Sarolaner, a novel parasiticide in the treatment of generalized demodicosis in dogs-a case study

Introduction

Demodicosis in dogs is a serious, debilitating and often life-threatening parasitic skin disease caused by proliferation of Demodex spp. mites in the hair follicles and sebaceous glands of the skin (Pereira et al., 2012) [11] . In dogs, three species of Demodex spp. mites have been identified of which D. canis being the most common demodectic mite (Mueller et al., 2020) [10] . These mites are considered part of the microbiota of most mammals and under normal circumstances, they live as commensals, feeding on their host's sebum and are only opportunistically pathogenic. Clinical signs of juvenile demodicosis in dogs typically occur in the first 18 months of life (Miller et al., 2013) [8] and reported to be associated with a temporary immune alteration or genetic disorders (Mueller et al., 2020) [10] . While in older dogs, it has been attributed to immunosuppressive conditions or medications (Mueller et al., 2020) [10] . Depending on the extent of skin lesions, demodicosis is categorized into localized or generalized forms (Mueller et al., 2012) [9] . Localized form ranges from four lesions to 50% of the body surface and have spontaneous remission without treatment while generalised form is characterised by alopecia, papules, pustules, exudation, erythema, crusting, comedones involving entire body region or five or more separate affected areas with a diameter greater than approximately 2.5cm or pododemodicosis involving two or more feet (Miller et al., 2013; Mueller et al., 2012) [8,9] . Deep skin scrapings are reported to be the diagnostic tool of choice in demodicosis suspected dogs. Trichograms have been considered as an alternative choice to deep skin scrapings particularly in the areas that are difficult to scrape, such as periocular and interdigital lesions Mueller et al., 2012; Beco et al., 2007) [9,1] . From the past, several miticidal options are available which includes amitraz rinses, ivermectin, moxidectin, doramectin, milbemycin oximes etc., They requires repeated administration, appears to be cumbersome, have narrow safety margin and often associated with adverse reactions (Johnstone, 2002; Singh et al., 2011) [6,14] . In contrast to them, isoxazolines (fluralaner, sarolaner, afoxolaner and lotilaner) a new group of parasiticides have been proved to be potent, safe and easy to administer (Mueller et al., 2020) [10] .

Sarolaner is currently authorized as chewable tablet with indications for the treatment of fleas, ticks, demodicosis, sarcoptic mange and ear mites in dogs (Becskei et al., 2016; Mueller et al., 2020) [15,10] . It acts by blocking arthropod GABA and glutamate-gated chloride channels, producing fast mite elimination and can be used safely for puppies from eight weeks of age (Mctier et al., 2016) [7] . This case study documents the therapeutic outcome of sarolaner in generalised demodicosis affected dogs.

Materials and Methods

In the present study, dogs presented to the small animal medicine ward, Department of Veterinary Clinical Complex, College of Veterinary Science, Proddatur with skin lesions suggestive of generalised demodicosis were selected. Detailed clinical examination was carried out. Deep skin scrapings were collected in the direction of hair growth and by squeezing the skin especially from the follicular papules and pustules (Becskei et al., 2018) [3] . The skin was scraped until capillary bleeding oozes so that sufficient depth of the scraping was obtained. Trichogram was performed by plucking hairs with foreceps in the direction of hair growth and placed on a slide in a drop of mineral oil or paraffin oil and covered with a cover slip. For a positive trichogram, plucking a large number of hairs (50-100) is recommended (Mueller et al., 2020) [10] . Treatment regimen included a single dose of Sarolaner (Simparica) @ 2 mg/kg orally monthly once, tab cephalexin @ 15 mg/kg bwt orally BID for two weeks, benzoyl peroxide shampoo for bathing and omega-3 and omega-6 fatty acids supplements @5ml orally BID. Response to the treatment was recorded based on resolution of skin lesions and skin scraping for mite reduction on Day 0, Day 30 and Day 60.

Results and Discussion

In the present study, demodicosis was confirmed in six dogs by identification of live Demodex canis mites, a minimum of four live mites (Mueller et al., 2012; Six et al., 2016) [9,15] on deep skin scrapings (Figure 1a, 1b) and trichogram (Figure 2). Since Demodex spp. mites are part of the normal microfauna, identification of one mite on several deep skin scrapings could be a normal finding and more than one mite with compatible clinical signs is strongly suggestive of clinical demodicosis (Mueller et al., 2020) [10] . Age of the dogs varied from six months to two years indicating an early age of onset (Carvalho et al., 2019) [5] and breeds presented were Nondescript, German shepherd and Bull Mastiff. Prominent lesions noticed were patchy alopecia all over the body, papules, pustules with exudation, epidermal collarette, excoriation, seborrhoea, hypotrichosis, erythema, ulcers, scaling and crusting lesions prominently over face and ventral side of the neck (Figure 3a, Figure 4a, Figure 5a, Figure 6a, Figure 7a and Figure 8a) similar with the findings of Six et al., 2016 [15] ; Carvalho et al., 2019 [5] ; Becskei et al., 2025 [4] . All the clinical parameters were within the normal range as desrcibed earlier by Prins et al., 2022 [13] . All the six dogs in the present study showed marked reduction in skin lesions and skin scrapings were negative for mites by Day 30 and also negative on Day 60 which were consistent with the findings of Six et al., 2016; Carvalho et al., 2019 [15,5] ; Prins et al., 2022 [13] . Treatment for generalized demodicosis should be monitored clinically and microscopically every month until the second negative skin scraping. Miticidal therapy should be continued four weeks beyond the second set of negative monthly scrapings to decrease the risk of a disease recurrence (Mueller et al., 2020) [10] . No adverse reactions were reported by the pet parents which was in accordance to the findings of Mctier et al., 2016 [7] ; Six et al., 2016 [15] ; Carvalho et al., 2019 [5] ; Becskei et al., 2018 [3] ; Becskei et al., 2025 [15] . This rapid and effective mite clearance with complete resolution of skin lesions (Figure 3b, Figure 4b, Figure 5b, Figure 6b, Figure 7b and Figure 8b) align with previously published research demonstrating high sarolaner efficacy. Sarolaner has high palatability and is fully and voluntarily consumed within one minute in 90.5% of cases (Becskei et al., 2016) [15] . The development of resistance to the isoxazoline derivatives is less likely to occur due to its selective inhibition of insect and acarid GABACls and GluCls (Mueller et al., 2020) [10] . Besides their ease of administration, these have a further advantage of reaching all body areas, which has particular importance in long-haired animals (Miller et al., 2013) [8] . In juvenile dogs, treatment of the demodicosis and possibly the secondary bacterial infection, if present, is typically sufficient without the need for further diagnostic investigation (Mueller et al., 2020) [10] . In contrast to this, adult-onset demodicosis was reported to be associated with diseases or drugs leading to a compromised immune system such as leishmaniosis, hyperadrenocorticism, hypothyroidism, neoplasia, babesiosis, ehrlichiosis and glucocorticoid treatment or chemotherapy for which detailed investigation is needed to rule out the possible predisposing factors (Pinsenschaum et al., 2019) [12] . In the present study, cephalexin was used to treat concurrent pyoderma as reported earlier by Prins et al., 2022 and Carvalho et al., 2019 [13,5] .

Conclusion

Despite the availability of multiple treatment options, generalized demodectic mange in dogs continues to be a severe, often a fatal dermatological condition and may be challenging to treat. From this study, sarolaner is found to be a rapid, effective, safer treatment and its palatability with convenient monthly dosing enhance pet parents compliance.

Acknowledgement

AcknowledgementWe thank the authorities of Sri Venkateswara Veterinary University, Tirupati, Andhra Pradesh and the College of Veterinary Science, Proddatur for the facilities provided in conducting this study.

References

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