Companion Animal Diseases and Mechanisms of Disease

Selected Companion Animal Diseases

Mechanisms of Disease

  • Degenerative Changes

    • Gradual but normal loss of function with aging.

    • Concept of ‘Wear and Tear’; conditions are expected.

    • Loss of function due to genetically programmed limits to longevity.

    • Regenerative Changes:

    • Hyperplastic: Increase in cell number.

    • Hypertrophic: Increase in cell size.

    • Remodeling: Structural changes in tissues.

Mechanical Mechanisms of Disease

  • Mechanical Factors:

    • Obstructions (blockages in pathways).

    • Strictures (narrowing of pathways).

    • Traumas: injuries from mechanical, thermal, or chemical sources.

    • Disrupted Motility:

    • Spastic (constricted) vs. Hypotonic (relaxed).

    • Autoimmune Disorders:

    • Loss of tolerance to self-antigens.

    • Allergies and immunosuppression are consequences.

    • Altered Metabolic Functions:

    • Resistance to insulin (Type II diabetes).

    • Intoxications:

    • Multiple classes, such as xylitol and antifreeze.

    • Nutritional Deficiencies and Excesses:

    • Issues related to food ratios and obesity.

    • Neoplastic Changes:

    • Loss of control of cell growth regulations.

Cell Growth Control

  • Normal Cell Growth:

    • Differentiation from stem cells is critical for growth.

    • Hypertrophy vs. Hyperplasia:

    • Hypertrophy: Enlargement due to increased cell size.

    • Hyperplasia: Enlargement due to increased cell number.

Neoplasia

  • Definition:

    • New growth that can be benign or malignant.

    • Major cause of death in pets; largely unknown causes.

    • Types of Neoplasms:

    • Benign: Growth confined within usual boundaries and does not invade surrounding tissues.

    • Malignant: Uncontrolled growth, invasive, does not respect boundaries.

    • Environmental Contributions:

    • Oncogenes interacting with environmental factors such as Feline Leukemia and Immunodeficiency Viruses.

Examples of Tumors

  • Benign Tumors:

    • Can grow large and impede normal function (e.g., hormone overproduction).

    • Cutaneous Histiocytomas are common.

  • Malignant Tumors:

    • Invasive and capable of metastasis to local, regional, and distant sites.

Immune Responses and Allergies

  • Allergic Reactions:

    • Acquired immune responses to foreign proteins, can be acute or chronic.

    • Symptoms include urticaria, rash, and pruritis.

    • Key emergency symptom: Laryngeal edema.

  • Immunosuppression:

    • Decreased immune capabilities due to various factors (e.g., FIV, stress).

  • Autoimmunity:

    • Immune system attacks self-tissues, leading to diseases like rheumatoid arthritis.

Mechanical Injuries

  • Types of Mechanical Injuries:

    • Blunt force impacts and crushing injuries.

    • Punctures from incidents like gunshot wounds.

  • Effects of Trauma:

    • Can significantly impact bodily function and recovery.

Metabolic Mechanisms

  • Hormonal Changes:

    • Disruption in hormone outputs (e.g., diabetes mellitus, hypothyroidism).

Nutritional Mechanisms

  • Nutritional Disorders:

    • Insufficient or excessive nutrient intake can lead to obesity or deficiencies.

  • BARF Diets:

    • Issues with bacterial overgrowth due to improper feeding.

Infectious Diseases

  • Characterization:

    • Infectious agents invade and establish a presence in host tissues, often causing damage.

    • Different types of pathogens: prions, bacteria, viruses, fungi, and protozoa.

  • Contagious vs. Infectious:

    • Contagious: Spread through direct contact (e.g., parvovirus).

    • Infectious: Can spread by indirect transfer mechanisms (e.g., rabies).

Canine and Feline Infectious Diseases

  • Examples:

    • Canine Distemper Virus: Major concerns include encephalitis and pneumonia.

    • Feline Panleukopenia: Severe infectious disease, also referred to as feline distemper.

Anemia in Companion Animals

  • Types of Anemia:

    • Blood Loss Anemia: Involving fleas, ticks, internal parasites.

    • Iron Deficiency Anemia and Aplastic Anemia due to bone marrow factors.

    • Autoimmune Hemolytic Anemia: Immune system mistakenly attacks red blood cells.

Lymphoma in Cats and Dogs

  • Lymphoma Staging:

    • Stage I to V, reflecting the spread and involvement of lymph nodes and organs.

  • Management:

    • Requires antineoplastic therapy; careful coordination and administration necessary.