What is Acariasis?
Acariasis in dogs, otherwise known as mange (in animals), is a disease caused by an infestation of the skin with microscopic arthropods called mites. Mites belong to the class Arachnida, and they infect humans, animals, and birds.
There are approximately 50,000 different species of mites. Many are harmless and live in our environment, but most live on the skin, in feathers, or mucus membranes of a host. Infestation can cause hair loss, rash, and pruritic dermatitis.
When seen in humans, it is generally called scabies. However, in animals and birds, the all-encompassing term is mange.
How Can You as a Vet be Confident in Your Diagnosis of Acariasis?
To reach a conclusive diagnosis of acariasis, other causes of alopecia and dermatitis must be ruled out. Therefore, a thorough dermatological examination is paramount for an accurate diagnosis.
Other causes of dermatological lesions include fungal and bacterial organisms, breed-related dermatopathies, autoimmune and endocrine disease.
Diagnosis starts with a thorough history of the patient’s ectoparasite and endoparasite preventative therapies, previous treatments and treatment failures, diet, concurrent clinical conditions, and any known familial clinical concerns.
Following a thorough history, a full dermatological workup is performed. This includes flea combing, fecal floatation, wood’s lamp examination, skin cytology, trichography, tape preparation, ear swab evaluation where indicated, and skin scraping.
Follow this link for a good description of how to correctly perform skin scraping. Depending on the patient’s presenting signs, further diagnostic testing may be needed. This includes skin biopsy, complete blood count, chemistry, and urinalysis.
Definitive diagnosis requires microscopic identification of the mite or direct observation via otoscopic examination of the ear canal. A negative test does not rule out a mite infestation. For example, Sarcoptes yield false-negative results up to 50% of the time.
In the case of negative testing but appropriate clinical signs, treatment is initiated, and the patient is observed for resolution of signs within two to four weeks.
The Background of the Disease
Canine acariasis (mange) affects many pets. It is primarily seen in dogs that are not on routine flea and tick preventives. This makes it a prevalent disease among shelters and stray pets. Transmission is by direct contact with another infected animal or human. Some mite species can survive several days in furniture, bedding, or clothing.
Demodex mites are generally acquired from the dam shortly after birth and can be normal skin inhabitants. The disease is commonly seen in young animals with immature immune systems. In the case of focal demodicosis, the condition is often self-resolving. With the advent of newer flea tick preventives, the disease is becoming more manageable and preventable.
What Are The Causes of The Disease?
The four most diagnosed mites in dogs are Sarcoptes Scabiei, Demodex canis, and Otodectus cynotis, and Cheyletiella spp. All four mites have clinical features that may help differentiate them.
Sarcoptes Scabiei (Sarcoptic mange)
Sarcoptes scabiei is highly contagious, and intense itching is a significant feature of an infestation. Clinical signs include thinning of the hair, alopecia (hair loss), pruritic dermatitis, and secondary bacterial dermatitis.
It burrows underneath the skin and is zoonotic (transmitted from animals to humans). The clinical feature of intense pruritus contrasts with the other major cause of acariasis in dogs, Demodex canis.
Demodex is a typical inhabitant of the skin and rarely causes itching unless there is a secondary infection. Demodex canis infects dogs and ferrets. Demodex folliculorum and Demodex brevis infect humans.
Demodex canis (Demodicosis, Demodectic mange)
Demodex resides in the hair follicles of their host. The disease occurs when Demodex overgrowth occurs due to the host dog’s immune system not functioning properly. This can be because the immune system is immature or if the dog has weakened immunity due to another disease process. Luckily, Demodex canis is not considered zoonotic.
D.folliculorum and D.brevis infect humans but rarely cause clinical symptoms unless there is a large overgrowth. Large numbers of mites lead to inflammation of hair follicles, causing a blockage, inflammation, and allergic skin disease. Signs associated with D. folliculorum are usually confined to the face, while symptoms associated with D.brevis occur all over the body.
Otodectes cynotis (Ear mites)
Otodectes cynotis is well known to infest cats but will also infest dogs, ferrets, and rabbits. Transmission is by direct contact with other infected animals. They cause an accumulation of ceruminous dark-colored discharge in the ears.
This is accompanied by intense head shaking and scratching at the ears.
Cheyletiella (Hair clasping mite, Walking dandruff)
Cheyletiella yasguri (Dogs), C.yasguri (cats), and Lynxacarus radovskyi (cats) are non-borrowing mites that live on the skin surface. They transmit between hosts by direct contact and hitch a ride on fleas, lice, and flies.
This family of mites is not host-specific and will infest dogs, cats, and rabbits. They cause flaky exfoliative dermatitis, mainly on the dorsum. The appearance of “walking dandruff” is caused by agitation of debris from the mites. Lynxacarus spp. Cause rust-colored dull hair coat and may be confined to the tail head or perineal region.
Available Treatment Options
A holistic approach to treatment is essential for success. All in-contact animals need treatment to prevent re-infestation. All bedding and living environments also benefit from treatment. In the case of a mature dog with generalized demodectic mange, identifying the predisposing cause is essential.
Several products are available for both treatment and prevention of mange. However, arguably the drug class Isoxazolines offer one of the most effective and convenient options.
Products belonging to the Isoxazoline drug class are marketed primarily for flea/tick prevention. This drug class was first launched in the United States in 2014. While these products are labeled for fleas and ticks, they have proven effective for treating and preventing sarcoptic and demodectic mange.
The following commercial flea/tick preventives belong to this drug class:
- Bravecto (fluralaner) tablets for dogs
- Bravecto (fluralaner) topical solution for cats and dogs
- Bravecto Plus (fluralaner and moxidectin) topical solution for cats
- Bravecto 1-month (fluralaner) tablets for cats
- Credelio (lotilaner) tablets for dogs and cats
- Nexgard (afoxolaner) tablets for dogs
- Simparica (sarolaner) tablets for dogs
- Simparica Trio (sarolaner, moxidectin, and pyrantel) tablets for dogs
- Revolution Plus (selamectin and sarolaner) topical solution for cats
These flea/tick preventives are safe and effective. Still, as the United States Food and Drug Administration (FDA) warns, isoxazoline products have been associated with neurological side effects in some pets. Reported signs include tremors, ataxia, and even seizures. A veterinarian can help you determine if the isoxazoline drugs are contraindicated in your pet.
Ivermectin is another practical but “off-label” treatment for mange in many species. There are several treatment protocols available. Most involve regular injections either weekly or every other week for four to six treatments.
Some dogs have a mutation of the ‘multidrug resistance mutation 1’ (MDR1) gene. This interferes with the body’s ability to metabolize many drugs, including ivermectin. Classically these dogs belong to the collie family (e.g., Shetland sheepdogs, Australian shepherds).
Therefore, ivermectin-based products should be used with caution in these breeds. In addition, a DNA test is now available to identify dogs that have this gene mutation.
Moxidectin/Imidacloprid (Advantage Multi)
Advantage Multi is labeled for both dogs and cats to prevent heartworm, fleas, and gastrointestinal parasites. It contains a macrocyclic lactone, the drug family well known for the treatment of mange. Importantly it is more recently labeled treatment and control of ear mites and sarcoptic mange.
Revolution is another flea/tick preventive that is label approved for treating sarcoptic mange in dogs. The release of Revolution Plus (Selamectin + Sarolaner) has offered two drug classes in one that can be utilized to combat mange.
Revolution is still effective in dogs. It is also used for the treatment of rabbits, guinea pigs, and ferrets. Multiple protocols have been described, but generally, it involves applying selamectin every two-four weeks for three or more treatments.
Historically the only option for treatment of mange was the application of dips that kill mites. Amitraz and lime-sulfur have traditionally been used but are messy, and newer treatment options have proven less troublesome.
Macroscopic and Microscopic Examination of Acariasis
The clinical syndrome of acariasis varies depending on the mite species involved. However, Alopecia, dermatitis, rash, and even papular urticaria are standard features of most. In addition, secondary bacteria or yeast infections usually compound the infestation.
There is no way to definitively diagnose a dermatopathy based on clinical signs alone. Microscopic evaluation of the mite is key to diagnosis.
Mites vary in size but range from 0.2mm to 0.5mm. The best microscopic evaluation is performed at x4 and x10. Sarcoptes scabiei has an oval body with four pairs of short legs. Demodex mites have eight short stubby legs.
Their body is elongated and cigar-shaped, well suited to living within a hair follicle. Otodectes cynotis is a large mite (0.5mm) and may be seen in situ along with their eggs via an otoscope. This mite has a large white oval body with four pairs of projecting legs.
Cheyletiella spp. Also have four paired legs, and their prominent feature is a characteristic ‘saddle shaped’ waist. In addition, its longer legs help differentiate it from Sarcoptes.
- Acariasis (scabies, mange) is a mite infestation of the skin.
- Mites are microscopic arthropods that can infect humans, animals, and birds.
- Infestation can cause hair loss, rash, and pruritic dermatitis.
- Transmission is by direct contact with another infected animal or human.
- Definitive diagnosis requires microscopic identification of the mite utilizing a skin scraping, flea comb, trichogram, tape preparation, ear swab, or otoscopic examination of the ear canal.
- A negative test does not rule out a mite infestation.
- Numerous products are available for both treatment and prevention of mange. Many are off-label for any given species but are proven highly effective.
- Consultation with a veterinarian is essential for the successful diagnosis, treatment, and prevention of canine ascariasis (mange).
Rochelle is a veterinarian board-certified in theriogenology (animal reproduction). She works as a general practitioner with a special focus on reproduction at Opelika Animal Hospital in Auburn Alabama. Rochelle always had a special affinity for animals growing up. As a veterinarian she is passionate about educating clients, empowering them with knowledge. This allows them to provide their pets the best preventive health care and embrace the human-animal bond.