Treatment Protocol of Canine Parasitic Dermatitis (Ticks, Mites, Fleas & Lice) in India

May 28, 2023

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Treatment Protocol of Canine Parasitic Dermatitis (Ticks, Mites, Fleas & Lice) in India

Pet owners have a close relationship with their dogs and often spend their leisure time cuddling them. In the pets various form of skin diseases caused by infestation of vectors like ticks, lice, fleas and mites. These all ectoparasites are responsible for canine parasitic dermatitis (demodecosis) which cause great damage to skin and also results in malodor from body. Among parasitic dermatitis, the most common ticks are Rhipicephalus sanguineus. Mange (acariasis) is a persistent contagious skin disease of animals and man caused by parasitic mites. Common mites which affect the dogs are Demodex spp, Sarcoptes scabei and Otodectic mange (Ear mites). Demodicosis is a mange caused by Demodex canis and follicular mite which infects follicles and sebaceous glands. The disease is common among canine species being manifested in three different forms Sarcoptic mange (canine scabies) is more serious, highly contagious and zoonotic. It can infect all species of animals including man. Clinical signs manifest in form of intense itch, injury to the skin, weeping skin lesions, crusts and scab formations often seen at the elbow and ear region Demodectic mange, (Red mange) is the third form and the most serious type caused by Demodex canis . Which is non- contagious and can only be seen in immunodeficient animals, old dogs and young puppies of about 3-months to a year infected in utero . The mites burrow deep into the skin, feeds and secrete substance that reduces the innate resistance of the animal. The disease is thought to be hereditary often seen in oily skinned and short haired dogs. Both the sexes have the same ability to transmit genetic predisposition to demodecosis. However, Marsalla (2010) reported a higher prevalence of disease in long haired dogs. Dogs with localized form of demodecosis develop alopecic areas around the eyelids, lips, mouth and front limb giving the animal a characteristic moth-eaten appearance. Infected puppies recover by their fourteenth month as their immunity develops. Otherwise, the disease becomes chronic and generalized showing large alopecic areas on various parts of the body which coalesce into large bald areas. The hair follicles may be plugged with debris and Demodex canis mites with draining sinus tracts emitting there by a strong foul odour. At this stage the animals may be at risk of secondary bacterial infection along with complications of pododemodecosis affecting the paws. Unlike other canines Demodex species mite Demodex corenei can reside in most superficial layer of epidermis. It is 50 per cent shorter than other form of Demodex canis Demodex injai, the large body demodex, is larger in all life stages than demodex canis Diagnosis is by taking deep skin scrapping in Potassium Hydroxide (KOH) or Sodium Hydroxide (NaOH) as 10% solution in order to digest the debris and release of mites . However, most of times it is difficult to identify mites under the microscope and treatment is often commenced based on the obvious clinical signs. A simple way of diagnosis is by “Pedal-pinna reflex” technique where by the dog moves its hind limb in scratching motion as the examiner gently manipulate and scratches the ear. This technique is effective for over 95% of most mange cases because these mites proliferate around the ear region at some point of time. Treatment is of a great controversy amongst veterinarians and there are different thoughts. Some group recommend small daily shots of ivermectin along with medicated bath for 3-4 weeks. Others prefer weekly injection of ivermectin shots or by oral route . As such, health status of dog as regard skin affection is of prime concern and a challenge to the field veterinarian to tackle as with. Assessment of hematobiochemical alteration with prompt therapeutic management is the dire need of hour. Therefore, an attempt is being made to study the etiology, prevalence and for evolving suitable therapeutic regimen to the treat canine dermatosis.

Parasites can take up residency in or on your canine family member through a variety of ways. Fleas, mites, ticks (just to name a few) can be found externally virtually everywhere on any dog exposed to the outside world or any part of it carried in on your shoes. Other parasites can inhabit the intestinal system of your pet through various methods of contact with fecal materials or areas contaminated with it. And, there are skin reactions and disease which accompany these many different types of parasites.

As in any dermatological case, the diagnostic approach for ectoparasitic skin diseases should be done in a systematic way.

A detailed history should always be obtained. The presence of pruritus as well as its characteristics should be recorded. Although pruritus constitutes a common manifestation of ectoparasitic skin diseases, its absence does not rule them out For example, localized demodicosis, some cases of cheyletiellosis and pediculosis are not pruritic or exhibit only slight pruritus.

Another important aspect of the history is the determination of the source of the suspected infestation. Most ectoparasites are transmitted by direct contact with infested animals or even humans. Demodectic mites could be considered an exception, although these mites are transmitted only early in life when pups are suckling and ingest them.

Most ectoparasites are contagious, and history could provide evidence for that when humans or other animals are affected in the household. However, there might be an ectoparasitic skin disease in the dog without contagion to occur.

After history has been obtained, a thorough clinical and dermatological examination has to be undertaken. Primary and secondary lesions along with their distribution pattern should be recorded. There are no pathognomonic skin lesions for ectoparasitic skin diseases, since a variety of both primary and secondary ones are usually present depending on the duration of the infestation, the parasite species involved and the specific immune response of the dog.

Symptoms of Skin Reaction Due to Parasites in Dogs

The symptoms of skin reaction due to parasites in dogs are quite similar to allergic skin reactions and, for the average pet parent, distinguishing between these two types of skin reactions can be challenging. Your veterinary professional will likely need to assist you in this determination. Here are some of the symptoms commonly found with skin reactions of either type:

Severe itching
Skin redness
Pimples or bumps
Hives
Crusting, bleeding or oozing lesions
Hair loss
Excessive licking or scratching by your pet

Types

There are two basic types of skin reactions from which your canine family member can suffer:

Allergic dermatitis – Caused by the canine’s allergy or sensitivity to certain environmental or topical elements and conditions or sensitivity or allergy to certain foods or ingredients
Parasitic dermatitis – Result from the bite, infestation or saliva of an external parasite like fleas, ticks, various types of mites and lice (not the human type)

DIAGNOSTIC TECHNIQUES FOR LOCATING ECTOPARASITES:

Skin Scraping

Skin scraping is the most frequently used test in small animal dermatology, aiming to find and identify small and microscopic ectoparasites. Skin scrapings should be obtained in any case of alopecia, pyoderma, keratinization disorder and pruritic dermatosis, although some veterinary dermatologists suggest all dogs with skin disorders should have a skin scraping.

There are two types of skin scrapings: superficial and deep. The species of suspected ectoparasite(es) determines the type of skin scraping to be performed. Some ectoparasites (e.g., Cheyletiela mites) live on the skin, subsisting on the debris and exudates that are produced on its surface, therefore superficial skin scrapings enhance the success in finding parasites. On the other hand, other ectoparasites (e.g., Demodexa nd Sarcoptes mites) live within the skin, for at least part of their life cycle; in these cases deep skin scrapings enhance the success in finding parasites in these cases.

The equipment needed to perform a skin scraping is mineral oil, a scalpel blade, microscope slides, coverslips and a microscope.

For a superficial skin scraping to be performed, sometimes clipping the hair coat may be necessary. Scissors rather than electric clippers should be used, because superficial mites can be lost if electric clippers are used. The lesion to be scraped should be moistened with mineral oil to aid the collection of skin debris. The skin is scraped using a dull surgical blade perpendicular to the skin surface to avoid the collected material to smear over surrounding hair and tissue. Debris is placed on a microscope slide containing one drop of mineral oil and slightly emulsified by using the blade. A coverslip is added and the slide is examined under low microscopic power (x10).

Deep skin scrapings collect debris from the intrafollicular and superficial dermal areas.

Before the skin scraping is performed, the affected skin should be squeezed between the thumb and the forefinger to extrude the mites from the hair follicles. Blood must be visible grossly to confirm that a sufficiently deep skin scraping has been performed. After debris collection the rest of the procedure is similar to that described for superficial skin scrapings.

Regardless of the type of skin scraping performed, a minimum of three sites should be scraped. The periphery of a typical unexcoriated lesion should be chosen for scraping, as most parasites move away from sites of inflammation. The microscope slides should be examined very carefully for mites, ova, and fecal pellets.

Acetate Tape Impression

This test is indicated when Cheyletiella mites, poultry mites, and lice are suspected. It is more reliable in dogs with heavy infestations. Clear, pressure-sensitive acetate tape is pressed to the hair surface and to the skin adjacent to parted hairs or in shaved areas. The tape is then stuck with pressure on a microscopic slide and examined. Attention must be paid to collect scale from the skin and not from the distal part of the hair. Superficial parasites are found very close to the skin surface.

Coat Brushings and Flotation

This technique is indicated in any pruritic or scaling dermatosis. Brushing debris may contain adult fleas, flea excreta, ticks, lice or Cheyletiella mites. In this test, large areas of the dog’s body are brushed and the collected scale and debris are put in a fecal flotation solution. A coverslip is applied to the surface of the flotation solution, allowed to stand for 10 minutes and then transferred to a microscope slide and examined. Hairs should be carefully examined for the presence of eggs glued to the shafts.

Trichoscopy

The examination of a hair plucking (a trichogram) under the microscope can provide diagnostic information regarding ectoparasite infestation. The bulb section must be examined for Demodex mites, since these are the only ectoparasites intimately associated with the proximal section of the hair, owing to their intrafollicular habitat. The hair shaft should also be examined for ectoparasites since lice and Cheyletiella lay their eggs along the proximal to mid-section of the hair shaft and attach their ova using either a cement-like substance or thread.

Ear Swabs

This test is used primarily to find Otodectes cynotis mites. Many species of ear mites migrate to the ear margins to deposit eggs; therefore, if swabs from the external ear canal are negative, skin scrapings from ear margins or the periaural skin should be performed.

The animal should be restrained and the external ear canal gently swabbed with a cotton-tipped swab. The collected debris should be transferred to a microscope slide by gently rolling the swab in a drop of mineral oil. A coverslip is then added and the slide examined under low microscopic power.

Serology

This test is particularly useful for diagnosing Sarcoptes mange when mites evade detection.

The test is an ELISA assay for determination of circulating anti-Sarcoptes IgG in the blood serum of suspected dog.

TREATMENT

The monoamine oxidase inhibitor Amitraz can be used as a topical acaricide applied as a 0.025%-0.05% sponge-on solution, for either weekly use or fortnightly treatment interval, for the treatment of sarcoptic mange, cheyletiellosis and generalized demodicosis. Half a milliliter of undiluted amitraz solution can be mixed with 30 ml of propylene glycol or mineral oil to treat demodectic otitis externa or localized lesions such as pododemodicosis.

Amitraz should not be used in Chihuahuas, in pregnant or nursing bitches or puppies less than 3 months of age. Care should be taken if the drug is being handled by, or applied to, a diabetic owner or patient respectively, as individuals exposed to it and its vapors can develop transient hyperglycaemia. It should also be noticed that the α2 adrenoreceptor agonistic properties of amitraz may induce central nervous system (CNS) depression, bradycardia and sedation.

Fibronil is a GABA receptor inhibitor and can be used either as 0.25% solution or as 10% concentrated solution at 30 days intervals, or every 15 days, for the treatment of flea and tick infestations, sarcoptic mange, cheyletiellosis and otoacariasis. For the treatment of sarcoptic mange it is mainly indicated for early infestations and for those individuals in which the use of alternative products is contraindicated (e.g., very young puppies and pregnant or nursing animals). A single otic application of two drops of 10% solution was effective in controlling Otodectes cynotis infestation in one study, with no adverse effects. Fibronil has the advantage, over other acaricidal drugs, that it can be used in puppies over one week of age.

Ivermectin has been used (off-label use) in the treatment of sarcoptic and otodectic mange and cheyletiellosis as s.c injections every 14 days or per os every 7 days, at the dosage of 0.3-0.6 mg/Kg for 30 days. Because the drug is not licensed for this purpose the owner consent should be obtained prior to its off-label use. Because idiosyncratic reactions can occur in Collies, Shetland sheepdogs, Australian shepherds, Bobtails and Border collies, this drug should not be used in these breeds or their crosses, as it can affect the CNS, causing ataxia, tremors, mydriasis, salivation, depression and even coma and death. Injectable ivermectin has been given daily per os at dosages of 0.6 mg/Kg for several months for treatment of canine generalized demodicosis (off-label use).

Milbemycin oxime is well tolerated by Collies and other breeds sensitive to ivermectin. It has been successfully used in sarcoptic mange and cheyletiellosis at the dosage of 1-2 mg/Kg per os once or twice weekly for 3 weeks (off-label use). For canine generalized demodicosis, a daily dosage of 0.5-2.0 mg/Kg has been described (off-label use). The drug can also be used in canine nasal mite infestation at the dosage of 0.5-1 mg/Kg.

Injectable moxidectin, given per os at the dosage of 0.4 mg/Kg every 15 days for two occasions, was useful to treat canine sarcoptic mange (off-label use). Administered per os daily at 0.2-0.4 mg/Kg/day it gave good results against canine generalized demodicosis. The drug can also be used for treatment of canine otoacariasis at the dosage of 0.2 mg/Kg per os or s.c twice, every 10 days. Contraindications for its use are the same as for ivermectin.

Selamectin is a novel avermectin and its spot-on formulation is the only systemic treatment licensed for the control of canine sarcoptic mange, cheyletiellosis, some ticks and fleas (adults and eggs), although it can be effective in canine otoacariasis in spite of being not registered for this use. The drug was effective against canine nasal mites when given 4 times at two weeks apart.

Imidacloprid blocks the post-synaptic nicotinic acetylcholine receptors and is safe and effective adulticide drug for flea control with residual activity. Imidacloprid 10% (w/v) in combination with permethrin 50% (w/v) in a spot-on formulation has been found to be effective against fleas and ticks.

Insect growth and development inhibitors (IGIs) do not kill adult fleas but will decrease the viability of eggs and/or interfere with the development of larvae and pupae. They are available as a spot-on or as orally administered formulations. IGIs are Lufenuron, Cyromazine, Methoprene and Pyriproxifen.

Permethrins and Pyrethrins are effective flea adulticides whose mechanism of action is achieved by disruption of Na+ channels that lead to paralysis and death of the parasite. They are also effective against lice infestations in dogs.

For flea control there are many additional products in the market available containing organophosphates, carbamates and other pyrethroids (apart from permethrin) and botanicals (apart from pyrethrins).

Parasitic Dermatitis in Canine