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Equine Clinical Immunology > Chapter 9 Vasculitis > Flashcards

Chapter 9 Vasculitis Flashcards

1
Q

What is an allergic reaction?

A

An overreaction of the immune system to a normally harmless substance called an allergen.

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2
Q

What are IgE-mediated allergies also known as?

A

Type I hypersensitivities.

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3
Q

What characterizes IgE-mediated allergies?

A

Immediate onset after exposure to an allergen, production of allergen-specific IgE, binding of IgE to tissue mast cells, and release of inflammatory mediators.

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4
Q

What are common IgE-mediated allergies in horses?

A

Culicoides hypersensitivity and urticaria (hives).

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5
Q

What is Culicoides hypersensitivity?

A

A seasonal, recurrent allergic dermatitis in horses caused by salivary allergens from Culicoides midges.

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6
Q

What are the clinical signs of Culicoides hypersensitivity?

A

Pruritus, alopecia, excoriations, secondary bacterial infections, and lesions on various parts of the body such as the mane, neck, tail, face, ears, chest, and belly.

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7
Q

What factors influence the prevalence of Culicoides hypersensitivity?

A

Environmental exposure, genetic predisposition, age of the horse, and housing style.

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8
Q

What are the immunologic mechanisms involved in Culicoides hypersensitivity?

A

Production of allergen-specific IgE, mast cell sensitization, degranulation, and release of inflammatory mediators like histamine, leukotrienes, prostaglandins, and cytokines.

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9
Q

What is mast cell sensitization?

A

The process by which IgE antibodies bind to high-affinity IgE receptors on tissue mast cells.

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10
Q

What is the Prausnitz-Küstner reaction?

A

A method to transfer allergic reactions from affected to healthy horses via IgE obtained from allergic horses.

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11
Q

What role do Th2 cells and regulatory T cells play in Culicoides hypersensitivity?

A

Increased Th2 cell responses and reduced regulatory T cell functions contribute to the development of clinical allergy.

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12
Q

What diagnostic techniques are used for detecting allergen-specific IgE in horses?

A

Intradermal allergy testing and serological assays like enzyme-linked immunosorbent assays (ELISAs).

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13
Q

What is intradermal allergy testing?

A

A method where small doses of allergens are injected into the skin to observe immediate inflammatory reactions at the injection site.

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14
Q

What is the main goal of allergy testing?

A

To identify the causing allergen(s) for developing a management plan toward allergen avoidance and hyposensitization.

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15
Q

What are the limitations of serological allergy testing in horses?

A

Poor performance due to numerous positive reactions, many of which are likely false positives.

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16
Q

What treatments are available for IgE-mediated allergies in horses?

A

Symptomatic treatments like steroids, anti-histamines, allergen avoidance, fly control measures, and supportive care for skin lesions.

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17
Q

What preventive measures can be taken for horses with Culicoides hypersensitivity?

A

Managing turn-out times, using fly sprays, fly masks, whole body blankets, and providing smooth surfaces or brushes for rubbing.

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18
Q

What is urticaria in horses?

A

A condition characterized by lesions on the skin that can be round or have various shapes, and may or may not be associated with pruritus.

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19
Q

What are common causes of urticaria in horses?

A

Food allergens, insect bites, environmental allergens, drug or vaccine administration, and blood transfusion.

20
Q

What histopathological findings are associated with urticaria?

A

Dermal edema with eosinophilic and/or lymphocytic perivascular infiltrates and increased numbers of mast cells, eosinophils, and macrophages in skin lesions.

21
Q

What is recurrent airway obstruction (RAO) in horses?

A

A condition suspected to be mediated by hypersensitivity type I, characterized by mucus production, neutrophil accumulation, bronchial hyperreactivity, and bronchospasm.

22
Q

What triggers RAO in susceptible horses?

A

Inhaled molds and organic dusts that induce inflammatory airway responses.

23
Q

What is the controversy regarding IgE’s role in RAO?

A

Studies show conflicting results, and evidence for a causal role of IgE in RAO pathogenesis is still unclear.

24
Q

What is the prognosis for horses with IgE-mediated allergies?

A

No cure exists, and allergies typically recur with allergen exposure. Clinical outcomes depend on allergen pressure and environmental conditions.

25
Q

What is the difference between an allergic reaction and an anaphylactic reaction?

A

Allergic reactions are typically localized and less severe, while anaphylactic reactions are systemic and life-threatening.

26
Q

What does the term ‘sensitization’ refer to in the context of allergies?

A

The process by which exposure to an allergen leads to the production of specific IgE antibodies, which prime the immune system for subsequent allergic reactions.

27
Q

What is the main allergen responsible for Culicoides hypersensitivity?

A

Salivary allergens from Culicoides midges.

28
Q

What percentage of Icelandic horses exported to Europe develop Culicoides hypersensitivity?

A

26-72%.

29
Q

What are common clinical signs of Culicoides hypersensitivity in horses?

A

Pruritus, alopecia, and excoriations.

30
Q

What is the role of regulatory T cells in allergies?

A

They reduce the allergic response by suppressing the activity of Th2 cells and other immune cells involved in allergic reactions.

31
Q

What is the function of histamine in allergic reactions?

A

Histamine causes vasodilation and increased vascular permeability, leading to symptoms like swelling, redness, and itching.

32
Q

What is the primary method for diagnosing urticaria in horses?

A

Intradermal allergy testing.

33
Q

What type of hypersensitivity is urticaria in horses believed to be?

A

Type I hypersensitivity.

34
Q

What is a common treatment for severe clinical signs of allergies in horses?

A

Steroids and anti-histamines.

35
Q

What are the main goals of allergy testing in horses?

A

Identify the causing allergen(s) and develop a management plan for allergen avoidance and hyposensitization.

36
Q

What environmental conditions can influence the prevalence of Culicoides hypersensitivity?

A

Temperature and humidity.

37
Q

What is a major complication associated with Culicoides hypersensitivity if not treated?

A

Secondary bacterial infections.

38
Q

How do Th2 cells contribute to allergies?

A

They produce pro-inflammatory cytokines that enhance the allergic response.

39
Q

What is the role of IgE in allergic reactions?

A

IgE binds to allergens and triggers the release of inflammatory mediators from mast cells and basophils.

40
Q

What is the effect of repeated allergen exposure in allergic horses?

A

It can lead to chronic inflammation and worsening of clinical signs.

41
Q

What is the importance of mast cell degranulation in allergies?

A

It releases inflammatory mediators like histamine, leading to the symptoms of an allergic reaction.

42
Q

What is a key diagnostic feature of intradermal allergy testing?

A

Formation of a wheal at the injection site.

43
Q

What is the first step in managing an allergic horse?

A

Identifying and avoiding the allergen.

44
Q

What is a potential side effect of steroid treatment in horses?

A

Decreased immune response and increased risk of infections.

45
Q

What does the term ‘inflamm-aging’ refer to?

A

Chronic low-grade inflammation associated with aging.

46
Q

What is the role of cytokines in allergies?

A

They increase vascular permeability and inflammation, contributing to the symptoms of an allergic reaction.

47
Q

What are the clinical signs of recurrent airway obstruction (RAO) in horses?

A

Mucus production, neutrophil accumulation, bronchial hyperreactivity, and bronchospasm.

Equine Clinical Immunology (32 decks)

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