Common worm parasites in pet birds include roundworms (e.g. Ascarids and Heterakis), Capillaria, strongyles, tapeworms and spiruroids (gizzard worms). Tape worms and spiruroids have an indirect lifecycle with a variety of beetles and insects acting as intermediate hosts and birds becoming infected by eating infected beetles or insects. Roundworms typically have a direct life cycle with birds becoming infected by eating worm eggs passed in the droppings of an already infected bird. Capillaria eggs may be transported by earthworms but earthworms are not essential and their life cycle may be direct, i.e. birds become infected by ingesting worm eggs from the droppings of other birds. With strongyles, worm eggs passed in the droppings hatch into larvae which climb onto plant material and are eaten by other birds that become infected.
Symptoms of Worm Infestation
Depending on the type of worm and species of birds affected, birds may show malabsorption, diarrhoea, vomiting, blood in the droppings or poor health. In birds with heavy worm burdens the abdomen may be swollen but the bird is typically emaciated, in extreme cases the muscle mass around the keel bone is much reduced, a condition described as ‘hatchet breast’. Death from intestinal blockage or rupture is possible in birds with heavy worm burdens, especially in young birds that have poor immunity.
The three main species areA. galli, which affects poultry, pigeons and parrots, A. columbae that affects pigeons and parrots and A. platyceri, which is restricted to parrots. Round worm eggs are thick shelled and can survive in the environment for many months. Infection occurs via ingestion of worm eggs containing larvae. The larvae are digested free from their eggs and the burrow into the intestinal lining causing discomfort and possible diarrhoea. It take around 3 weeks from the time a bird ingests round worm eggs until they complete their life cycle, the adults mature and are capable of laying eggs which are passed in the bird’s droppings.
Birds most at risk of serious disease are young birds that have just fledged and are feeding on the ground where adult birds have passed droppings with worm eggs. Adult birds will generally have some immunity to keep worm numbers in check but young birds generally have poor immunity and may become infected with overwhelming numbers worms which can cause intestinal blockage, a life threatening complication of disease.
Heterakis is a type of roundworm that lives in the caeca (equivalent to the human appendix) in chickens, pheasants, peacocks and related gallinaceous birds. In general Heterakis worm species don’t cause disease on their own but they can carry an amoeba-like organism Histomonas meeagridis which causes ‘Black Head’.
Commonly known as “Hair-worms”, these thin little worms burrow deep into the lining of the small intestine and oesophagus causing ulcers. There are a variety of species each affecting different species of birds, all of which cause serious disease. Like roundworms Capillaria worms have a direct life cycle and birds are affected by eating soil or other objects contaminated with droppings of infected birds. Earthworms can act as carriers.
These are flat, segmented worms that typically pass their eggs by shedding egg-containing segments (‘proglottids’) from their tail end. These segments are large enough to be seen with the naked eye but are only passed intermittently so it may be difficult to identify tapeworm eggs microscopically in bird’s droppings unless a proglottid has ruptured. The life cycle is indirect and a range of insect and invertebrates serve as intermediate hosts. A variety of different but related tapeworm species with different intermediate hosts are found in different species of birds, including chickens, finches, cockatoos and parrots.
In most cases tapeworms are not very pathogenic and cause only mild ill-health or loose droppings. The exception is with insectivorous finches, such as parrot finches, where it is not unusual for tapeworms to cause intestinal blockage and death.
Spiruroids – Eye, gizzard and stomach worms
These are a diverse group of worms that live mainly in the crop, proventriculus gizzard and eye and cause a range of disease, the severity of which depends on the species of worm. They have an indirect life cycle with a variety of insects and beetles acting as intermediate hosts.
Eye worms (Oxyspirura sp) live under the eyelids of cockatoos and can cause irritation and conjunctivitis. The intermediate host is the cockroach
Gizzard worms (Acuaria skrjabini) are most commonly seen in finches where they burrow under the hard koilin lining of the ventriculus (the gizzard) where grit is stored to help grind and digest seed. With heavy infestations the distended gizzard can be felt as a hard lump under the skin in the upper abdomen. Ill health and death can occur in badly affected birds. Acuaria spiralis, a species affecting chickens, burrows deeply into the proventriculus resulting in ulcer formation, heavy infestations can be fatal. Gongylonema ingluvicola affects the crop of fowls and can cause regurgitation.
Syngamus or Gape worms
Gape Worm (Syngamus trachea) is a fascinating parasite that we most commonly encounter at Bird Vet Melbourne in wild baby Blackbirds and in chickens but it can be found in a wide variety of species. It lives in the lining of trachea (wind pipe) and the bronchi, with the smaller male worm remaining continually attached to the larger female in a Y configuration. It causes head shaking, coughing, ‘gapping’ and respiratory distress. Deaths can occur in severe cases. Eggs are passed intermittently in the droppings.
Treating and Preventing Worm Parasites.
With any bird disease whether an individual bird will become sick depends on how nasty and prevalent the pathogen is, how good or poor the bird’s immune system is and the environmental conditions in which the bird lives. Drugs alone are not the answer to disease. Especially with worm parasites, it is important to understand the life cycle of the worm and stop your birds from getting access to more worm eggs, ensure your birds are in good physical condition and that the environment in which they are living is healthy.
Common drugs used to kill adult worms include levamisole (brand names include Avitrol and Nilverm), ivermectin (Ivomec) and moxidectin (Cydectin) for roundworms, Capillaria, spiruroids and gape worm. Praziquantel is used for tapeworms. These drugs (and other worming preparations) come in different formulations and strengths and recommendations for treatment may vary between species. They should be used according to the manufacturer’s recommendations or specific veterinary advice sought. Resistant strains of worms are sometimes encountered, especially with Capillaria, and change of medication may be required.
Care must be taken in treating birds with heavy worm burdens as death may occur if all the worms are killed at once and intestinal or respiratory blockage occurs. In very sick birds it may be prudent to initially treat with half the normal dose of worming medication and give supportive treatment with crop feeding etc. Some days later, when some of the worm burden has been reduced and the bird’s condition is better, repeat the worming using a full dose.
Understanding the life cycle of worm parasites is a key to their treatment and control as no medication will stop a bird from picking up an infected worm egg and starting the cycle over again. Disinfectants do not kill worm eggs. The environment should be thoroughly cleaned and litter removed and changed at the same time as worming is taking place. Compost heaps should be removed to control infected intermediate hosts. Worming should be repeated on at least three occasions at three weekly intervals to try to break the life cycle. Regular worming should be carried out every 3 months in aviary birds or birds, such as free- range chickens that have contact with wild birds.