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Detecting Trichinella infections using inverse microscopy and an improved larval counting technique

Published online by Cambridge University Press:  18 June 2013

G. Makrutzki*
Affiliation:
Institute of Food Hygiene, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, Germany
K. Riehn
Affiliation:
Department of Nutrition & Home Economics, Hamburg University of Applied Science, Hamburg, Germany
A. Hamedy
Affiliation:
Institute of Food Hygiene, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, Germany
D. Petroff
Affiliation:
Coordination Centre for Clinical Trials, Medical Faculty, University of Leipzig, Leipzig, Germany
D. Hasenclever
Affiliation:
Institute for Medical Informatics, Statistics and Epidemiology, Medical Faculty, University of Leipzig, Leipzig, Germany
H. Meiler
Affiliation:
Städtisches Veterinäramt, Hof, Germany
E. Lücker
Affiliation:
Institute of Food Hygiene, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, Germany

Abstract

Several methods for the detection of Trichinella in meat are legally prescribed in regulation (EC) No 2075/2005, which prescribes the magnetic stirrer method for pooled sample digestion (MSM) as the reference method. However, the MSM's multistage protocol requires several preparatory steps that seem to be accountable for the loss of larvae. Here we present a modified MSM (mMSM) based on: (1) an inversion of the optical path using inverse microscopy; and (2) a modified larval counting basin (mLCB, ‘Trichoview’). This enables one to examine samples of up to 40 ml and reduces the examination area from 72 to 10.3 cm2. Preparatory steps that might cause the loss of Trichinella larvae are eliminated from the new protocol. Correspondingly, the overall analytical time is reduced. In a direct and blinded comparison using 60 digest samples containing spiked vital Trichinella larvae (1–90 L1), both methods performed well for both small and large numbers of L1. However, 1278 of 1285 L1 (99.4%) were detected using the mMSM, while MSM recovered only 1225 L1 (95.3%). The improvement stems largely from samples with small numbers of L1: in all samples spiked with fewer than 10 L1, the recovery rate of mMSM was 100% compared to only 93% with MSM. Our data suggest that the use of the mMSM can improve the recovery rate by about 4% and therefore reduce the chances of a false-negative result in a sample containing 5 larvae by a factor of about 4.

Type
Research Papers
Copyright
Copyright © Cambridge University Press 2013 

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