Efficacy of daily amitraz on generalised demodicosis in dogs

Fifty dogs with generalised demodicosis were treated with daily applications of 0·125 per cent amitraz solution over half the body. This was applied once a day, alternating the body half treated. Nine dogs were lost to follow-up; the remaining dogs were classified as either a success (25 dogs, 61 per cent) or a failure (16 dogs, 39 per cent) according to their response to treatment. Eight of the failures were due to persistent demodicosis and eight relapsed within one year after treatment. All eight of the relapsed dogs were cured after a second course of daily amitraz treatment. For the 25 dogs considered treatment successes, the median duration of treatment was 6·5 weeks (range, three weeks to nine months), and the median interval from completion of treatment to last post treatment evaluation was 3·4 years (range, two to four-and-a-half-years). Including the eight dogs that were cured after retreatment, the daily amitraz applications were curative in 33 of 41 dogs (80 per cent) with generalised demodicosis.     

Evaluation of a topical treatment, alone and in combination with a detergent, for generalized demodicosis

Thirty dogs (20 treated, 10 controls) with naturally-acquired generalized demodicosis were utilized to evaluate the bio-activity and safety of a liquid concentrate formulation of amitraz, with or without the addition of a nonionic detergent. The detergent was added to the treatment mixture to enhance wetting and thereby reduce the number of treatments required to return diseased animals to a normal state. Three--six miticide treatments were topically applied to dogs at 14-day intervals, at a concentration of 250 parts per million active drug. The liquid concentrate with or without detergent, was equally effective and safe as a dermatotherapy for demodicosis; addition of the nonionic detergent grossly improved the wetting characteristics of the treatment mixture; however, it did not alter the biological activity or the safety of the therapy.     

Evaluation of cytokine messenger RNA expression in peripheral blood mononuclear cells from dogs with canine demodicosis

Using RT-PCR and semi-quantitative PCR, mRNA expression for canine interferon (IFN)-gamma, interleukin (IL)-2, IL-4, IL-5, IL-10, tumor necrosis factor (TNF)-alpha and transforming growth factor (TGF)-beta in peripheral blood mononuclear cells (PBMCs) was examined in dogs with or without demodicosis. mRNA expression for IFN-gamma as well as TNF-alpha in dogs with demodicosis (localized (LD) and generalized (GD)) was slightly lower than those in dogs without demodicosis (healthy controls). Expression of IL-5 mRNA in dogs with demodicosis was higher than that in control dogs, but there were no significant differences in IL-4 and IL-10 mRNA expression levels among the three groups. On the other hand, expression levels of TGF-beta mRNA in dogs with GD were higher than those in control dogs and dogs with LD. The expression levels of IL-5 and TGF-beta mRNA decreased in all three dogs with GD which showed resolution of the clinical signs. Taken together, these results suggest that the Th2-like response in PBMCs from dogs with demodicosis is up-regulated, and that subsequent increased expression of IL-5 and TGF-beta mRNA in dogs with GD is reversible after treatment. Therefore, these cytokines, particularly IL-5, might be a useful clinical index of the clinical course in demodicosis. Also, increased TGF-beta mRNA expression might be a key factor for revealing the difference in the mechanism of onset between LD and GD.     

The role of apoptosis in immunosuppression of dogs with demodicosis

The aim of the present study was to evaluate the status of apoptosis in peripheral blood leukocytes of dogs with demodicosis. A total of 26 dogs suffering from demodicosis, and positive for Demodex canis mites by skin scraping, participated in the study, 13 with localized demodicosis (LD) and 13 with generalized demodicosis (GD). A further 13 clinically healthy dogs, all of whom were negative for mites upon skin scraping, were used as controls. The dogs with GD revealed significantly higher (P ≤ 0.0001) percentage of leukocytes with externalization of phosphatidylserine (PS) and depolarized mitochondrial membrane potentials (ΔΨm) as compared with the dogs with LD and healthy controls. These dogs also revealed significantly lower values (P ≤ 0.0001) of hematological parameters viz. hemoglobin, total erythrocytes count total leukocytes count, lymphocytes, monocytes and neutrophils. Significantly higher (P ≤ 0.0001) percentages of leukocytes with externalization of PS and depolarized ΔΨm were also found in dogs with LD as compared with the healthy controls. These dogs also revealed significantly lower values of Hb (P ≤ 0.0001), TEC (P=0.025), TLC (P ≤ 0.0001), lymphocytes (P=0.008), monocytes (P ≤ 0.0001) and neutrophils (P=0.03). It is concluded that premature apoptosis of PBL may be implicated in the immunosuppression of the dogs with demodicosis.     

Relative sensitivity of hair pluckings and exudate microscopy for the diagnosis of canine demodicosis

This study was designed to compare the sensitivity of deep skin scraping, hair plucking, and exudate microscopy for the diagnosis of canine demodicosis. Sixty-seven dogs diagnosed with demodicosis were enrolled in the study. Thirty dogs had localized and 37 had generalized demodicosis. Twenty-seven of the 67 dogs had complicated (secondarily infected) and 40 had noncomplicated form. On each dog, a single lesion was randomly selected to obtain one deep skin scraping, hair plucking, and, when present (n = 13) exudate. For skin scraping and exudate microscopy, an area under a cover slip measuring 2.2 x 2.2 mm was examined, while trichography included the evaluation of 100 hair shafts. At least one parasitic element was found in 85.1% of trichograms, and 100% of exudate preparations. The number of parasitic elements was higher in skin scrapings compared to the other two methods. The diagnostic sensitivity of skin scrapings was higher than that of hair pluckings for the total number of samples (P = 0.002) and for those obtained from dogs with the localized (P = 0.004) and the noncomplicated (P = 0.002) forms of the disease. The diagnostic sensitivity of hair pluckings was higher in generalized and complicated demodicosis compared to the localized and noncomplicated variants. Based on these results, exudate microscopy may be equally sensitive to deep skin scrapings, and trichography may be of value in generalized and complicated demodicosis, although a negative result cannot rule it out.     

Dermatologic disorders of Chinese Shar Peis: 58 cases (1981-1989).

A retrospective study on the skin diseases of Chinese Shar Peis was conducted over a 9-year period. Skin disease was found in 58 (49.2%) of the 118 dogs studied. Folliculitis was the most common clinical finding (43 of 58 dogs). In 6 dogs, there was no apparent reason for the folliculitis; however, it was secondary to allergic dermatitis, demodicosis, IgA deficiency, or hypothyroidism in the other dogs. Approximately 20% of the dogs had more than one of these disorders. Serum IgA concentration was measured in 7 dogs and was low in all 7.     

Suppression of in vitro lymphocyte transformation by serum from dogs with generalized demodicosis.

Serum from dogs with generalized demodicosis suppressed the in vitro reactivity of peripheral lymphocytes to phytohemagglutinin. Suppression occurred with peripheral lymphocytes from normal dogs or from dogs with generalized demodicosis. Serums from dogs in remission were no longer suppressive. The data indicate that peripheral lymphoid cells obtained from dogs with generalized demodicosis do not respond differently in vitro to phytohemagglutinin than do lymphoid cells from normal dogs when either is cultured in the presence of serum from normal dogs.     

P‐26 New aspects of canine demodicosis and the possibility of treatment with selamectin

The purpose of this study was to evaluate 55 clinical cases of canine demodicosis and to compare the results of treatment using amitraz (solution), selamectin (spot‐on), ivermectin (injection) and cythioate (oral tablets). Data from the 55 cases was collected and evaluated after clinical and microbiological examination. Treatment was selected depending on the severity of demodicosis and compliance of the owner. The cases were followed for 12 months and the status of the patients was grouped on two levels: recovered (58%), or relapsed (42%). Five dogs (9%) were euthanized. The disease was commonly diagnosed in purebred dogs. Demodicosis was more common in dogs under 2 years of age (65%), in males (64%), and in the short‐haired breeds (75%). Demodicosis was generalized in 73% of cases, localised in 23% and affected the feet (pododemodicosis) in 4% of cases. Recovery was the highest in dogs between 1 and 2 years of age (73%), and in the localized cases (92%). Nonspecific treatment with glucocorticoids prior to the diagnosis lowered the rate of recovery (4%), but treatment with glucocorticoids for proven atopic dermatitis improved the rate of recovery (41%). All drugs (amitraz, selamectin, cythioate) administered for the localized form were effective (100% recovered). Recovery in generalized demodicosis was 60% using ivermectin, 55% using amitraz, 44% with the combination of amitraz and selamectin (two treatments with amitraz followed by selamectin), and 43% in cases where selamectin was used alone. Funding: Pfizer Animal Health.     

Field efficacy of moxidectin in dogs and rabbits naturally infested with Sarcoptes spp., Demodex spp. and Psoroptes spp. mites

The efficacy of moxidectin 1% injectable for cattle was evaluated in dogs and rabbits with naturally acquired sarcoptic, demodectic or psoroptic mites. Twenty-two dogs with generalised demodicosis were orally treated with 0.4mg/kg moxidectin daily. Forty-one dogs suffering from sarcoptic mange were treated with 0.2-0.25mg/kg moxidectin either orally or subcutaneously every week for three to six times. Seven rabbits were treated orally with 0.2mg/kg moxidectin twice 10 days apart. Of the 22 dogs with demodicosis, 14% were stopped treatment because of side effects, 14% were lost and of the remaining 72% all were cured (mean therapy duration 2.4 months). Thirty-seven of the sarcoptic mange-infected dogs finished treatment and were cured. In 17% of dogs, side effects were noted. All seven rabbits treated for psoroptic mange were cured and did not show any side effect. Our results indicate that moxidectin is effective and a good alternative for the treatment of demodicosis and scabies in dogs and psoroptic mange in rabbits. Side effects seem to occur more frequently if applied subcutaneously, therefore the oral route should be preferred.     

Influence of systemic antibiotics on the treatment of dogs with generalized demodicosis

Canine generalized demodicosis (CGD) is a skin disease with distinct breed predispositions. Secondary bacterial infections are common. Dogs typically receive miticidal therapy in combination with antibacterial treatment. Whether antibiotics influence the duration of acaricidal therapy is unknown at the moment. There is also debate over how common short-tailed Demodex mites occur in demodicosis. This study evaluated the influence of systemic antibiotics on the course of CGD, the occurrence of short-tailed Demodex mites in demodectic dogs and the influence of furunculosis on treatment outcome. Breed predispositions for CGD in Moscow were identified. Fifty-eight dogs were randomly distributed in two groups. Both were treated with ivermectin 600 mcg/kg q24h orally and benzoyl peroxide shampoo weekly. The dogs in one group (AB) were additionally treated with systemic antibiotics for at least 1 month, dogs in the other group (NAB) were not. Monthly examinations, skin scrapings and impression smears were performed. Prior to the study there was no difference in clinical severity, presence of pyoderma and mite numbers between groups. There was no significant difference in duration until first negative skin scrapings and resolution of bacterial infection. In dogs with furunculosis the number of the mites was significantly higher than in dogs without furunculosis but the duration until microscopic remission albeit longer, was not significantly different. Short-tailed Demodex mites were found in 25% of the cases. Pugs and English Bulldogs were predisposed. Based on these results, systemic antibiotics may not impact as much as previously thought on the actual success of CGD treatment.     

In vitro studies of the effect of propylthiouracil and ronnel on thyroxine-5'-monodeiodinase activity in steers

This study compares in vitro effects of propylthiouracil (PTU) and ronnel on the conversion of thyroxine (T4) to triiodothyronine (T3) in liver and kidney from Angus steers. Tissues were homogenized and incubated with T4 (1.3 microM) in the presence of 0 to 59 microM PTU or 0 to 49.7 microM ronnel. The T3 generated during a 30-min incubation was measured by radioimmunoassay. It was found that 1.47, 5.9 and 59 microM PTU decreased T4 to T3 conversion in liver and kidney by 62 and 88, 71 and 100, and 81 and 100%, respectively. The inhibition caused by 1.47 and 5.9 microM PTU was overcome by addition of 2 mM dithiothreitol (DTT). Ronnel in concentrations of 1.24, 6.22, 49.7 microM decreased T4 to T3 conversion in liver and kidney 46 and 45, 51 and 72, and 78 and 95%, respectively. However, with ronnel, the addition of DTT caused further inhibition. A Lineweaver-Burk plot of the data obtained using .32 to 6.43 microM T4 with 1.47 and 5.9 microM PTU or 6.22 and 12.44 microM ronnel indicated that PTU is an uncompetitive inhibitor (Ki = 1.67 microM) and ronnel is a noncompetitive (Ki = 15.5 microM) inhibitor of T4-5'-monodeiodination. The data suggest that decreased conversion of T4 to T3 by PTU or ronnel may be responsible for the increased plasma concentrations of T4 and slightly decreased plasma concentrations of T3 reported in steers treated with levels of both PTU and ronnel that are associated with growth stimulation.     

P-29 Pustular dermatosis caused by fire ant (Solenopsis invicta) stings in a dog

The purpose of this study was to evaluate 55 clinical cases of canine demodicosis and to compare the results of treatment using amitraz (solution), selamectin (spot-on), ivermectin (injection) and cythioate (oral tablets). Data from the 55 cases was collected and evaluated after clinical and microbiological examination. Treatment was selected depending on the severity of demodicosis and compliance of the owner. The cases were followed for 12 months and the status of the patients was grouped on two levels: recovered (58%), or relapsed (42%). Five dogs (9%) were euthanized. The disease was commonly diagnosed in purebred dogs. Demodicosis was more common in dogs under 2 years of age (65%), in males (64%), and in the short-haired breeds (75%). Demodicosis was generalized in 73% of cases, localised in 23% and affected the feet (pododemodicosis) in 4% of cases. Recovery was the highest in dogs between 1 and 2 years of age (73%), and in the localized cases (92%). Nonspecific treatment with glucocorticoids prior to the diagnosis lowered the rate of recovery (4%), but treatment with glucocorticoids for proven atopic dermatitis improved the rate of recovery (41%). All drugs (amitraz, selamectin, cythioate) administered for the localized form were effective (100% recovered). Recovery in generalized demodicosis was 60% using ivermectin, 55% using amitraz, 44% with the combination of amitraz and selamectin (two treatments with amitraz followed by selamectin), and 43% in cases where selamectin was used alone.
Funding: Pfizer Animal Health.     

Fat absorption in dogs with demodicosis or zinc-responsive dermatosis.

Quantitative absorption of long-chain triglycerides was studied in normal dogs, dogs with demodicosis and dogs which had been successfully treated for zinc-responsive dermatosis. The mean serum triglyceride concentration of dogs treated for zinc-responsive dermatosis was significantly lower than that of normal dogs before (P less than 0.01) and at one hour (P less than 0.01) and two, three and four hours (P less than 0.001) after feeding vegetable oil. No significant difference was detected in the mean serum triglyceride concentration of dogs with demodicosis and normal dogs at any of the sampling times.     

MHC class II expression by follicular keratinocytes in canine demodicosis--an immunohistochemical study

MHC class II proteins present fragments of extra cellular antigen to stimulate CD4(+) T lymphocytes. Aim of this study was the detection of MHC class II antigens on different cutaneous cells in canine demodicosis. Histopathological and immunohistochemical examination of skin biopsies from 44 dogs with demodicosis is reported. The control group consisted of skin biopsies taken from 10 necropsied dogs without obvious skin lesions. The immunohistological assessment of the MHC class II expression revealed MHC class II proteins on different cell types of infiltrating inflammatory cells, i.e. APCs (antigen-presenting cells), macrophages, T lymphocytes and B lymphocytes. The plasma cells, however, only showed expression in 32 (73%) of 44 cases. Generally it was noticeable that most plasma cells but never all of them expressed MHC class II. Neutrophils, mast cells and eosinophils were MHC class II negative. Furthermore, in 39 biopsies (89%) from dogs with demodicosis MHC class II positive follicular keratinocytes were found. The control group did not show MHC class II expression on epithelial cells. Concerning the endothelial cells, a total of 25 biopsies (57%) showed MHC class II expression in which different vascular plexuses were affected by staining. This examination shows that MHC class II expression in the skin of dogs suffering form demodicosis is elevated. Especially the MHC class II expression by follicular keratinocytes seems to be conspicuous. We hypothesize that this is in association with the development and the maintenance of follicular inflammation.     

Changes in oxidative stress indices, zinc and copper concentrations in blood in canine demodicosis

Status of certain oxidative stress indices and zinc and copper concentrations in blood were estimated in dogs with localized demodicosis (LD) and generalized demodicosis (GD). In comparison to healthy control, erythrocytic lipid peroxides level and superoxide dismutase activity were significantly (P < 0.01) higher in both LD as well as GD. However, level of reduced glutathione and activity of catalase were significantly (P < 0.01) lower in both LD and GD. Blood zinc and copper levels in dogs with LD and GD were significantly (P < 0.01) lower than healthy control. Significant (P < 0.01) differences were also observed in different oxidative stress indices and zinc and copper levels in between LD and GD groups. From the present study, it was concluded that demodicosis is associated with oxidative stress and antioxidant supplementation may be beneficial in management of canine demodicosis.     

Deficient cutaneous response to PHA-P in healthy puppies from a kennel with a high prevalence of demodicosis.

Intradermal injection of phytohemagglutinin was used to evaluate the integrity of cell-mediated immunological reactions in Doberman puppies thought to be predisposed to demodicosis. Results indicate a statistically significant deficiency of cutaneous delayed response in these dogs when compared with age matched Beagles, adult Dobermans or random control dogs of various ages and breeding. The high prevalence of demodicosis in the kennel of origin may have been due to the observed deficiency of cutaneous immune function.     

Treatment of demodicosis in dogs: 2011 clinical practice guidelines

Background and Objectives – These guidelines were written by an international group of specialists with the aim to provide veterinarians with current recommendations for the diagnosis and treatment of canine demodicosis. Methods – Published studies of the various treatment options were reviewed and summarized. Where evidence in form of published studies was not available, expert consensus formed the base of the recommendations. Results – Demodicosis can usually be diagnosed by deep skin scrapings or trichograms; in rare cases a skin biopsy may be needed for diagnosis. Immune suppression due to endoparasitism or malnutrition in young dogs and endocrine diseases, neoplasia and chemotherapy in older dogs are considered predisposing factors and should be diagnosed and treated to optimize the therapeutic outcome. Dogs with disease severity requiring parasiticidal therapy should not be bred. Secondary bacterial skin infections frequently complicate the disease and require topical and/or systemic antimicrobial therapy. There is good evidence for the efficacy of weekly amitraz rinses and daily oral macrocyclic lactones such as milbemycin oxime, ivermectin and moxidectin for the treatment of canine demodicosis. Weekly application of topical moxidectin can be useful in dogs with milder forms of the disease. There is some evidence for the efficacy of weekly or twice weekly subcutaneous or oral doramectin. Systemic macrocyclic lactones may cause neurological adverse effects in sensitive dogs, thus a gradual increase to the final therapeutic dose may be prudent (particularly in herding breeds). Treatment should be monitored with monthly skin scrapings and extended beyond clinical and microscopic cure to minimize recurrences. Editor’s Note – A brief review article by R. Mueller has been published: Evidence‐based treatment of canine demodicosis, Tierarztl Prax Ausg K Kleintiere Heimtiere 2011; 39: 419–24. This is not considered to constitute duplication of the article published here in Veterinary Dermatology.     

Efficacy of 1.25% amitraz solution in the treatment of generalized demodicosis (eight cases) and sarcoptic mange (five cases) in dogs

Eight dogs with generalized demodicosis and five with sarcoptic mange were treated with 1.25% amitraz solution applied weekly and associated with an antidote treatment (atipamezol, 0.1 mg kg⁻¹ IM once: and yohimbine 0.1 mg kg⁻¹ once daily for 3 days, orally). Results of skin scrapings were used to determine whether therapy should be continued or stopped. The median number of treatments for demodicosis and sarcoptic mange was three (range 2–5) and two (range 1–3), respectively. Some side-effects were observed but all were stopped with antidote treatment; no failure or relapses occurred at 6–36 months after treatment.     

Lymphocyte transformation suppression caused by pyoderma--failure to demonstrate it in uncomplicated demodectic mange

Three dogs with demodectic mange uncomplicated by a bacterial infection and 9 dogs with demodectic mange and pyoderma were tested for their lymphocyte response to phytomitogens in vitro and for the presence of the serum's lymphocyte immunoregulatory factors (SLIF) suppressing blastogenesis. None of the 3 dogs with uncomplicated demodectic mange showed any detectable dysfunction of their lymphocytes or presence of the blastogenesis suppressing SLIF. Their lymphocytes generally responded to the mitogens with more blastogenesis than lymphocytes from healthy controls. On the other hand, in the group of 9 dogs with demodicosis complicated by a bacterial infection, high levels of the blastogenesis suppressing SLIF for concanavalin A-sensitive cells were detected in 4 dogs, for phytohemagglutinin-sensitive cells in 2 dogs, and for pokeweed mitogen-sensitive cells in 1 (of only 3 tested) dog. Dysfunction of lymphocytes per se (detected by a decreased blastogenesis in nonsuppressive normal canine and bovine sera) was detected in 3 dogs with demodicosis with pyoderma. The success of the treatment of demodectic mange or the bacterial skin infection did not correlate with the previous presence or absence of the blastogenesis suppressing SLIF. The treatment of pyoderma was less successful in dogs with an increase in blastogenesis of unstimulated cells in fresh normal canine serum over that in autologous serum. All 3 dogs with a detected dysfunction of their lymphocytes either died or were euthanatized as untreatable cases. It is concluded that the development of demodectic mange per se did not cause the appearance of the blastogenesis suppressing SLIF, which was primarily related to the appearance and extent of the secondary bacterial skin infection.     

Comparison of acetate tape impression with squeezing versus skin scraping for the diagnosis of canine demodicosis

This study compared the sensitivity of acetate tape impression and skin squeezing with that of deep skin scraping for the diagnosis of demodicosis in dogs. Demodex canis was detected in 100% of acetate tape impressions obtained after skin squeezing and in 90% of deep skin scrapings. There was a significant difference (P < 0.001) between the techniques in the total number of mites detected. Acetate tape impression with skin squeezing was found to be more sensitive than deep skin scraping and is an alternative diagnostic method for canine demodicosis.