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Trichinella spyralis

Among the different test methods available to diagnose the infection of Trichinella spyralis (trichinellosis), muscle biopsy is used to directly observe larvae under the microscope, either by pressing tissue samples between two slides or proceeding with enzymatic digestion of a finely minced portion of the biopsy sample. Brightfield microscopy is the traditional method for the detection of larvae, while more sensitive epi-fluorescence microscopy suffer from poor image quality due to low magnification factor of the lenses involved during observation. The present case study describes a new device for fluorescence microscopy, which can be employed on small microscopes at an affordable price. Furthermore it can be adapted on existing microscopes. Battery operation is also possible.

Introduction

Nematode worms of the genus Trichinella are parasites circulating in both wild and domestic animals. Humans acquire the infection by ingestion of raw or undercooked meat, mainly swine, harbouring the nurse cell-larva complex. The parasites are typically recognized by traditional white light microscopy, but the method is tricky and failures of veterinary control due to human error are frequent. Technicians are required to be familiar with the use of white light microscopy and the evaluation of Trichinella larvae morphology, to distinguish them from other parasites as well as debris and muscle fibres in the sample. The relative complexity of this method represents a major drawback, while fluorescence microscopy is credited with improved sensitivity. The identification of Trichinella using the fluorescent dye Propidium Iodide after enzymatic digestion makes both stadiums of newborn larva and nurse cell-larva complex visible. Propidium Iodide is excited by green light and emits in the region from ~580nm to ~680nm (red).

FLUOLED® Easy: transmitted light fluorescence for the detection of Trichinella spyralis

Traditional reflected light fluorescence microscopy is unable to deliver high quality images at the very low magnifications (typically 5x and 10x) required by the dimensions of the parasites. So a unique, proprietary illumination system was developed using high-power solid-state (LED) light sources in transmitted light rather than reflected light. The adaptor (1) is clamped over the microscope base and holds the light emitting diode (2) inside. A 45° mirror (3) reflects light emitted by the diode through the condenser on the sample. Form and shape of adaptor may change from figure. Fluorescence emitted by the sample is filtered by an optical filter (4) before reaching the observer.

FLUOLED® Easy (fig. on left) on a transmitted light microscope: the LED fluorescence module is designed to attach to a standard bright field microscope and is used in transmission mode.
FLUOLED® Easy (fig. on left) on a transmitted light microscope: the LED fluorescence module is designed to attach to a standard bright field microscope and is used in transmission mode.
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Fluorescent staining after enzymatic digestion makes both stadiums of newborn larva and nurse cell-larva complex visible.

Results

Transmitted-light fluorescence microscopy proved to be a valuable technology for observation of Propidium Iodide stained Trichinella spyralis. The use of a high power solid-state (LED) source enabled increased performance, significantly increased light source lifetime, reduction of initial costs and operating costs, and reduction of maintenance and heat production. Main FLUOLED® Easy product benefits are:

  • High contrast fluorescence images allow easier detection of parasites.
  • Light source lifetime: typically 30.000 hours, thus allowing many years of operation and cost savings.
  • Fraen’s transmitted light fluorescence system combines the advantage of increased sensitivity of fluorescence microscopy with high levels of signal intensity provided by the use of low power
  • No need of any special alignment procedure.
  • No warm-up time required for the light source.
  • Allows transmitted light bright field observation.
  • Battery pack option for field operation.


NOTICE: As part of the United States' Critical Infrastructure supply chain, Fraen is committed to making every effort to continue its manufacturing operations during the current COVID-19 crisis. We have enacted numerous procedures to protect our employees based on recommended guidelines, and are in constant communication with our customers and suppliers. If you have a question about Fraen's current activities or plans, please do not hesitate to contact us.