Pathology: Skin

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Questions and Answers

Which layer of the skin serves as a physical barrier and is involved in temperature regulation?

Epidermis (correct)

Subcutis

Dermis

Hypodermis

The skin is the smallest organ in the body.

False

What is the primary reason for veterinary consultations regarding skin disease?

Cosmetic and economic importance

The skin consists of three layers: Epidermis, dermis, and __________.

hypodermis Signup and view all the answers

Match the skin layers with their descriptions:

Epidermis = Outer layer providing protection Dermis = Middle layer with blood vessels and nerves Hypodermis = Inner layer with fatty tissue Subcutis = Another name for hypodermis Signup and view all the answers

What is a significant factor in the diagnosis of skin diseases?

Clinical history and examination Signup and view all the answers

Deep bacterial infections are less serious than superficial bacterial infections.

False Signup and view all the answers

List one autoimmune disease associated with the skin.

Pemphigoid Signup and view all the answers

What is the major disadvantage of a skin biopsy?

The cost exceeding $300 Signup and view all the answers

Itchy dogs are generally good candidates for a skin biopsy.

False Signup and view all the answers

What is the recommended number of skin biopsy samples to be collected for increased diagnostic accuracy?

at least 3 and preferably 5 Signup and view all the answers

Photosensitization causes damage primarily in the ______ cells of the skin.

basal epidermal Signup and view all the answers

What is the primary function of the keratin layer in the epidermis?

To prevent infections and waterproof the body Signup and view all the answers

The basal cell layer of the epidermis contains cells that can divide indefinitely.

True Signup and view all the answers

Match the following types of photosensitivity with their descriptions:

Congenital photosensitivity = Caused by inherited defects in metabolism of biological pigments Primary photosensitivity = Caused by ingestion of photodynamic chemicals Secondary photosensitivity = Resulting from the presence of photodynamic compounds due to liver damage Spring eczema = A clinical syndrome of solar-induced dermatitis seen in cattle Signup and view all the answers

What is the term for hair loss?

Alopecia Signup and view all the answers

Which diagnostic test allows for a diagnosis of demodicosis?

Skin scrape Signup and view all the answers

Exposure to the sun only causes chronic skin lesions.

False Signup and view all the answers

The skin lesions caused by inflammation within the dermis are called __________.

Dermatitis Signup and view all the answers

What is the purpose of including a detailed history when submitting skin biopsies?

maximize chances of diagnosis Signup and view all the answers

Match the type of skin lesion with its definition.

Pustule = Focal accumulation of inflammatory cells Vesicle = Fluid-filled space within the epidermis Crust = Dried exudate or sebum on the skin surface Pruritus = Associated with itching Signup and view all the answers

A ______ punch is recommended to take a skin biopsy.

6mm Signup and view all the answers

What is anagen?

The growth phase of the hair follicle Signup and view all the answers

What feature helps to distinguish photosensitization clinically?

Location of lesions on thinly-haired areas Signup and view all the answers

Dermatosis refers to inflammation within the dermis.

False Signup and view all the answers

Spring eczema in calves is typically severe and progresses quickly.

False Signup and view all the answers

What is the process called when mature squames slough off the skin?

Desquamation Signup and view all the answers

The __________ are responsible for the production of hair.

follicular epidermal cells Signup and view all the answers

What can be sent with biopsy submissions to assist in diagnosis?

photographs Signup and view all the answers

All skin diseases will become infected by the ______ present on the skin.

commensal bacteria Signup and view all the answers

Match the term with its definition.

Erythema = Reddening of the skin due to hyperemia Folliculitis = Inflammation of the hair follicle Myxedema = Dermal edema due to increased mucin Keratinocyte = Epithelial cell within the epidermis Signup and view all the answers

Which of the following is NOT a type of photosensitivity?

Tertiary photosensitivity Signup and view all the answers

Which layer of skin primarily contains adipose tissue?

Hypodermis Signup and view all the answers

Sequentially taking a thorough clinical history is unimportant in diagnosing skin diseases.

False Signup and view all the answers

Which method can be used to obtain diagnostic samples for skin diseases?

Skin scrapes Signup and view all the answers

Inflammation of the hypodermis is known as __________.

Panniculitis Signup and view all the answers

What does 'pigmentary incontinence' refer to?

Pigment falling into the dermis from the epidermis Signup and view all the answers

What type of photosensitization is commonly caused by the ingestion of sporidesmin toxin in New Zealand sheep and cattle?

Secondary photosensitization Signup and view all the answers

Dogs are the only domestic animals that develop melanomas as a result of sun exposure.

False Signup and view all the answers

What is the clinical name for the sunburn observed in sheep due to secondary photosensitization?

Facial eczema Signup and view all the answers

Increased serum gamma-glutamyl transferase (GGT) is used to confirm the presence of __________ photosensitization.

secondary Signup and view all the answers

Match the condition with its corresponding type:

Acral lick dermatitis = Behavioural disease Callus = Hyperplastic orthokeratotic epidermis Skin fold dermatitis = Chronic rubbing and moisture Feline psychogenic alopecia = Excessive grooming Signup and view all the answers

What are common areas predisposed to sunburn in sheep?

Face and ears Signup and view all the answers

Chronic sun exposure primarily leads to the development of neoplasia in various domestic animals.

True Signup and view all the answers

What fungus produces the sporidesmin toxin that causes secondary photosensitization in New Zealand?

Pithomyces chartarum Signup and view all the answers

The excessive grooming behavior in cats leading to hair shaft breakage is known as __________.

feline psychogenic alopecia Signup and view all the answers

What is a common clinical manifestation resulting from acral lick dermatitis in dogs?

All of the above Signup and view all the answers

Skin fold dermatitis occurs only in dogs.

False Signup and view all the answers

What is a characteristic histological finding in feline psychogenic alopecia?

Normal hair shafts within the follicles Signup and view all the answers

Thermal burns can be classified into ______ degrees based on their severity.

three Signup and view all the answers

Match the condition to its description:

Acral lick dermatitis = Focal area of marked epidermal hyperplasia Callus = Hyperplastic area over bony prominences Skin fold dermatitis = Retention of moisture and secondary infection Injection site reactions = Nodular accumulation of lymphocytes Signup and view all the answers

Which of the following diseases is commonly referred to as puppy pyoderma?

Superficial pustular dermatitis Signup and view all the answers

What is the primary factor contributing to frostbite in animals?

Sudden exposure to extreme cold Signup and view all the answers

Superficial pustular dermatitis is a contagious disease.

False Signup and view all the answers

What bacterium is responsible for exudative epidermatitis of pigs?

Staphylococcus hyicus Signup and view all the answers

Cold agglutination disease primarily affects cats and can occur even during moderately cold temperatures.

True Signup and view all the answers

The disease commonly seen in sheep due to moisture trapped in the fleece is called _____ rot.

fleece Signup and view all the answers

What is the most important part of the skin's physical barrier against bacteria?

Keratin Signup and view all the answers

In _________, an abnormal composition of plasma proteins causes blood agglutination in cats.

cold agglutination disease Signup and view all the answers

What is the primary cause of pyotraumatic dermatitis?

Self-trauma leading to moisture retention Signup and view all the answers

Which of the following can disrupt the skin's chemical barrier?

Immunosuppression Signup and view all the answers

Dermatophilosis occurs exclusively in dogs.

False Signup and view all the answers

What environmental factor is a predisposing cause of equine pastern dermatitis?

Chronic moisture Signup and view all the answers

Bacteria can cause disease without any skin disorder present.

False Signup and view all the answers

Match the skin infection with its description:

Superficial pustular dermatitis = Caused by overgrowth of normal skin bacteria due to loss of skin defenses Cold agglutination disease = Results in blood clotting at cold temperatures Frostbite = Tissue damage caused by extreme cold exposure Seborrhea = Disruption of epidermal maturation leading to softer keratin Signup and view all the answers

The bacterium involved in dermatophilosis is called _____ congolensis.

Dermatophilus Signup and view all the answers

What is a common nicknamed form of equine pastern dermatitis?

Mud fever Signup and view all the answers

What type of bacteria commonly cause skin infections in companion animals?

Staphylococcus pseudintermedius Signup and view all the answers

Match the following diseases with their associated causative agents:

Superficial pustular dermatitis = Loss of skin defenses Exudative epidermatitis = Staphylococcus hyicus Dermatophilosis = Dermatophilus congolensis Fleece rot = Pseudomonas aeruginosa Signup and view all the answers

Superficial bacterial infections are typically confined to the _________.

epidermis Signup and view all the answers

Foot rot is caused exclusively by one type of bacterium.

False Signup and view all the answers

What is often necessary for the clinical cure of most bacterial skin diseases?

Restoration of skin defenses Signup and view all the answers

Most bacterial skin diseases will not recur if proper treatments are provided.

False Signup and view all the answers

Which bacterial infection is particularly common due to cat bites?

Cat bite abscesses Signup and view all the answers

What environmental condition increases the likelihood of frostbite in animals?

Cold temperatures Signup and view all the answers

Infections of penetrating wounds can lead to the formation of _____ and pyoderma.

abscesses Signup and view all the answers

What is an effective treatment approach for dermatophilosis?

Reducing skin moisture Signup and view all the answers

Bacteria such as __________ can cause superficial pustular dermatitis, particularly in young animals.

Staphylococcus Signup and view all the answers

Name one common underlying cause of pyotraumatic dermatitis.

Atopy or flea allergy dermatitis Signup and view all the answers

Which season is most likely to see an increase in cases of cold agglutination disease in cats?

Winter Signup and view all the answers

Hair shafts are a significant part of the skin's defenses against bacterial infection.

True Signup and view all the answers

What is the most common cause of dermal infection with mycobacteria in animals?

Contaminated puncture wounds Signup and view all the answers

Feline leprosy is caused exclusively by biting flies.

False Signup and view all the answers

What visible characteristic can be found in lesions caused by botryomycosis?

Sulphur granules Signup and view all the answers

Pox viruses cause localized skin disease in many food animal and avian species, but they are most pathogenic in __________.

younger animals Signup and view all the answers

Match the following diseases with their associated viruses or causative agents:

Contagious ecthyma = Parapox virus Feline leprosy = Saprophytic mycobacterium Cow pox = Pox virus Bovine herpes virus 1 = Infectious bovine rhinotracheitis Signup and view all the answers

Which of the following is a common disease associated with herpes viruses in cattle?

Infectious pustular vulvovaginitis Signup and view all the answers

Telecom infections are primarily the result of viral agents.

False Signup and view all the answers

What type of lesions do herpes viruses cause in animals?

Intraepidermal vesicles Signup and view all the answers

What is the most common skin neoplasm of horses?

Equine sarcoid Signup and view all the answers

Feline sarcoids are a common neoplasm typically found on the ears and paws of cats.

False Signup and view all the answers

Infections with papillomaviruses most often result in __________.

hyperplastic papillomas Signup and view all the answers

Match the viral disease to its primary affected animal:

Orf = Humans Papular stomatitis = Calves Contagious ecthyma = Sheep and goats Coital exanthema = Horses Signup and view all the answers

What is commonly known as ringworm?

Dermatophytosis Signup and view all the answers

Which of the following conditions is most associated with dermatitis due to herpes viruses?

Erosion formation Signup and view all the answers

Equine sarcoids are caused by an infection of __________ papillomavirus.

bovine Signup and view all the answers

Which dog breed has a predisposition for developing viral plaques?

Pug Signup and view all the answers

Surgical excision is an effective long-term solution for recurring lesions caused by mycobacterial infections.

False Signup and view all the answers

All cats can potentially develop Malassezia dermatitis.

False Signup and view all the answers

What do bovine fibropapillomas typically develop around in bulls?

Penis Signup and view all the answers

Bovine herpes viruses can cause inflammation of the __________ due to milking irritation.

teat Signup and view all the answers

What fungal organism is the most common cause of Dermatophytosis?

Microsporum canis Signup and view all the answers

Symptoms of cutaneous fungal infections in animals typically include areas of crusting and __________.

alopecia Signup and view all the answers

Match the following diseases with their associated organisms:

Dermatophytosis = Microsporum canis Malassezia dermatitis = Malassezia pachydermatis Cryptococcosis = Cryptococcus neoformans Equine sarcoid = Bovine papillomavirus Signup and view all the answers

What can be a consequence of viral plaques in dogs?

Malignant transformation Signup and view all the answers

Fungal infections in animals are typically pruritic (itchy).

False Signup and view all the answers

What are the three categories of fungal skin diseases?

Cutaneous, subcutaneous, and systemic Signup and view all the answers

Cryptococcosis commonly accesses the body via the __________.

lungs Signup and view all the answers

Where do lesions from Cryptococcosis typically develop on the body?

Face, ears, and paws Signup and view all the answers

What percentage of people with AIDS develop an infection with C. neoformans?

10% Signup and view all the answers

C. neoformans infections are most commonly associated with healthy individuals.

False Signup and view all the answers

Which specific type of mites are primarily responsible for demodicosis in dogs?

Demodex mites Signup and view all the answers

Demodicosis is common in dogs, particularly breeds with a short, dense __________ coat.

hair Signup and view all the answers

What is the primary reason for the hair loss in dogs with demodicosis?

Presence of mites Signup and view all the answers

Pruritus is a common feature of demodicosis in dogs.

False Signup and view all the answers

What is the primary mode of transmission for sarcoptic mange?

Contact with an infected animal Signup and view all the answers

Sarcoptic mange is best considered a __________ reaction.

hypersensitivity Signup and view all the answers

Which of the following is NOT associated with sarcoptic mange?

Hair loss due to follicular presence Signup and view all the answers

A skin scraping is a highly effective method for diagnosing sarcoptic mange.

False Signup and view all the answers

What is the main aim of treatment for demodicosis in older dogs?

Restoring immune function Signup and view all the answers

Match the following skin diseases with their descriptions:

Demodicosis = Caused by Demodex mites, often in younger dogs Sarcoptic mange = Caused by Sarcoptes scabiei, associated with severe pruritus C. neoformans infection = Typically occurs in immunocompromised individuals Ectoparasitic diseases = Transmitted by contact and affect both small and large animals Signup and view all the answers

What are typical clinical signs of demodicosis in dogs?

Facial alopecia and erythema Signup and view all the answers

The treatment of ectoparasites is an important source of __________ for veterinarians.

income Signup and view all the answers

What is the most common allergen responsible for dermatitis in dogs and cats?

Flea saliva Signup and view all the answers

Atopy is primarily caused by food allergens.

False Signup and view all the answers

Which body areas are most commonly affected by flea allergy dermatitis?

Dorsolumbar, thigh, ventral abdomen, and flanks Signup and view all the answers

Mosquito-bite hypersensitivity leads to ulcerated lesions on the non-haired skin of the ______.

nose Signup and view all the answers

Match the following allergic conditions with their descriptions:

Flea allergy = Most common allergic dermatitis in pets Atopy = Environmental allergens causing seasonal itching Food allergy = Non-seasonal allergic reaction with skin manifestations Contact allergy = Allergens from substances in direct contact with the skin Signup and view all the answers

What characterizes urticaria (hives) in animals?

Multifocal dermal edema Signup and view all the answers

Food allergies typically result in a consistent distribution of lesions on the body.

False Signup and view all the answers

What histological feature is often seen in flea allergy dermatitis?

Intraepidermal eosinophilic pustules Signup and view all the answers

Eosinophilic plaques in feline allergic dermatitis often appear on the ______ abdomen.

ventral Signup and view all the answers

Match the following allergic reactions with their descriptions:

Flea allergy dermatitis = Most common in dogs and cats Food allergies = Causes increased defecation and can include diarrhea Atopy = Associated with pollen and has a seasonal pattern Contact dermatitis = Triggered by substances like plastics and dyes Signup and view all the answers

Which allergic condition is characterized by the strong genetic basis?

Atopy Signup and view all the answers

Equine allergies generally present as generalized skin reactions.

False Signup and view all the answers

What type of cells mainly infiltrate eosinophilic plaques in allergic dermatitis?

Eosinophils and mast cells Signup and view all the answers

Which of the following are the most common areas affected by human-adapted S scabiei mites?

Hands, wrists, genitals, and abdomen Signup and view all the answers

Human-adapted S scabiei mites can spontaneously resolve without treatment.

False Signup and view all the answers

Atopy is estimated to account for around ______% of all canine skin disease.

10 Signup and view all the answers

What are the two categories of diseases caused by flies?

Allergies and myiasis Signup and view all the answers

Immune-mediated skin diseases are more common in __________ animals.

companion Signup and view all the answers

What release is caused by mast cell degranulation in allergic reactions?

Chemokines for eosinophils, histamine, and other pro-inflammatory substances Signup and view all the answers

All allergens produce distinct histological lesions.

False Signup and view all the answers

Identify one unique manifestation of allergic skin disease found in cats.

Miliary dermatitis Signup and view all the answers

Allergic reactions in animals are often associated with overproduction of _______.

IgE Signup and view all the answers

Match the following types of allergens with their descriptions:

Atopy = Inhaled allergens leading to skin lesions Contact allergens = Allergens absorbed through the skin Food allergens = Allergens ingested causing reactions Insect allergens = Allergens from bites or stings of pests Signup and view all the answers

Which of the following can trigger allergic skin disease in animals?

Any antigen Signup and view all the answers

Canine allergies typically do not cause lesions due to self-trauma.

False Signup and view all the answers

What histological cell types are predominant in allergic skin disease?

Eosinophils and mast cells Signup and view all the answers

The skin lesions created by chronic allergic reactions are often and .

thickened, darker Signup and view all the answers

Which type of skin conditions are autoimmune diseases commonly associated with?

Hypersensitivity reactions Signup and view all the answers

Flea infestation can cause anemia in older animals.

False Signup and view all the answers

Which of the following is an autoimmune disease affecting dogs and cats?

Pemphigus foliaceus Signup and view all the answers

Pemphigus foliaceus can develop secondary to drug therapy.

True Signup and view all the answers

What is the primary treatment recommendation for allergic reactions in pets?

Identification and removal of the offending allergen Signup and view all the answers

The disease characterized by the loss of cellular adhesion in the epidermis due to antibodies is called __________.

pemphigus foliaceus Signup and view all the answers

Match the following conditions with their characteristics:

Pemphigus erythematosus = Mild variant of pemphigus foliaceus Discoid lupus erythematosus = Triggered by UV radiation Hypothyroidism = Most common canine endocrinopathy Non-thyroid endocrinopathy = Includes various hormonal imbalances Signup and view all the answers

What body area is typically first affected in pemphigus foliaceus?

Face Signup and view all the answers

Discoid lupus erythematosus is considered a true autoimmune disease.

False Signup and view all the answers

What is the commonly affected area in dogs with discoid lupus erythematosus?

Lightly haired areas such as the nasal planum, muzzle, and pinnae Signup and view all the answers

Autoimmune skin disease constitutes what percentage of cases in companion animal dermatology referral centers? __________

1 - 4% Signup and view all the answers

Match the breed with the skin conditions they are predisposed to:

Chow Chow = Pemphigus foliaceus Collie = Discoid lupus erythematosus Akita = Pemphigus foliaceus German Shepherd = Discoid lupus erythematosus Signup and view all the answers

What is the primary characteristic of primary seborrhea in dogs?

It is genetically mediated with a greasy hair coat. Signup and view all the answers

What diagnostic test is required for definitive diagnosis of autoimmune diseases?

Biopsy Signup and view all the answers

Juvenile sterile granulomatous dermatitis involves bacterial infections.

False Signup and view all the answers

Most dogs with hypothyroidism display symmetrical alopecia.

False Signup and view all the answers

What is the mean age at diagnosis for pemphigus foliaceus in dogs?

4 years Signup and view all the answers

What causes the unpleasant odor associated with seborrhea?

Breakdown of immature keratin by yeasts or bacteria. Signup and view all the answers

In cases of hypothyroidism, skin lesions may include loss of hair in areas of __________.

friction Signup and view all the answers

Feline plasma cell pododermatitis is also referred to as __________.

cushion pad Signup and view all the answers

Match the following skin conditions with their characteristics:

Seborrhea = Disordered maturation of keratinocytes Juvenile pyoderma = No bacterial involvement Feline plasma cell pododermatitis = Massive plasmacytic infiltration Primary seborrhea = Genetically mediated disease Signup and view all the answers

Which of the following is NOT a feature of pemphigus foliaceus?

Symmetrical hair loss Signup and view all the answers

Which treatment is commonly effective for juvenile sterile granulomatous dermatitis?

Corticosteroid treatment Signup and view all the answers

Secondary seborrhea will resolve only after treating the primary skin disease.

True Signup and view all the answers

What age group of puppies is most commonly affected by juvenile sterile granulomatous dermatitis?

Less than 4 months of age. Signup and view all the answers

Seborrhea can occur as a primary or __________ process.

secondary Signup and view all the answers

What histological finding is common in cases of seborrhea?

Hyperkeratosis with keratin spikes Signup and view all the answers

What is the primary histological change observed in dogs with non-thyroid endocrinopathies?

Increased numbers of resting telogen follicles Signup and view all the answers

Histological examination can differentiate between the four non-thyroid endocrinopathies in dogs.

False Signup and view all the answers

Which endocrinopathy in dogs is characterized by alopecia that spares the head and extremities?

Hyperadrenocorticism Signup and view all the answers

In dogs, cyclical flank alopecia is believed to be triggered by changes in the ______.

photoperiod Signup and view all the answers

Match the following endocrinopathies with their descriptions:

Hyperadrenocorticism = Alopecia that spares the head and extremities Cyclical flank alopecia = Spontaneously resolving patches of alopecia Growth hormone responsive dermatosis = Alopecia due to reduced growth hormone Sex hormone responsive dermatosis = Alopecia related to excessive adrenal sex hormones Signup and view all the answers

What is a clinical feature of starvation in food animals?

Brittle hair production Signup and view all the answers

Calcinosis cutis is a common finding in horses with PPID.

False Signup and view all the answers

What is the treatment recommendation for cyclical flank alopecia?

No treatment is recommended Signup and view all the answers

The skin lesions associated with non-thyroid endocrinopathies are characterized by ________ symmetrical alopecia.

bilaterally Signup and view all the answers

What type of alopecia is commonly seen in dogs with sex hormone responsive dermatosis?

Symmetrical alopecia Signup and view all the answers

Dystrophic calcification is the only unique condition in dogs related to chronic hyperadrenocorticism.

True Signup and view all the answers

What causes alopecia in growth hormone responsive dermatosis in mature animals?

Decreased growth hormone production Signup and view all the answers

Horses with PPID fail to shed their winter coats and appear excessively ______.

shaggy Signup and view all the answers

Match the following disorders with their related species:

Hyperadrenocorticism = Dogs PPID = Horses Iodine deficiency goitre = Food animals Nutritional disorders = Food animals Signup and view all the answers

Study Notes

Pathology of the Skin: Learning Objectives

Understand pathogenesis and diagnosis of common skin diseases.
Recognize the role of clinical history and examination in skin disease diagnosis; value of skin biopsy.
Differentiate development of superficial vs. deep bacterial skin infections.
Grasp genetic basis and pathogenesis of allergic skin diseases in animals.
Identify variations in clinical presentation of allergic skin diseases across dogs, cats, and horses.
Comprehend pathogenesis of key autoimmune skin diseases, including pemphigoid diseases and discoid lupus erythematosus.
Identify histological lesions related to canine non-thyroid endocrinopathies; list associated diseases.
Know tests for diagnosing neoplastic and non-neoplastic skin tumors.

General Considerations

Skin is the largest organ; important for cosmetic and economic reasons in veterinary consultation.
Skin diseases can be primary or secondary to other bodily diseases.
Limited skin responses complicate gross differentiation between diseases.

Function and Normal Histology of the Skin

Skin functions: barrier, temperature regulation, blood pressure, serum electrolyte regulation, vitamin D production, and immune system component.
Normal skin consists of three layers: Epidermis (5-50 cells thick), Dermis, Hypodermis.
Basal cells in the epidermis are stem cells that differentiate into keratinized cells at the surface.
Hair follicles are epidermal invaginations; hair is keratin produced by these cells.
Adnexal glands (apocrine and sebaceous) are present in the dermis for hair maintenance.

Glossary of Terms

Alopecia: hair loss; Dermatitis: inflammation in the dermis; Hyperkeratosis: increased keratin thickness; Folliculitis: hair follicle inflammation; Spongiosis: fluid accumulation in the epidermis.

Diagnosing Skin Disease

Clinical history should include age, sex, breed, pruritus, duration of lesions, and systemic health signs.
Clinical examination focuses on lesion distribution and characteristics for presumptive diagnoses.
Diagnostic samples can include skin scrapes, Sellotape strips, and cytology of biopsies.
Skin biopsy advantages: broad diagnostic range but costly; histology can confirm multiple skin diseases. Examine only primary lesions for accurate diagnosis.

Environmental and Physical Diseases

Solar cutaneous diseases relate to skin's susceptibility based on hair, keratin thickness, and pigmentation.
Photosensitization: can be congenital, primary (chemical ingestion), or secondary (liver damage causing phylloerythrin buildup).
Spring eczema is a solar-induced dermatitis unique to New Zealand, with mild manifestations in calves and severe in adults.
Chronic sun damage can lead to skin neoplasia, such as squamous cell carcinomas and hemangiosarcomas.

Dermatological Conditions

Acral lick dermatitis: chronic self-trauma in dogs resulting in epidermal hyperplasia; often behavioral.
Feline psychogenic alopecia: excessive grooming leads to hair shaft breakage; often seen in anxious cats.
Callus: hyperplastic epidermis due to pressure from hard surfaces; leads to secondary infections.
Injection site reactions from vaccines can vary by species; nodular reactions in most species, vasculitis in some dog breeds.
Skin fold dermatitis arises when skin surfaces rub together; moisture leads to bacterial infection, commonly in dogs and cattle.
Temperature extremes: burns classified by degree (1st epidermis, 2nd epidermis and dermis, 3rd full thickness).### Burns and Frostbite
Superficial dermal burns lead to blistering and significant exudation.
Severe dermal damage causes coagulative necrosis, thrombosis, and infarction, inhibiting exudation.
Secondary infections in devitalized dermis can be fatal.
Frostbite is rare in New Zealand, primarily affecting extremities like dairy cow teats.
Neonates and animals moved from warm climates are more susceptible to frostbite.
Exposure to extreme cold causes sustained blood vessel contraction, leading to tissue hypoxia.
Cats can develop 'cold agglutination disease' (cryofibrinogenemia), where cold temperatures cause blood agglutination and tissue damage.
Symptoms resembling frostbite can occur without extreme cold due to abnormal plasma proteins.

Infectious Diseases

Skin is constantly exposed to infectious agents; bacterial infections typically require predisposing factors.
Viral and fungal infections can occur without prior skin disorders.

Bacterial Skin Disease

Skin defenses include physical barriers (hair, keratin), chemical barriers (fatty acids, immunoglobulin), and a resident microbial barrier.
Keratin serves as a vital physical barrier, providing a dry environment that inhibits bacterial colonization.
Infection occurs when skin defenses are disrupted by friction, moisture, or altered epidermis maturation.
Restoration of skin defenses is crucial for resolving bacterial infections.
Staphylococcus pseudintermedius commonly causes bacterial skin infections in companion animals.
Most strains are antibiotic-susceptible in New Zealand, making routine cultures less informative.

Superficial Bacterial Infections

Confined to the epidermis, these infections include:
- Superficial pustular dermatitis: Overgrowth caused by impaired skin defenses, common in young animals. Not contagious and typically resolves as defenses are restored.
- Pyotraumatic dermatitis (hot-spot dermatitis): Caused by self-trauma and moisture, often associated with allergies.
- Dermatophilosis: Caused by Dermatophilus congolensis in chronically damp conditions. Treated by reducing moisture and restoring defenses.
- Exudative epidermatitis of pigs: Caused by Staphylococcus hyicus, resulting in greasy, malodorous exudation, particularly in young pigs.
- Fleece rot and equine pastern dermatitis: Result from moisture entrapment, leading to bacterial proliferation and skin damage.
- Interdigital dermatitis and foot rot: Caused by chronic moisture allowing infection by Fusobacterium necrophorum and other bacteria.

Deep Bacterial Infections

Defined by bacteria and neutrophils within the dermis (pyoderma) and require more intensive treatment.
Persistence of bacteria complicates resolution, necessitating prolonged antibiotics.
Common examples include:
- Staphylococcal folliculitis and furunculosis: Often in dogs, sheep, and horses, commonly linked to pressure points or trauma.
- Infections of penetrating wounds: Common cat bite abscesses from contaminated puncture wounds.
- Mycobacterial infections: Nodular lesions observed in several species, including cutaneous leprosy in cats and dogs.
- Botryomycosis: Nodular bacterial infections, often from wound infections leading to yellow "sulphur granules."

Viral Skin Disease

Pox viruses: Cause skin disease in various species, with zoonotic potential.
- Parapox viruses in New Zealand cause papular stomatitis in calves and contagious ecthyma in sheep and goats.
Herpes viruses: Economically important in cattle and can cause various conditions, including mammillitis and coital exanthema.
Papillomaviruses: Cause hyperplastic papillomas, typically self-limiting but can be persistent in some cases, particularly in young animals.

Fungal Skin Disease

Sub-classified as cutaneous, subcutaneous, or systemic.
Fungal infections involve keratinized layers of the epidermis, with potential inflammation in the dermis.### Ringworm (Dermatophytosis)
Commonly referred to as ringworm, it's the most prevalent fungal skin disease in animals and humans.
Young, immunosuppressed animals are most susceptible, especially in humid, overcrowded environments.
Microsporum canis is the primary causative agent in cats and dogs, thriving particularly in long-haired breeds.
Fungi invade keratin in hair shafts, leading to inflammation and epidermal hyperplasia.
Hair shaft damage can cause breakage, and severe cases may lead to furunculosis.
Typical lesions manifest as crusting and alopecia; fluorescence with Wood’s lamp can aid diagnosis, more common in cats.
Fungal cultures are also diagnostic without requiring biopsies.
Most animals develop immunity after infection, leading to spontaneous resolution.
Infecting nails can lead to soft, discoloured nails that easily break.
Trans-species infections of M. canis can occur in humans, though animals typically do not experience pruritus.

Malassezia Dermatitis

Caused by the yeast Malassezia pachydermatis, mainly seen in dogs, particularly small breeds.
Typically originating from ear canals, it proliferates due to impaired skin defenses, often from secondary atopy.
Clinical signs include hyperpigmentation, lichenification, alopecia, and an unpleasant odour.
Treatment revolves around addressing underlying conditions, with excessive keratin removal often being curative.
West Highland White Terriers show congenital susceptibility, complicating treatment.

Cryptococcosis

Caused by Cryptococcus neoformans, usually enters via the lungs.
From the lungs, it predominantly infects the nasal cavity, skin, and reproductive organs.
Common lesions are nodular, often found on the face, ears, and paws.
Diagnosis is confirmed through cytology or histology.
Surgical excision may be curative for isolated cutaneous lesions but may indicate potential systemic involvement.
Notably affects cats, but all species can be infected; it's more serious in immunocompromised humans.

Demodicosis

Primarily affects dogs, caused by Demodex mites which are host-specific and generally asymptomatic.
Risk factors include age (common in dogs under one year) and certain breeds, such as pit bulls.
Symptoms manifest as erythematous, alopecic, crusting areas mainly on the face and forelegs.
Diagnosis is achieved through skin scraping, revealing large numbers of mites.
Histological findings include follicle distention, pigmentation changes, and potential for secondary bacterial infection.

Sarcoptic Mange

Caused by Sarcoptes scabiei, significantly affects pigs and dogs; transmitted through direct contact.
Characterized as a hypersensitivity reaction, where even few mites trigger severe pruritus.
Clinical lesions start on ears, elbows, and neck due to self-trauma; histologically shows hyperplasia and eosinophilic dermatitis.
Treatment often leads to dramatic improvement and can serve as a confirmation of diagnosis.

Fleas

Major parasites for cats and dogs, causing irritation and potentially anemia in young animals.
Fleas predominantly trigger allergic skin disease, leading to significant discomfort.

Chorioptic Mites

Affect cattle, horses, goats, and sheep, typically found on lower limbs and sensitive areas causing crusting and alopecia.

Immunity and Allergic Skin Disease

Immune-mediated diseases are common in companion animals, rarely affecting food animals.
Allergic skin diseases result from excess IgE production, with genetic predispositions playing a role.
Environmental allergens lead to localized or systemic reactions, characterized by inflammation and self-trauma lesions.

Flea Allergy

Flea saliva is the most common cause of allergy-related dermatitis in dogs and cats, affecting typical flea-occupied areas.
Histological findings may include eosinophilic pustules, but fleas can be difficult to detect.

Atopy

Atopy prevalence has increased with better flea control measures; environmental allergens are typically involved.
Seasonal patterns are common, with pruritus mainly around the face and feet; predisposition to ear infections is notable.
Genetic predisposition is significant, affecting up to 50% of animals with a family history of allergies.

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This quiz explores the impact of frostbite and cold agglutination disease in animals, particularly focusing on dairy cows and other species. Learn about the effects of extreme cold on tissue health and the risk factors involved in these conditions. Understand how environmental changes affect animal health and management strategies.