Ectoparasites are organisms that live on or in the skin of another living organism. Depending on the severity of the infestation, they can cause significant harm to our dogs directly and indirectly. Ectoparasites aren’t just vampires that suck blood for nutrition. There are two kinds, one type lives permanently on the skin of the host, and the other type feeds on blood and/or body cells for itself or the development of its offspring.

These parasites transmit diseases to their host via microorganisms (pathogens). They are vectors for diseases like borreliosis (Lyme disease), babesiosis, ESME (early summer meningoencephalitis/tick paralysis), and of course tapeworms (fox tapeworm).

All ectoparasites are members of the arthropoda phylum, and are subdivided into insects (six-legged) and arachnids (eight-legged). Examples of insects are fleas, Trichodectes canis (dog biting louse/lice), lice, mosquitoes, and flies. Ticks and mites, on the other hand, are examples of arachnids.

Quite often, an illness and/or infestation by endoparasites that results in an immunodeficiency makes the animal an easy target for a major infestation. A dog’s immune system may also be weakened by stress, hormonal disorders, or poor living conditions such as inadequate food, keeping, or care – making it prone to a severe infestation of endoparasites.

For example, demodex canis (hair follicle mites) in a dog lead to deep, therapy resistant pyodermatitis. An infected dam can also transmit follicle mites to pups through its milk during the first three days. Besides infesting subcutaneous connective tissue, mites also infect lymph nodes and the spleen. Generally, ectoparasites cause specific, acute to chronic dermatological problems.

Diagnosis requires careful examination of the dog’s skin and coat for presence of parasites, often with a magnifying glass or under the microscope. Important symptoms include bald spots, severe itchiness, eczema, eggs (nits), or deposits of flea feces. To identify parasites living in the skin, it is necessary to biopsy a skin scraping or examine the hair.

From a therapeutic standpoint, you must first kill the parasite, using chemotherapy if necessary!
Temporary guests like ticks harm their host by transmitting pathogenic organisms that can cause acute and/or chronic diseases. Often, chemotherapy is the only approach to avoid diminished performance or death of the animal.
Ectoparasites [Greek] – defined as parasites living on the surface of their host.
Ectoparasites are six-legged insects or eight-legged arachnids that live on the skin of another living organism and suck their blood, for instance, as a nutrient. Ectoparasites transmit microorganisms that cause diseases. For us of relevance are ticks (borreliosis and ESME or early summer meningoencephalitis/tick paralysis), whereas in tropical countries mosquitoes are of relevance for causing malaria along with flies (worm diseases), and fleas (plague). Some parasites like lice and mites cause specific skin diseases by taking up permanent residence, in a sense.

We will delve into this group below, but not say much about temporary, accidental parasites like mosquitoes and fleas or about insects that are poisonous for humans. This discourse first addresses the pathogens and the diseases they cause, and then moves on to medications relevant for treating infestations of such parasites. 

Parasites transmit pathogens that cause diseases like borreliosis, babesiosis, ESME, malaria, and of course tapeworms.

Ectoparasites live both in and on the skin of a host. They differ in that some parasites live permanently on the host, while others are in transit to get nutrients for themselves or for the development of their offspring.

Ectoparasites are members of the arthropoda phylum, subdivided into:
-    Arachnids (ticks, mites)
-    Insects (Trichodectes canis or dog biting louse/lice), lice, fleas, and diptera 

General symptoms are: 
-    Itching caused when the parasites move on the skin, or by their products of metabolism
-    Subsequent scratching, licking, scrubbing causes dermatitis or eczema 
-    Often pyogenic organisms cause secondary infections
-    Trichorrhexis (hairs split or break easily) or hair loss could be a primary or secondary illness 
-    The parasites‘ products of metabolism can cause allergies (fleas, simulium or blackfly)
-    A major infestation of blood-sucking insects can lead to anemia 
-    The constant burden of these pests later turns into diminished performance, development disorders, weight loss, etc.

The following is a brief summary of each kind of parasite: 

Ticks
These are blood-sucking arachnids, and can cause diseases like borreliosis, meningitis, Q fever (rickettsia), or babesiosis canis in canines.

Fleas
These insects are bloodsuckers and attack mostly omnivores and carnivores. Only the females suck blood, with about 1% of the entire population living off of hosts. The remainder is found in areas where animals are present. Flea eggs are very robust and can survive up to a year without food.

Diptera
Among this order are mosquitoes, horseflies, flies, and louse flies. They are real pests for animals and often cause myiasis, which is an invasion by dipterous larvae. They are either direct pathogens or carriers of other parasites and viruses. The spot where they bite either hurts or itches. Their secreted poisons and salivary toxins can cause allergies, rashes, eczema, and possibly even an allergic shock.

The warble fly is unique in that its larval stages develop in the body of the victim. 

Demodex canis (hair follicle mite)
Cattle, horses, and hogs attacked by arachnids exhibit only a mild form of folliculitis, whereas dogs in contrast often develop deep, therapy resistant pyodermatitis. Young animals are often infected by their parents, and those with low resistance always tend to experience relapses. Besides infesting subcutaneous connective tissue, mites also infect lymph nodes and the spleen.

Mange
Mange is caused by one of several kinds of mites (arachnids): 
-    Sarcoptes, caused by the burrowing mite
-    Psoroptes, which never affect carnivores
-    Chorioptes, found only on cattle and horses 

A physician/vet must notify the authorities of a case of mange, especially if it involves Sarcoptes or Psoroptes! 


Ear mites (Notoedres, Otodectes)
These mites often cause an inflammation of the outer ear in dogs and cats. The suborder, Notoedres cati, leads to head mange in cats.

Cheyletiella (walking dandruff)
A severe infestation by such mites leads to mange-like symptoms in carnivores. 

Harvest mite (Trombicula autumnalis)
These mites prefer areas of the skin like lips, around the eyes, between the toes, ears, bridge of the nose, etc. They also sit on top of a cat’s tail, but horses and cattle are seldom attacked.

Lice
Lice are bloodsucker insects, specific to certain hosts, and cause severe itching. They attach their eggs (nits) to the animal’s coat, which are visible with a good magnifying glass as tiny white spots.

Trichodectes canis (dog biting louse / lice)
This parasite, a member of the insect family, feeds itself with dandruff and secretions from glands in the animal’s skin. Only major infestations bother the animals.

Diagnosis requires careful examination of the dog’s skin and coat for presence of parasites, often with a magnifying glass or under the microscope. Important symptoms include bald spots, severe itchiness, eczema, eggs (nits), or deposits of flea feces. To identify parasites living in the skin, it is necessary to biopsy a skin scraping or examine the hair.

These days, preventive measures include the use of a collar, ear clips, or compounds with special active ingredients for topical applications. But exercise care when applying these, since they often trigger allergies. The animal’s living area can be cleaned with the use of sprays or mist/fog devices.  

Once the infestation has been confirmed, the first goal is to kill the parasites on the animal and in its surroundings. Insecticides and acaricides are applied either locally (powder, spray, ointment, bath, etc.), orally, via an injection, or topically (Percutan). It is critical to get rid of parasites, especially fleas, in the animal’s entire environment, where almost all of the brood lives.

In general, the animal’s resistance is increased by optimizing the intake of vitamins and food. Fruit vinegar raises external and internal resistance against insects. Since many insects fly only during the day or at dawn or dusk, changing the daily rhythm can also help prevent infestation. Thus allowing grazing animals to stay on the meadows tends to minimize the possibility of a severe infestation.

One can also take a naturopathic approach using homeopathy, phytotherapy, acupuncture, ozone therapy, or dietary therapy (e.g. a yeast cure) – but please seek a specialist!