Insects & Arthropods

This section will discuss insect and arthropod parasites – those creepy-crawlies that can cause skin infestations, transmit diseases, and generally make us uncomfortable. We’ll cover ticks, mites, lice, bed bugs, and the scabies mite, focusing on their etiology, epidemiology, and transmission

Ticks

Etiology: Ticks are arachnids (related to spiders) that feed on the blood of humans and animals. They are vectors for various pathogens, including bacteria, viruses, and protozoa
Epidemiology
- Geographic Distribution: Worldwide, with different species prevalent in different regions
- Risk Factors
  - Spending time in wooded or grassy areas, especially during tick season (spring and summer)
  - Hiking, camping, hunting, or working outdoors
  - Living in areas with high tick populations
- Disease Transmission: Ticks transmit various diseases, including Lyme disease, Rocky Mountain spotted fever, ehrlichiosis, anaplasmosis, babesiosis, and others
Transmission
- Tick Bite: Ticks attach to the skin and feed on blood. Pathogens are transmitted through the tick’s saliva during feeding
- Life Cycle
  - Ticks have a complex life cycle involving eggs, larvae, nymphs, and adults
  - Ticks require blood meals to progress from one stage to the next
  - Ticks can acquire pathogens from infected hosts and transmit them to subsequent hosts

Mites

Etiology: Mites are tiny arachnids that can infest the skin, causing various skin conditions. Examples include:
- Scabies mites (Sarcoptes scabiei): Cause scabies, a highly contagious skin infestation characterized by intense itching
- Chigger mites (Trombiculidae family): Cause chigger bites, characterized by itchy red welts
- Dust mites (Dermatophagoides spp.): Common allergens that can trigger allergic reactions, such as asthma and eczema
Epidemiology
- Global Distribution: Worldwide, with different species prevalent in different environments
- Risk Factors
  - Scabies: Close contact with infected individuals, crowded living conditions, poor hygiene
  - Chigger bites: Spending time in grassy or wooded areas
  - Dust mites: Exposure to dust, especially in bedding, carpets, and upholstery
- Contagious Infestations: Scabies is highly contagious and can spread rapidly in crowded settings
Transmission
- Scabies: Direct skin-to-skin contact with an infected individual
- Chigger bites: Attachment of chigger larvae to the skin
- Dust mites: Inhalation of dust mite allergens
- Life Cycle
  - Mites have a complex life cycle involving eggs, larvae, nymphs, and adults
  - Scabies mites burrow into the skin, lay eggs, and feed on skin cells
  - Chigger larvae attach to the skin and feed on tissue fluids
  - Dust mites feed on dead skin cells and thrive in warm, humid environments

Lice

Etiology: Lice are wingless insects that feed on the blood of humans. There are three types of lice that infest humans:
- Head lice (Pediculus humanus capitis): Infest the scalp and hair
- Body lice (Pediculus humanus humanus): Infest clothing and feed on the skin
- Pubic lice (Pthirus pubis): Infest pubic hair and other coarse body hair
Epidemiology
- Global Distribution: Worldwide, with different types of lice prevalent in different populations
- Risk Factors
  - Head lice: Close contact with infected individuals, sharing hats, combs, or other personal items
  - Body lice: Poor hygiene, crowded living conditions, lack of access to clean clothing and bedding
  - Pubic lice: Sexual contact with infected individuals
- Contagious Infestations: Lice infestations are highly contagious and can spread rapidly in crowded settings
Transmission
- Head lice: Direct head-to-head contact with an infected individual, sharing hats, combs, or other personal items
- Body lice: Contact with infested clothing, bedding, or other personal items
- Pubic lice: Sexual contact with an infected individual
- Life Cycle
  - Lice have a simple life cycle involving eggs (nits), nymphs, and adults
  - Lice lay eggs on hair shafts or clothing fibers
  - Nymphs hatch from eggs and feed on blood
  - Adult lice mate and lay eggs

**Bed Bugs (Cimex lectularius)**

Etiology: Bed bugs are small, wingless insects that feed on the blood of humans and animals, typically at night
Epidemiology
- Global Distribution: Worldwide, with increasing prevalence in recent years
- Risk Factors
  - Travel to areas with bed bug infestations
  - Bringing infested furniture, luggage, or other items into the home
  - Living in multi-unit dwellings (e.g., apartments, hotels)
- Nocturnal Feeders: Bed bugs are nocturnal feeders and hide in cracks and crevices during the day
Transmission
- Bites: Bed bugs feed on blood by biting exposed skin, typically while sleeping
- Life Cycle
  - Bed bugs have a simple life cycle involving eggs, nymphs, and adults
  - Bed bugs require blood meals to progress from one stage to the next
  - Bed bugs can survive for months without feeding

**Scabies (Sarcoptes scabiei)**

Etiology: Scabies is a contagious skin infestation caused by the scabies mite (Sarcoptes scabiei), a tiny burrowing mite
Epidemiology
- Global Distribution: Worldwide, with higher prevalence in crowded living conditions and areas with poor hygiene
- Risk Factors
  - Close contact with infected individuals
  - Crowded living conditions (e.g., nursing homes, prisons)
  - Poor hygiene practices
- Intense Itching: Scabies is characterized by intense itching, especially at night
Transmission
- Direct Skin-to-Skin Contact: Scabies is transmitted through prolonged, direct skin-to-skin contact with an infected individual
- Life Cycle
  - Female mites burrow into the skin, lay eggs, and deposit feces
  - Larvae hatch from eggs and migrate to the skin surface
  - Larvae mature into nymphs and then adults
  - Mating occurs on the skin surface
  - The entire life cycle takes about 2-3 weeks

Key Takeaways

Vectors for Disease: Ticks are important vectors for various diseases, including Lyme disease and Rocky Mountain spotted fever
Contagious Infestations: Lice and scabies are highly contagious and can spread rapidly in crowded settings
Hygiene and Sanitation: Poor hygiene and sanitation contribute to the spread of lice and scabies
Travel and Infestations: Travel can increase the risk of exposure to bed bugs and other arthropod parasites

Key Terms

Arthropod: An invertebrate animal with an exoskeleton, segmented body, and jointed appendages (e.g., insects, arachnids)
Vector: An organism that transmits a disease agent from one host to another
Mite: A tiny arachnid that can infest the skin
Lice: Wingless insects that feed on the blood of humans
Bed Bug: A small, wingless insect that feeds on the blood of humans and animals, typically at night
Scabies: A contagious skin infestation caused by the scabies mite
Infestation: The presence of parasites on or within a host
Pruritus: Itching
Nits: The eggs of lice
Exoskeleton: The external protective covering of arthropods
Arachnid: A class of arthropods that includes spiders, mites, and ticks

Brain

Additional Parasites