MEASURING PARASITE BURDEN: Evaluating faecal analysis - page 1
Keywords: MEASURING PARASITE BURDEN: Evaluating faecal analysis
By Tkennix on 03/10/2011
Level: Bachelor Honours Degree (BA, BEng, BSc etc)
Page Number: 1 of 2 pages: 1 2
MEASURING PARASITE BURDEN: Evaluating faecal analysis
techniques; WORKSHEET
Instructions:
Answer the following questions using the information gained during the practical session
and your own additional research;
1. Present your results summarising nematode egg counts per site to estimate the parasitic
burden (by species) of wild rabbit populations from local habitats. Include a brief
summary of main trends, comment on any differences/ similarities between sites.
(15marks)
2. Parasitic load of an animal may be affected by a range of internal and external factors.
Construct a table to list these factors and specify the consequence to their host
(20 marks)
3. Outline how you would maximise the accuracy of your method for estimating
nematode parasite burden from faecal egg counts using the McMaster slide technique
(15 marks)
4. Give a critical evaluation of different methods used for estimating parasitic worm
burden from faecal samples and explain the advantages and disadvantages of each.
(25 marks)
Collection of faecal samples
Faecal samples should be collected as soon as possible after emission. Early morning
is often a good time to collect faeces. Faecal pellets should be collected into a sterile
plastic container which is then marked with the ID of the animal (where known) and
the time, date and place of collection. Samples can be kept in a fridge for up to 48
hours before analysis. Longer storage is not recommended as the eggs can hatch;
this will lead to a distorted count. Samples should not be frozen as the eggs may
rupture and this will prevent identification.
Stage Two: Preparation of samples
· Place approximately 20g of faecal matter (ten large rabbit pellets, or a
tablespoon full of other faeces) in a plastic dish
· Break/mash the sample up with a metal fork to mix the faecal pellets
(parasite eggs are often shed unevenly and one pellet may contain many
eggs whilst another contains none; mashing several pellets together gives a
more accurate overall egg count)
· Place 3g of faecal matter (a level teaspoon) into a plastic tea strainer
(aperture of mesh approx. 0.15-0.25mm)
· Measure out 45ml of saturated salt solution (370g of NaCl dissolved in 1 litre
of hot water) and pour this slowly over the faecal matter, mashing and
pushing the sample through the strainer with a small spoon. Collect the
filtrate in a dish or bowl.
22
Stage Three: Carrying out an egg count using a McMaster slide1
· Using a Pasteur pipette, fill both chambers of a McMaster slide with the
suspension
· Wait for 60 seconds to allow the worm eggs to float to the surface of the
chambers
· Using a compound microscope (x10, x40, x100), carry out a count of all
visible,
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