Worm control in backyard poultry

Worm control in backyard poultryWorm control in backyard poultry
Author : Alastair Johnston
Date : November 28, 2011
Alastair Johnston examines worm species that infest fowl, game, wild and water birds and looks at diagnosis, treatment and prevention of conditions
Summary
The general signs associated with worm infections are discussed, including unthriftiness, diarrhoea, drops in egg production and mortality. The main worms affecting poultry are Syngamus, Ascaridia, Capillaria, Amidostomum and Raillietina species. All of these can be more prevalent on freerange poultry units. Syngamus trachea can cause dyspnoea or mortality if the trachea becomes blocked. Ascarids rarely cause disease, however, Capillaria infection can lead to poor performance, including egg production drops. Heterakis is the host for the microscopic organism, Histomonas meleagridis, which causes blackhead in free-range chickens and turkeys. Tapeworms can cause problems in young chickens, but do not usually cause severe disease.
Diagnosis is based on a combination of clinical signs in the flock, examination of worm eggs in faeces and the presence of adult worm stages during postmortem examination of birds that have died from infection or were culled. Techniques of preventing worm infection include removal of faeces from housing and the range areas, harrowing of the range area and a good disinfection procedure in the area within and around the poultry house.
The products utilising flubendazole (including dose rates), which are licensed for use in poultry, including in-feed formulations and drinking water applications, are listed. Application methods are also discussed.
Key words
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unthriftiness, nematodes, range management, worm egg counts, flubendazole
IN the past few years, keeping poultry in gardens as pets or as part of a larger group on smallholdings has increased dramatically in the UK.
Television has contributed to a growing interest in the home production of eggs and birds for future meat production. This has led to an increase in the occurrence of birds presented to mixed or small animal practitioners, with signs of diseases resulting from this extensive rearing system.
Parasitic infections, including those resulting from worm infestations, are becoming much more prevalent in backyard flocks and are now one of the more common diagnoses to consider when presented with unthrifty birds at the surgery.
Clinical signs of parasitism due to worm infestations are:
• general unthriftiness;
• diarrhoea;
• death in severe cases.
Furthermore, these parasites can make the flock more susceptible to other diseases, such as viral challenge. Often we see worm build-up in flocks where other problems have been ongoing.
The types of worms that affect poultry health are:
• Nematode (respiratory)
– Amidostomum anseris (gizzard worm);
Syngamus trachea
Syngamus tracheaaffects chickens, turkeys and game birds – causing the condition known as gapes. A related worm, Cyathostoma bronchialis, causes a similar condition in geese.
Syngamus parasitises the trachea of a large selection of wild, as well as domestic, birds. Hence, it is common for the infection to appear in free-range chickens that are, potentially, in close contact with wild birds.
Clinical signs of gasping result from dyspnoea, due to physical blockage of the airway. Birds tend to stand with outstretched necks and open mouths (Figure 1). In more chronic infections this can lead to severe loss of condition. High rates of mortality can be experienced with this infection. Adult worms can easily be spotted on the internal mucosal surface of the trachea at postmortem examination (Figure 2).
The life cycle of the gapeworm most frequently involves the earthworm, although it can also have a direct life cycle. The nematode can survive for up to four years in earthworms. Hence, the disease is not common in poultry reared on impervious floors.
Ascaridia galli
Ascaridia galli are the largest nematodes found in poultry. Adult worms live in the lumen of the small intestine and grow up to 12cm long. Thus, they are easily visible at postmortem examination (Figure 3). The larval stages can invade the mucosa, leading to enteritis. Clinical signs include illthrift and loose abnormal droppings, especially in younger, growing birds, although, on rare occasions of very heavy infestation, the worms can totally block the intestine and lead to mortality. The life cycle is direct, involving the ingestion of eggs from pasture and straightforward development through larval stages into adult worms.
Heterakis gallinarum
The caecal worm, Heterakis gallinarum, rarely causes direct problems in chickens or turkeys, which are its main hosts. At approximately 1cm to 2cm in length these adult worms are visible to the
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naked eye in the host’s caecal contents.
The main economic effect of Heterakis infection lies in its role as a carrier of protozoan parasite Histomonas meleagridis. This organism can cause high levels of mortality in domestic turkeys and free-range hens – a condition known as blackhead.
Earthworms can ingest the caecal worm egg containing the histomonad organism from droppings on the ranging area, or sometimes from litter areas on the periphery of free-range hen or turkey houses. Ingestion of the earthworms by turkeys or chickens will then infect the primary hosts. The caecal worm egg containing the histomonad organism can also be ingested directly by the turkey or hen. Thus, one should not house chickens and turkeys together. Allowing turkeys to range on pasture that chickens have previously occupied will increase the risk of infection.
Capillaria
While Capillaria species is the most difficult worm to spot in poultry intestine at the postmortem examination it can cause the most severe pathogenic effects in a flock.
Different species will infect different types of poultry and involve either intermediate hosts or have a direct life cycle (Table 1). Probably the most common is C obsignata and it can cause disease in both free-range and housed flocks when present in higher numbers. These worms cause haemorrhage and thickening of the intestinal walls, leading to poor absorption of nutrients and, therefore, stunted growth. Signs of diarrhoea, weakness and a drop in egg production have also been reported in infected flocks.
Amidostomum anseris
Amidostomum anseris is the most important nematode in geese and can cause severe disease in goslings, include anorexia, anaemia, emaciation and death. The worm parasitises the gizzard and this is where it causes erosions.
Other worms
Trichostrongylus tenuis can infect the caeca of a variety of domestic poultry and wild birds. T tenuis is an important pathogen of grouse and has been reported as causing disease in goslings.
Tapeworms
A large number of cestode species have been recognised as infecting birds, both in the wild and domestically. Most appear to be of low pathogenicity and, therefore, are of negligible importance in commercial poultry flocks. However, they require intermediate hosts, such as earthworms, slugs,
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snails and insects, to complete the life cycle and, therefore, may be more of a problem in smaller backyard flocks.
Raillietina cesticullus seems to be one of the most pathogenic of tapeworms infecting poultry – developing up to 15cm long. Principally, it infects chickens, and, in heavy infestations, causes weight loss. R cesticullus tends to lead to more problems in younger chickens (under 10 weeks old).
Diagnosis
Weight loss and general unthriftiness in a backyard flock would suggest a build-up of worms might be included in the differential diagnoses.
Identifying adult worms of the Ascarid and Heterakis species during the postmortem examination of birds that have died with worm infestations is straightforward. Capillaria species can be more difficult to spot and careful examination of mucosal washings under a dissecting microscope may be the only way to identify adult worms in the intestine.
The identification of worm eggs from faecal samples under a conventional microscope is relatively easy (Thienpont et al, 2003).
It is important to select a representative sample of faeces from the living areas of backyard poultry. These should be relatively fresh as preventing the sample becoming too dried out before examination in the laboratory is also important.
The interpretation of worm egg count results will depend on the type of housing system and environment for the poultry. As a rule of thumb, the following counts can be considered to be the maximum acceptable levels:
• Ascarid species – 5,000 eggs per gram faeces;
• Heterakis species – 1,000 eggs per gram faeces; and
• Capillaria species – zero eggs per gram faeces.
Testing faeces of birds about to enter a flock can be very useful in establishing the risk that may be encountered. This can be carried out during a quarantine period on the smallholding or prior to arrival on the unit.
Infection treatment and prevention
Management practices and stocking rates will have a huge impact on the levels of worm
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infestations affecting backyard poultry flocks. The build-up of worms can occur if little attention is paid by owners to basic hygiene practices over a prolonged period. Cleaning the inside of poultry housing, especially the floor areas, can help reduce worm burdens in flocks as well as other bacterial and viral diseases.
Most disinfectants commonly used in poultry housing have some degree of activity against worm eggs. Dehydrating agents are also effective in acting as a desiccant in poultry houses, on scratching areas and in close vicinity to the living area.
Regularly removing faecal material from scratching areas and the range is very important to reduce further challenge in the flock. We must also remember that exposing the faecal matter – and, therefore, worm egg and larval stages – to sunlight, is a very effective way of reducing infective burdens on the ground. Thus, a basic harrowing of the range with a rake or similar implement is very important. Moving drinkers and feeders around the range area will help reduce poaching of the ground and also the build-up of worm eggs in the vicinity.
A number of licensed products for treating worms in domestic poultry are available and all have flubendazole as their active ingredient. These are listed in Table 2. The egg withdrawal period for all these products in chickens is zero.
The normal treatment time for all these products is seven consecutive days. After three weeks it may be necessary to repeat the seven-day treatment on sites suspected to have a build-up of worm eggs. The in-feed five per cent formulation and two-and-a-half per cent in 2.4kg bags and 240g tubs are licensed for inclusion at the feed mill. These are generally used when medicating large volumes of poultry feed and need a veterinary medicated feed script prior to incorporation into the feed. A 60g tub of one per cent premixture is designed to be incorporated into smaller volumes of feed and could be suitable for use in backyard flocks of poultry. In this circumstance, care must be taken to mix the medication well with the feed and ensure an even spread throughout the batch. Mixing the required volume of medication, initially into a cupful of feed, followed by mixing into progressively larger volumes of feed, does help to ensure an even spread. Inclusion of cooking oil into the feed can also help bind the powder to the feed material so the powdered medication does not drop to the bottom of the feeder.
Mixing the emulsion form of flubendazole in drinking water is more straightforward, but ensure the product is evenly distributed throughout the drinking water container.
Reference
Thienpont D, Rochette F and Vanparijs O F J (2003). Diagnosing Helminthiasis Through Coprological Examination (3rd edn), Janssen Animal Health.
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