Pashu Sandesh, 24 October 2018
Shimala Yadav, Ravi Prakash Pal, Mayank Parwari, Shahid Hassan Mir and Lamella Ojha
Demodex canis and Demodex mitesis occurs naturally in the hair follicles of most dogs in low numbers, these mites never cause problems. However, in certain situations, such as an underdeveloped or impaired immune system, intense stress, or malnutrition, the mites can reproduce rapidly, causing symptoms in sensitive dogs. Demodicosis is an inflammatory parasitic disease of dogs characterized by the presence of larger than normal numbers of demodectic mites accomplished with pruritis, itching, alopecia, crusting, scaling, otitis, pustules, nonhealing wounds, nodules, and ulcerative disorders.
Demodectic mites such as Demodex canis (major cause), Demodex cornei and Demodex injai
Season wise highest and lowest were in March (4.15%) and December (1.39%) respectively, sex wise male dogs (3.67%) was higher than that in female dogs (2.74%) and age wise dogs of 1 to 5 year old were more commonly infected than other age groups (Chen, 2012). Breed wise short haired breeds are more susceptible to infection as compared to the long haired breeds, might be possible due to well-developed sebaceous glands in these breeds (Kumar, 2018).
D. canis is a normal resident of a dog's skin and ear canal. Transmission occurs from the bitch to nursing neonates by direct contact during the first 2 or 3 days of neonatal life. Mites may be demonstrated in the hair follicles of puppies by the time they are 16 hours old. The mites are first observed on the muzzle of the puppies, which emphasizes the importance of direct contact and nursing. The thermotactic zone of D. canis is between 16° to 41°C (60° to 106°F).
The entire life cycle of the mite is spent on the skin. The parasite resides within the hair follicles and rarely in the sebaceous glands, where it subsists by feeding on cells, sebum, and epidermal debris. The life cycle of Demodex is that an egg (fusiform) develops into 6 legged larvae that then develops into an 8 legged nymph differentiated from an adult by it lack of an “armor-like” breastplate.
Pathogenesis demodicosis is a complex and not completely understood; evidence of hereditary predisposition, immunosuppression, natural and itrogenic causes are directly associated with the development of the disease.
a) Localized Demodicosis: Localized demodicosis occurs as one to several small, circumscribed, erythematous, scaly nonpruritic to pruritic areas of alopecia, most commonly on the face and the forelegs. Pruritis in demodicosis is variable but it is complicated by the secondary pyoderma. Most cases occur in young dogs (3–6 months of age) and resolve (spontaneously over 6-8 weeks) without treatment.
b) Generalized Demodicosis: Generalized demodicosis usually covers large areas of the body (e.g., facial area and all feet). Juvenile-onset generalized demodicosis occurs in dogs aged between 3 to 18 months and adult-onset generalized demodicosis occurs in dogs older than 12 to 18 months. The characteristic signs observed in both types of generalized demodicosis are: erythema and scaling together with secondary pyoderma, patchy to diffuse alopecia, pruritus and peripheral lymphadenopathy. English bulldogs may be predisposed to this nodular presentation. Staphylococcus intermedius is the most common bacterial organism to complicate generalized demodicosis
c) Demodectic Pododermatitis: Demodicosis can be present on the feet of dogs without generalized lesions. The case history reveals whether the dog once had generalized demodicosis that healed, except for the foot lesions, or whether the paws were the only part of the body ever affected. The digital and interdigital lesions are especially susceptible to secondary pyodermas due to Pseudomonas aeruginosa.
Surface Sampling:-Skin scraping, acetate tape impression, and flea combing are all techniques to find microscopic adult mites and immature forms of mites (ova, larvae, and nymphs). Hairs may be removed, and exudates may be collected and examined microscopically. Generally, multiple scrapings from new lesions should be obtained by scalpel blade until true capillary bleeding is obtained and not blood from laceration.
Histopathology: - Skin biopsy specimens from dogs with localized or generalized demodicosis show follicles containing mites and keratinous debris. Interface mural folliculitis, in which plasma cells, lymphocytes, macrophages, mast cells, and eosinophils are found around the follicles and lymphocytes (CD3+ and CD8+) are found infiltrating the epithelium, is a consistent finding. Perifollicular granulomas surrounding mite fragments can be seen in approximately 25% of cases and 20% have a suppurative furunculosis as the main pattern. Perifollicular melanosis is also a common finding in skin biopsy specimens from dogs with generalized demodicosis.
Differential Diagnosis: Dermatophytosis, Generalized pyoderma, Muzzle folliculitis or furunculosis (acne) or early lesions of juvenile cellulitis and lupus erythematosus.
i) Formamidine compound: (Amitraz) Topical amitraz is FDA-approved for treating generalized demodicosis in dogs older than 4 months of age. Amitraz, a miticide and insecticide, is a monoamine oxidase inhibitor (MAOI), prostaglandin synthesis inhibitor, and an alpha 2-adrenergic agonist. Amitraz liquid concentrate is to be used as a 0.025% (250 ppm) dips every two weeks for three to six topical treatments until no live mites are found. A new spot-on formulation containing metaflumizone and amitraz can be used as a topical treatment for generalized demodicosis in dogs older than 1 year of age. Atipamesole (50µg/ kg intramuscularly) can reverse the signs of amitraz toxicosis within 10 minutes. Amitraz collars are not recommended for treating demodicosis. Dogs with respiratory problems or diabetes should not use amitraz.
ii) Macrocyclic lactones: Macrocyclic lactones include the avermectins (ivermectin and doramectin) and milbemycins (milbemicin oxime and moxidectin). This class of drugs selectively binds to glutamate-gated and gamma-aminobutyric acid (GABA)-gated chloride cannels in the mite’s nervous system, resulting in cell hyper polarization, mite paralysis, finally death. Macrocyclic lactones do not readily cross mammalian blood-brain barrier. Safety in mammals is due to the lack of glutamate gated chloride channels in the peripheral nervous system and restriction of GABA to a central nervous system.
1) Ivermectin: For generalized demodicosis, the ivermectin should be given orally at a dose of 300 to 600µg/kg/day. Side effects of daily including depression, stupor, coma, ataxia, mydriasis, tremors, emesis, drooling and seizures; death can also result. Blindness has also been reported in dogs.
2) Milbemycin oxime: Oral milbemycin oxime is recommended at a dose rate of 1.5 to 2 mg/kg/ day, although the dose ranges of 0.5 to 3.1 mg/kg/day have been used. Side effects of daily milbemycin oxime administration are similar to those of ivermectin and include depression, stupor, coma, ataxia, and seizures. The major limitation of this drug is expense.
3) Moxidectin and Doramectin: Moxidectin given orally at 400 µg/kg/day may be effective in treating generalized demodicosis. Doramectin is another avermectin, can be used at 600µg/kg/week subcutaneous injection. This drug should not be used in ivermectin sensitive breeds of dogs.
iii) Isoxazoline compounds: A new class of insecticides/acaricides, are effective against Demodex mite. Compounds like fluralaner, sarolaner and afoxolaner are recommended for treatment of demodicosis. Fluralaner, sarolaner and afoxolaner have similar mechanisms of action, antagonistically binding primarily to the arthropod gamma-aminobutyric acid and glutamate receptor regulated chloride channel and inhibiting the arthropod nervous system, causing paralysis and death.
Alternative and supportive therapies: Using natural remedies for mange, on the other hand, can enhance the dog’s immune system, so that the body can fight off the mange mite infection by itself. Natural remedies such as nutritious foods, herbs and other supplements can be used to treat the skin problem topically. Lots of raw dark leafy vegetables like broccoli, watercress should be added to diet which help in quick recovery from demodectic mange. Raw foods increase the antioxidents which minimize damage to cells, they are useful whenever disease is present and immune support is needed. Adding dietary supplements is also important to help relieve the dog’s itch and improve his skin conditions. Fish oil provides omega-3 fatty acids and can be very effective in easing an itch. Other sources of omega-3 fatty acids include flaxseed oil and pumpkin seed. Jatropha curcas oil along with Withania somnifera root extract revealed higher efficacy against demodectic mange. Powdered garlic, and goldenseal, mixed in olive oil, can be applied to areas of skin infested with Demodex mange. Garlic contains sulphur compounds which mites dislike. Diluted garlic oil can therefore be used topically to the affected areas. Since garlic is antibacterial as well, applying garlic oil to the affected areas will have the added benefit of minimizing bacterial infection. High quality natural food, processed food or those high in sugars should be avoided.
Rubbing of copious quantities of vegetable oil into the skin are said to starve Demodex mites of oxygen. Neem oil, together with lavender oil, can make an effective skin rinse against mange. To make the skin rinse, 1-part lavender oil, 1-part neem oil and 10 parts almond oil should be mixed and applied to affected areas once or twice daily. Yarrow is excellent in wound healing, stops the bleeding from oozing wounds. Yarrow oil, salve, or ointment can be applied to the affected areas. Other herbs that are effective against mange include yellow dock, Echinacea, Calendula and aloe vera.
Homeopathic treatment: Commonly used homeopathic remedies are Sulphur, Psorinum and Silicea. A treatment protocol for mange consists of the combined usage of neem oil (externally) and homeopathic (orally). The neem oil kills the mange mites on contact, while the homeopathic deals with the animal’s constitutional predisposition to getting mange (this helps to reduce the likelihood of the mange recurring). The homeopathic preparation contains arsenicum album, graphites, hepar sulph, kali arsenicum, psorinum, and sulphur.
Shimala Yadav1, Ravi Prakash Pal2, Mayank Parwari3, Shahid Hassan Mir2 and Lamella Ojha2
1 M.V.Sc scholar, Animal Nutrition Division, ICAR-NDRI, Karnal
2 Ph.D scholar, Animal Nutrition Division, ICAR-NDRI, Karnal
3 M.V.Sc scholar, Cliinical Medicine, Anand, Gujrat