Pathologies

Introduction
Seborrheic dermatitis is a chronic skin condition affecting both dogs and cats, characterized by an imbalance in sebum production, which can result in dry or oily skin, flaking, and a foul odor. Although not always painful, this condition can cause significant discomfort for pets and lead to secondary infections if left untreated. This article explores the causes, symptoms, and available treatments for this condition.

Causes
Seborrheic dermatitis can be primary or secondary, and distinguishing between the two is key to proper treatment.

• Primary seborrheic dermatitis: Genetic in origin, it is more common in certain dog breeds such as Cocker Spaniels, Basset Hounds, and West Highland White Terriers. Cats can also be affected, though it is less common.
• Secondary seborrheic dermatitis: Can develop as a result of underlying conditions, including:
  • Allergies (environmental or food-related).
  • Bacterial or fungal infections.
  • Parasites such as fleas or mites.
  • Endocrine diseases like hypothyroidism in dogs.

Symptoms
Seborrheic dermatitis primarily affects the skin and coat and may present as either dry seborrhea (seborrhea sicca) or oily seborrhea (seborrhea oleosa). In some cases, pets may display a combination of both. Symptoms include:

• Dry or oily skin: Depending on the type, the skin may be flaky and dry or oily and greasy to the touch.
• Flaking (dandruff): Seborrhea often appears as small whitish flakes in the coat. In cats, this is commonly seen at the base of the tail.
• Itching (pruritus): Causes excessive scratching and licking, increasing the risk of secondary infections.

Diagnosis
Diagnosing seborrheic dermatitis in pets involves a physical examination and symptom analysis. To determine whether it is primary or secondary, the veterinarian may perform tests such as:

• Blood tests to rule out underlying diseases.
• Skin cultures and microscopic evaluations to identify infections or abnormalities.
• Skin scrapings to rule out mites.
• Biopsies for deeper analysis in complex cases.

Introduction
Hyperkeratosis is a dermatological condition that mainly affects dogs and, less frequently, cats. It is characterized by abnormal thickening of the skin, particularly on the nose, pressure points, and paw pads. This condition can cause discomfort and even pain if not properly managed. This article explains what hyperkeratosis is, its causes, symptoms, and how to treat it to ensure your pet’s well-being.

Causes
Hyperkeratosis is a skin disorder caused by excessive production of keratin, a protein that forms the outer layer of the skin. This leads to thickening and hardening of the skin in specific areas, such as the paw pads (plantar hyperkeratosis) or the nose (nasal hyperkeratosis), making them dry, rough, and sometimes painful for pets.

Identifying the underlying cause is crucial for proper treatment. The most common causes include:

• Genetics: Certain dog breeds, such as Labrador Retrievers, Bulldogs, and Cocker Spaniels, are more prone to developing hyperkeratosis due to hereditary factors.
• Aging: As pets age, they may experience skin changes, such as increased keratin thickness.
• Underlying diseases: Hyperkeratosis may be a symptom of other conditions, including:
  • Leishmaniasis in dogs.
  • Viral infections, such as canine distemper.
  • Autoimmune diseases, such as lupus.
• Nutritional deficiencies: A lack of essential fatty acids or an inadequate diet may contribute to the development of hyperkeratosis.

Symptoms
The most common symptoms of hyperkeratosis include:

• Thickening and hardening of the skin on the nose, paw pads, or pressure points.
• Extreme dryness in affected areas.
• Cracks that may cause pain.
• Difficulty walking due to hardened paw pads.
• In severe cases, bleeding or secondary infections.

Introduction
Flea Allergy Dermatitis (FAD) is an allergic skin condition that primarily affects pets over one year old. It is commonly observed in dogs and cats with underlying skin diseases, such as atopic dermatitis. Pets with FAD often experience skin damage due to constant scratching, biting, or licking, which can lead to secondary infections.

Causes
FAD is caused by a hypersensitivity reaction to proteins in flea saliva. This condition is more common in warm and humid climates, which promote flea proliferation.

Often, flea control treatments are used inconsistently, leaving pets vulnerable to infestations during unprotected periods. To prevent this, it is important to apply treatments according to your veterinarian’s recommendations, ensuring year-round flea protection for your pet.

Symptoms

• Intense pruritus (itching): Typically occurs in the caudal areas of the animal, especially near the tail.
• Papules: Small bumps on the skin, often accompanied by excoriations from scratching.
• Presence of fleas or flea dirt: Small dark specks visible on the pet’s coat.
• Secondary infections: These may result from excessive scratching or licking and can include bacterial infections or yeast infections caused by Malassezia.

Introduction
Contact dermatitis is an inflammatory skin reaction that occurs when the skin comes into contact with an irritant or allergen.
This condition can affect both dogs and cats and, while less common than other forms of dermatitis, it can cause significant discomfort and may lead to secondary infections if not properly treated.

Causes
Contact dermatitis in dogs and cats can be caused by:

• Irritants such as detergents, disinfectants, or insecticides.
• Plants, chemically treated grass, and synthetic materials found in collars, bedding, or toys.
• Inappropriate topical products and metals like nickel, which may trigger allergic reactions.

Identifying and eliminating the irritant is crucial for preventing and managing this condition effectively.

Symptoms
The severity of lesions depends on the duration of exposure. Common symptoms include:

• Erythematous areas: Skin with pink to red discoloration.
• Alopecic areas: Hairless patches.
• Pruritus (itching): Ranges from moderate to severe intensity.
• Excoriations and crusts: Resulting from scratching.
• Papules: Small raised bumps, and/or vesicles (small fluid-filled bumps) on the skin.

Introduction
Food allergies are adverse immune reactions to certain foods or additives present in them. They affect both dogs and cats, although they are more common in dogs.
This condition can be challenging to identify and manage, as many symptoms can overlap with other skin or digestive diseases.

Causes
Food allergies in dogs and cats are primarily caused by specific proteins, both animal-based (e.g., beef, chicken, fish, or eggs) and plant-based (e.g., corn, wheat, or soy). Additives and preservatives in commercial pet foods may also trigger reactions in sensitive pets.

Prolonged exposure to the same food and genetic factors also play a role, with higher prevalence in breeds such as Labrador Retrievers, French Bulldogs, and Siamese cats. These allergies result from the immune system's response to certain ingredients, causing dermatological or digestive symptoms that require identifying and eliminating the allergen.

Symptoms
Food allergy symptoms are primarily dermatological and digestive.

Dermatological Symptoms

• Non-seasonal pruritic dermatitis: Persistent itching throughout the year.
• Skin lesions: Including hair loss (alopecia), excoriations, and crusts.
• Secondary skin infections.
• Erythematous-ceruminous otitis: Inflammation of the ears with redness and excess earwax. Approximately 25% of dogs with food allergies present this as their sole skin-related symptom.
• In cats: Signs such as miliary dermatitis (small bumps and crusts on the skin) and lesions associated with the feline eosinophilic complex (ulcers and plaques related to allergies).

Digestive Symptoms

• Vomiting.
• Diarrhea.
• Soft stools.
• Increased frequency of defecation.

Introduction
Dermatophytosis refers to fungal infections of the skin, hair, or nails. The most common fungi responsible in dogs and cats belong to the genera Microsporum and Trichophyton. These fungi feed on keratin, a protein found in the outer layer of the skin, hair, and nails, allowing them to thrive and cause lesions.

Causes
Ringworm is highly contagious and easily transmitted through:

• Direct contact with infected animals.
• Indirect contact via contaminated objects such as brushes, bedding, and toys.
• Exposure to contaminated surfaces, as the fungi can survive for long periods in the environment.

Certain factors increase the risk of dermatophytosis, including:

• Hot and humid climates.
• Immunosuppression in animals.
• Young animals, as their immune systems are not fully developed.
• Long hair, which provides an ideal environment for fungal growth.

Symptoms
The most common lesion is a circular hairless (alopecic) area, often red and crusty around the edges. While itching (pruritus) is mild to moderate, some pets may scratch the affected areas. Red, scaly, dry, and inflamed skin is also commonly observed.

In severe cases, the fungus can affect the nails, causing deformities and thickening, which complicates the infection.

Common sites for lesions include:

• Limbs.
• Face.
• Ear flaps.
• Tail.

Introduction
Lice are external parasites that live on the fur and skin of animals. These small, wingless insects feed on either skin or blood, depending on the type of lice. The most common types of lice in pets are:

• Chewing lice (Mallophaga): Feed on skin cells and hair, primarily affecting dogs.
• Sucking lice (Anoplura): Feed on blood and are more common in cats.

It is important to note that lice are species-specific, meaning lice from pets do not infest humans and vice versa.

Causes
Lice infestations in dogs and cats typically occur through direct contact with infected animals, as lice do not survive long off their host. Infested environments, such as contaminated bedding, blankets, or grooming tools, can also be sources of transmission, especially in overcrowded or unhygienic conditions. Pets that do not receive regular care are at a higher risk of infestation.

Symptoms
Pediculosis presents with itching and skin irritation, prompting animals to scratch, rub, or bite themselves. Common signs include:

• A rough or unhealthy coat appearance.
• Severe infestations of sucking lice: Can cause anemia.
• Severe infestations of chewing lice in dogs: Rarely lead to anemia.
• Constant irritation and skin bites may result in restlessness, and wounds caused by lice feeding or the pet’s scratching may become infected.

Introduction
Sarcoptic mange, also known as “scabies,” is a highly contagious skin disease caused by the mite Sarcoptes scabiei var. canis. It primarily affects dogs but can also infect cats and, in some cases, humans. This infestation causes extreme discomfort in pets and can lead to serious health issues if left untreated.

Causes
Sarcoptic mange is caused by microscopic mites that burrow into the skin of the host to lay eggs and reproduce. This activity triggers intense itching and inflammation. The disease spreads easily through direct contact with infected animals or contaminated objects such as bedding and toys.

Symptoms
The hallmark symptom of sarcoptic mange in dogs is intense itching (pruritus). As the mites feed and damage the skin, the dog experiences severe itching and scratching. Other common symptoms include:

• Hair loss (alopecia): Often around the ears, face, abdomen, and legs, resulting from scratching and biting.
• Crusts and wounds: Caused by intense scratching and biting of the affected areas.
• Red, inflamed skin (erythema): In affected areas.
• Secondary infections: Due to constant scratching and skin damage.

In severe cases, the mange can spread over the entire body, and the condition may become chronic if not treated promptly.

Introduction
Ticks are arachnids that attach to the skin of animals to feed on their blood. Their presence on dogs and cats is more common in warm and humid weather. Besides being an annoyance to pets, ticks are vectors of various zoonotic diseases that can also impact human health.

Risk Factors
Ticks are commonly found in outdoor environments, especially wooded areas, tall grass, and shrubs. The following factors increase the risk of tick infestations:

1. Outdoor exposure: Pets that spend a lot of time outdoors are more likely to encounter ticks.
2. Warm, humid climate: Ticks thrive in warm and humid conditions, although in some regions, they can be active year-round.
3. Lack of prevention: Pets without regular preventive treatments, such as spot-on applications, oral medications, or collars, are at higher risk.
4. Long and dense coats: Ticks can hide more easily in thick fur, making detection more difficult.

Symptoms
Although ticks are small, their bites can lead to immediate and long-term symptoms, including:

• Excessive scratching or licking: Ticks can irritate the skin, causing pets to scratch or lick more than usual.
• Redness and swelling: Tick bites often result in inflamed, red areas, sometimes accompanied by rashes.
• Lethargy or loss of appetite: In severe infestations, tick bites can lead to anemia and weakness in pets.

Introduction
Pyodermas are bacterial skin infections that can affect both dogs and cats, although they are more common in dogs. These infections can range in severity from surface-level infections to deep pyodermas involving multiple skin layers. Understanding the causes, symptoms, and treatment options for this condition is essential to keeping your pet's skin healthy and comfortable.

The term "pyoderma" refers to a bacterial skin infection, most often caused by Staphylococcus pseudintermedius, a bacterium normally present on the animal's skin that proliferates when the natural skin barrier is compromised.

Types of pyoderma in pets:

1. Surface pyoderma: Affects the outermost skin layer, presenting with redness, itching, and small pustules.
2. Superficial pyoderma: Involves the upper layers of the skin, including hair follicles. It commonly appears as pustules, redness, and hair loss in affected areas and is the most frequent form of pyoderma.
3. Deep pyoderma: The most severe type, affecting deeper layers such as the dermis and subcutaneous tissue. It can cause abscesses, nodules, significant pain, and severe inflammation.

Causes
Pyodermas develop when the pet’s skin is weakened or compromised. Common causes include:

• Allergies: Food, environmental, or contact allergies can irritate the skin, facilitating infections.
• Parasites: Fleas, ticks, and mites irritate the skin and lead to scratching, increasing the risk of pyoderma.
• Hormonal imbalances: Conditions like hypothyroidism or Cushing’s disease affect skin health and predispose pets to pyodermas.
• Wounds or scratches: Any skin injury can become infected if not properly treated, particularly in sensitive or exposed areas.

Symptoms
The severity and extent of lesions depend on the type of pyoderma. Common signs include:

• Papules: Small raised bumps on the skin.
• Pustules: Raised bumps filled with pus.
• Nodules: Larger skin elevations, deeper than papules.
• Erosions and crusts.
• Scaling: Flaky or scaly skin.
• Abscesses: Localized pockets of pus.
• Pigmentation changes in affected areas.

Other symptoms may relate to underlying causes, such as itching from allergies or lethargy from hormonal imbalances.

Introduction
Malassezia dermatitis is one of the most common causes of skin and ear problems in dogs and cats. These infections are typically caused by Malassezia pachydermatis, a yeast that is part of the normal skin and mucosal flora in dogs. However, under certain conditions, this yeast can overgrow, leading to irritation and inflammation.

Causes
Malassezia is a fungus that naturally resides on the skin of dogs and cats. Under normal conditions, it does not cause harm, but certain factors can trigger overgrowth, leading to infection. Common triggers include:

• Humidity and moisture.
• Excessive oil production in the skin.
• Weakened immune system.
  Some breeds, such as West Highland White Terriers, Dachshunds, Cockers, and German Shepherds, are more prone to these infections.

Symptoms
Malassezia dermatitis may be localized or generalized. Commonly affected areas include the face (ear canal and perioral skin), armpits, ventral neck, and distal limbs (interdigital spaces and nails). Symptoms vary but often include:

• Intense itching: Pets may scratch constantly, especially in affected areas.
• Redness and inflammation: Skin irritation and redness are common, especially on the paws, neck, and armpits.
• Strong odor: Infected areas often emit an unpleasant odor, which is particularly noticeable in the ears.
• Scaly or greasy skin: The skin may feel oily or show visible flakes.
• Recurrent ear infections: Ear infections caused by Malassezia often involve dark discharge and a strong smell.

Introduction
Alopecia refers to partial or complete hair loss in one or more areas of an animal’s body. While it can be a symptom of various dermatological conditions, it is commonly associated with diseases such as atopic dermatitis, where intense itching leads to excessive scratching and subsequent hair loss, or endocrine disorders like hypothyroidism. This article discusses the causes, symptoms, and treatments for alopecia in dogs and cats, along with tips for maintaining a healthy coat.

Causes
The causes of alopecia in pets are diverse and may include:

• Parasites: Fleas, mites, and other external parasites are among the most common causes. Persistent itching can lead to self-inflicted hair loss.
• Infections: Fungal infections (e.g., ringworm) and bacterial infections can result in localized hair loss.
• Allergies: Food, environmental, or contact allergies can irritate the skin, causing excessive scratching and licking that leads to alopecia.
• Hormonal imbalances: Disorders like hypothyroidism or Cushing’s syndrome disrupt hair growth and can cause localized or generalized hair loss.
• Stress: Stress and anxiety, especially in cats, can result in compulsive grooming and hair loss.
• Genetics: Certain breeds are predisposed to alopecia, particularly in specific areas of the body.

Symptoms
In addition to visible hair loss, alopecia may present with other symptoms that help identify the underlying cause:

• Red or inflamed skin in affected areas.
• Constant scratching or licking.
• Scales, crusts, or dandruff on exposed skin.
• Unpleasant odor if secondary infections are present.
• Behavioral changes, such as restlessness or compulsive grooming.

Introduction
Solar dermatitis is an inflammation of the skin caused by prolonged sun exposure without adequate protection. It primarily affects areas with little to no hair, such as the nose, ears, abdomen, and back, particularly in pets that spend time outdoors. Light-skinned dogs, such as Bulldogs and Dalmatians, and hairless cats, like the Sphynx, are especially susceptible to solar dermatitis.

Symptoms
The severity of solar dermatitis symptoms depends on the duration of sun exposure and the pet’s skin type. Common symptoms include:

• Redness of the skin: The affected area appears red and inflamed, similar to human sunburn.
• Crusting or ulcers: In severe cases, the skin may develop crusts or ulcers, causing significant discomfort.
• Itching and discomfort: Pets may excessively scratch or lick the irritated areas, exacerbating the condition.
• Hair loss (alopecia): Hair may fall out in exposed areas due to sun damage.