Is there a correlation between canine adult-onset demodicosis and other diseases?

Could there be an association between Hashimoto's thyroiditis and demodex infestation?

BACKGROUND

Human demodex mites are parasites that live in the pilosebaceous unit and can result in the disease demodicosis. While demodicosis may occur as a primary skin disease; immunosuppression, and topical or systemic immunosuppressive treatments can cause secondary demodicosis. It is known that thyroid hormones may cause skin changes, such as xerosis, and thereby may also modulate immune responses in the skin.

OBJECTIVES

The aim of this study is to investigate whether or not that the changes occurring in the skin of patients with Hashimoto's Thyroiditis (HT) predispose to demodex infestation.

METHODS

Seventy-eight patients being followed for a diagnosis of HT at Kocaeli University Endocrinology Outpatient Clinic, between January 2019 and March 2020, constituted the patient group. The control group consisted of 41 patients who did not have any chronic systemic or dermatological disease and were shown to have no thyroid disease by laboratory tests. Demodex intensity in the malar regions of the patient and control groups was determined using the standardized skin surface biopsy (SSSB) method and compared with each other.

RESULTS

HT patients were significantly more likely to have increased demodex density and suggestive SSSB results than the controls (p<0.001, p=0.012, respectively). A significant correlation was found between demodex intensity and the findings of xerosis (p=0.010, p=0.011) and spiny follicular papules (p=0.008, p=0.008) in the patient or control groups, respectively. However, a significant correlation was identified between the demodex density and the symptoms of burning-stinging (p=0.028), and feelings of dryness (p=0.018) roughness (p=0.028) only in the control group.

CONSLUSION

Xerotic skin and/or impaired immune responses as a result of autoimmune changes in patients with HT may lead to secondary demodicosis.

Localized Demodicosis in a Dog After Fluticasone Propionate Treatment for Chronic Bronchitis

An 11-year-old, castrated male Shetland Sheepdog presented for a 3-week history of localized nonpruritic alopecia and scaling affecting the peri-nasal region. The dog was being managed for several comorbidities, including chronic bronchitis successfully controlled with the chronic administration of inhaled fluticasone propionate. The physical examination was unremarkable aside from erythema, symmetrical alopecia, scaling and follicular casts affecting the peri-nasal region. Deep skin scrapings and histopathological examination from the lesional skin revealed several live demodex mites consistent with Demodex canis. Transcriptome analysis of lesional skin demonstrated significant downregulation of several cytokines involved in the T helper (Th) 2 and Th17 pathway with moderate upregulation of Th1 cytokine IFN-γ and T-cell recruitment chemokine CXCL10. The dog was immediately treated with oral fluralaner. Clinical signs of demodicosis resolved after 8 weeks and a trichogram was negative for live and/or dead demodex mites. The dog has remained on twice-daily administration of inhaled fluticasone and oral fluralaner every 3 months for 15 months without a demodicosis relapse, in addition to medication to manage the dog's comorbidities. To the author's knowledge, this is the first case of localized demodicosis caused by an inhaled glucocorticoid in a dog.

Diagnosis and treatment of demodicosis in dogs and cats: Clinical consensus guidelines of the World Association for Veterinary Dermatology

BACKGROUND

Demodicosis is a common disease in small animal veterinary practice worldwide with a variety of diagnostic and therapeutic options.

OBJECTIVES

To provide consensus recommendations on the diagnosis, prevention and treatment of demodicosis in dogs and cats.

METHODS AND MATERIALS

The authors served as a Guideline Panel (GP) and reviewed the literature available before December 2018. The GP prepared a detailed literature review and made recommendations on selected topics. A draft of the document was presented at the North American Veterinary Dermatology Forum in Maui, HI, USA (May 2018) and at the European Veterinary Dermatology Congress in Dubrovnik, Croatia (September 2018) and was made available via the World Wide Web to the member organizations of the World Association for Veterinary Dermatology for a period of three months. Comments were solicited and responses were incorporated into the final document.

CONCLUSIONS

In young dogs with generalized demodicosis, genetic and immunological factors seem to play a role in the pathogenesis and affected dogs should not be bred. In old dogs and cats, underlying immunosuppressive conditions contributing to demodicosis should be explored. Deep skin scrapings are the diagnostic gold standard for demodicosis, but trichograms and tape squeeze preparations may also be useful under certain circumstances. Amitraz, macrocyclic lactones and more recently isoxazolines have all demonstrated good efficacy in the treatment of canine demodicosis. Therapeutic selection should be guided by local drug legislation, drug availability and individual case parameters. Evidence for successful treatment of feline demodicosis is strongest for lime sulfur dips and amitraz baths.