Opportunistic fungal infections in dogs treated with ciclosporin and glucocorticoids: eight cases

Pharmacology of drugs used in autoimmune dermatopathies in cats and dogs: A narrative review

Immunosuppressive drugs are the mainstay of treatment for many feline and canine autoimmune skin diseases, either as monotherapy or in combination with other drugs. Treatment with these drugs is often lifelong and may have long-term consequences on the affected animal's overall quality-of-life. Clinicians need to understand the pharmacology of immunosuppressants in planning and executing the treatment regimen for the best possible clinical outcome, as well as reducing the risk of adverse effects. This review paper will focus on the mechanism of action, pharmacokinetics and pharmacodynamics, clinical uses and adverse effects of immunosuppressive drugs used to treat autoimmune dermatoses in cats and dogs. These include glucocorticoids, ciclosporin A, azathioprine, chlorambucil, mycophenolate mofetil, oclacitinib and Bruton's tyrosine kinase inhibitors.

Retrospective evaluation of leflunomide as an adjunctive therapy in dogs with non-associative immune-mediated thrombocytopenia: 20 cases (2008-2021)

OBJECTIVE

To describe leflunomide as an adjunctive therapy in the treatment of non-associative immune-mediated thrombocytopenia.

MATERIALS AND METHODS

A retrospective study of dogs with a diagnosis of non-associative immune-mediated thrombocytopenia treated with leflunomide March 2008 to September 2021 was conducted. Data collected included signalment, clinical signs, physical examination findings and diagnostic testing performed. Medications administered, duration of hospital stay, time to platelet concentration >150×109/L and adverse events during leflunomide therapy were recorded. Relapses within a year of diagnosis were reported.

RESULTS

A total of 20 client-owned dogs met inclusion criteria. Nineteen of 20 dogs (95%) achieved a platelet concentration >150×109/L with leflunomide and prednisone combination therapy and four dogs (21.1%) relapsed during treatment or shortly after treatment. Adverse effects included diarrhoea (n=5), mild lymphopenia (n=9) and mild intermittent anaemia (n=1). A single dog developed hepatotoxicity presumed to be secondary to leflunomide therapy that resolved after drug discontinuation. One dog was treated for aspiration pneumonia during treatment. Two dogs were euthanased while receiving leflunomide.

CLINICAL SIGNIFICANCE

Length of hospitalisation, time to platelet recovery, treatment response and relapse rate were comparable with alternative treatment protocols. Most adverse effects did not require leflunomide dose adjustment; however, two dogs died while undergoing leflunomide treatment and there is compelling evidence that one of these dogs experienced fatal infection secondary to immune-suppression. Hepatotoxicity remains a known complication of leflunomide treatment and serial biochemistry testing is recommended.

Perspectives on pharmacologic strategies in the management of meningoencephalomyelitis of unknown origin in dogs

There are many non-infectious inflammatory diseases, assumed to be immune-mediated in origin, recognized to affect the nervous system in canine patients. Concentrating on meningoencephalomyelitis of unknown origin, we will discuss the medications used to treat the underlying disease process, focusing on their adverse effects, therapeutic monitoring when necessary and effectiveness. The literature overwhelmingly supports the use of a steroid/ Cytosar® or steroid/ cyclosporine treatment protocol with the steroid tapered after the acute phase of the disease, leaving the secondary medication to control the disease long term. The decision on when and how quickly to taper the steroid is clinician dependent as a best practices has not been established in the literature. Also discussed will be the supportive care treatments often needed in the acute phase of these patients' diagnosis and treatment such as anti-edema and anti-epileptic agents.

Methylprednisolone Induces Extracellular Trap Formation and Enhances Bactericidal Effect of Canine Neutrophils

Methylprednisolone is a glucocorticoid and can negatively influence immune defense mechanisms. During bacterial infections in the dog, neutrophils infiltrate infected tissue and mediate antimicrobial effects with different mechanisms such as phagocytosis and neutrophil extracellular trap (NET) formation. Here, we investigated the influence of methylprednisolone on canine NET formation and neutrophil killing efficiency of Gram positive and Gram negative bacteria. Therefore, canine blood derived neutrophils were treated with different concentrations of methylprednisolone over time. The survival factor of Staphylococcus pseudintermedius, Streptococcus canis or Escherichia coli was determined in presence of stimulated neutrophils. Additionally, free DNA and nucleosomes as NET marker were analyzed in supernatants and neutrophils were assessed for NET formation by immunofluorescence microscopy. Methylprednisolone concentrations of 62.5 and 625 µg/mL enhanced the neutrophil killing of Gram positive bacteria, whereas no significant influence was detected for the Gram negative Escherichia coli. Interestingly, higher amounts of free DNA were detected under methylprednisolone stimulation in a concentration dependency and in the presence of Streptococcus canis and Escherichia coli. The nucleosome release by neutrophils is induced by bacterial infection and differs depending on the concentration of methylprednisolone. Furthermore, immunofluorescence microscopy analysis identified methylprednisolone at a concentration of 62.5 µg/mL as a NET inducer. In summary, methylprednisolone enhances NET-formation and time-dependent and concentration-dependent the bactericidal effect of canine neutrophils on Gram positive bacteria.

Neutropenia in dogs receiving vincristine for treatment of presumptive immune-mediated thrombocytopenia

BACKGROUND

Neutropenia is an adverse effect of vincristine when used in multidrug chemotherapy protocols.

OBJECTIVE

To determine the incidence of neutropenia, identify potential risk factors for neutropenia, and determine the effect of neutropenia on outcome, in dogs receiving vincristine for treatment of immune-mediated thrombocytopenia (ITP).

ANIMALS

One hundred twenty-seven client-owned dogs presumptively diagnosed with ITP.

METHODS

In this retrospective cohort study, medical records were reviewed to identify dogs presumptively diagnosed with ITP, and treated with vincristine, over a 15-year period. Logistic regression was used to identify risk factors for the development of neutropenia in dogs receiving vincristine. Time to platelet count ≥40 000 platelets/μL, survival, and duration of hospitalization were compared between neutropenic and non-neutropenic dogs.

RESULTS

Vincristine was administered to 127 dogs with presumptive ITP; 19 became neutropenic. Administration of cyclosporine was significantly (P < .001) associated with the development of neutropenia (odds ratio: 12.97, 95% confidence interval: 4.17, 40.35). There was no difference in median time to ≥40 000 platelets/μL between neutropenic dogs (4 days; range, 1-14 days) and non-neutropenic dogs (3 days; range, 0-48 days). Percentage survival to discharge was 95% in both groups, but median duration of hospitalization was significantly longer in neutropenic dogs (6 days; range, 3-22 days) compared to non-neutropenic dogs (4 days; range, 2-15 days).

CONCLUSIONS AND CLINICAL IMPORTANCE

Cyclosporine administration was associated with the development of neutropenia in dogs receiving vincristine, which might be related to effects on metabolism of vincristine. Neutrophil counts should be monitored in dogs receiving vincristine treatment for ITP, particularly if administered in conjunction with cyclosporine.

Excessive Cyclosporine-Associated Immunosuppression in a Dog Heterozygous for the MDR1 (ABCB1-1Δ) Mutation

Pharmacodynamic monitoring was used to titrate cyclosporine dosing in a dog with immune-mediated hemolytic anemia. Development of a suspected secondary infection, with subsequent discovery of an unexpectedly high level of T-cell suppression despite a relatively low cyclosporine dose, prompted an investigation into the cause of possible excessive immunosuppression. Blood cyclosporine concentrations were within expected target ranges, and the dog was determined to be heterozygous for the multidrug resistance protein 1 (MDR1; ATP-binding cassette sub family B member 1-1Δ) gene mutation. The MDR1 mutation was suspected to have contributed to the excessive immunosuppression experienced by this patient. This case highlights the need to monitor immunosuppressive therapy in the individual patient, especially when the patient is not responding to therapy at typical dosages or when secondary infections develop at dosages lower than expected to cause significant immunosuppression. Pharmacodynamic monitoring can be used to help identify unexpected excessive immunosuppression in dogs receiving cyclosporine, and MDR1 genotyping should be further explored as a potential method of predicting and preventing its occurrence.

Successful Treatment of Cutaneous Curvularia geniculata, Nocardia niigatensis, and Viral Papillomatosis in a Dog During the Therapeutic Management of Immune-Mediated Hemolytic Anemia

Opportunistic infections represent a major cause of mortality in immunocompromised patients. Discontinuation or reduction of immunosuppressive medications is recommended with the development of opportunistic infections, which may cause a relapse or worsening of the immune-mediated disease. A 7.5-year-old, spayed female great Dane was diagnosed with immune-mediated hemolytic anemia with initial immunosuppressive therapy consisting of oral prednisone, ciclosporin and mycophenolate mofetil. The patient developed diffuse right forelimb pyogranulomatous fungal dermatitis with deep draining tracts 6 weeks into immunosuppressive treatment with Curvularia geniculata growth. Oral once daily terbinafine and itraconazole were initiated; ciclosporin was immediately discontinued and the mycophenolate mofetil/prednisone doses were reduced. The right forelimb skin lesions resolved after 4 weeks, but the patient presented with a diffuse severe neutrophilic dermatitis on the left forelimb; 16S rRNA sequencing identified Nocardia niigatensis. Cutaneous nocardiosis was treated with oral enrofloxacin and doxycycline; systemic immunosuppressive therapies were continued for immune-mediated hemolytic anemia control. One month later, the left forelimb lesions completely resolved but the patient developed several multifocal, exophytic warts; the clinical features and histopathology were consistent with viral papillomas. Within the following 4 weeks, the patient developed severe diffuse papillomatosis of the left forelimb, which was successfully treated with 2 weeks of every other day topical imiquimod administration. In this case, successful treatment of cutaneous opportunistic bacterial, fungal and viral infection was possible with proper treatment even though the immunosuppressive drug treatments could not be discontinued.

ACVIM consensus statement on the treatment of immune-mediated hemolytic anemia in dogs

Immune‐mediated hemolytic anemia (IMHA) causes severe anemia in dogs and is associated with considerable morbidity and mortality. Treatment with various immunosuppressive and antithrombotic drugs has been described anecdotally and in previous studies, but little consensus exists among veterinarians as to the optimal regimen to employ and maintain after diagnosis of the disease. To address this inconsistency and provide evidence‐based guidelines for treatment of IMHA in dogs, we identified and extracted data from studies published in the veterinary literature. We developed a novel tool for evaluation of evidence quality, using it to assess study design, diagnostic criteria, explanation of treatment regimens, and validity of statistical methods. In combination with our clinical experience and comparable guidelines for humans afflicted with autoimmune hemolytic anemia, we used the conclusions of this process to make a set of clinical recommendations regarding treatment of IMHA in dogs, which we refined subsequently by conducting several iterations of Delphi review. Additionally, we considered emerging treatments for IMHA in dogs and highlighted areas deserving of future research. Comments were solicited from several professional bodies to maximize clinical applicability before the recommendations were submitted for publication. The resulting document is intended to provide clinical guidelines for management of IMHA in dogs. These guidelines should be implemented pragmatically, with consideration of animal, owner, and veterinary factors that may vary among cases.

Opportunistic Invasive Cutaneous Fungal Infections Associated with Administration of Cyclosporine to Dogs with Immune-mediated Disease

Background

Opportunistic invasive fungal infections (OIFIs) occur in dogs administered immunosuppressive medications. However, the epidemiology of OIFIs among dogs undergoing immunosuppressive treatment is poorly understood. The aims of this study were to (1) estimate the incidence of OIFIs among dogs diagnosed with certain immune‐mediated diseases and treated with immunosuppressive drugs, and (2) determine if administration of particular drug(s) was a risk factor for OIFIs.

Hypothesis

Dogs receiving cyclosporine treatment (alone or as part of a multidrug protocol) are at higher risk of developing OIFIs.

Animals

One hundred and thirteen client‐owned dogs diagnosed with select immune‐mediated diseases: 42 with IMHA, 29 with ITP, 34 with IMPA, and 8 with Evans syndrome.

Methods

Retrospective cohort study. Medical records of dogs presenting to the Texas A&M University, Veterinary Medical Teaching Hospital between January 2008 and December 2015, and treated for 1 or more of IMHA, IMPA, ITP, or Evans syndrome were retrospectively reviewed. Dogs that did not develop an OIFI were excluded if they died, were euthanized, or were lost to follow‐up within 120 days of initiation of immunosuppressive treatment.

Results

Fifteen dogs of 113 (13%) were diagnosed with an OIFI based on 1 or more of cytology, culture, or histopathology. The odds of developing an OIFI were greater among dogs that were treated with cyclosporine (OR = 7.1, P = 0.017; 95% CI, 1.5–34.4) and among male dogs (OR = 5.1, P = 0.018; 95% CI, 1.4–17.9).

Conclusions and Clinical Importance

OIFIs were significantly more likely in male dogs and those receiving cyclosporine. It is important to consider OIFIs as a potential complication of immunosuppressive treatment, particularly cyclosporine.

Canine autoimmune hemolytic anemia: management challenges

Immune-mediated hemolytic anemia is one of the most common manifestations of canine immune-mediated disease, yet treatment regimens remain nonstandardized and, in some cases, controversial. The main reason for this, as for most diseases in veterinary medicine, is the lack of large-scale placebo-controlled trials so that the efficacy of one treatment over another can be established. Most of the evidence used for treatment comes from retrospective studies and from personal preference and experience, and because of this, treatment regimens tend to vary among institutions and individual clinicians. Management of immune-mediated hemolytic anemia includes immunosuppression, thromboprophylaxis, and supportive care measures to help prevent and treat concurrent conditions.