Diagnosis of Internal Parasitism and the effect of worms on the host
Bill Pomroy

Egg Counts
There is a relationship between the number of worms and the number of their egg in faeces
Different types of worms produce different types of eggs
All the trichostrongylid worms produce similar eggs which we can’t tell apart

Eggs in Ruminant Faeces

"Normal strongylid egg – the..."
Normal strongylid egg – the main egg type we are interested in when doing counts

"Normal strongylid egg with smaller..."
Normal strongylid egg with smaller Strongyloides eggs – these contain a first stage larvae when they are passed in faeces

McMaster Egg counts
Most common technique used
Relies on the use of a floatation fluid in which eggs float and heavier debris in faeces sinks
Floatation fluid needs to be at least Sp. Gravity of 1.2
Common floatation media are various salt solutions including
Saturated common salt (NaCl)
Sodium nitrate (specific gravity of 1.2)

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"The other key to this..."
The other key to this technique is the use of a special counting chamber called a McMaster slide

"2g of faeces is added..."
2g of faeces is added to 28ml of floatation fluid within the coarse sieve (tea strainer)

"The faeces and fluid are..."
The faeces and fluid are mixed until all the lumps are broken down and the eggs “liberated”

"The sieve containing coarser material..."
The sieve containing coarser material is then removed leaving the floatation media and smaller faecal material including eggs

"The fluid is then thoroughly..."
The fluid is then thoroughly stirred with a back and forth motion.  If not evenly stirred the eggs come to the surface and you do not end up with a representative count

"Fill each chamber of the..."
Fill each chamber of the counting slide separately going back and refilling the pipette each time

"Focus on the gridlines in..."
Focus on the gridlines in the chamber which are on the underside of the top slide
Use the 4X objective lens first and then change to the 10X
It should then be possible to see a line of each grid on each side of your field of view
Strongylid eggs are about the same length as the gridlines are wide (don’t confuse with coccidial oocysts
Count the number of strongylid eggs in each chamber, add them together and multiply by 50 to give you a count of egg per gram of faeces

US recommendations are that a cut-off value of 1000 eggs/g indicates the goats need treating
Goats can die with egg counts of only 2000 eggs/g so be careful
Haemonchus  is a very prolific egg layer with about 6000 per day but Trichostrongylus only produces about 600 per day and Nematodirus many fewer than this
The immune response can reduce the ability of individual worms to produce eggs so more eggs per worm in young than old, especially with sheep

Haemonchus and FAMACHA
This is a system that has been developed by the South Africans and is only suitable for Haemonchus
Relies on examination of the colour of the conjunctiva of the eye, more particularly the bottom conjunctiva of the eye
They have produced a chart and an experienced operator can detect wormy goats
Remember other causes of anaemia such as liver fluke

"Note the sheep on the..."
Note the sheep on the left is normal and the black one on the right has pale conjunctiva – it is suffering clinical haemonchosis

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Counting Worms
Haemonchus is big enough to see with the naked eye
Trichostrongylus and Ostertagia are not
Counting worms is a skilled job for trained professionals but nevertheless a big burden of Haemonchus is generally easy to spot with some experience

Haemonchus in a goat abomasum
Mature adults are 2-3cm long

"Haemonchus doesn’t cause scouring but..."
Haemonchus doesn’t cause scouring but all the other trichostrongylids do when the infection is large

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Effect of other trichostrongylid species on the host
Mucus browsers essentially induce the host to try to get rid of them
The host then redirects protein metabolism to the gut to produce more cells, more mucus and antibodies and other immune mediators to fight off the infection, not necessarily effectively
Has a dramatic effect on the protein metabolism
Wormy sheep look like starved goats/sheep
Slightly wormy goats/sheep don’t grow as well as uninfected sheep

"Abomasum of a goat showing..."
Abomasum of a goat showing nodules and unevenness associated with the host’s response to the worms

"Goat abomasum:"
Goat abomasum: note the nodule formation, this is particularly caused by Ostertagia