Canine generalized demodicosis treated with varying doses of a 2.5% moxidectin+10% imidacloprid spot-on and oral ivermectin: parasiticidal effects and long-term treatment outcomes

Advocate(®) (2.5% moxidectin+10% imidacloprid) (Bayer HealthCare, Leverkusen, Germany) is a multiparasiticidal spot-on authorized for treating canine demodicosis in many countries. This blinded, randomized three-phase clinical trial compared its efficacy employing different dosing regimens with that of ivermectin. In the blinded first phase, 58 dogs suffering from generalized demodicosis were randomly assigned to one of four groups and treated with monthly, biweekly or weekly applications of Advocate(®), or with oral ivermectin (IVR) at 500 μg/kg daily. Dogs were evaluated clinically and multiple skin scrapings undertaken every 4 weeks until parasitological cure was achieved (defined as two consecutive series of deep skin scrapings at monthly intervals negative for all life forms). Forty dogs completed the 16-week initial blinded phase, with 5 cases achieving parasitological cure. Five dogs were deemed treatment failures and subsequently treated with ivermectin. The treatment protocol was then changed for the remaining 35 dogs and this cross-over phase (Phase 2) was maintained for a further 8 weeks with an additional 9 dogs achieving parasitological cure. Thereafter, all remaining animals were treated with IVR until cured (Phase 3). Overall, 26 dogs achieved parasitological cure during the clinical investigation. Of these, 23 remained disease-free for at least 12 months while two were lost to follow up and one died of unrelated causes. A total of 32 (55.2%) dogs were withdrawn at various stages of the investigation including the 5 dogs that were judged treatment failures. Other reasons for withdrawal included: non-compliance, lost to follow-up, ivermectin toxicity or reasons unrelated to the investigation. No adverse effects were attributable to the use of Advocate(®). Parasiticidal efficacy was assessed by changes in mite counts (live adult, juvenile and egg) and skin lesion extent & severity scores. Statistical significance was assessed using ANCOVA with initial mite counts or skin scores used as the covariate to account for variations in disease severity. Planned pairwise comparisons were used to identify differences between treatment groups. The efficacy of Advocate(®) increased with its rate of application across all measures of efficacy. Although ivermectin was shown to be more effective than Advocate(®) applied once weekly, both treatment protocols produced clinically satisfactory results. It was concluded that weekly application of Advocate(®) can be recommended as effective for the treatment of canine generalized demodicosis without the potential for toxicity associated with ivermectin.

Demodicosis caused by Demodex canis and Demodex cornei in dogs

Two mongrel dogs aged between 7 and 9 months in a same house were presented to the clinics with a history of chronic dermatitis associated with pruritus. Clinical examination revealed presence of primary and secondary skin lesions on the face, around the ears, chin, neck, fore limbs and lateral abdomen. Examination of skin scrapings revealed Demodex cornei (majority) and D. canis (minority) in both the dogs. By using hair pluck examination D. canis were detected and by tape impression smears examination large number of adult short-tail Demodex mites were found. D. cornei was identified by based on the morphological characters including short opisthosoma with blind and round terminal end. Mean length of total body, opisthosoma of both types of the mites were differed statistically significant (P < 0.01) but gnathosoma and podosoma did not differ significantly (P > 0.05). Dogs were treated with daily oral ivermectin @ 500 μg/kg/day, external application of amitraz along with supportive therapy. After completion of 45 days of therapy dogs were recovered completely without any side effects.

Efficacy of two formulations of afoxolaner (NexGard® and NexGard Spectra®) for the treatment of generalised demodicosis in dogs, in veterinary dermatology referral centers in Europe

Background

A multi-centre field trial was conducted to evaluate the efficacy of afoxolaner based chewables (NexGard® or NexGard Spectra®) for the treatment of generalised demodicosis caused by Demodex canis in dogs under field conditions in France, Italy and Poland.

Methods

Client-owned dogs, diagnosed positive for Demodex mites by pre-treatment skin scrapings and presenting clinical signs of generalised demodicosis were included. Dogs were orally treated with afoxolaner three times at monthly intervals. Of the 50 dogs enrolled, 48 completed the whole study. Efficacy of the treatments was assessed monthly by Demodex mite counts and physical examination with special regard to the severity and extension of skin lesions.

Results

Treatments were well tolerated in all dogs and resulted in a rapid reduction of mites, with all post-treatment mite counts significantly lower than baseline. The number of mites was reduced by 87.6%, 96.5% and 98.1% on Days 28, 56 and 84, respectively. In addition, the skin lesion severity and extent scores as well as the pruritus were all significantly lower at all post-treatment visits compared to the pre-treatment assessment.

Conclusions

This clinical field study demonstrated that monthly administrations of afoxolaner in NexGard® or NexGard Spectra®, offered a convenient and reliable solution for the treatment of canine generalised demodicosis.

The status of Demodex cornei: description of the species and developmental stages, and data on demodecid mites in the domestic dog Canis lupus familiaris

Demodecosis canina is one of the most important dog parasitoses, but its aetiology is still not well known. There are currently two known species of demodecid mite specific to the domestic dog Canis lupus familiaris Linnaeus, 1758 (Carnivora: Canidae). These are Demodex canis Leydig, 1859 (Acariformes: Demodecidae) and Demodex injai Desch & Hillier, 2003. There have also been many reports of the so-called 'short form', considered to be a separate species functioning under the name Demodex cornei nomen nudum, for which, however, no formal valid description has been documented. Taxonomic analysis of short forms of dog demodecid mites, associated with the stratum corneum, was performed, in line with the taxonomic criteria of Demodecidae systematics. This form was found to be a distinct species with features that differ from those of the other known species of this family. The species, including the adult and immature stages, is described. It is likely that different Demodex species parasitizing the domestic dog may be responsible for differentiated symptoms and different courses of demodecosis. However, the basis for clarifying this issue should be the correct, unambiguous identification of the species causing parasitosis.

Efficacy of topically administered fluralaner or imidacloprid/moxidectin on dogs with generalised demodicosis

Background

Canine demodicosis is classified as localised or generalised according to the extent of the disease. Chronic generalised demodicosis is a difficult skin disease to treat and unlikely to resolve without therapy. This laboratory study compared the efficacy of two topical spot-on medications, fluralaner or a combination of imidacloprid and moxidectin, against naturally acquired generalised demodicosis in dogs.

Methods

Sixteen client-owned dogs with naturally acquired generalised demodicosis were randomly allocated to 1 of 2 study groups consisting of 8 dogs each. On Day 0, dogs in 1 group were treated once with fluralaner spot-on solution. Dogs in the other group were treated with the imidacloprid/moxidectin spot-on solution on 3 occasions (Days 0, 28 and 56) or weekly in severe cases. Mites were counted in skin scrapings and demodectic lesions were evaluated on each dog before treatment, and at 28-day intervals over the 12-week period. Deep skin scrapings were made from the same 5 sites on each dog at each examination.

Results

After administration of fluralaner, miticidal efficacy was 99.7% at Day 28, > 99.9% at Day 56 and 100% at Day 84. Efficacy in dogs treated topically with the imidacloprid and moxidectin combination, was 9.8% at Day 28, 45.4% at Day 56 and 0% at Day 84, and was significantly (P < 0.01) lower than the fluralaner treated group at each post-treatment time point.

Conclusions

A single topical administration of fluralaner eliminated Demodex sp. mites on dogs with generalised demodicosis. Topical imidacloprid/moxidectin combination treatment administered 3 times at 28-day intervals, or more frequently, did not eliminate mites from most treated dogs.

Efficacy of oral fluralaner for the treatment of canine generalized demodicosis: a molecular-level confirmation

BACKGROUND

Canine generalized demodicosis is a common parasitic disease caused by the proliferation of Demodex mites. The introduction of isoxazoline class treatments in veterinary dermatology has resulted in apparently effective treatment of generalized demodicosis. The objective of this study was to evaluate the effectiveness of fluralaner for the treatment of canine generalized demodicosis using real-time PCR for the detection and quantification of Demodex DNA.

METHODS

Twenty privately owned dogs with clinical symptoms of generalized demodicosis and deep skin scrapings positive for Demodex canis mites were enrolled in the study. Following diagnosis (day 0) each dog was treated with fluralaner at the recommended commercial dose for tick and flea treatment (25-56 mg/kg) based on body weight. Clinical and mite count assessments, and hair sampling for molecular analyses were performed on days 0, 28, 56, 84 and 112. Demodex DNA was detected and quantified using real-time PCR.

RESULTS

A single oral dose of fluralaner reduced Demodex mite counts in skin scrapings by an average of 98.9% in all dogs by day 28. No mites were recovered from skin scrapings from any treated dog by day 56, at which time the dog was considered to be clinically cured, with total hair regrowth. There were significant differences among examined dogs in qPCR cycle threshold (Ct) values on days 0, 28, 56, 84 and 112. Demodex DNA levels decreased (increasing Ct values) throughout the study. Mite DNA was present on day 112, possibly from dead mites, at values significantly lower than in samples taken on days 0, 28 and 56. Based on qPCR testing of diluted samples, the Demodex mite population was reduced by approximately 1000-fold on day 112.

CONCLUSIONS

Oral administration of fluralaner at the recommended dose to dogs with generalized demodicosis is highly effective for reducing Demodex mite populations and resolving clinical signs of generalized demodicosis. The presence of mite DNA may indicate that treatment did not kill all Demodex mites.

A retrospective study of cases of canine demodicosis submitted to a commercial diagnostic laboratory servicing the United Kingdom and Ireland (2017-2018): Part 1 - Signalment, lesion distribution, treatments, and concurrent diseases

Canine demodicosis, due to an overpopulation of Demodex spp. mites, remains one of the most common dermatological diseases encountered in small animal practice. The aims of this study were to interrogate submitted histories and diagnostic report results from a large cohort of dogs (n = 508) diagnosed with demodicosis either through histological analysis or the finding of Demodex spp. mites on skin scrapings by a UKAS accredited commercial laboratory servicing the United Kingdom (UK) and Ireland in the years 2017 and 2018. The main findings revealed that short-coated breeds were more likely to develop juvenile-onset (JO) demodicosis, whereas medium- and long-coated breeds were more likely to develop adult-onset (AO) disease. Pododemodicosis was reported more commonly in adult, long-coated breeds. Skin scrapings were positive in only 83.3% of samples that had a corresponding positive biopsy result; this finding highlights the necessity to perform further diagnostic tests if demodicosis remains clinically suspected despite a negative skin scraping result. Concurrent underlying diseases, potentially associated with immunosuppression, were reported in 42/221 (19%) of dogs with AO demodicosis. Serum allergy and Sarcoptes ELISA assays were positive in individual animals in both the JO and AO groups; the clinical significance of these latter findings requires careful interpretation in dogs with confirmed demodicosis.

Molecular Characterization of Chitin Synthase Gene of Demodex canis from Mizoram, India

AIMS

Canine demodicosis is a parasitic condition affecting the skin of dogs. The present study was designed to characterize chitin synthase gene of Demodex canis. The molecular technique was used for better understanding of this gene.

METHODS

A total of 75 dogs which are reared as pets with or without showing any skin lesions were examined during the study period. Skin scrapings were examined by indirect method using 10% potassium hydroxide solution under 10 × microscope. DNA samples were extracted from positive skin samples and were subjected to PCR for molecular identification.

RESULTS

A total of 25 dogs irrespective of age, sex, breed or coat showed positive result for D. canis. The PCR revealed a single amplified product of 339 bp length which exactly matched with D. canis. The chitin synthase gene was amplified by PCR, subsequently cloned, sequenced, and compared with available data in GenBank for the particular gene of D. canis. Only one single nucleotide polymorphism (SNP) was noticed at 231 position of the chitin synthase gene sequence when compared to other isolates.

CONCLUSION

The molecular technique confirms with the morphological identity of D. canis. This report signifies the value of peculiar tool to identify 'follicular mite' even from apparently healthy skin.

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.

A retrospective study of cases of canine demodicosis submitted to a commercial diagnostic laboratory servicing the United Kingdom and Ireland (2017-2018) part 2; Aerobic culture and antimicrobial susceptibility results

Clinical diagnostic reports from 508 cases of canine demodicosis diagnosed either by histological or skin scraping analysis from a United Kingdom Accreditation Service (UKAS) accredited veterinary diagnostic laboratory servicing the United Kingdom (UK) and Ireland were evaluated. Of the 508 cases, 284 had skin swabs submitted for culture on the same day the skin biopsy and/or skin scraping were obtained. Dogs with juvenile-onset (JO) demodicosis represented 57.4% of these cases, whilst adult-onset (AO) cases comprised 42.6%. The data revealed that overgrowth of pathogenic bacteria was more common in AO demodicosis cases (75.2%) in comparison to the JO cases (57%). Adult-onset cases also had increased involvement of bacteria belonging to multiple genera and/or yeast (28.9%) in comparison to JO cases (18.4%). Pruritus was significantly associated with an overgrowth of Staphylococcus pseudintermedius (p < 0.001). Resistance to one or more antimicrobial classes was noted in S. pseudintermedius isolates from 56.3% of JO cases with 10.3% of these cases being classified as Multi-Drug Resistant (MDR). Similarly, 51.9% of S. pseudintermedius isolates from the AO cases were noted to be resistant to one or more antimicrobial class with 8.6% of these cases being considered MDR. Cephalosporins were the most frequently administered antimicrobial class noted in submission histories, followed by the penicillin and fluoroquinolone classes. Whilst our findings reveal a high prevalence of concurrent overgrowth of pathogenic bacteria warranting therapeutic intervention in canine demodicosis, the presence of resistance within isolates highlights the need for prudent selection and targeted use of antimicrobial therapy that encompass the key principles of antimicrobial stewardship.