Mites (Acari)

Chapter 26: Mites (Acari)

Introduction

  • Over 250 species of mites recognized as causing health-related problems in humans and domestic animals.

  • Common health problems from mites include:

    1. Temporary skin irritation from bites.

    2. Persistent dermatitis from invasion into skin/hair follicles.

    3. Mite-induced allergies.

    4. Transmission of pathogenic microbes/parasites.

    5. Intermediate hosts for parasites, particularly tapeworms.

    6. Invasion of respiratory passages and other internal organs.

    7. Psychological conditions: acarophobia (fear of mites), delusory acariosis (belief of mite attack).

  • Infestation diseases are referred to as acarinism and illnesses caused by mites as acariasis.

Taxonomy

  • Mites (Acari) classified into two major groups:

    • Superorder Parasitiformes (Anactinotrichida): Child orders include Ixodida, Mesostigmata, Trombidiformes, Sarcoptiformes.

    • Superorder Acariformes (Actinotrichida): Contains Trombidiformes and Sarcoptiformes.

  • Orders causing animal health problems: Ixodida, Mesostigmata, Trombidiformes, Sarcoptiformes.

  • Identification of medically important mites often requires expert assistance.

Morphology

  • Mite bodies have two major regions:

    • Gnathosoma: Anterior region with mouthparts (pedipalps, chelicerae).

    • Idiosoma: Posterior part with legs and other sensory devices.

  • Important characteristics for taxonomy include:

    • Size and arrangement of sclerotized plates.

    • Chaetotaxy (seta arrangement).

    • Position of respiratory structures (spiracles).

  • Mites have four pairs of legs as adults & nymphs (three pairs as larvae).

  • Respiratory system includes tracheal ducts.

Internal Morphology

  • Mites have a unique digestive system processing liquefied food by salivary glands that also produce anticoagulants.

  • Excretory structures include coxal glands and Malpighian tubules.

Life History

  • Developmental stages: egg -> prelarva -> larva -> protonymph -> deutonymph -> tritonymph -> adult.

  • Various taxonomic groups can suppress developmental stages, resulting in diverse life history patterns.

Behavior and Ecology

  • Behavioral and ecological aspects discussed in individual species accounts.

  • Mites may infest homes unnoticed but can cause allergies upon exposure.

  • Common outdoor mite interactions, such as chiggers (trombiculid mites), often cause dermatitis in humans.

Public Health Importance

  • Mites can infest households, causing allergic reactions & dermatitis.

  • Mites like Dermanyssus, a parasite of birds or rodents, cause issues when their hosts are absent.

  • Many occupational hazards arise from exposure to mite-infested environments, causing irritation to those working with feed & materials.

Mite-Induced Dermatitis

  • Dermatitis cases caused by various mite families:

    • Dermanyssidae: Commonly observed cases with specific examples:

      • Dermanyssus gallinae (Chicken mite): Infests birds, causing dermatitis in humans when they bite at night.

      • Dermanyssus americanus: Less frequently reported but potential dermatitis concerns.

  • Cheyletidae (e.g., Cheyletiella species): Known to cause dermatitis in humans and animals via contact.

  • Sarcoptidae: Includes scabies mites causing intense itchiness and subsequent skin disease.

Mite-Borne Diseases

  • Significant mite-borne diseases include:

    • Rickettsialpox: Caused by Rickettsia akari transmitted via house mouse mites.

    • Tsutsugamushi disease: Caused by Orientia tsutsugamushi, transmitted via chigger bites.

  • Mite-borne diseases often induce public health issues, especially respiratory allergic conditions.

Veterinary Importance

  • Mites cause skin conditions, allergic reactions, and can invade internal systems of domestic and wild animals.

  • Common health issues in animals include:

    • Sarcoptic mange: Significant skin disease in various species; notorious examples include dogs and livestock.

    • Psoroptic mange and chorioptic mange in livestock.

    • Demodectic mange among pets leading towards chronic infections.

  • Parasite vector relationships explored, including their roles as intermediate hosts for tapeworms and bacterial pathogens.

Conclusion

  • Knowledge of mite taxonomy, morphology, behavior, and public health relevance is crucial for effectively managing their impact on both human health and veterinary concerns.

  • Further study and awareness are important for mitigating health risks associated with these diverse organisms.