Page 6 - National Poultry Newspaper

Are worms a problem?
Vet’s
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by ROD JENNER
Roundworms.
FREE range production has many positive ben- efits – exposure to inter- nal parasites is not one of them.
This month we discuss one of the challenges fac- ing free range layer farm- ing: intestinal worms.
To understand them better, we need to know more about them – their lifecycle, their hosts, their impacts and how best to control them.
There are four major types of intestinal worms found in poultry: round- worms, hairworms, caecal
worms and tapeworms.
Roundworms (ascaridia galli)
These are the most com- monly seen intestinal worm.
They are white, up to 5cm long and may be vis- ible in droppings in heavy infestations.
A severe infestation can cause a reduction in nutri- ent absorption, intestinal blockage and death.
Occasionally, they mi- grate up a hen’s repro- ductive tract and become included in a developing egg.
This is a seriously un- wanted consequence of heavy infestations.
The lifecycle of round- worms is direct – eggs are expelled in the hen’s droppings and are directly infective if eaten.
The eggs can survive in the environment for long periods, so are difficult to eradicate once an infec- tion is established in a free range system. Hairworms (capillaria)
These are much smaller (hair-like) and barely vis- ible with the naked eye but can cause significant damage, even in only moderate infestations.
There are two main spe- cies – one lives in the crop and the other in the small intestine.
Caecal worms (hetera- kis gallinarum)
These worms spend most of their time in the caecae.
Caecal worms are gen- erally harmless but can be the intermediary host of another parasite, histo- monas meleagridis, the
cause of blackhead dis- ease.
So, though chickens are generally not impacted by caecal worms, controlling the worms is still impor- tant for blackhead control. Tapeworms
Several species of tape- worms are found in poul- try.
Tapeworms require an intermediate host to com- plete their lifecycle.
These intermediate hosts include ants, beetles, houseflies, slugs, snails, earthworms and termites.
They spend most of their life in the intestines and generally cause little impact on performance, unless the worm burden physically occludes the intestine.
There are no approved medications for use against tapeworms, so controlling the intermedi- ate hosts of tapeworms is vital in preventing initial infections and reducing the risk of reinfection. The impacts of worm infestations
• Reduced vitality, poor body weight gain leading to unevenness or stunted birds, reduced egg pro- duction and egg size, de- crease in shell strength and reduced yolk colour.
• Affected birds may be dull and show pale combs. • Increased cannibalism through vent pecking due
to straining.
• Death, in very heavy
infestations.
Treatment options
There are only two an- thelmintics (drugs for
intestinal worm control) currently registered for use in Australia – pipera- zine and levamisole.
Each of these is suit- able for use in laying birds with no withholding peri- od for eggs, while levami- sole has a seven-day with- holding period for meat.
There are some funda- mental differences between these two products – pip- erazine only has activity against roundworms, not hairworms, caecal worms or tapeworms.
Levamisole on the other hand is effective against round, caecal and hair- worms.
It is wise to rotate be- tween the two types of anthelmintics to reduce the risk of resistance de- velopment.
However there are limi- tations – there are no products registered for use in poultry in Aus- tralia for the control of tapeworms, so controlling the intermediate hosts of tapeworms is vital in pre- venting initial infections and reducing the risk of reinfection.
There are also no prod- ucts registered for the control of blackhead, so it becomes even more im- portant to control its inter- mediate host, the caecal worm.
Effective control of in- testinal parasites is aimed at breaking the cycle of infection.
Strategic use of anthel- mintics during rearing will help to reduce chal- lenge, and giving a pro- phylactic treatment before moving hens from rear- ing to production sheds will assist in breaking the infection cycle, but this needs to be combined with other good manage- ment practices such as limiting stock density on the range, rotation of the range, good drainage, and the removal of heavily contaminated soil around the shed before new pul- lets arrive.
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Hairworms.
Caecal worm.
Tapeworm.
Page 6 – National Poultry Newspaper, April 2019
www.poultrynews.com.au

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