Trichostrongylus tenuis
Encyclopedia
Trichostrongylus tenuis, also known as the strongyle worm, is a gut nematode
found in the United Kingdom
, sensitive to Pyrantel pamoate
. Larva
e have a short migration inside the mucosa of the intestine and return quickly to the digestive tract.
This endoparasite causes a condition often called strongylosis or 'grouse disease' and which can be the cause of regular crashes in grouse
populations. When the adult worm burrows into the caeca
walls it causes a lot of damage and internal bleeding which in itself is harmful to the grouse. The worms ultimately reduce the digestive efficiency thus affecting the condition of the grouse.
The eggs of the strongyle worm found in the caecal droppings of Red Grouse
, hatch out into a microscopic larvae
stage. Living within the dropping they feed off bacteria
and organic matter they develop through two moult
s reaching their third larval stage, 'L3'. The 'L3' larvae is now at its infective stage so it 'swims' up heather
stalks, on a thin film of liquid, to the young shoots where it is most likely to be ingested by a host. Once in the body of a host they enter one of the two caecum in the intestine of the host where the larvae develop into adult worms. The adults mate within the caeca and the female can lay over 100 eggs a day which are passed out in the caecal dropping.
The development of the parasite can vary greatly depending on the conditions, namely temperature and humidity. The eggs and larvae can both tolerate periods of low temperature but neither can survive in hot and dry weather. In perfect conditions with high humidity and temperatures exceeding 15 °C most eggs will hatch within 24 hours, compared with at 5°C where the eggs may take several days to hatch out. The larvae can remain active above 6 °C with relative humidity but when it is colder they halt their development but stay alive. With the climate changing as it is the worms find tolerable conditions for much of the year but they are picked up by grouse at two main periods of the year. The grouse may ingest infective larvae from the heather tips in the summer and early spring. During autumn and winter not all ingested 'L3' larvae will develop in to adults, the larvae may begin to moult and temporarily halt their development and attach themselves to the caecum wall, they are said to be in an 'arrested' state. The larvae over-winter in the bird's intestine and in March/April when conditions are more favourable they resume their development.
With some other parasites young birds play host to more of the parasites than adults, as the adults develop immunity to the parasites but not in the case of the strongyle worm. With age the worm burden in grouse generally increases as and each worm in the intestine of the grouse has to be individually ingested and the adult birds appear to have little resistance to the parasite. The burden of worms is obtained when the birds feed on heather and the young birds feed mainly on insects, for this reason this parasite has little direct bearing on chick survival but can badly affect adults and immature birds.
High worm burdens in grouse can lead to mortality and poor condition leading to easy predation and poor reproduction. The strongyle worm burrows into the caecal mucosa which affects the bird's ability to control the scent it emits making them particularly susceptible to mammalian predators who hunt using scent. High burden leading to poor condition of the hen grouse may not affect the clutch size but can affect her ability to incubate the eggs or brood the chicks so this parasite may indirectly affect chick mortality.
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
found in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, sensitive to Pyrantel pamoate
Pyrantel pamoate
Pyrantel pamoate or Pyrantel Embonate , is used as a deworming agent in the treatment of hookworms and roundworms in domesticated animals such as horses, cattle, sheep, pigs, cats, dogs, and many other species. It is a combination of pyrantel and pamoic acid...
. Larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e have a short migration inside the mucosa of the intestine and return quickly to the digestive tract.
This endoparasite causes a condition often called strongylosis or 'grouse disease' and which can be the cause of regular crashes in grouse
Grouse
Grouse are a group of birds from the order Galliformes. They are sometimes considered a family Tetraonidae, though the American Ornithologists' Union and many others include grouse as a subfamily Tetraoninae in the family Phasianidae...
populations. When the adult worm burrows into the caeca
Cecum
The cecum or caecum is a pouch, connecting the ileum with the ascending colon of the large intestine. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine. It is also separated from the colon by the cecocolic...
walls it causes a lot of damage and internal bleeding which in itself is harmful to the grouse. The worms ultimately reduce the digestive efficiency thus affecting the condition of the grouse.
The eggs of the strongyle worm found in the caecal droppings of Red Grouse
Red grouse
The Red Grouse is a medium sized bird of the grouse family which is found in heather moorland in Great Britain and Ireland. It is usually classified as a subspecies of the Willow Grouse but is sometimes considered to be a separate species Lagopus scoticus...
, hatch out into a microscopic larvae
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
stage. Living within the dropping they feed off bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
and organic matter they develop through two moult
Moult
In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...
s reaching their third larval stage, 'L3'. The 'L3' larvae is now at its infective stage so it 'swims' up heather
Calluna
Calluna vulgaris is the sole species in the genus Calluna in the family Ericaceae. It is a low-growing perennial shrub growing to tall, or rarely to and taller, and is found widely in Europe and Asia Minor on acidic soils in open sunny situations and in moderate shade...
stalks, on a thin film of liquid, to the young shoots where it is most likely to be ingested by a host. Once in the body of a host they enter one of the two caecum in the intestine of the host where the larvae develop into adult worms. The adults mate within the caeca and the female can lay over 100 eggs a day which are passed out in the caecal dropping.
The development of the parasite can vary greatly depending on the conditions, namely temperature and humidity. The eggs and larvae can both tolerate periods of low temperature but neither can survive in hot and dry weather. In perfect conditions with high humidity and temperatures exceeding 15 °C most eggs will hatch within 24 hours, compared with at 5°C where the eggs may take several days to hatch out. The larvae can remain active above 6 °C with relative humidity but when it is colder they halt their development but stay alive. With the climate changing as it is the worms find tolerable conditions for much of the year but they are picked up by grouse at two main periods of the year. The grouse may ingest infective larvae from the heather tips in the summer and early spring. During autumn and winter not all ingested 'L3' larvae will develop in to adults, the larvae may begin to moult and temporarily halt their development and attach themselves to the caecum wall, they are said to be in an 'arrested' state. The larvae over-winter in the bird's intestine and in March/April when conditions are more favourable they resume their development.
With some other parasites young birds play host to more of the parasites than adults, as the adults develop immunity to the parasites but not in the case of the strongyle worm. With age the worm burden in grouse generally increases as and each worm in the intestine of the grouse has to be individually ingested and the adult birds appear to have little resistance to the parasite. The burden of worms is obtained when the birds feed on heather and the young birds feed mainly on insects, for this reason this parasite has little direct bearing on chick survival but can badly affect adults and immature birds.
High worm burdens in grouse can lead to mortality and poor condition leading to easy predation and poor reproduction. The strongyle worm burrows into the caecal mucosa which affects the bird's ability to control the scent it emits making them particularly susceptible to mammalian predators who hunt using scent. High burden leading to poor condition of the hen grouse may not affect the clutch size but can affect her ability to incubate the eggs or brood the chicks so this parasite may indirectly affect chick mortality.