Worm Egg Counts

Question 1

What are Faecal Egg Counts

Answer 1

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

Question 2

Selective/targeted therapy

Answer 2

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

Question 3

Refugia

Answer 3

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

Question 4

What is a Direct Smear test?

Answer 4

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

Question 5

Advantages and Disadvantages of Direct smear tests

Answer 5

Advantages
* Cheap
* Short processing time

Disadvantages
* Qualitative
* Very low accuracy, precision and sensitivity

Question 6

What is a Cornell-Wisconsin test?

Answer 6

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

Question 7

Advantages and Disadvantages of Cornell-Wisconsin tests

Answer 7

Advantages
* Cheap
* High limit of detection

Disadvantages
* Time-consuming
* Low accuracy

Question 8

What is a McMaster test?

Answer 8

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

Question 9

Advantages and Disadvantages of McMaster test

Answer 9

Advantages
* Cheap
* Medium processing time

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

Question 10

What is a FLOTAC test?

Answer 10

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

Question 11

Advantages and Disadvantages of FLOTAC test

Answer 11

Advantages
* Cheap
* High sensitivity

Disadvantages
* Time consuming
* Requires a centrifuge

Question 12

What is a Mini-FLOTAC test?

Answer 12

A modified version of FLOTAC
Without centrifugation step
Requires less volume

Question 13

Advantages and Disadvantages of Mini-FLOTAC test

Answer 13

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

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

Question 14

What is a FECPAK test?

Answer 14

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

Question 15

Advantages and Disadvantages of FECPAK test

Answer 15

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

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

Question 16

What is a Parasight System test?

Answer 16

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

Question 17

Advantages and Disadvantages of Parasight System test

Answer 17

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

Question 18

FECR

Answer 18

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)

Question 19

FECR times for different anthelmintic groups

Answer 19

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

Question 20

FECR Calculation

Answer 20

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

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