Successful management of generalized canine demodicosis with secondary bacterial dermatitis in a geriatric dog: A case study

Introduction

Canine demodicosis or red mange is an important parasitic skin disease of dogs that results from excessive multiplication of Demodex mites within the hair follicles and, in some cases, the sebaceous glands. Demodex canis is the most commonly associated mite with canine demodicosis, although other species and morphologically different forms of Demodexhave also been reported in dogs (Leydig, 1859; Izdebska & Fryderyk, 2011; Hnilica, 2010, Swathi et al., 2016) [5,4,3,12,13] . Clinical demodicosis develops when the mite population increases considerably and the host is unable to maintain normal control over mite multiplication (Fondati et al., 2010; Singh & Dimri, 2014) [2,11] . Age is a clinically important factor in canine demodicosis, as the epidemiological data indicating that adult-onset demodicosis is considerably less common than juvenile-onset disease, making its occurrence in an older dog particularly relevant from a clinical perspective (O'Neill et al., 2020; Swathi (2016) [10,12,13] . This case report highlights the importance of long term oral ivermectin treatment protocols and topical therapies to counter secondary bacterial infection instead of systemic antibiotic/antimicrobial therapy in an adult dog.

Case history and observations

A 13-year-old intact male golden retriever dog weighing approximately 35 kg was presented to the Veterinary Clinical Complex, Veterinary Hospital Bhoiguda, PVNR Telangana Veterinary University, India, with a history of progressively worsening dermatological lesions of approximately four months' duration. According to the owner, the condition initially manifested as localized alopecia around the face and periocular region, which gradually progressed to generalized hair loss involving multiple body regions despite treatment received with Fluralaner elsewhere. The dog exhibited persistent pruritus, erythema, scaling, crust formation, facial excoriations, and progressive deterioration of health. The owner also reported excessive licking of the paws, intermittent scratching, and gradual loss of body condition. Appetite remained normal, although the dog's activity level had decreased over the preceding weeks because of persistent dermatological discomfort.

Diagnosis and treatment Deep Skin Scrapings

Deep skin scrapings were obtained from multiple representative lesions, including the periocular region, muzzle, trunk, and affected paws. Hair over the selected sites was clipped, and the skin was gently squeezed to express follicular contents before scraping. A sterile scalpel blade coated with liquid paraffin was used to scrape the skin until capillary bleeding was observed, thereby ensuring adequate sampling of hair follicles where Demodex canis mites resides.

The collected material was transferred onto clean glass slides containing mineral oil and examined microscopically under low power (10×) magnification. Microscopic examination revealed live cigar shaped Demodex canis mites and multiple developmental stages (Figure 1). Detection of multiple life stages from several anatomical locations confirmed active generalized demodicosis according to current WAVD diagnostic recommendations.

Impression Smear Cytology

Impression smear cytology was performed using direct glass-slide impressions obtained from erythematous and crusted lesions before topical cleansing. Smears were airdried and stained using Field's stain for microscopic examination.

Cytological evaluation demonstrated large numbers of degenerating neutrophils with intracellular coccoid bacteria together with abundant extracellular cocci (Figure 2). Occasional macrophages and keratin debris were also observed. These findings were consistent with secondary superficial bacterial pyoderma. Both forelimbs and hindlimbs exhibited erythema, alopecia, and inflammatory lesions involving the paws, consistent with pododemodicosis. Mild lichenification and seborrhoeic changes were observed over chronically affected regions. Palpation of the skin revealed moderate follicular thickening without evidence of nodular lesions or draining tracts.

Based on the distribution of lesions and laboratory findings, generalized canine demodicosis complicated by secondary bacterial pyoderma was considered the principal clinical diagnosis.

Discussion

The occurrence of generalized demodicosis in a 13-yearold dog represents an unusual presentation and makes the present case clinically relevant, as reported by O'Neill et al., 2020 and Swathi 2016) [10,12,13] , that adult onset demodicosis was considerably less frequent than juvenileonset disease in dogs. Adult-onset disease may have different underlying associations from juvenile-onset disease, and therefore the identification of an underlying systemic condition becomes an important part of the clinical evaluation (Miller et al., 2019; O'Neill et al., 2020) [7. 10] . The immunological role in canine demodicosis has been discussed extensively (Singh & Dimri, 2014) [11] contributing to excessive multiplication of Demodex mites, apart from that we have also emphasised on building skin barrier owing to the old age of the dog, by advising Derma support diet. The clinical findings in our case study including alopecia, erythema, follicular casts, pustules, crusting and scaling were in agreement with Miller et al., 2019 [7] and Mueller et al., 2012 [9] , who also reported that pruritus become pronounced when secondary bacterial infection is present.

Oral ivermectin has been used as a systemic acaricidal treatment and has demonstrated efficacy against generalized canine demodicosis in accordance with the reports of Zhou et al., (2020) [14] and Mueller (2004) [9] . Theparasitological clearance, where Demodex mites were not detected in the deep skin scrapings from same lesion sites by 6 weeks was similar to the findings of Chansiripornchai and Chansiripornchai (2008) [1] . Treatment was continued beyond clinical improvement and microscopic clearance of mites to reduce the likelihood of recurrence, as per the recommendations of Mueller (2004) [9] and Zhou et al., 2020 [14] . Many authors like Miller et al., 2019 [7] and Mueller et al., 2012 [9] reported that secondary bacterial infection as a common complication of generalized demodicosis and may significantly worsen the clinical condition of affected dogs.

We have resorted to topical spray to control superficial pyoderma as per guidelines by the International Society for Companion Animal Infectious Diseases (ISCAID, 2025) instead of using systemic antibiotics Loeffler et al., 2025 [6] .

Conclusion

The present case highlights that generalized demodicosis in an old dog has to be a differential while handling dermatological cases. The clinical improvement during ivermectin therapy should be correlated by performing repeated skin scrapings examination for Demodex mites before the treatment is considered complete. The author also emphasising on consideration of effective topical sprays and derma support diets instead of resorting to systemic antimicrobial therapies. This report reinforces the importance of integrating meticulous diagnostic evaluation, appropriate acaricidal therapy, management of concurrent bacterial infections, and regular follow-up into the clinical management of generalized canine demodicosis. Such a comprehensive approach can result in an excellent prognosis even in geriatric patients presenting with advanced dermatological disease.

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