Strongyloides stercoralis Flashcards
Classification
Metazoa - nematode
Indirect or direct
Hosts
Direct life cycle
Human is final host
Transmission and life cycle
Free living cycle
Larvae are passed in the stool of infected final host. These larvae develop into either infective filariform larvae or into free living adult males and females that mate and produce eggs from which eventually infective filariform larvae hatch.
The filariform larvae penetrate the human host skin to initiate the parasitic life cycle. This second generation of filariform larvae cannot mature into free-living adults and must find a new host to continue the life cycle.
Parasitic life cycle
Filariform larvae in soil penetrate human skin. It has been thought that they end up in the intestines by coughing up and swallowing, but there are also alternative routes.
In the intestine, the larvae molt twice and become adult female worms.
The females live in the intestines and produce eggs via parthenogenesis (parasitic males do not exist), which yield rhabditiform larvae. The rabditiform larvae can either be passed in the stool or can cause autoinfection.
In this parasite autoinfection occurs so worm load can increase!
Diagnosis
Microscopy:
identification of larvae in stool. In low infection burden microscopy has low sensitivity.
Serology:
Antibody detection. When they cannot find anything in microscopy, but still suspect infection.
Molecular:
PCR and LAMP methods.
