Fig (XII)
12.
Trichostrongylus pergracilis. Eggs showing different stages of development, leading up to the production of the fully formed larva, seen issuing from the egg in the last figure. obvious that the whole of the grouse moor must be peppered over with countless millions of these young larvæ, which, by a method I suggested two years ago, can readily be separated from the heather on which they live. We shall return later to the pathological conditions set up by the presence of these worms. They obviously pass directly into their host, and do not pass through the body of any other animal. 13. Syngamus trachealis. -The red-or forked-worm, which is so terrible a pest in the fowl-yard and pheasant hatcheries, has been found once or twice in the grouse, [GROUSE but it is quite negligible from the point of view of the disease. Probably the absence of earth-worms in the peaty soil of the moors largely accounts for the rarity of this parasite in the trachea of the grouse.
Family. TRICHOTRACHELIDÆ. 14. Trichosoma longicolle. This worm, allied to the ordinary whip-worm in man, occurs comparatively frequently, but in small numbers. It is always found in the duodenum frequently associated with Hymenolepis tetraonis. It may also serve to break the continuity of the mucosa of the alimentary canal, and thus set up trouble. But its presence is not associated with any serious lesions.
Family. ASCARIDE. 15. Heterakis papillosa. - This common parasite of poultry and pheasants occurred in some of the hand-reared birds at Frimley, but it has not been found in the wild specimens.
Family. FILARIDÆ. 16. Filaria smithi. - A larval form of some species of Filaria has been discovered by Dr. Sambon in the blood of the grouse.
As far as one knows at present, it causes little or no damage.
PROTOZOA (Unicellular animals). 17. Amœba lagopodis (new species).-A species of amœba has been found both in the droppings and in the rectum. There is no reason to believe that this animal sets up any such disease as "black-head" common in turkeys, which was once attributed to amœbæ, and is known to be caused by a coccidium. 18. Monocystis sp.-On three occasions Dr. Fantham found the spores of a Monocystis sp., possibly one of the species that inhabit the earth-worm; they seem to cause no harm. 19. Leucocytozoön lovati. -This species has been found by Dr. Seligman, Dr.
Sambon, and Dr. Fantham in smears from the blood of two or three birds. The degree of infection was slight. 20. Hæmoproteus mansoni. This parasite has again been recorded from the blood corpuscles of the grouse, and Dr. Sambon thinks that its alternate host may be the grouse-fly. 21. Eimeria (Coccidium) avium. This dangerous parasite is considered below under the heading "Coccidiosis." 22. Trichomonas eberthi. - This minute GROUSE] flagellate lives in the cæca and intestines of apparently healthy birds. It is common in fowls. 23. Monocercomonas sp. Forms of Monocercomonas were also seen in the cæca of grouse. They were not found in large numbers. 24. Spirochata lagopodis, n. sp. This parasite was found by Dr. Fantham in small numbers in the blood of three birds. It caused a slight alteration in the relative constituents of the blood of the birds, but was not associated with any specific disease. 25. Spirochata lovati, n. sp.-This Spirochæta was seen alive and in stained specimens by Dr. Fantham. It occurred in the cæca and intestine of several of the many birds examined, and was not especially associated with disease. As far as the Grouse Inquiry have at present published their results, it seems that the grouse suffer from two very definite diseases-the first associated with the presence of Coccidia in the duodenum and cæca, and the second with the presence of Trichostrongylus pergracilis in the cæca, and to a lesser degree with Hymenolepis in the duodenum.
COCCIDIOSIS.1 Dealing first with Coccidiosis :- One of the aims of grouse-preservers is to have numbers of healthy young grousechicks in order to produce stocks of strong birds. Bad seasons for grouse are partly due to epizoödics among the young broods in the spring, and the chief cause of mortality among grouse-chicks is a small, onecelled microscopic animal parasite, Eimeria (Coccidium) avium. This parasite penetrates the lining membrane of the gut of the bird (Fig. 14), and gradually destroys it, thereby setting up digestive troubles in the form of intestinal inflammation (enteritis), accompanied by acute diarrhea, which usually terminates fatally. The disease is termed Coccidiosis. Grouse-chicks are most susceptible to coccidiosis during the first six weeks of their life, and if they can survive this period unattacked, they usually reach adult life.
The principal external symptom of coccidiosis is diarrhea, which is especially seen in the character of the cæcal (soft) droppings. These droppings in some cases are very pale yellow in colour, and are much looser than those of healthy grouse. When a small quantity of infected droppings is 1 This section is contributed by Dr. Fantham.
VOL. II diluted with water and examined under the microscope, numbers of oval, thick-walled cysts (Fig. 13) containing spores of the parasite can be seen. Frequently in fresh A D