Life cycle Strongyloides Stercoralis Flashcards
What is the classification of Strongyloides Stercoralis?
Helminth in the category of nematode
How is Strongyloides Stercoralis transmitted?
Larvae that penetrate skin
What are the 2 lifecycles of Strongyloides Stercoralis?
Free living cycle
Parasitic life cycle
What are the steps of the Strongyloides Stercoralis Free living cycle (outside of human host)?
- Rhabditiform larvae are passed in the stool of an infected definitive host
- develop into either infective filariform larvae (direct development) [6] or free-living adult males and females
- that mate and the female worms produce fertilized eggs
- from the embryonated eggs rhabditiform larvae hatch
- and eventually become infective filariform (L3) larvae this takes 3-4 days
- The filariform larvae penetrate the human host skin to initiate the parasitic cycle. This second generation of filariform larvae cannot mature into free-living adults and must find a new host to continue the life cycle.
What are the lifecycle steps of Strongyloides Stercoralis Parasitic lifecycle in the human host?
- Filariform larvae in contaminated soil penetrate human skin when skin contacts soil [6] , and migrate to the small intestine
- It has been thought that the L3 larvae migrate via the bloodstream and lymphatics to the lungs, where they are eventually coughed up and swallowed. However, L3 larvae appear capable of migrating to the intestine via alternate routes (e.g. through abdominal viscera or connective tissue). In the small intestine, the larvae molt twice and become adult female worms
- The females live embedded in the submucosa of the small intestine and produce eggs via parthenogenesis (parasitic males do not exist)
- which yield rhabditiform larvae. The rhabditiform larvae can either be passed in the stool [1] (see “Free-living cycle” above), or can cause autoinfection by reinfecting the same host again by penetrate either the intestinal mucosa or the skin of the perianal area, resulting in autoinfection
What is autoinfection in Strongyloides Stercoralis?
Once the filariform larvae reinfect the host, they are carried to the lungs, pharynx and small intestine as described above, or disseminate throughout the body. The significance of autoinfection in Strongyloides is that untreated cases can result in persistent infection, even after many decades of residence in a non-endemic area, and may contribute to the development of hyperinfection syndrome
What type of life cycle has Strongyloides Stercoralis?
Indirect life cycle
What is the definitive host and what is the intermediate host for Strongyloides Stercoralis?
Human is intermediate host
Soil is definitive host
What are reservoirs for Strongyloides Stercoralis?
Soil
Domestic dogs
Domestic cats
Other primates
What are the 2 phases of clinical Strongyloidiasis?
Acute Strongyloidiasis
Chronic Srongyloidiasis
What are the symptoms and causes of acute Strongyloidiasis infection?
Acute Strongyloidiasis is related to the path of the parasite through the skin to the small intestine. The symptoms are usually non specific but it can be : Rash during penetration through the skin; tracheal irritation & dry cough when larvae travel to alveoli ; diarrhea, constipation, abdominal pain, and anorexia when it arrives in the small intestine.
What are the symptoms and causes of chronic Strongyloidiasis infection?
Chronic strongyloidiasis can last for years due to out infection. Can be asymptomatic or have gastrointestinal or pulmonary symptoms
What causes disseminated strongyloidiasis?
occurs when the larva migrate beyond the organs of autoinfective cycle.
What is the hyperinfection syndrome caused by Strongyloides Stercoralis?
the explosive multiplication of infective larvae and thus the worm burden within a host. This usually happens in immunocompromised individuals.
What is the incubation time for Strongyloides Stercoralis infection?
Pathogenesis of Strongyloidiasis is caused by adult female parasite filariform and takes 23/32 days.
