Are these worms Strongyloides?Pictures from Miles Beaman History: Stool from a 4 yr old NT child, who also had rhabditiform larvae of Strongyloides and Hymenolepis. Rick Speare Tropical Health Solutions firstname.lastname@example.org http://www.tropicalhealthsolutions.com/strongyloides-ID-1 7 May 2013
Life cycle of Strongyloidesstercoralis • From http://www.dpd.cdc.gov/dpdx/HTML/Strongyloidiasis.htm Free-living adults can be used to identify species
Initial question • These are adult female nematodes (see the eggs in the uteri). • Are they free-living females of Strongyloides or are they females of a free-living nematode that has contaminated the faeces (i.e., not a parasite at all)?
Compare the morphology • Free-living female of Strongyloides (Speare 1989 p.24) • Note: • Rhabditiform oesophagus • No mid-bulb in oesophagus • Vulva at mid body
Neck Bulb Body
Conclusion: The parasites are free-living females of Strongyloides spp • Comparison between oesophagus of free-living females of Strongyloides (A) and a rhabditoid nematode (B). Note the lack of a mid-bulb in Strongyloides. (Speare 1989 p.27)
Q2: What Strongyloidesspecies? • People in Australia are usually infected with S. stercoralis. • So one could go with the odds and make this diagnosis on probability alone. • However, infection with other species of Strongyloides is possible, particularly S. fuelleborni, a parasite of non-human primates that infects people in Africa. • S. kellyialso occurs in the wilds of Papua New Guinea.
For free-living females the region of the vulva allows species to be identified. Vulva
Conclusion: Strongyloidesstercoralis • In the specimen, the narrowing of the body diameter at the vulva is minor and the axis of the vulva is approximately at right angles to the body axis. • This is consistent with S. stercoralis.
Develoing larvae of S. stercoralis(probably L2) • Note the Trichuristrichiura (whipworm) egg also.
Identification • Strongyloidesstercoraliswith development of the indirect life cycle with free-living adults and second generation of developing larvae. • Only females are seen but for them to be fertile there must have also been free-living males. • This stage could have been reached after 2 days in the external environment at about 25°C. • The sample also had Trichuristrichiura. • So the 4 year old child had three helminth parasites – S. stercoralis, Trichuristrichiura, and Rodentolepis nana (dwarf tapeworm).
Is this result unexpected? • Sadly, no! • Strongyloidiasis is endemic in many rural and remote Indigneous communities in the top two thirds of Australia. See the map presented by Dr Jenny Shields at the 8th National Workshop on Strongyloidiasis - http://www.jcu.edu.au/phtmrs/abc/JCU_121270.html • Other soil transmitted helminths (like whipworm and dwarf tapeworm are present in many of the communities.
Epidemiology of infection with S. stercoralisin a Qld remote Indigenous community • If infected children are not treated, they will have the parasite for the rest of their life!
Is it time for a national Strongyloides control program? Definately! Diagnosis and treatment of individual cases is essential, but unless Strongyloides is managed as a community problem the high prevalences of strongyloidiasis will persist.
References • Speare, R. Identification of species of Strongyloides. In "Strongyloidiasis: an important roundworm infection of man". Ed. D.I. Grove. Taylor Francis, London. 1989;11-82. • Shield J. Strongyloides distribution in Australia. 8th National Workshop on Strongyloidisis. Canberra, 23-24 March 2013 - http://www.jcu.edu.au/phtmrs/abc/JCU_121270.html