Abstract Book of EAVLD2012 - eavld congress 2012

S1- P - 21
ANALYSIS OF THE EFFICIENCY OF THE MCMASTER METHOD IN RAYNAUD’S MODIFICATION IN
DETECTION OF TOXOCARA SP. AND TRICHURIS SP. EGGS IN CARNIVORES FAECES
Maciej Kochanowski, Joanna Dąbrowska, Jacek Karamon, Tomasz Cencek
National Veterinary Research Institute, Departament of Parasitology and Invasive Disease, Pulawy, Poland
McMaster method, efficiency, carnivores, Toxocara, Trichuris
Introduction
Carnivores animals are the hosts of the important zoonotic
intestinal parasites. Faeces of these animals, containing eggs of
dangerous parasites are a potential source of infection for
humans. The particular importance in the spread of dangerous
invasive parasitic forms may have a common use of this faeces
as natural organic fertilizers. The aim of study was to determine
the efficiency of McMaster method in Raynaud’s modification
(Raynaund, 1970) in the detection of parasite eggs of the genera
Toxocara and Trichuris present in the faeces of carnivores, using
faeces samples enriched with known numbers of eggs.
Materials & methods
Four variants of this McMaster method (counting in one grid, two
grids, the whole McMaster chamber and flotation slide) were
used to examine dog faeces samples enriched with Toxocara sp.,
Trichuris sp. and Ascaris suum eggs. A. suum eggs were the
control of influence of the parasite eggs properties on the results.
One hundred and sixty enriched samples were prepared from
dog faeces (20 repetitions for each eggs level) containing 15, 25,
50, 100, 150, 200, 250 and 300 eggs of the three types of eggs in
1 g of faeces. Moreover, to compare the influence of kind of
faeces on the efficiency of the method 160 pig faecal samples
were prepared and enriched with A. suum eggs.in the same way
Results
The highest (worst) limit of detection (Table 1) in all McMaster
variants were obtained with eggs of Toxocara sp. (from 25 to 250
eggs / g faeces, depending on the variant) - about twice higher
than for Trichuris sp. and A. suum eggs (from 15 to 100 eggs / g
feces). The highest (worst) limit of detection for flotation in the
tube were obtained for Trichuris sp. eggs (100 eggs / g) - it was
4-times higher than the results for other types of eggs (25 eggs /
g). The best results of the limit of detection, sensitivity, the lowest
coefficients of variation (providing about repeatability) were
obtained with the use of whole McMaster chamber variant. There
was no significant impact of faeces properties (dog and pig
faeces) on the obtained results. Multiplication factors (to estimate
the real number of eggs in 1 g of faeces) were calculated on the
basis of the transformed equation of the trend line illustrating the
relationship between number of eggs found by the examination
and the number of eggs added to the sample. Multiplication
factors for eggs of Toxocara sp. and Trichuris sp. were higher
than planned by Raynaud, and for A. suum were comparable with
them. The multiplication factor estimated for flotation in the tube
(flotation slide variant) for all types of examined parasite eggs
were significantly higher than that given by Raynaud (Table 2).
Table 1: Limit of detection for all variants of the McMaster method
in Raynaund’s modification
Variants
Dog faeces
Pig faeces
of the method Toxocara Trichuris Ascaris Ascaris
one grid 250 100 100 50
two grids 100 50 25 25
whole chamber 25 15 15 15
flotation slide 25 100 25 25
Discussion & conclusions
Most of the publications about detection of parasite eggs are
based on material from natural or experimental infection. For that
reason the real number of eggs in faeces can not be properly
assessed (Vadlejch et al, 2011; Mes et al, 2007). Therefore, in
order to obtain the most reliable results in our experiment the
material enriched with a known number of parasite eggs was
used. The results of experiments indicate that detection of
parasite eggs of carnivores by McMaster method in Raynaud’s
modification differs from the basic parameters of this
modification. There were significant differences in the efficiency
of the method according to the type of parasite eggs. In the case
of Toxocara sp. eggs examined in the McMaster chamber there
were observed significantly lower numbers of detected eggs in 1
g of faeces than obtained for Trichuris sp. and A. suum eggs.
Most likely reason of the lowest detection Toxocara sp. eggs in
the McMaster chamber is the specific shell structure of these
eggs – namely, they have strong adhesive properties
(Overgaauw, Knapen, 2008). It can result in higher losses of
parasite eggs during performing of the method. The variant in the
tube (flotaion slide) was characterized by the lowest number of
detected eggs in the case of Trichuris sp. It is probably related to
the high specific gravity of the Trichuris sp. eggs affects to less
effective flotation process in tube. According to our study the
detection of Toxocara sp. eggs in McMaster chamber is twice
lower than planned by Raynaud. In the case of Trichuris sp. eggs
it is slightly lower. However, A. suum eggs in pig and dog feces,
were detected in number close to the assumptions of McMaster
method in Raynaud’s modification. Detection of all three types
parasite eggs as a result of the tube flotation (flotation slide
variant) is several times lower than the assumptions of Raynaud's
modification (which is at the level of detection obtained in the
variant of two grids of McMaster chamber). Our results allowed
us to assess the real efficiency of the McMaster method in
Raynaud’s modification in carnivore feces samples enriched with
a known number of parasite eggs. The investigation carried out
with selected (important to the diagnostic and the zoonotic point
of view) two types of nematodes (Toxocara sp. and Trichuris sp.)
showed a significant effect of parasite genus on the detection
efficiency. However, it is desirable to extend calibration of the
method for other kinds of parasites whose eggs differ significantly
in the morphology - in particular with regard to the eggs of
tapeworms.
References
1. Mes T., Eysker M., Ploeger H., 2007. A simple, robust and semiautomated
parasite egg isolation protocol. Nature Protocols.
2. Overgaauw P., Knapen F., 2008. Toxocarosis, an important zoonosis.
European Journal of Companion Animal Practice Vol. 18 Issue 3 (2008).
3. Raynaud J., 1970. Etude de l’efficacite d’une technique de coproscopie
quantitative pour le diagnostic de routine et le controle des infestations
parasitaires des bovins, ovins, equines et porcins. Annales de
Parasitologie (Paris). 45 pp. 321-342
4. Vadlejch J., Petrtyl M., Zaichenko I., Cadkova Z., Jankovska I.,
Langrova I., Moravec M., 2011. Which McMaster egg counting technique is
the most reliable? Parasitology Research 109(5): 1387-1394 (2011)
Table 2: Multiplication factors for estimation of the number of
eggs in 1g of faeces, for all variants of the McMaster method in
Raynaund’s modification
Variants
Dog faeces
Pig faeces
of the method Toxocara Trichuris Ascaris Ascaris
one grid 244 145 108 111
two grids 120 78 54 63
whole chamber 40 26 22 22
flotation slide 49 62 35 43