Medical Microbiology

Nematoda(Roundworms) 583

gyloidesfuelleborniismainlyaparasiteofAfricanmonkeys,butisalsofound

inhumans.

Morphology,lifecycle,andepidemiology(Fig. 1 0. 15 ).OnlyStrongyloides

femalesareparasitic.Theyare 2 – 3 mmlongandliveinthesmallintestine

epithelium,wheretheyproducetheireggsbyparthenogenesis.Duringthe

intestinalpassagefirst-stagelarvae(0.2–0.3mmlong)hatchfromtheeggs

andareshedinstool(whereaseggsareshedinS.fuelleborniinfections).

Withinafewdaysfirst-stagelarvaedevelopintoinfectivethird-stagelarvae.

Strongyloidesstercoralis:LifeCycle

1

2

5

3

4

6a

6b

7

8

Fig. 1 0. 15 1 FemaleStrongyloidesfromthesmallintestine; 2 first-stagelarva(L1)

shedinstool; 3 L2larva; 4 infectiveL3larva; 5 developmentofL1larvatoadult

stagesincludingfourmoltings( 6 );6afree-livingmale(nothost-bound);6bfree-

livingfemale; 7 eggoffree-livinggeneration; 8 larvahatchedfromegg,develops

intoinfectivelarvaincludingtwomoltings.

10

Kayser, Medical Microbiology © 2005 Thieme