Worm Egg Counts Flashcards

1
Q

What are Faecal Egg Counts

A

Method of detecting and quantifying worm eggs in faecal samples
Useful for gastrointestinal parastites

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2
Q

Selective/targeted therapy

A

Only treating animals which exceed a certain cut-off value of parasite burden
Reduces a selection pressure for anthelmintic resistance

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3
Q

Refugia

A

An area in which a population of organisms can survive through a period of unfavourable conditions

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4
Q

What is a Direct Smear test?

A

Small amount of faeces mixed with saline
(or iodine for better contrast)
Placed on microscope slide

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5
Q

Advantages and Disadvantages of Direct smear tests

A

Advantages
* Cheap
* Short processing time

Disadvantages
* Qualitative
* Very low accuracy, precision and sensitivity

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6
Q

What is a Cornell-Wisconsin test?

A

Centrifugal flotation of eggs in a salt solution in a tube
Collection onto a coverslip
Counting under a microscope

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7
Q

Advantages and Disadvantages of Cornell-Wisconsin tests

A

Advantages
* Cheap
* High limit of detection

Disadvantages
* Time-consuming
* Low accuracy

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8
Q

What is a McMaster test?

A
  • Faeces is mixed in a flotation solution
  • Loaded onto chambers of a slide
  • Floated eggs are counted
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9
Q

Advantages and Disadvantages of McMaster test

A

Advantages
* Cheap
* Medium processing time

Disadvantages
* Sensitivity limit is 50 eggs/g of faeces
* Requires specialised slide
* Required ability to distinguish between eggs

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10
Q

What is a FLOTAC test?

A

Centrifugal-flotation of eggs in a specialised device
Subsequent examination of the top layer

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11
Q

Advantages and Disadvantages of FLOTAC test

A

Advantages
* Cheap
* High sensitivity

Disadvantages
* Time consuming
* Requires a centrifuge

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12
Q

What is a Mini-FLOTAC test?

A

A modified version of FLOTAC
Without centrifugation step
Requires less volume

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13
Q

Advantages and Disadvantages of Mini-FLOTAC test

A

Advantages
* High sensitivity
* Accurate
* Precise
* Medium processing time

Disadvantages
* Detection of some parasites
○ E.g. trematodes
* Requires centrifugation

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14
Q

What is a FECPAK test?

A

Eggs are floated in a flotation solution
Accumulated into a single viewing area and imaged

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15
Q

Advantages and Disadvantages of FECPAK test

A

Advantages
* Does not require technical skills as eggs identified and counted remotely
* Digitalised images

Disadvantages
* Low accuracy and precision
* Medium sensitivity
* Time-consuming

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16
Q

What is a Parasight System test?

A

A faecal sample is mixed with water and filtered to remove debris
Eggs are labelled with a fluorescent dye
Imaged and counted using an automated algorithm

17
Q

Advantages and Disadvantages of Parasight System test

A

Advantages
* High precision
* Does not require technical skills
* Fast
* Automated counting
* Digitalised images

Disadvantages
* Expensive
* Some results need to be confirmed visually
* Does not detect overlying eggs
* Cannot differentiate in the presence of high debris background

18
Q

FECR

A

Fecal Egg Count Reduction Test
Considered gold standard in detecting anthelmintic resistance
Method:
* Measure FEC at time of treatment
* Measure again at defined times after treatment
(times depend on which anthelmintic group used)

19
Q

FECR times for different anthelmintic groups

A

3-7 days after using levamisole
8–10 days after using a benzimidazole
14–17 days after using a Macrocyclic lactones
* If unsure or using multiple anthelmintics then repeat FEC after 14 days

20
Q

FECR Calculation

A

Find reduction in eggs/gram of faeces as a %
1-(T2-T1)/100

Cut off is 95% (resistance is inferred if FECR <95%)