs and is less common in cats.
Infections can occur in high humidity (e.g Summer), after swimming or as a secondary infection to allergic skin disease. Dogs with floppy ears and skin folds are at risk, but all dogs can be affected. Yeast infections cause itchy skin with hair loss, reddened areas and thickening of the skin. Skin lesions are usually accompanied by an offensive smell. Yeast is a fungus and infections are usually treated using ear ointments and medicated shampoos. 

If you notice that your pet is itching or scratching more than normal, bring them in to see a vet. They will obtain a history of your pet's symptoms and perform a full health check before examining your pet's coat, skin and ears. Depending on the results from the examination, your vet may recommend further tests to determine the cause of the itch. 

Once a diagnosis is made, the vet will devise a treatment plan and schedule regular appointments as required to monitor your pet's progress. 

Call us for further advice or to book an appointment with a vet. 

Disclaimer :The contents of the Arden House Animal Hospital website are for informational purposes only. The content is not intended to be a substitute for professional veterinary advice, diagnosis, or treatment. Always seek the advice of your veterinary surgeon with any questions you may have regarding your animal’s medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.