An equine case of urticaria associated with dry garlic feeding

Equine allergic skin diseases: Clinical consensus guidelines of the World Association for Veterinary Dermatology

BACKGROUND

Allergic skin diseases are common in horses worldwide. The most common causes are insect bites and environmental allergens.

OBJECTIVES

To review the current literature and provide consensus on pathogenesis, diagnosis, treatment and prevention.

MATERIALS AND METHODS

The authors reviewed the literature up to November 2022. Results were presented at North America Veterinary Dermatology Forum (2021) and European Veterinary Dermatology Congress (2021). The report was available to member organisations of the World Association for Veterinary Dermatology for feedback.

CONCLUSIONS AND CLINICAL RELEVANCE

Insect bite hypersensitivity (IBH) is the best characterised allergic skin disease. An immunoglobulin (Ig)E response against Culicoides salivary antigens is widely documented. Genetics and environmental factors play important roles. Tests with high sensitivity and specificity are lacking, and diagnosis of IBH is based on clinical signs, seasonality and response to insect control. Eosinophils, interleukin (IL)-5 and IL-31 are explored as therapeutic targets. Presently, the most effective treatment is insect avoidance. Existing evidence does not support allergen-specific immunotherapy (ASIT) using commercially available extracts of Culicoides. Hypersensitivity to environmental allergens (atopic dermatitis) is the next most common allergy. A role for IgE is supported by serological investigation, skin test studies and positive response to ASIT. Prospective, controlled, randomised studies are limited, and treatment relies largely on glucocorticoids, antihistamines and ASIT based on retrospective studies. Foods are known triggers for urticaria, yet their role in pruritic dermatitis is unknown. Recurrent urticaria is common in horses, yet our understanding is limited and focussed on IgE and T-helper 2 cell response. Prospective, controlled studies on treatments for urticaria are lacking. Glucocorticoids and antihistamines are primary reported treatments.

Garlic (Allium Sativum) Supplementation Improves Respiratory Health but Has Increased Risk of Lower Hematologic Values in Horses

Simple Summary

The hypotheses of this study were that garlic supplementation may help to clear mucus in the airways, but also causes declining hematologic values in prolonged feeding. The results show that long-term supplementation of dried garlic on the level of 32 mg/kg BW improved respiratory health in terms of reduced amount of tracheal symptoms and accumulation of tracheal exudates. However, the garlic supplemented horses showed slightly declining hemoglobin (Hb), hematocrit (HcT) and red blood cells (RBC) values.

Abstract

Garlic (Allium sativum) is claimed to have numerous beneficial properties to the health of humans and animals. It is commonly used for example to treat respiratory diseases and infections in horses’ lungs. However, in addition to its possible positive influences, garlic may also have adverse health effects. The hypotheses of this study were that garlic supplementation may help to clear mucus in the airways, but also causes declining hematologic values in prolonged feeding. To our knowledge, this is the first organized study in controlled conditions to show the health effects of garlic supplementation for horses so far. The results show that long-term supplementation of dried garlic on the level of 32 mg/kg BW seemed to reduce the amount of tracheal symptoms and accumulation of tracheal exudates. Additionally, the number of neutrophil cells in the tracheal mucus was numerically smaller in the garlic supplemented horses. However, the garlic supplemented horses showed slightly declining Hb, HcT and RBC values during an 83-day study period. Consequently, it is possible that even low garlic supplementation levels can be detrimental to the horse’s hematology when the supplementation period is long.

Comparing immediate-type food allergy in humans and companion animals-revealing unmet needs

Adverse food reactions occur in human as well as veterinary patients. Systematic comparison may lead to improved recommendations for prevention and treatment in both. In this position paper, we summarize the current knowledge on immediate-type food allergy vs other food adverse reactions in companion animals, and compare this to the human situation. While the prevalence of food allergy in humans has been well studied for some allergens, this remains to be investigated for animal patients, where owner-reported as well as veterinarian-diagnosed food adverse reactions are on the increase. The characteristics of the disease in humans vs dogs, cats, and horses are most often caused by similar, but sometimes species-dependent different pathophysiological mechanisms, prompting the specific clinical symptoms, diagnoses, and treatments. Furthermore, little is known about the allergen molecules causative for type I food allergy in animals, which, like in human patients, could represent predictive biomarkers for risk evaluation. The definite diagnosis of food allergy relies-as in humans-on elimination diet and provocation tests. Besides allergen avoidance in daily practice, novel treatment options and tolerization strategies are underway. Taken together, numerous knowledge gaps were identified in veterinary food allergy, which need to be filled by systematic comparative studies.

Update on equine allergies

Horses develop many skin and respiratory disorders that have been attributed to allergy. These disorders include pruritic skin diseases, recurrent urticaria, allergic rhinoconjunctivitis, and reactive airway disease. Allergen-specific IgE has been detected in these horses, and allergen-specific immunotherapy is used to ameliorate clinical signs. The best understood atopic disease in horses is insect hypersensitivity, but the goal of effective treatment with allergen-specific immunotherapy remains elusive. In this review, updates in pathogenesis of allergic states and a brief mention of the new data on what is known in humans and dogs and how that relates to equine allergic disorders are discussed.

Pruritus: an overview of current concepts

Pruritus is an integral part of the patient's symptoms in numerous dermatological and systemic diseases in humans and animals. Comparable to chronic pain, pruritus can have a dramatic impact on the quality of life of the patient. In recent years, pruritus has been defined as an autonomous, pain-independent sensation, and itch-specific neurons, mediators, spinal neurons and cortical areas have been identified. These observations have not only improved our understanding of the neurobiology of itch but will also lead to improved diagnosis and to the development of new and more efficient therapeutic options. This article reviews the role of itch fibres and their response to various mediators of pruritus including histamine, vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), and substance P (SP), and opioids. Substances that may be involved in the induction or modulation of itch may be termed pruritogenic mediators and examples discussed include proteases, lipid mediators, neuropeptides, opioids and various cytokines. There is no single, generally accepted clinical classification of chronic pruritus. In the past pruritus has been classified on the basis of the neuroanatomical origin and on the potential underlying disease. Therapeutic options for the management of pruritus are discussed including topical and systemic therapies, assuming that trigger factors have been eliminated where possible. Topical agents may include capsaicin, the calcineurin inhibitors tacrolimus and pimecrolimus, and cannabinoid agonists such as N-palmitoyl ethanolamine. Systemic therapies may include antihistamines, anticonvulsants, opiate receptor antagonist or agonists, antidepressants, ciclosporin, and UV light.

Proteinaceous cytotoxic component of Allium sativum induces apoptosis of INT-407 intestinal cells

Garlic has long been known for its wide array of therapeutic effects, including hypolipidemic, antihypertensive, antimicrobial, and possibly anticancer effects; conversely, some adverse effects of garlic, such as acute pain and neurogenic inflammation, have also been reported. However, information detailing the toxicological significance of garlic is scarce. In this study, the cytotoxicities of fresh garlic extract (FGE) and boiled garlic extract (BGE) and their underlying toxic mechanisms were investigated using INT-407 intestinal epithelial cells. A brief exposure (20 minutes) to FGE induced a concentration-dependent increase in cell death (37 +/- 2% at 300 microg/mL), but no cytotoxic effects were induced after exposure to BGE. For FGE, only the high-molecular-mass (>10-kDa) proteins were associated with cytotoxic effects. FGE-treated cells showed morphological changes such as increased cell rounding and fragmentation, suggesting programmed cell death (apoptosis). Apoptosis of FGE-treated cells was evaluated by observing the fragmented multinuclei stained with Hoechst 33342. From the cell cycle analysis, the increase in hypodiploidic cells and in the G2/M phase cell population suggested not only apoptosis but also cell cycle arrest of FGE-treated cells. Pretreatment with N-acetyl-l-cysteine almost completely prevented FGE-induced cell death, suggesting that reactive oxygen species (ROS) may play a key role in FGE-associated cytotoxicity. Consumption of fresh garlic may be linked to potential cytotoxicity of intestinal cells when ROS scavengers are not present.

Allergenic potency of spices: hot, medium hot, or very hot

Spices are the most attractive ingredients to confer an authentic taste to food. As they are derived from plants, they harbour allergenic potency and can induce symptoms ranging from mild local to severe systemic reactions. Due to the content of pharmacologically active substances of spices, the diagnosis of allergy and the differentiation from intolerance reactions may be difficult. Association with inhalative allergies via IgE cross-reactivity, but also direct gastrointestinal sensitization plays a role. This article is a botanical and allergological overview of the most important spices and molecules responsible for eliciting IgE-mediated reactions or cross-reactions. As no curative treatments are known at present, strict avoidance is recommended and, therefore, accurate labelling of pre-packed food is necessary.