40 Questions
What is the typical duration of the life cycle of two-host ixodid ticks?
Over two years
What is the stage of the tick life cycle that usually overwinters?
Nymphs
Which host is usually a larger herbivore?
Second host
What is the name of the disease caused by a tick-borne virus of the Bunyaviridae family?
Crimean-Congo hemorrhagic fever
What is the stage of the tick life cycle that seeks out the first host?
Larvae
What is the purpose of the female tick dropping off the second host?
To lay eggs
Can humans serve as both the first and second hosts for ticks with a two-host life cycle?
Yes
What is the typical duration of the life cycle of three-host hard ticks?
Over three years
What is the primary purpose of using permethrin on clothing?
To repel ticks from attaching to the body
What is the most effective way to prevent ticks from attaching to the body while walking in wooded areas?
Wearing long trousers and applying permethrin to clothing
What is the name of the tick-borne encephalitis (TBE) vaccine approved by the U.S. Food and Drug Administration?
TICOVAC
Why should you avoid sleeping on the floors of mud houses?
Because ticks are more likely to be present on floors
What is the purpose of examining the body frequently for ticks?
To remove attached ticks from the body
What is the benefit of using metal beds in areas with high tick infestation?
Ticks have difficulty climbing on metal surfaces
What is the purpose of tucking trousers into boots or socks?
To prevent ticks from crawling up the legs
What is the type of insecticide used to impregnate clothing to prevent tick bites?
Pyrethroid
What is a challenge in diagnosing scabies?
Excoriations may change the appearance of the lesions
Why is it important to decontaminate bedding and clothing?
To kill scabies mites and their eggs
What is a common misdiagnosis of scabies?
All of the above
How can scabies be prevented?
By avoiding skin-to-skin contact with infested persons
What is the habitat of Demodex folliculorum?
Sebum gland on the skin around nose and face
What is a common symptom of Demodex folliculorum infestation?
Blackheads and acne
Why is it important to treat all close contacts of an infested person?
To prevent indirect spread of scabies
How long should lindane 1% lotion be left on the skin?
12 to 24 hours
What type of organisms do ticks feed on?
Reptiles, amphibians, and mammals
What is the primary characteristic of an oblige hematophage?
It feeds on the blood of animals
What is the primary way that ticks can infect humans and animals with diseases?
Through their bite
Which of the following diseases is NOT typically spread by ticks?
Malaria
What is the main difference between the morphology of hard ticks and soft ticks?
Hard ticks have a dorsal shield, while soft ticks do not
What is the typical life cycle of most ticks?
Egg, larva, nymph, adult
What is the advantage of some species of ticks molting on their host?
They do not have to risk finding another host
Why are multiple-host tick species able to exist?
Because they have a great reproduction rate and can survive for a long time without food
What is a common symptom of scabies?
Pruritus
Where are burrows typically noted in scabies infestations?
Hands, wrists, and genitalia
What is the likely representation of erythematous papules in scabies?
An immune response
What is the complication of intense itching in scabies?
Skin sores
Who is at risk for a severe form of scabies called crusted, or Norwegian, scabies?
Immunocompromised, elderly, disabled, or debilitated persons
What is the characteristic of crusted scabies?
Thick crusts of skin that contain large numbers of scabies mites and eggs
How can persons with crusted scabies transmit scabies?
Through both direct skin-to-skin contact and indirect contact with contaminated items
How can scabies be confirmed?
On microscopic examination of scrapings from burrows and papules
Study Notes
Ticks and Tick-Borne Diseases
- Ticks can feed on reptiles, amphibians, and mammals, and can become larger and more visible after feeding on blood.
- Tick bites can transmit diseases caused by bacteria, viruses, and protozoans to humans and animals.
- Some of the diseases spread by ticks include:
- Lyme disease
- Colorado tick fever
- Tularemia
- Powassan virus
- Ehrlichiosis
- Southern tick-associated rash illness (STARI)
- Rocky Mountain spotted fever
- Tick paralysis
- Anaplasmosis
- Spotted fever
- Babesiosis
- Relapsing fever
- Heartland virus
Morphology of Ticks
- Hard ticks have a dorsal shield, which covers the entire dorsal surface in males and only a small portion in females.
- Soft ticks have a leathery body surface and do not have a dorsal shield.
- Mouthparts of ticks are sub-terminally attached and not visible from the dorsal view.
Life Cycle of Ticks
- Most ticks go through four life stages: egg, six-legged larva, eight-legged nymph, and adult.
- Each stage requires a host, and some species can molt on the host.
- Female ticks drop from the host to lay eggs, and the cycle repeats.
- Two-host and three-host ticks have different life cycles that can span over two or three years.
Personal Protections and Prophylactic Measures
- Personal strategies to avoid ticks include:
- Avoiding grassy areas with shrubs
- Wearing long trousers and socks
- Applying permethrin (an insect repellent) to clothing
- Prophylactic measures include:
- Vaccines (e.g. TICOVAC for tick-borne encephalitis)
- Removing attached ticks and examining the body frequently
Clinical Features and Diagnosis of Scabies
- Scabies causes pruritus, burrows, and erythematous papules on the skin.
- Burrows typically appear on the hands, wrists, and genitalia, while erythematous papules are seen on the trunk.
- Scabies can lead to skin sores and bacterial infections.
- Diagnosis can be confirmed through microscopic examination of scrapings from burrows and papules.
Crusted (Norwegian) Scabies
- Crusted scabies is a severe form of scabies that affects immunocompromised, elderly, disabled, or debilitated persons.
- It is characterized by thick crusts of skin containing large numbers of scabies mites and eggs.
- Crusted scabies is highly contagious and can be transmitted indirectly through contaminated items.
Treatment of Scabies
- Treatment involves applying a topical cream (e.g. lindane or permethrin) to the entire body, washed off several hours after application.
- Bedding, clothing, and towels used by infested persons should be decontaminated by washing in hot water and drying in a hot dryer.
Follicle Mites (Demodex folliculorum)
- Follicle mites cause blackhead, pimples, and acne.
- They are more prevalent in those with oily skin.
- Habitat: sebum gland on the skin around the nose and face.
- Larger numbers of Demodex folliculorum mites can cause unwanted symptoms and skin problems.
Learn about the biology of ticks, their feeding habits, and the diseases they can transmit to humans and animals, including Lyme disease, Rocky Mountain spotted fever, and more.
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