helminths in faeces
TRANSCRIPT
Helminths in faeces
General considerations
Parasitic Disease
Number of Infections(millions)
Morbidity (%)
Mortality(number)
(%)
Ascariasis 1,472 23 60,0000.004
Hookworm infections 1,298 12 65,000
0.005Lymphatic filariasis 120 37
Onchocerciasis 18 4.2 45,0000.25
Schistosomiasis 200 10 20,0000.01
Trichuriasis 1,049 21 10,0000.001
Courtesy The Ohio State University
Bethony J. et al. 2006. Lancet 367:1521-1532.
Soil-transmitted helminth infections: ascariasis, trichuriasis, and
hookworm
Bethony J. et al. 2006. Lancet 367:1521-1532.
• Ascaris lumbricoides• Trichuris trichiura• Necator americanus and
Ancylostoma duodenale• Strongyloides stercoralis• Enterobius vermicularis• Toxocara canis and
Toxocara cati
• 807-1221 x 106
• 604-795 x 106
• 576-740 x 106
• 30-100 x 106
• 4-28% of children• 2-80% of children
Bethony J. et al. 2006. Lancet 367:1521-1532.
High worldwide prevalence, except Europe, North America, Australia,
and Japan
Helminths: morbidity (%) mortality (n)
Ascaris lumbricoides Ancylostoma-Necator Onchocerca volvulus Schistosoma spp. Trichuris trichiura
23 60 000 12 65 000 4.2 45 000 10 20 000 21 10 000
www.biosci.ohio-state.edu/∼parasite/morbidity.html
Helminths in faeces
• Adult worms (Ascaris lumbricoides, Enterobius vermicularis,...), fragments of worms (proglottids of Taenia saginata,...).
• Eggs and larvae.
Ascaris lumbricoides Adult male worm, with a curved tail (Unstained).
Ascaris lumbricoides Adult worm (Unstained).
Ascaris lumbricoides
Fertile bile-stained egg with a thick, mammillated shell, measuring 55-75 μm (Unstained).
Strongyloides stercoralis
First stage rhabditoid larva in faeces. The lenght varies from 180 to 380 μm (Unstained).
Eggs of helminths (worms) in faeces
• Eggs with an operculum: trematodes.
• Eggs with a spine: schistosomes.
• Eggs having hooklets (hexacanth larva of Taenia saginata): cestodes.
• Eggs sometimes containing a larva: nematodes or roundworms.
• Size is essential for identification.
Ocular micrometer disk
• Each objective must be calibrated with reference material.
• Can be roughly checked with a counting chamber, with RBCs ...
Courtesy Ash L.R. & Orihel T.C.
Courtesy CDC
Concentration procedures
• Are base on differences in specific gravities
• Two most commonly used methods:
– zinc sulfate flottation method
– formalin-ether sedimentation method
Formalin-Ethyl Acetate (Ether)
Sedimentation Concentration (Modified
Ritchie-Method)
Specific gravities
• S.G. of Zn-sulfate 33 %: 1.180• S.G. of formol-solution 10 %: 1.019• S.G. of ether: 0.714• S.G. of parasites: Ancylostoma 1.055; Giardia
1.060; Entamoeba histolytica (coli) and Endolimax nana 1.065 - 1.070; Ascaris 1.110; Trichuris 1.150, Chilomastix mesnili 1.180; Ascaris (unfertilized) 1.200 (Bailenger, 1965).
Editorial Commentary
• One or multiple (three) specimens tested.• Lack of clear evidence.• If testing is worth doing it is worth doing
well.
Jon. E. Rosenblatt. 2006. CID. 42:979-980.
Estimation of worm burdens through egg counts
• Direct fecal smear of 2 mg (Beaver)• Number of adult worms correlated to
number of eggs present Ascaris lumbricoides 1/2 Trichuris trichiura 10 Ancylostoma duodenale 5 Necator americanus 10 to 20
Eosinophilia > 10%With helminths,insects (myasis),
not with protozoa excepting Isospora belli and Dientamoeba
fragilis (with pinworms?)
Charcot-Leyden
Crystals
associated with
eosinophils
found in faeces
or sputum
Charcot-Leyden
Crystals
associated with
eosinophils
found in faeces
or sputum
Auto-infectiousEnterobius vermicularis
Hymenolepis nana
Strongyloides stercoralis