Ticks & Parasites_wk11(1)

Animal Disease: Ticks & Parasites

Overview

  • Presenter: Melissa L. Hayden MS, CVT, LAT

Week 12 Schedule

  • Focus: Prions (Chapter 8)

  • Research Pathogen Paper: Rough Draft due by November 17th

Ticks

General Information

  • Ticks are arthropods that can transmit various pathogens including:

    • Bacteria

    • Viruses

    • Parasites

  • Behavior: "Questing" for hosts.

Characteristics

  • Primitive and obligate blood-sucking parasites.

  • Target vertebrates across all classes.

Types of Ticks

  • Hard ticks (Family: Ixodidae)

  • Soft ticks (Family: Argasidae)

  • One African species (Nuttallielloidea) that does not cause disease in hosts.

Epizootiology

  • Worldwide, around 100,000 human illnesses annually due to ticks.

  • Implications for livestock include:

    • Blood loss and anemia.

    • Bite wounds leading to secondary bacterial infections.

    • Production losses.

    • Possible paralysis or infection.

Identification of Ticks

  • Identified based on characteristics:

    • Shape

    • Size

    • Mouthparts

    • Color

    • Dorsal shield (scutum)

    • Caudal abdominal markings (festoons)

Life Cycle of Ticks

  • Stages: Egg → Larva → Nymph → Adult

    • Duration: 6 weeks to 3 years for cycle completion.

    • All stages (except egg) require a blood meal.

Disease Transmission

  • Method of transmission varies by tick species and life stage.

  • Example: Ixodes scapularis (Lyme disease) requires attachment of 24-52 hours for infection.

Lyme Disease

General Overview

  • Causative agent: Borrelia burgdorferi

    • Recognized in 1975 as the most common tick-borne disease in the U.S.

  • Vectors: Ixodes scapularis (Black-legged or Deer tick).

Epidemiology

  • Widespread across 49 states and D.C., primarily in the Northeast, upper Midwest, and Pacific coastal areas.

  • Transmission risk increases primarily during nymph stage bites, within 24-52 hours after attachment.

Clinical Signs in Animals

  • Dogs: Fever, anorexia, lethargy, lameness; can progress to chronic arthritis.

  • Horses: Arthropathy, uveitis, encephalitis.

  • Cattle: Arthropathy, skin lesions, multisystemic disease.

  • Cats: No consistent clinical signs.

Clinical Signs in Humans

  • Symptoms include fever, chills, headache, fatigue, and erythema migrans ("Bullseye" rash).

Diagnosis and Testing of Lyme Disease

  • Diagnostic methods:

    • ELISA (Enzyme-linked immunosorbent assay)

    • IFA (Immunofluorescence assay)

    • Western blot

    • PCR (Polymerase chain reaction)

Treatment

  • Animals: Doxycycline or Amoxicillin, NSAIDs.

  • Humans: Doxycycline, Amoxicillin, or Cephalosporin.

Other Common Tick-borne Diseases

  • Ehrlichiosis & Anaplasmosis

  • Q Fever

  • Rocky Mountain Spotted Fever

  • Tularemia

  • Relapsing Fever

Treatment Protocol for Rickettsial Diseases

  • Treatment typically involves antibiotics for 21-30 days (Tetracycline family) alongside supportive care (anti-inflammatory drugs and IV fluids).

Parasites

Terminology

  • Ectoparasites: Live on the surface of the host.

  • Endoparasites: Live within the host.

  • Definitive Hosts: Hosts where parasites reach sexual maturity and reproduce.

  • Intermediate Hosts: Hosts required for further development of the parasite.

Types of Parasites

  1. Protozoa: Unicellular eukaryotic organisms.

  2. Helminths: Multicellular eukaryotic organisms.

  3. Arthropods: Multicellular organisms with jointed appendages and exoskeletons.

Infection Sources

  • Protozoan: Exists as single cell in cyst or trophozoite form.

  • Helminths: Develop from eggs or larvae.

  • Arthropods: Comprise 80% of all living species on Earth; special adaptations include jointed appendages and a protective exoskeleton.

Specific Types of Helminths

  • Nematodes: Round worms.

  • Cestodes: Segmented flat worms (e.g., Dipylidium caninum).

  • Trematodes: Flat worms (e.g., Liver fluke in cattle).

Transmission of Parasites

Requirements for Transmission

  1. Source of infection.

  2. Mode of transmission.

  3. Susceptible host.

Life Cycles

  • Direct (Simple): Involves a definitive host only.

  • Indirect (Complex): Involves a definitive host and one or more intermediate hosts.

Diagnosis of Parasites

  • Specimens used for diagnosis:

    • Stool

    • Blood

    • Sputum

    • Urine and vaginal

    • Cerebrospinal fluid

    • Serologic tests