Written by Dr. Grant Richards – Allfarm Animal Health (Hastings, Victoria).
Everyone seems to have heard of gapeworm. The main reason is that when you internet search “poultry respiratory disease” or “difficulty breathing” (or related terms) the Search Engines quickly tell you about Gape Worm.
Gapeworm – or Syngamus trachea in Latin – when translated, loosely means ‘together in the wind pipe’. It is also the scientific name for gapeworm.
This parasite will infect chickens, turkeys, guinea fowl, pheasants, peafowl and quail. There is a similar worm that affects geese, Cyathostoma brochialis, but this one is different.
With gapeworm the males and females are intertwined most of the time and the males are permanently attached. On post mortem the worms are easily seen in the trachea (wind pipe). The presence of the worms causes irritation to the tracheal lining. Because the Search Engines say it’s important, it is – isn’t it? In 30 years plus of poultry post mortems I can not tell you have many tracheas I have cut open, and I have never seen one. However, I have lost count of the number of times I have seen the symptoms described on the computer in sick, gasping birds. This article will provide some sane background for you.
Mode of Infections
Eggs are laid by the female worm in the trachea whereby they are coughed up and then swallowed, exiting via the intestines in the faeces. The eggs take two weeks to develop and become infective. A snail, earthworm or another bird may eat the infective eggs. Both snails and earthworms can harbour an intermediate stage of this parasite for years. The infective larvae hatches very quickly after the infective eggs have been eaten and gets into the bloodstream of the bird, whence it makes a beeline for the liver and then lungs. The larvae grow in the lungs for a short time before emerging into the small air passages of the lungs. Here they seek and find a partner and start to lay eggs. The cycle is complete.
Symptoms of Infection
The damage in the lungs by large infections will cause signs of respiratory disease. The presence of the worms in the trachea will cause coughing and sneezing. If there is a shortage of air the bird will adopt a typical stance with the head out, beak open and breathing in a laboured manner. Infected birds also stand with eyes closed, are skinny and weak, and look sick.
This parasite does not show any respect for a particular age group and so any livestock on the ground are fair game. The younger the bird, the more severe the impact from infection. This is simply due to the smaller diameter of the trachea: smaller ones are easier to block with a worm or two and some inflammation.
Wild birds or anything that eats earthworms can carry the parasite around. This means that any area that was once free of gapeworms can become infected due to a wild bird defecating eggs into a pen.
Consider Similar Conditions
Before panicking and assuming all heavy breathing is a sign of gapeworm, think again. Heavy breathing is a symptom of some sort of respiratory infection. Gapeworm is probably not very common in Australia in chickens. Your birds’ heavy breathing could be from another cause entirely. These characteristic symptoms can also be found in the following diseases and conditions:
- Fungal infection in lungs (Aspergillus).
- Mycoplasma infection with secondary bacterial infection (chronic respiratory disease).
- Infectious laryngotracheitis (ILT) acute and chronic stages.
- Dust irritation.
- Air sac mites.
- Ammonia burn due to low levels of ventilation.
- Upper respiratory tract bacterial infection.
- Infectious coryza.
- Cholera – acute.
- Wet forms of fowl pox.
- Chronic Vitamin A deficiency.
Confirming Gapeworm Infection
If you think you have a gapeworm issue then the first step is to ensure there is a proper postmortem carried out. This needs to be detailed and the lower areas of the bronchi need careful examination or even histology sections. It is important to locate the worms.
Sick birds should be euthanased and deep-frozen. Lungs deteriorate rapidly after death and so freezing will protect this deterioration and improve the chances of finding the minute male worms, the intermediate stages and any bigger, more easily seen, females. Some labs do not like having frozen samples, but in this instance it is worthwhile. Air sacs deteriorate quickly and so also ask the lab to check for air sac mites using some direct smears of the air sac membranes.
Caecal Samples Important
You should also collect faecal samples from birds showing respiratory signs and have these carefully examined for the presence of parasite eggs. Syngamus tracea eggs have a characteristic shape. When collecting samples for caecal analysis it is critical that two sets of samples are obtained, one with standard faecal samples and the second , in a separate container, containing brown caecal samples (caramel coloured runny poo). These latter are important to eliminate Heterakis eggs and improve the diagnosis, because the eggs look similar.
It is unlikely that if the infection is present only one chicken will have the adult worms present. The bottom line is look and eliminate options from the list above. Time taken collecting the correct samples and from birds showing any symptoms is always worthwhile. Send the samples to a lab that specialises in poultry samples (like Para-site Diagnostic Services – free sample kits for testing can be accessed here) and specify that you are looking for Gapeworm eggs. Their results will also give you an idea of other worms present, such as Large white roundworms or Capillaria or tapeworms. You may need to sample several times because there is little information on how many eggs adults lay.
Some thought is required on the rare diagnosis of gapeworm. There is some similarity between the life cycles of gapeworm and that of lungworms in cattle, sheep and goats. Therefore, the best treatments will be those that specifically detail on the label that they have claim against lungworms.
The anthelmintics required will need to have a systemic effect. One good compound would be Ivermectin, and some the benximidazoles (white drenches) are also suitable.
There is no information either as to the older birds becoming immune or if they develop a tolerance. I suspect they do, and probably an immune response.
Following a positive diagnosis, you will need to be aware that they eggs will infect the environment and so an ongoing regime may be required. As with all drench programs , test efficacy 14 days post treatment. Retest; make sure it has worked.
Much more information is required to sort this parasite out. I would be interested in hearing from any poultry keepers where the presence of this worm has been confirmed or who are suspicious that this worm may be present in their birds.
Published by Australasian Poultry Magazine.
Written and reproduced with permission Dr Grant Richards, Allfarm Animal Health (Hastings, Victoria).
Copyright 2019 – Grant Richards