24 Questions
What is the name of the bacteria that causes scrub typhus?
Both a and b
What is the primary mode of transmission of scrub typhus?
Through bites of infected chiggers (larval mites)
What are the common symptoms of scrub typhus?
Fever, headache, body aches, and sometimes rash
What is the typical size of a chigger?
About 1/20 inch long
What is the name of the mite vector that transmits scrub typhus?
Leptotrombidium deliense
What is the typical characteristics of the larval stage of the chigger?
Three pairs of legs and no constriction in the front part of the body
What is the typical color of the chigger mite?
Bright red
What are the typical hosts of the chigger mites?
A wide variety of animals such as snakes, turtles, birds, and small mammals as well as humans
What is the diameter of chigger larvae?
1/150 to 1/120 inch
What is the purpose of the salivary secretion injected into the host by chigger larvae?
To break down skin cells for digestion
How do chigger larvae typically find a host?
By crawling on soil or up grass blades
What is the purpose of the straw-like feeding tube formed by chigger larvae?
To suck up partially-digested skin cells
How is scrub typhus fever typically transmitted?
Through the bite of an infected chigger
What is the role of the dermatologist in diagnosing scabies?
To remove some skin to examine under a microscope
What stage of the chigger's life cycle is responsible for transmitting scrub typhus fever?
Larva
What is the shape of chigger eggs?
Globular
What is the typical duration of symptoms after exposure to a chigger bite?
A week or more
What is the primary method of preventing scrub typhus?
Avoiding areas with high vegetation and brush
What is the typical outcome for people who are treated early with doxycycline for scrub typhus?
They usually recover quickly
What is the purpose of treating clothing and gear with 0.5% permethrin?
To kill chiggers
What is the potential consequence of scratching a chigger bite?
It may result in secondary infections
What is the characteristic of the red welt that develops after a larva is fully fed?
It has a hard, white central area
What is the most effective time to administer antibiotics for scrub typhus?
Soon after symptoms begin
What is the purpose of dressing children in clothing that covers arms and legs or covering their gear with mosquito netting?
To prevent bites from infected chiggers
Study Notes
Background on Scrub Typhus
- Scrub typhus, also known as bush typhus, is a disease caused by the bacterium Orientia tsutsugamushi (formerly known as Rickettsia tsutsugamushi).
- The disease is spread to humans through the bites of infected chiggers (larval mites).
Life Cycle of Chiggers
- The life cycle of chiggers consists of several stages: egg, deutovum, larva, protonymph, deutonymph, tritonymph, and adult.
- Only the larval stage bites humans.
- Eggs are laid in damp soil during the first warm spring weather.
Symptoms of Scrub Typhus
- Common symptoms include fever, headache, body aches, and sometimes a rash.
- A dark, scab-like region at the site of the chigger bite (eschar) may form.
- Enlarged lymph nodes and rash may also occur.
- In severe cases, organ failure and bleeding can occur, which can be fatal if left untreated.
Transmission
- Scrub typhus fever is not spread from person-to-person.
- The disease is spread through the bite of an infected chigger.
Diagnosis
- Diagnosis is made by examining a skin scraping under a microscope to detect the presence of chiggers or their eggs.
Pathogenesis
- Chigger larvae pierce the skin and inject a salivary secretion containing powerful digestive enzymes that break down skin cells.
- The digestive fluid causes surrounding tissues to harden, forming a straw-like feeding tube.
Treatment and Prevention
- Scrub typhus should be treated with the antibiotic doxycycline.
- No vaccine is available to prevent scrub typhus.
- Prevention measures include avoiding contact with infected chiggers, using EPA-registered insect repellents, and wearing protective clothing.
- Treating clothing and gear with 0.5% permethrin can also help prevent chigger bites.
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