Demodicosis in Dogs

Abstract
Canine demodicosis is a skin disease caused by the overgrowth of Demodex mites viz. Demodex canis, D. injai and D. cornei in dogs. While these mites normally live harmlessly on dog’s skin, weakened immune systems due to age, illness, or genetics can allow their populations to multiply, leading to alopecia, red and irritated skin, and sometimes secondary bacterial infections. Puppies and immunocompromised dogs are at higher risk, though any dog can be susceptible for the condition. Proper examination of dogs and collection of demodicosis suspected skin scraping, while treatment ranges from supportive care in mild cases to medication and targeted therapies for more severe forms. Maintaining good and balanced nutrition diet, regular grooming, and prompt veterinary care helps to prevent and manage demodicosis, ensuring healthy skin and overall well-being for dogs.
Introduction
Canine demodicosis, also known as demodectic mange or follicular mange or red mange, is a common parasitic skin disease in dogs caused by Demodex mites. These mites are part of the normal skin fauna of dogs and usually reside in the hair follicles and sebaceous glands without causing harm but under certain conditions, their population can explode, resulting in a range of skin problems. This condition has global relevance, affecting countless dogs regardless of environment, breed, sex, or age, though certain populations are disproportionately impacted.
Causes and Predisposing Factors
The primary cause of canine demodicosis in dog is Demodex canis although other species viz. D. injai and D. cornei are also reported in dogs.
Through contact: Neonatal contact with an infected mother for an hour results infection.
Immune System: The disease typically manifests when the dog’s immune response is compromised. Young puppies are especially at risk due to their immature immune systems and increased sebaceous activity. In older dogs, immunosuppression from diseases or medications may trigger demodicosis.
Genetics: Some dog breeds like Staffordshire terrier, Staffordshire bull terrier, Chinese shar-pei and French bulldog have a genetic predisposition, especially for the generalized form of the disease.
Types of Canine Demodicosis
Localized Demodicosis: It is characterized as patchy areas, alopecia initially occurs on the head and forelimbs with mild inflammation, and often resolves without treatment. It is most common in pups of 3 to 9 months of age.
Generalized Demodicosis: This form involves widespread skin lesions, inflammation. In severe condition generalized deep pyoderma occurs. In the beginning squamous form or red mange appears where hair follicles are distended with mites and cellular debris, the follicular epithelium is atrophic, hyperkeratosis is progressively evident followed by exfoliation of cornified epithelium from the surface and severe alopecia. Hyperpigmentation gives skin coppery red appearance. As the condition progresses the large area of animal body affected and the animal shows thickened and wrinkled skin with a ‘mousy’ odour. This results in pustular form of demodicosis due to bacterial invasion (Staphyloccus spp.) of the dermis. The pustules later become large and form abscess. Such lesions are often visible around abdomen, legs, elbows, feet and face. In extensive form of canine demodicosis death occurs due toxemia and emaciations.
Clinical Signs:
Affected dogs show the following clinical signs: Alopecia, especially on fore and hind limbs, face, neck, and trunk. There is redness of the skin, pustules, crust, thickened skin, follicular casts, and sometimes abnormal pigmentation. The dogs also suffer from severe itching and discomfort, they start licking, scratching, biting, and chewing at affected areas. Presence of abscess in secondary bacterial infection.
Diagnosis
Proper examination of the skin of the dog. Deep skin scrapping can be collected from infected skin lesions as well as pustules and abscess of the suspected infected dog. Scrapping should be deep enough to assure sampling of the hair follicle and hence should cause capillary oozing.
Skin scrapings should be boiled in 10% KOH solution in the laboratory and examined under 10x or 40x of microscope for the presence of mites. The mite appears elongated chigger shaped,0.1-0.4mm, they have a head, four pairs of stumpy legs in the thorax and an elongated abdomen. Mouthparts consist of a paired palp, chelicerae, and an unpaired hypostome.
In the pustular form, impression smear can be made and stained and evaluated for the presence of bacterial organisms.
Hematological profile: There will be elevations in white blood cells (especially neutrophils and eosinophils). The C- reactive protein will be higher in the serum of the dogs suffering from acute phase of infection.
Molecular Diagonsis: Infected skin debris and pus from the abscess of the infected dog can be collected and Polymerase Chain Reaction (PCR) or Real Time Polymerase Chain Reaction (RT-PCR) can be used for the detection of Demodex spp DNA in it.
Impact and Pathophysiology
Demodex infestation can interfere with the skin’s barrier function and induce local and systemic inflammation in infected dogs. The body’s response includes oxidative stress, evidenced by heightened markers such as malondialdehyde (MDA), superoxide dismutase (SOD), and reduced antioxidant enzymes. While the disease occurs globally, street dogs and neglected populations are especially vulnerable due to malnutrition, lack of routine care, and environmental stressors.
Treatment:
Topical applications of benzyl benzoate, mupirocin, benzoyl peroxide, chlorhexidine, ethyl lactate and amitraz are found to be effective. Macrocyclic lactones such as ivermectin and doramectin, used in both injectable or oral form in the dogs, have shown good results. A newer group of isoxazoline drugs, which includes fluralaner, afoxolaner, and sarolaner, are highly effective for topical use and safe oral agents also. Proper antibiotics should be given to the dogs suffering from secondary bacterial infection due to demodicosis. Multi vitamin syrup like Nutripet, Zipet etc., can be used to enhance immunity.
Management
Supporting Therapy: Addressing underlying immunosuppressive conditions such as dogs suffering from intestinal parasitism should be periodically dewormed with anthelminthic. Dogs suffering from endocrine diseases, whelping should be kept in a stress free environment. The dose of glucocorticoids should be minimized or completed stopped for some time in the dogs undergoing treatment of demodicosis for improving their immunity. For the dogs undergoing chemotherapy supportive care should be taken by providing them nutritious diet including meats, eggs and liver along with fresh clean water for proper hydration and to maintain their weight and improve immunity. Further fish oil provides omega -3 fatty acids which can be used as effective food for easing itch in Demodex infected dogs. To maintain the hygiene in dogs suffering from demodicosis along with secondary bacterial infection antimicrobial bath with benzoyl peroxide or chlorhexidine should be given. Infected dog’s kennel or living area should be cleaned properly with disinfectants and should be provided with clean bedding material. Regular check-ups and monitoring by vets are necessary for controlling the demodicosis infection.
Prognosis: Localized demodicosis generally resolves, but generalized form of demodicosis cases can be severe and life-threatening without proper treatment.
Prevention
Regular veterinary care by providing early detection and intervention of the disease
Prompt management of skin issues by regular grooming of ticks and fleas, avoiding exposure of dogs to pollen, tall grasses and leaf piles will minimize skin allergy in dogs.
Breeding with dogs with a known genetic predisposition should be avoided, examples: Staffordshire bull, terrier, French bulldog etc.
Ensuring optimal nutritional and balanced diet, regular grooming and minimizing stress.
Conclusion
Canine demodicosis remains a significant cause of skin disease and discomfort in dogs, especially among puppies and street populations. Vigilant monitoring, effective diagnostic practices, and comprehensive veterinary care are essential for controlling outbreaks and ensuring canine welfare.
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Rabeya Begam, Amrit Gogoi, Keneisezo Kuotsu, Sashitola Ozukum, Soya Rungsung and Lalsangpuii
College of Veterinary Sciences & Animal Husbandry, CAU (I) Jalukie, Peren, Nagaland-797110
Corresponding Author: Rabeya Begam