This disease is prevalent in cattle in whom it was first recognized as parasitic by Bollinger. It has been observed in man in a considerable number of cases.
As the name implies, the disease is due to a microbe, whose botanical position and life-history have not been fully made out. It consists of short threads, arranged in a radiating fashion, many springing from a common centre. The threads are usually clubbed at their outer extremities, but they are not always so. They are united in the centre of the clump by a matted mass of fibres. The little masses thus form peculiar radiating bodies of a globular or oval form, having a somewhat glandular aspect. From the radiating arrangement the fungus is called the Ray-fungus or Actinomyces , a ray). The individual clumps are of very small size, not visible to the naked eye, but they may be united into larger masses as the heads in a cauliflower. These larger masses appear as small yellow sulphur-coloured grains in the discharges and new-formations, giving the characteristic indications of the disease.
Whether in animals or man each fungus-head constitutes a centre of irritation, and granulation tissue forms around it. By coalescence there are formed bulky masses of granulation tissue. There is no tendency to caseation, but rather to formation of pus on the one hand and cicatricial tissue on the other. The disease usually presents itself in cattle in the form of bulky round tumours, which are mostly in the neighbourhood of the jaws, but may be in any part of the body. These tumours usually contain a yellow pus in which, and in the granulation tissue which lines them, the fungus-heads are found. In man there is a more extended formation of granulation tissue, and more of a suppurative character.
In Actinomycosis of the face and neck, the fungus has obtained entrance by breach of surface in the mouth, usually in connection with carious teeth, so that the commencement is usually in connection with the jaw. There is a formation of granulation tissue around the jaw, usually the inferior maxilla, extending to parts around. The process is a chronic one, and by degrees the lesion extends to the surface. Abscesses form which discharge and leave fistulous openings. Sometimes the new-formation extends to the vertebrae or base of the skull, especially when the upper jaw has been the starting point.
The respiratory organs may be the primary seat. There may be a superficial actinomycosis, producing simply a suppurative bronchitis. More usually the fungus is in the substance of the lung, giving rise to chronic condensations and indurations, in isolated patches. These enlarge and coalesce, and they often break down so as to form cavities. The process is a chronic one and somewhat resembles that in phthisis pulmonalis, but differs in respect that it does not usually attack the apices of the lungs. The disease is apt to involve the pleura and the neighbouring pericardium. It not infrequently extends to the bodies of the vertebrae, causing them to become carious. There is here a slow inflammatory process with exuberant granulations and suppuration. The abscess may reach the surface by a course similar to that of a tubercular abscess of bone.
The alimentary canal is more rarely the primary seat of actinomycosis. There are nodules and ulcers formed and the" disease extends to the peritoneum, leading to the formation of granulation tissue and abscesses in the cavity of the peritoneum. There may be perforation of the bladder, intestine, or abdominal wall.
Madura foot, or Mycetoma, a disease in which the tissues are penetrated by sinuses, is regarded by some authors as a form of Actinomycosis. The microbes though allied are probably distinct.
In some cases the fungus gets into the blood and is disseminated in various organs. In that case there are abscesses produced, and the disease is like a chronic pyaemia.
Bollinger, Centralbl. f. d. med. Wissensch., 1877, No. 27; Ponfick,' Die Actinomjcose des Menschen, 1882; Isbael, Actinomycosis in man, Syd. Soc, 1886; Shattock, Path, trans., vol. xxxvi.; Acland, ditto, vol. xxxvii. An exhaustive account of Actinomycosis is given by Bostroem in Ziegler's Beitrage, vol. ix., 1891; Kanthack (Madura foot), Journ. of Path., i., 1892; Boyce and Surveyor, Phil, trans., vol. 185, 1894.