Equis ISSN 2398-2977

Feces: parasitology

Contributor(s): Annalisa Barrelet, Sheelagh Lloyd, Frank Taylor


Print off the Owner factsheet on Samples - how they help your vet to give to your clients.


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  • Flotation solutions.
  • Saturated salt solution, specific gravity 1.19 at 20°C.
  • MgSO4 solution, specific gravity 1.28 at 15°C (400 g MgSO4 in 1000 ml water).
  • Sugar solution, specific gravity 1.28 at 15°C (450 g granulated sugar dissolved in 350 ml warm water).
  • Due to heavier weight of trematode eggs (very unlikely in horses unless grazing on flukey land with ruminants), much higher concentrations of fluid are required (1.30-1.35).
  • ZnSO4 solution, specific gravity 1.36 (371 g ZnSO4 in 1000 ml water).

Nematode eggs

  • Eggs of strongyles, Strongyloides westeri  Strongyloides westeri  , Parascaris equorum  Parascaris equorum   and Dictyocaulus arnfieldi  Dictyocaulus arnfieldi  . Sometimes Anoplocephala  Anoplocephala spp  eggs will be seen.
  • McMaster technique  Feces: parasitology - McMaster worm egg count  :
    • 3 g feces mixed in a pestle and mortar with 42 ml saturated salt solution.
    • The suspension poured through a 1 mm aperture sieve (tea strainer) and liquid squeezed out of the feces.
    • The suspension or filtrate well mixed with a wide-mouthed pipet drawn up and used to fill the McMaster chambers.
    • The filtrate should be mixed to fill each chamber separately.
    • In a 2 chamber slide all the eggs in both grids (volume 0.3 ml) are counted and multiplied by 50 to give eggs per g feces.
  • FECPAK technique:
    • 20 g of feces are suspended in 80 ml water.
    • A 45 ml sample of the mixed suspension is made up to 230 ml with saturated salt solution.
    • The suspension is poured through a 1 mm aperture sieve.
    • Aliquots are used to fill the slide.
    • All the eggs in the grids (volume 1 ml) are counted and multiplied by 20 to give eggs per g feces.
    • This technique produces similar mean counts but with lower variability as the McMaster technique and is more sensitive at very low counts.


  • Centrifugation/flotation techniques are more sensitive than the McMaster technique.
  • The technique of choice for Anoplocephalaspp   Anoplocephala spp   with a sensitivity of approximately 60%, reaching 92% in horses with >20 worms.
  • Proudman and Edwards technique:
    • 40 g feces are mixed vigorously with 5-10 ml water in a beaker.
    • The mixture is strained through a coarse sieve and collected in two 10 ml centrifuge tubes.
    • The tubes are spun at 1200 gfor 10 min, the supernatant discarded and the pellets resuspended in saturated sucrose solution and spun at 1200 gfor 10 min.
    • The tubes are then filled to a slightly convex meniscus with saturated sucrose solution and a coverslip applied.
    • After 2 h the coverslips are removed vertically and placed on a microscope slide and the eggs counted.
  • Cornell-Wisconsin technique:
    • 5 g feces mixed will with 12 ml water and strained through a tea strainer, including washing out the mixing vessel with 2-3 ml water, the liquid squeezed out of the debris until dry.
    • The filtrate is centrifuged in a 15 ml tube at 264 gfor 3 min (free swinging bucket centrifuge).
    • The pellet is suspended in saturated sucrose, the tube filled to a convex meniscus and a coverslip applied.
    • The tube is centrifuged at 264 gfor 5 min.
  • Baermann technique for D. arnfieldiL1 and infective nematode L3:
    •  D. arnfieldi  Dictyocaulus arnfieldi   eggs hatch within a few hours so that identification of L1 in feces will be necessary if the feces have been held at room temperature for any time.
    • Spread 50 g or more of feces on a piece of double gauze or medical wipe in a Baermann apparatus   Feces: parasitology - Baermann technique 01    Feces: parasitology - Baermann technique 02  .
    • Stand for 6-8 h or overnight.
    • Remove the bottom 10 ml of fluid and either centrifuge or stand for a few hours and examine the sediment microscopically.
  • Fecal culture for nematode larvae:
    • Break up a fecal sample - commonly horse feces can be cultured as it is, if very dry add a bit of water or if wet, mix in some sawdust (bake the sawdust in the oven or autoclave and then dry to ensure sterile).
    • Half-fill a jar with a loose fitting cap.
    • Incubate in the dark (retards fungal growth) at 27°C for 7 days or at room temperature for 10-20 days.
    • Recover the larvae from the feces and washings of the jar by the Baermann technique.
  • Fecal egg count (FEC) reduction test (FECR):
    • Used to check efficacy of a given anthelmintic.
    • FEC performed on day of dosing and 10-14 days later.
    • A reduction of 90% is expected, and a reduction of much less than this suggests that drug-resistant cyathostomes are present.



Result Data

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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Lester H E & Matthews J B (2014) Faecal worm egg count analysis for targeting anthelminitc treatment in horses: Points to consider. Equine Vet J 46 (2), 139-145 PubMed.
  • Presland S L, Morgan E R & Coles G C (2005) Counting nematode eggs in equine fecal samples. Vet Rec 156 (7), 208-210 PubMed.
  • Craven J, Bjorn, Henriksen S A, Nansen P, Larsen M & Lendal S (1998) Survey of anthelminitic resistance on Danish horse farms, using 5 different methods of calculating fecal egg count reductionEquine Vet J 30 (4), 289-293 PubMed.
  • Proudman C J & Edwards G B (1992) Validation of a centrifugation/flotation technique for the diagnosis of equine cestodiasis. Vet Rec 131, 71-72 PubMed.
  • Egwang T G & Slocombe J O D (1981) Efficiency and sensitivity of techniques for recovering nematode eggs from bovine feces. Can J Comp Med 45, 243-248 PubMed.