Deworming Sheep
Written by Mara |
Deworming sheep and lambs is an important part of health management. However, it is not advisable to deworm as a standard, routine measure. Frequent and ill-considered use of wormers leads to resistance in worms. And resistance is irreversible. That is why a well-considered worming policy is essential.
Which worms occur in sheep?
Various worm species can occur in the gastrointestinal tract and airways of sheep. The most important ones in the Netherlands are:
1. Haemonchus contortus (barber’s pole worm)
This is currently the most important and most problematic worm species in the Netherlands.
- Lives in the abomasum
- Sucks blood and therefore causes anaemia
- No diarrhoea, but pale mucous membranes, lethargy and sometimes sudden death
- Occurs mainly from May to October
- Resistance to multiple products is increasingly common
Haemonchus overwinters in the sheep itself. As a result, in spring almost the entire worm population is in the animals, a crucial moment with an increased risk of resistance development if treated incorrectly.
2. Teladorsagia and Trichostrongylus (gastrointestinal worms)
These worms live in the abomasum and small intestine.
Symptoms:
- Diarrhoea
- Reduced growth
- Poor feed efficiency
- Reduced appetite
They partly overwinter on pasture and can cause problems into autumn and sometimes winter.
3. Nematodirus (spring worm)
Mainly occurs in young lambs during their first grazing season.
Characteristics:
- Infective larvae develop inside the egg
- Outbreaks often occur after cold winters followed by a sudden rise in temperature
- Severe, watery diarrhoea with extreme thirst and death can occur
Lambs quickly build up immunity after an infection.
4. Lungworms
Several types of lungworm occur in sheep, namely the large lungworm (Dictyocaulus filaria) and several species of small lungworms.
They cause coughing and reduced condition.
5. Liver fluke
Occurs on wet land with snails as an intermediate host. It causes:
- Liver damage
- Weight loss
- Poor condition
- Chronic problems
Read more in the blog Liver fluke in sheep: recognising, preventing and treating.
6. Tapeworm (Moniezia expansa)
In sheep in the Netherlands, one tapeworm species occurs: Moniezia expansa. This white, flat tapeworm can grow up to 10 metres long.
The worm consists of:
- A head (scolex) with four suckers
- Segments (proglottids) that become wider towards the back
Each segment contains both male and female reproductive organs and is full of eggs.
Life cycle
- Intermediate host: grass mites
- Lambs can become infected in the first days of life
- The worm becomes sexually mature in about 40 days
- One worm can produce up to 1 million eggs per day
- Lifespan: about half a year
- Animals then develop immunity
Identification
- Rice-grain-like segments visible on the faeces
- Eggs identifiable via faecal testing
- The number of eggs says nothing about the severity of infection
Symptoms
Tapeworms usually cause few symptoms. Only in heavy infections do we see:
- Reduced appetite
- Lethargy
- Stunted growth
- Constipation, rarely
Treatment
Treatment is rarely necessary. Only benzimidazoles, such as albendazole and fenbendazole, work against tapeworm. Other groups of wormers are not effective.
