Flukes are flat "worms" with a leaf-shaped outline, somewhat like a plaice or other flat fish (to which the name of fluke is also given). Some species are roughly cylindrical in shape. Parasitic flukes range from 3 to 25 mm. or more in length and may be 2 to 10 times longer than they are broad. The mouth is near the anterior end and usually surrounded by a sucker. A second sucker may be present on the ventral surface. Flukes feed on body fluids and in most species after digestion, the waste products are passed out of the mouth owing to the absence of an anus. Both male and female organs are present in the majority, although blood flukes are not hermaphroditic.
Most flukes (blood flukes being an exception) require two intermediate hosts for their development, the first of which must be a mollusk. The other intermediate host is usually a cold-blooded creature such as another type of invertebrate, but sometimes a fish. Birds become infested by eating the second intermediate hosts, or in the case of blood flukes by being attacked whilst in water by stages of the parasite released from infected mollusks. Flukes require moisture and warmth, and when in the intermediate host, occasional periods of dryness to stimulate reproduction. A few flourish fairly well in temperate climates, but most rapid development occurs in warm, and especially tropical areas, this being the case with many disease-producing organisms.
Clinical signs can vary considerably, ranging from general malaise, lack of appetite, thirst and diarrhea to anemia or jaundice. When the parasites infest the rectum and cloaca, they may interfere with egg laying. Flukes in the respiratory tract can cause asphyxia. A heavy burden such as the presence of several hundred causing obstruction in the gut or in a duct may kill the host. Flukes are regional in their distribution and if birds live in an area where they are known to occur, or if birds are acquired which have been recently obtained from the wild, samples of the excreta should be submitted to a suitable laboratory or veterinarian for examination. Diagnosis depends upon finding the typical fluke eggs in the droppings or flukes in the gut, liver, or other internal organs upon post-mortem examination, because clinical signs are never diagnostic in themselves.
Treatment and control:
Flukes are well known to farmers and are common in cattle and sheep. In these animals control is effected more by removing the possibility of re-infestation than by treatment of infested animals, and in birds the same principles apply. Shady, muddy puddles and other suitable habitats for water snails should be avoided in aviaries. A copper sulphate dressing if used in a planted aviary will kill most mollusks, but it is somewhat toxic to the birds. A heavy shower of rain or the use of a water-can will help to wash the dressing down to the grass roots and to reach the snails. Treatment of individuals using carbon tetrachloride, tetrachlorethylene, or hexachlorethane, although suitable for farm animals, is extremely toxic to birds and liable to kill them more quickly than the flukes themselves.
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Hamilton & District Budgerigar Society Inc.