3. MITES, LICE + FLEAS

Ectoparasites Overview

Topic: Ectoparasites

Ectoparasites are organisms that live on the exterior of a host, which includes a variety of species such as mites, lice, and fleas. Understanding ectoparasites is crucial in the field of animal parasitology because they can have significant health implications for their hosts.

Relevance

Ectoparasites not only affect the health of individual animals but can also have broader implications for pet owners and veterinary practices. They are a major concern in both domestic and wild animal populations due to their potential to spread diseases.

Clinical Signs of Ectoparasites

1. Pruritus (Itching)

  • Causes: This is primarily caused by the feeding and movement of mites on or within the skin.

  • Behaviors: Affected animals will often display behaviors such as excessive scratching and chewing at the site of infestation.

2. Alopecia (Hair Loss)

  • Cause: Alopecia typically results from excessive grooming as animals try to alleviate itching or discomfort.

  • Effects: This can lead to patches of hair loss that may become more pronounced with ongoing infestation.

3. Dermatitis

Symptoms commonly associated with dermatitis include:

  • Redness: Areas of inflammation can appear on the skin.

  • Inflammation: Swelling particularly around the areas where the ectoparasites have caused damage.

  • Irritation: May be accompanied by signs of distress in the animal.

  • Secondary Infections: The damaged skin can lead to bacterial infections if left untreated.

4. Hyperkeratosis

  • Description: This condition involves the thickening and hardening of the skin, which may occur in response to chronic irritation.

  • Impact: It can result in further discomfort and lead to complications in skin health.

Evaluation Techniques

1. Gross Visual Inspection

  • Methodology: Veterinarians may perform a thorough examination of the skin, hair, or ears for any visible abnormalities such as lesions, redness, or unusual hair loss.

2. Skin Scraping

  • Technique: A small area of skin is scraped to collect samples of mites for testing.

  • Utility: Particularly useful for diagnosing burrowing and follicle mites; often the initial diagnostic test conducted for suspected mite infestations.

Examination Methods

1. Microscopic Examination

  • Purpose: Allows for the identification of various life stages of mites, including:

    • Mites

    • Eggs

    • Larvae

    • Nymphs

2. Otoscope Examination

  • Specific Use: Primarily used for diagnosing ear mites (e.g., Otodectes cynotis), enabling direct observation of mites within the ear canal.

3. Tape Impression

  • Procedure: A piece of tape is applied to the skin to collect surface mites for analysis.

  • Limitations: Not recommended for diagnosing burrowing or follicular mites as it may not capture them effectively.

Mites Overview

Phylum Arthropoda – Class Arachnida

Mites are characterized by their diverse shapes, which can include:

  • Round

  • Oval

  • Cigar-shaped

1. Sarcoptes Scabiei Mite

  • Description: Known for causing scabies in various species.

2. Canine Demodectic Mange Mite

  • Genus: Demodex spp.

  • Scientific Name: Demodex canis

  • Impact: Specifically affects canine health and overall well-being, leading to conditions such as demodectic mange.

3. Demodex Canis

  • Health Effects: Can cause severe skin issues leading to discomfort, potential secondary infections, and social implications due to the visible symptoms.

Arthropod Structure

1. Pretarsi

  • Details: The first pair of legs that often play a role in crawling and gripping surfaces.

2. Pedicel

  • Description: A projection from the first pair of legs; its structure can be jointed or entire and varies by species. Sarcoptes, for instance, has stalked pedicels.

3. Palpal Claws

  • Overview: These are part of the capitulum; their presence may vary among different mite species.

Common Mite Species

  • Cheyletiella: Known as "Walking Dandruff"; their entire life cycle from egg to adult spans at least 10-14 days.

  • Ear Mites (Otodectes Cynotis): Symptoms may include "coffee ground" ear discharge and dark brown waxy material, often leading to ear scratching and discomfort.

Identification of Different Mite Species

  • Sarcoptes scabiei

  • Otodectes cynotis

  • Cheyletiella blakei

  • Demodex spp.

Insects Overview

Phylum Arthropoda – Class Insecta

Insects possess a general body plan that includes:

  • Head: Contains sensory organs.

  • Thorax: Features three pairs of legs; wings may be present in certain species.

  • Abdomen: Houses essential organ systems.

Life Cycle of Lice

  • Metamorphosis: Involves simple metamorphosis stages:

    • Egg

    • Nymph

    • Adult

  • Reproduction: Adult females adhere their eggs to the hair of hosts, which can be cats or dogs.

Fleas Overview

Scientific Names

  • Cat Flea: Ctenocephalides felis

  • Dog Flea: Ctenocephalides canis

Morphology and Habits

  • Location: Adult fleas are typically found on the skin of their hosts.

  • Transmission: Fleas are transmitted through host-to-host contact and can live in infested environments.

  • Zoonotic Potential: Fleas will bite humans but do not infest them.

Flea Life Cycle

  • Egg Laying: The female flea lays eggs in the environment.

  • Lifecycle Stages: Larvae spin cocoons and feed on organic debris before emerging as adults.

  • Flea Dirt: The presence of flea dirt on a host can indicate active infestations.

Flies Overview

Characteristics

  • Wings: Adults usually have two pairs of wings.

  • Immature Stages: Typically exhibit a worm-like form known as maggots.

  • Significance: Cuterebra larvae can cause health issues in infested animals.

References

  • Robinson, E., Hendrix, C. (2022). "Diagnostic Parasitology for Veterinary Technicians, 6th Edition". St. Louis: MO. Elsevier.

  • Additional veterinary texts and sources include: Sirois M. (2020), Bassert, J.M., & McCurnin, D.M. (2022).

  • Images and figures referenced from the mentioned literature.