Determination of CD4+ and CD8+ T cells in the peripheral blood of dogs with demodicosis

Effects of Increasing Levels of Purified Beta-1,3/1,6-Glucans on the Fecal Microbiome, Digestibility, and Immunity Variables of Healthy Adult Dogs

Yeast-purified beta-1,3/1,6-glucans (BG) can modulate dogs' immune systems and microbiome, but the optimal inclusion dose remains unknown. The aim of the study was to evaluate the effects of 0.0, 0.07, 0.14, and 0.28% inclusion of BG in a dry extruded diet on the digestibility, immunity, and fecal microbiota of healthy adult dogs. Eight male and female border collies [n = 4; body condition score (BCS) = 5] and English cocker spaniels (n = 4; BCS = 5), aged 3.5 ± 0.5 years, were randomly distributed into two 4 × 4 balanced Latin squares. Fecal microbiota (using 16S rRNA sequencing, Illumina®), apparent digestibility coefficients (ADC) of nutrients, fecal concentrations of short-chain fatty acids (SCFA) and branched-chain fatty acids (BCFA), ammoniacal nitrogen, lactic acid, IgA and pH, lymphocyte immunophenotyping, intensity and percentage of phagocytosis and oxidative burst were determined. No differences were observed in Faith (p = 0.1414) and Pielou-evenness (p = 0.1151) between treatments, but beta diversity was different between 0.0% and 0.14% BG groups (p = 0.047). Moreover, the Firmicutes phylum was the most abundant in all groups and exhibited the highest relative abundance after the consumption of 0.14% BG, a finding considered beneficial for the canine microbiome. The Erysipelotrichaceae and Ruminococcaceae families, along with the Faecalibacterium and Prevotella genera, considered favorable for their involvement in butyrate production and other metabolites, showed increased abundance after the consumption of 0.14% BG. The potentially pathogenic Proteobacteria phylum displayed lower abundance after the consumption of 0.14% BG. Fecal concentrations of the evaluated compounds and pH did not differ after consumption of the BG at all percentages. Higher crude protein ADC was found after 0.14 and 0.28% BG consumption (p < 0.0001), but no differences were found for other nutrients. Phagocytosis, oxidative burst, and lymphocyte populations were not modulated by any of the treatments; however, 0.14% BG modulated the lymphocyte T CD4+:CD8+ ratio (p = 0.0368), an important marker of immune system efficiency. The inclusion of 0.14% BG resulted in the best responses and was the best dose evaluated.

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.

Mite Burden and Immunophenotypic Response to Demodex musculi in Swiss Webster, BALB/c, C57BL/6, and NSG Mice

Detection methods for Demodex musculi were historically unreliable, and testing was rarely performed because its prevalence in laboratory mice was underestimated. Although infestations are unapparent in most mouse strains, D. musculi burdens are higher and clinical signs detected in various immunodeficient strains. The parasite's influence on the immune system of immunocompetent mice is unknown. We characterized mite burden (immunocompetent and immunodeficient strains) and immunologic changes (immunocompetent strains only) in naïve Swiss Webster (SW; outbred), C57BL/6NCrl (B6; Th1 responder), BALB/cAnNCrl (BALB/c; Th2 responder) and NOD. Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG; immunodeficient) mice after exposure to Demodex-infested NSG mice. Infested and uninfested age-matched mice of each strain (n = 5) were euthanized 14, 28, 56, and 112 d after exposure. Mite burden was determined through PCR analysis and skin histopathology; B-cell and CD4+ and CD8+ T-cell counts and activation states (CD25 and CD69) were evaluated by using flow cytometry; CBC counts were performed; and serum IgE levels were measured by ELISA. Mite burden and PCR copy number correlated in NSG mice, which had the highest mite burden, but not in immunocompetent strains. Infested immunocompetent animals developed diffuse alopecia by day 112, and both BALB/c and C57BL/6 mice had significantly increased IgE levels. These findings aligned with the skewed Th1 or Th2 immunophenotype of each strain. BALB/c mice mounted the most effective host response, resulting in the lowest mite burden of all immunocompetent strains at 112 d after infestation without treatment. Clinically significant hematologic abnormalities were absent and immunophenotype was unaltered in immunocompetent animals. Topical treat- ment with imidacloprid-moxidectin (weekly for 8 wk) was effective at eradicating mites by early as 7 d after treatment. IgE levels decreased substantially in infested BALB/c mice after treatment. These findings demonstrate a need for D. musculi surveillance in mouse colonies, because the infestation may influence the use of infested mice in select studies.

Quantification of immuno-regulatory cytokine and toll-like receptors gene expression in dogs with generalized demodicosis

The proliferation of Demodex mites is mainly controlled by host immunity; however, the precised mechanism of host-mite interplay and host immune response in the cutaneous microenvironment of dogs with generalized demodicosis (GD) are not yet established. In the present study, we envisaged the alterations in the expression of toll-like receptors (TLRs) and immuno-regulatory cytokine gene in the skin lesions and peripheral blood mononuclear cells (PBMCs) of dogs with GD. The expression of TLR2, TLR6, IFN-γ, TGF-β and IL-10 genes in the skin lesions and PBMCs of 15 dogs with GD was quantified by qRT-PCR. Compared to healthy dogs, significantly elevated expression of TLR2 (P = 0.048), TGF-β (P = 0.04) and IL-10 (P = 0.012) were found in the PBMCs of dogs with GD. Conversely, there was significantly reduced expression of TLR6 gene (P = 0.021) in the PBMCs of these dogs. The infested dogs also revealed significantly elevated expression of TLR2 gene (P = 0.034) in the skin lesions, while, the expression of the TLR6 gene was found to be significantly (P = 0.004) reduced. Interestingly, significant alterations in TGF-β (P = 0.105) and IL-10 (P = 0.162) genes expression were not observed in the skin lesions of diseased dogs. Our findings suggest that Demodex mites contribute to a different systemic and cutaneous immune response in dogs for their proliferation, and consequently the development of GD. Therefore, Demodex mites might be inducing the immunosuppression through activating the systemic over-expression of immunosuppressive cytokines; however, in the cutaneous lesions, the expression of immunosuppressive cytokines remained unaltered. Both systemic and local over-expression of TLR2 and reduced expression of TLR6 genes might be responsible for the inflammatory signs of canine demodicosis and helping to the mite to escape the host immunity.

The balancing act: Immunology of leishmaniosis

Immune control of Leishmania infantum, the causative agent of most canine leishmaniosis (CanL), requires a balancing act between inflammatory and regulatory responses. This balance is specifically between the proinflammatory T helper 1 type (Th1) CD4+ T cells that are responsible for controlling parasite replication and T regulatory 1 cells which mediate an immunosuppressive, regulatory, response needed to dampen overabundant inflammation but if predominant, result in CanL progression. How this delicate immune cell interaction occurs in the dog will be highlighted in this review, focusing on the progressive changes observed within myeloid lineage cells (predominantly macrophages), B cells and T cells. After exposure to parasites, macrophages should become activated, eliminating L. infantum through release of reactive oxygen species. Unfortunately, multiple parasite and host factors can prevent macrophage activation allowing parasites to persist within them. T cells balance between a productive T_H1 type CD4+ response capable of producing IFN-γ which aids macrophage activation versus T cell exhaustion which reduces T cell proliferation, IFN-γ production and allows parasite expansion within macrophages. Neutrophils and Th17 cells add to the inflammatory state, aiding in parasite removal, but also leading to pathology. A regulatory B cell population increases IL-10 production and down regulates the T_H1 response allowing parasite growth. All of these immune challenges affect the balance between progression to clinical disease and maintaining sub-clinical disease. Vaccines and immunotherapies targeted at recovering or maintaining T and B cell function can be important factors in mending the immune balance required to survive CanL.

Immune mechanisms in human and canine demodicosis: A review

Demodex mites are saprophytic parasites of the mammalian skin, mostly found in or near pilosebaceous units of hairy regions. While they can be found in healthy humans and animals without causing any clinical manifestations, they were suggested to create pathogenic symptoms when they appear in high densities under favourable conditions (ie, demodicosis). Nevertheless, their role as the primary causative agent of the pathogenic conditions in humans is debated today. Canine demodicosis, which is highly prevalent in certain dog breeds, provides a valuable tool for studying the pathogenesis of human demodicosis. Canine and human demodicosis are caused by different Demodex species, and the clinical manifestations in former could be life-threatening. Nevertheless, current literature suggests similar immune responses and immune evasion mechanisms in human and canine demodicosis; cellular immunity appeared to have a central role in protection against demodicosis, and Demodex mites were shown to influence both innate and adaptive immune response to escape immune attack. The aim of this review is to summarize the relevant literature on demodicosis obtained from studies conducted on both organisms, and draw the attention to the effect of mite-associated factors (eg, microbiota) on the different clinical manifestations displayed during human and canine demodicosis.

Pre- and post-therapy circulating immuno-stimulatory and immuno-suppressive cytokines in dogs with juvenile-onset generalized demodecosis

Overproliferation of Demodex mites in dogs with compromised immunity attributed to the development of canine demodecosis. Whether clinical signs of canine demodecosis are triggered by genetically-mediated specific immunodeficiency in dogs or the Demodex mites induce lesions in hair follicles and result in compromised immunity is yet to be fully explored. To unravel the concealments of immunosuppression in canine demodecosis the present study was aimed to estimate the levels of circulating cytokines, pre- and post-therapy in nine dogs with juvenile-onset generalized demodecosis. At day 60 post-therapy of recommended amitraz rinse, significant (p ≤ 0.02) reduction in circulating IL-10 level was observed compared to its level before the start of the therapy (day 0). However, significant alterations in circulating levels of TNF-α and IFN-γ were not observed in these dogs at day 60 post-therapy as compared to their day 0 levels. A strong positive correlation between circulating level of IL-10 and mites population was observed both on day 0 (r² = 0.656; p ≤ 0.005) and day 60 post-therapy (r² = 0.575; p ≤ 0.018). Therefore, our findings suggest that Demodex mites induce immunosuppression in dogs during clinical disease and mites burden seems to be responsible for the development of generalized demodecosis.

Skin-homing T-cell responses associated with Demodex infestation and rosacea

AIMS

Our aim was to investigate the skin-homing T-cell immune responses triggered in patients with Demodex infestation and/or rosacea.

METHODS

Collected whole blood samples were divided into four groups: control subjects; nonrosacea patients with Demodex infestation (Demodex group); papulopustular rosacea (PPR) patients without Demodex infestation (Rosacea group); and PPR patients with Demodex infestation (Rosacea/Demodex group). Following ex vivo activation, skin-homing CLA+CD4+ T-cell subset levels were monitored by flow cytometry.

RESULTS

When compared with control subjects, among skin-homing CD4+ T-cell subsets analysed, Demodex patients had higher T_H 9 and T_reg cell levels; Rosacea subjects displayed elevated T_H 1 cell levels; and Rosacea/Demodex patients exhibited increased frequencies of T_H 9 and T_H 22 cells. In contrast to Rosacea subjects, Rosacea/Demodex group members displayed higher T_H 2 cell levels; and when compared with Demodex groups, they had higher T_H 1 and T_H 2 but lower T_reg cell levels. Demodex group members also exhibited higher T_reg but lower T_H 1 and T_H 22 levels than Rosacea/Demodex group subjects.

CONCLUSIONS

The skin-homing T-cell responses associated with Demodex infestation and rosacea formation seem to influence each other. The present as well as future studies could contribute to the development of effective treatment strategies for demodicosis and rosacea.

Demodex canis targets TLRs to evade host immunity and induce canine demodicosis

Widespread incidence of Demodex mites throughout the mammalian class and occasional serious and fatal outcomes in dogs warrant an insight into the host-parasite interface especially. Therefore, this study was aimed to unravel the interplay between innate immune response and canine demodicosis. The dogs diagnosed to have natural clinical demodicosis were allocated into two groups; dogs with localized demodicosis (LD) and with generalized demodicosis (GD). The expression of toll-like receptors (TLRs) 2, 4 and 6 genes in peripheral blood mononuclear cells of these dogs was quantified by real-time PCR. Significantly increased TLR2 gene expression, while significantly diminished TLR4 and TLR6 gene expressions were observed in demodicosed dogs (LD and GD) as compared with the healthy ones. Even the expression of TLR2 gene was found to differ significantly between the dogs with LD and GD. Therefore, it can be inferred that clinical demodicosis in dogs is coupled with an up-regulation of TLR2 and down-regulation of TLR4 and TLR6 gene expressions. Overexpression of TLR2 gene might be responsible for Demodex-induced clinical manifestations, while TLR4 and TLR6 gene down-regulations could be the paramount strategy of Demodex mites to elude the host-immune interface.

Demodex canis regulates cholinergic system mediated immunosuppressive pathways in canine demodicosis

Demodex canis infestation in dogs remains one of the main challenges in veterinary dermatology. The exact pathogenesis of canine demodicosis is unknown but an aberration in immune status is considered very significant. No studies have underpinned the nexus between induction of demodicosis and neural immunosuppressive pathways so far. We have evaluated the involvement of cholinergic pathways in association with cytokines regulation as an insight into the immuno-pathogenesis of canine demodicosis in the present study. Remarkable elevations in circulatory immunosuppressive cytokine interleukin-10 and cholinesterase activity were observed in dogs with demodicosis. Simultaneously, remarkable reduction in circulatory pro-inflammatory cytokine tumour necrosis factor-alpha level was observed in dogs with demodicosis. Findings of the present study evidently suggest that Demodex mites might be affecting the cholinergic pathways to induce immunosuppression in their host and then proliferate incessantly in skin microenvironment to cause demodicosis.

Prebiotic potential of Jerusalem artichoke (Helianthus tuberosus L.) in Wistar rats: effects of levels of supplementation on hindgut fermentation, intestinal morphology, blood metabolites and immune response

BACKGROUND

Many studies have been conducted using purified prebiotics such as inulin or fructooligosaccharides (FOS) as nutraceuticals, but there is very little information available on the prebiotic potential of raw products rich in inulin and FOS, such as Jerusalem artichoke (JA; Helianthus tuberosus L.). The present experiment aimed to evaluate the prebiotic effects of JA tubers in rats.

RESULTS

Seventy-two Wistar weanling rats divided into four groups were fed for 12 weeks on a basal diet fortified with pulverized JA tubers at 0 (control), 20, 40 and 60 g kg(-1) levels. Enhanced cell-mediated immunity in terms of skin indurations (P = 0.082) and CD4+ T-lymphocyte population (P = 0.002) was observed in the JA-supplemented groups compared with the control group. Blood haemoglobin (P = 0.017), glucose (P = 0.001), urea (P = 0.004) and calcium (P = 0.048) varied favourably upon inclusion of JA. An increasing trend (P = 0.059) in the length of large intestine was apparent in the JA-fed groups. The tissue mass of caecum (P = 0.069) and colon (P = 0.003) was increased in the JA-supplemented groups, accompanied by higher (P = 0.007) caecal crypt depth. The pH and ammonia concentrations of intestinal digesta decreased and those of lactate and total volatile fatty acids increased in the JA-fed groups.

CONCLUSION

The results suggest that JA had beneficial effects on immunity, blood metabolites, intestinal morphometry and hindgut fermentation of rats.

Longitudinal assessment of T-lymphocyte subpopulations during generalized demodicosis in dogs and their relationship with remission

BACKGROUND

The pathogenesis of canine generalized demodicosis is poorly understood but is thought to involve dysfunction of the immune system. Previous studies showed diminished CD4+ T lymphocyte counts in affected dogs, but none has evaluated this subpopulation through resolution of the disease.

HYPOTHESIS/OBJECTIVES

In this longitudinal study, we tested whether quantification of CD4+ cells, CD8+ cells and the ratio of CD4+ to CD8+ cells are good indicators of immunological status and could be used as biomarkers of treatment efficacy and prognosis.

ANIMALS

Sixteen dogs of several breeds with diagnoses of generalized demodicosis, plus 30 age/breedmatched healthy dogs.

METHODS

Total lymphocytes, CD4+, CD8+ and CD4+:CD8+ ratio were quantified at four time points: at diagnosis, 30 days after diagnosis (during treatment), at first negative parasitological examination and at clinical cure.

RESULTS

Absolute numbers of CD4+ cells were significantly lower in affected dogs at the time of diagnosis. Absolute numbers of CD4+ and CD8+ cells were significantly augmented in affected animals compared with control dogs after treatment was established, and this persisted until the first negative parasitological examination, at which time the CD4+ counts equalled those of the control group.

CONCLUSIONS AND CLINICAL IMPORTANCE

Our findings suggest that longitudinal quantification of CD4+ and CD8+ T lymphocytes is a useful indicator of the efficacy of demodicosis treatment.

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.

Immunology and pathogenesis of canine demodicosis

Demodex mites colonized the hair follicles and sebaceous glands of mammals millions of years ago and have remained relatively unchanged in this protected ecologic niche since then. The host immune system detects and tolerates their presence. Toll-like receptor-2 of keratinocytes has been demonstrated to recognize mite chitin and to elicit an innate immune response. The subsequent acquired immune response is poorly understood at present, but there is experimental and clinical evidence that this is the main mechanism in the control of mite proliferation. A transgenic mouse model (STAT(-/-) /CD28(-/-) ) has demonstrated that the immune response is complex, probably involving both cellular and humoral mechanisms and requiring the role of co-stimulatory molecules (CD28). It is known that a genetic predisposition for developing canine juvenile generalized demodicosis exists; however, the primary defect leading to the disease remains unknown. Once the mite proliferation is advanced, dogs show a phenotype that is similar to the T-cell exhaustion characterized by low interleukin-2 production and high interleukin-10 and transforming growth factor-β production by lymphocytes, as described in other viral and parasitic diseases. Acaricidal treatment (macrocyclic lactones) decreases the antigenic load and reverses T-cell exhaustion, leading to a clinical cure. Although in recent years there have been significant advances in the management and understanding of this important and complex canine disease, more research in areas such as the aetiology of the genetic predisposition and the immune control of the mite populations is clearly needed.

Treatment of canine generalized demodicosis associated with hyperadrenocorticism with spot-on moxidectin and imidacloprid

BACKGROUND

Canine generalized demodicosis associated with hyperadrenocorticism is often problematic and might be intractable. The aim of this study was to report the efficacy of a weekly application of spot-on moxidectin/imidacloprid in dogs with hyperadrenocorticism and secondary generalized demodicosis.

METHODS

Dogs with hyperadrenocorticism and secondary generalized demodicosis were included. The condition of hyperadrenocorticism was treated and stabilized with trilostane before and throughout the study period in all dogs.

RESULTS

Average total live adult mite counts before treatment and after four, eight and 12 weeks of spot-on moxidectin/imidacloprid (2.5/10 mg/kg) applications were 20.1±6.3 (range, 13-33), 0.5±0.7 (range, 0-2; 6/11 were negative), 0.2±0.4 (range, 0-1; 9/11 were negative), 0.2±0.4 (range, 0-1; 9/11 were negative) and 0.1±0.3 (range, 0-1; 10/11 were negative) respectively; this difference was significant (P<0.001). Ten of 11 dogs (90.1%) achieved clinical remission, as demonstrated by the absence of demodectic mites at any life stage at monthly scrapings for eight consecutive weeks, and maintained remission throughout the 12-month follow-up period.

CONCLUSION

The weekly application of spot-on moxidectin/imidacloprid appeared to be effective and safe against generalized adult onset canine demodicosis associated with hyperadrenocorticism.

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.