Ectoparasitic Skin Disease in Dogs

Your family pet has the dubious honor of being an environmental “host” to various ectoparasites, all of which have the potential of causing skin problems, conditions and diseases for your doggy family member.  While these skin problems, conditions and diseases are not only uncomfortable and inconvenient for both you and your dog, they can also lead to other systemic health issues for your pet, some of which can be serious.

Ectoparasitic skin disease in dogs is a skin disease which occurs as a result of an infestation of external parasites (ectoparasites) which live and get their sustenance from the consumption of blood or epithelial skin cells of the canine host.

Since there are a variety of ectoparasites from which your canine family member can suffer and, the symptoms will vary depending upon the ectoparasite currently living on your dog, here are some of the symptoms you may see:

• Intense itching and scratching (this may be all over the pet’s body or isolated to a small area)
• Loss of hair in various areas or all over the body
• Various types of skin eruptions, some of which are crusty and may ooze pus or even bleed
• Head shaking or scratching of ears
• Gastrointestinal worms appearing in the feces (looks like grains of white rice)
• Muscle paralysis which can be progressive and lead to death

Types  

The types of ectoparasitic skin disease in dogs is dependent upon the ectoparasite which has taken up residence on your canine family member.  Here are some of the more common ones:

• Ticks - Various species found in a variety of places worldwide, some can cause serious health complications
• Fleas - Can be found virtually worldwide and in various climates and can be responsible for intestinal worms
• Mites - Ear mites, demodex (causes demodectic mange) and sarcoptes (causes scabies)
• Lice - This is not as common an ectoparasite in dogs but can be quite bothersome as well as zoonotic (passable between animals and humans)

There are a number of ectoparasites which can infest your canine family member and cause a variety of skin diseases when they do.  While the method of infestation and infection may differ between the ectoparasites which can inhabit your pet, here are some of the mechanisms which are believed to be at the root of the skin disease:

• Fleas saliva contains histamine-like compounds, enzymes, amino acids and polypeptides (chains of amino acids and essential portions of proteins); as the fleas feed on your pet’s blood, their saliva is injected, with the resulting dermatitic skin irritation and inflammation
• Ticks inject a toxin into the host’s bloodstream when biting and feeding, causing a multitude of systemic issues which are dependent upon the species of tick who is eating at your pet; muscular paralysis is the most dangerous symptom of the paralysis tick and brown dog tick species (certainly infections can result from the bites and feeding of any of the tick species)
• Mites can also inject toxins into the canine host which cause a variety of skin conditions, some of which don’t show symptoms early on nor do they show up with any visible disease conditions until the disease has progressed to the scaly and scabby skin conditions noted in scabies and cheyletiella; demodex is a special kind of mite which can, ultimately, become a skin disease which can be very difficult to treat and eliminate from your pet
• Lice can be either the blood-sucking type or the chewing type; both type of ectoparasites deposit toxins into the skin and blood of their host which creates various types of skin eruptions and itching

The similarity of the mechanisms and methods used cause very similar skin irritations and inflammatory reactions to the host,  making the diagnosis of the offending ectoparasite difficult to tie down. This is where your input can be vital to your vet.  This is some of the information he will need:

• Breed of dog being treated -  Some breeds are predisposed to certain skin conditions; if your canine family member is a mixed breed, this may still be a factor
• Age of the patient - This factor comes into play because some ectoparasites like Sarcoptes Scabiei, Otodectes cynotis or Demodex canis are particularly attracted to puppies
• Symptoms noted, their duration and severity, was the onset sudden or gradual
• Other animals in the household - do they have skin conditions, too
• Are there any human family members with skin diseases, either chronic or intermittent (scabies and ringworm, for example, are zoonotic meaning that they can be passed between humans and animals)
• Dietary regimens and any changes made, when changes were made and the reasons for doing so
• Living conditions - This can include where your pet sleeps, his bedding, bathing and grooming regimen, where he exercises or plays
• General health history of your pet and any vaccinations received and their dates, if this information is not readily available to the attending veterinary professional

Some testing modalities may be utilized by your veterinary professional after his physical examination to diagnose:

• Superficial skin scrapings
• Deep skin scrapings
• Trichogram - Epilation of hairs from areas difficult to scrape with safety 
• Tape preparations - Sticky tape applied to the skin to collect debris for analysis

The samples collected from these various testing modalities will be examined microscopically in an attempt to identify the uninvited inhabitant of the skin and hair of your pet.  An appropriate treatment plan will be developed and initiated when the results of these tests have been analysed.

There are a number of ectoparasiticides which are commonly in use for the treatment of ectoparasitic skin disease in dogs.  These are, of course, dependent upon the particular ectoparasite which is determined to be the offender of your pet.  Here are some of the products which have been developed for use in this area.  Your veterinary professional will know what products to utilize and the appropriate way to administer it:

• Macrocyclic lactones - Selamectin, eprinomectin and moxidectin
• Cholinesterase inhibitors - Organophosphates and carbamates 
• Chlorinated hydrocarbons - Less popular due to environmental issues
• Neonicotinoids - A class of insecticides also known as Nitroguanidine, Neonicotinoid, Chloronicotine, Chloronicotinyl 
• Formamidines
• Oxidiazines
• Isoxazolines
• Insect growth regulators
• Phenylpyrazoles
• Pyrethrins and pyrethroids 
• Spinosyns
• Repellents
• Synergists

Your veterinary professional will determine the product he feels will work the most effectively and safely for your pet.  The methods of administration of the above types of ectoparasiticides are aimed at customer convenience:

• Aerosol 
• Powders
• Shampoos
• Sprays
• Dips
• Rinses
• Mousses
• Spot-ons
• Injectables
• Oral tablets 
• Oral liquids
• Various types of impregnated collars

The newer spot-on method of administration has shown itself to be much more reliable and successful than some of the other methods of treatment.

Recovery of ectoparasitic skin disease in your canine family is generally good if it is diagnosed and treated in an appropriate and timely manner.  Since these ectoparasites live in many of the areas in which your pet does, it will be important to take steps to avoid future episodes of reinfestation and reinfection.  This will require some changes in your pet’s living routine as well as those routines in which you and your human (and other animal) family members are currently involved.

If the skin disease which has been identified in your pet is a zoonotic one (such as scabies or ringworm), be prepared to treat yourself and other family members if needed.  All in all, appropriate and timely treatment with continued monitoring and management should go a long way toward keeping your family pet healthy and happy.