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All roundworms begin as eggs. These eggs are produced by female adult roundworms living in the gut of the animal.
Step 2
These eggs are passed out in the animal’s dung onto the ground.
Step 3
The eggs hatch into larvae, given the right environmental conditions (sufficient moisture levels and temperature).
Step 4
The larvae develop and become infective. They move up blades of grass in water droplets, where they can be eaten by grazing sheep.
Step 5
Once ingested, the larvae enter the gut of the animal and either develop into adults quickly, or they may stay in an “inhibited” stage until a later time (for example, during a summer drought or winter cold).
When the external conditions are “right” (i.e. favourable for worm survival) all the inhibited larvae develop into adults.
Introduction to Sheep Worm Monitoring
The table below offers a summary of the most important roundworms of sheep in Australia
Internal Parasite
Site of Infection
Teladorsagia circumcinta
(Small brown stomach worm)
Absomasum
Haemonchus contortus
(Barber's pole worm)
Absomasum
Trichostrongylus spp.
(Black scour worm)
Small Intestine
Nematodirus spp.
(Thin-necked intestinal worm)
Small Intestine
Oesophagostomum spp.
(Nodule worm/Large bowel worm)
Large Intestine
Sheep Internal Parasites & Best Practice Worm Monitoring
Barbers Pole Worm
Haemonchus contortus
What is it?
Barbers Pole is a round worm nematode
Resides in the abomasum (4th stomach) - burrow in and attach through the lancet on their head
The females have a banded (barber pole) colouration and can be 20mm to 30mm in length (males are pale pink and 15mm in length)
Each female can lay 10 000 eggs per day and an animal can have thousands of females feeding off it
These eggs are laid and passed with the faeces to hatch and develop to L3 larvae in 7 days
The ideal environmental conditions are warm moist spring, summer, and autumn seasons
The L4 larval stage can become inhibited from transitioning to adult stage and migrate into abomasal wall until seasonal conditions become more viable for egg laying
Widespread resistance to anthelmintic groups and even multi-combinational drenches
What are the Symptoms?
The females are blood feeders and can consume 0.05ml / day each
This can lead to anaemia, lethargy, weakness and death
Animals will show pale gums and pale eyelids
Sheep with good nutrition and with high condition scores can be affected, collapse and die but are more resilient than poorer condition score sheep
What does it mean for you?
Affects all sheep irrespective of condition score, age or breed
Clinical and Sub-clinical production losses
Death by anaemia
Loss of condition and depressed growth rates
Reduction in meat and wool production
Solutions & Next Steps
Drenching with an effective sheep drench
WEC to monitor egg output with larvae differentiation
Quarantine new sheep until potential risk is accessed
Recovery from a severe infection is slow and requires the provision of adequate nutrition
Black Scour Worm
Trichostrongylus spp.
What is it?
Black scour worm is a round worm nematode
There are several species T. colubriformis, T.vitrinus, T. rugatus (arid regions) & T. axei (found in abomasum)
6-8mm in length and the L4 larvae burrow into the GI mucosa of the abomasum or small intestine to mature
Females produce 200 eggs per day
Causes diarrhoea, especially in young sheep
The ideal environmental conditions are in late summer and autumn
T. colubriformis occurs in the warmer summer rainfall areas while T. vitrinus occurs more frequently in winter rainfall areas
Widespread resistance to anthelmintic groups and even multi-combinational drenches
What are the Symptoms?
Black scour worm causes damage to villi of the small intestine
Symptoms include:
appetite loss
lethargy
malabsorption
scours (generally black in colour)
the malnutrition and dehydration effects may result in death
What does it mean for you?
Affects all sheep irrespective of condition score, age or breed
Clinical and Sub-clinical production losses
Death through scouring
Loss of condition and depressed growth rates
Reduction in meat and wool production
Solutions & Next Steps
Drenching with an effective sheep drench
WEC to monitor egg output with larvae differentiation
Quarantine new sheep until potential risk is accessed
Recovery from a severe infection is slow and requires the provision of adequate nutrition
Small Brown Stomach Worm
Teladorsagia circumcincta
What is it?
Small Brown stomach worm is a round worm nematode
Small in size (8-12mm)
Resides in the abomasum (4th stomach) - causes lesions on the mucosal wall
Females can lay 100 eggs per day
Small brown stomach worm has a winter dominant lifecycle
Widespread resistance to anthelmintic groups and even multi-combinational drenches
What are the symptoms?
Small brown stomach worm causes inflammation to the mucosal wall
Interferes with digestion resulting in less metabolisable energy and protein available
Symptoms include:
scours
rapid weight loss
immune depletion
physical damage to the mucosa
anaemia, loss of plasma proteins
loss of appetite & milk suppression
death
What does this mean for you?
Affects all sheep irrespective of condition score, age or breed
Clinical and Sub-clinical production losses
Death through scouring and malnutrition
Rapid loss of condition and depressed growth rates
Reduction in meat and wool production
Solutions & Next Steps
Drenching with an effective sheep drench
WEC to monitor egg output with larvae differentiation
Quarantine new sheep until potential risk is accessed
Recovery from a severe infection is slow and requires the provision of adequate nutrition
Nodule Worm
Oesophagostomum columbianum
What is it?
Found in the Summer rainfall areas of Northern NSW and Southern Qld
Causes nodules predominantly in the large intestine and colon
Economic loss for sausage casings
What are the symptoms?
Soft faeces, may contain blood and have high levels of mucous
Unthrifty sheep
What does this mean for you?
Affects all sheep irrespective of condition score, age or breed
Clinical and Sub-clinical production losses
Death through scouring
Rapid loss of condition and depressed growth rates
Reduction in meat and wool production
Solutions & next steps
Drenching with an effective sheep drench
WEC to monitor egg outlay with larvae differentiation
Quarantine new sheep until potential risk is accessed
Large mouthed bowel worm
Chabertia ovina
What is it?
Chews and damages the mucosal plugs of the intestinal lining
Causes thickening and haemorrhage of the intestinal lining
Winter rainfall distribution
The female worm lays 3,000-5,000 eggs/day
Occurs primarily in lambs
What are the Symptoms?
Soft faeces, may contain blood and have high levels of mucous
Unthrifty sheep
What does this mean for you?
Affects all sheep irrespective of condition score, age or breed
Clinical and Sub-clinical production losses
Death through scouring
Rapid loss of condition and depressed growth rates
Reduction in meat and wool production
Solutions & next steps
Drenching with an effective sheep drench
WEC to monitor egg outlay with larvae differentiation
Quarantine new sheep until potential risk is accessed
Small intestinal worm (exacerbates mixed infections)
Cooperia spp
What is it?
6-9mm in size, often seen coiled up
Live in small intestine
Lay 1-400 eggs per day
What are the symptoms?
Increases the symptoms of mixed infections
What does this mean for you?
Affects all sheep irrespective of condition score, age or breed
Clinical and Sub-clinical production losses
Death through scouring
Rapid loss of condition and depressed growth rates
Reduction in meat and wool production
Solutions & next steps
Drenching with an effective sheep drench
WEC to monitor egg outlay with larvae differentiation
Quarantine new sheep until potential risk is accessed
Thin-necked intestinal worm (primarily lambs)
Nematodirus spp
What is it?
Live in small intestine
Require frosts to trigger hatching
Large, hardy eggs (reside in the environment for months)
Larva develops within egg (50-100 eggs/day)
What are the symptoms?
Ill thrift, scours, dehydration
Death within 2-3 days
What does this mean for you?
Affects all sheep irrespective of condition score, age or breed
Clinical and Sub-clinical production losses
Death through scouring
Rapid loss of condition and depressed growth rates
Reduction in meat and wool production
Solutions & next steps
Drenching with an effective sheep drench
WEC to monitor egg outlay with larvae differentiation
Quarantine new sheep until potential risk is accessed