INFECTIOUS ENTERO-HEPATITIS IN TURKEYS.
Blackhead. Definition: Infectious protozoan disease of cæca and liver and general toxicæmia. Microbiology: Amœba in cæca, liver, etc. Symptoms: Attacks young, dulness, drooping, ruffling, moping, anorexia, greenish diarrhœa, icteric or dusky mucosæ, blackening of gobble, etc. Lesions: Enlarged thickened cæca, epithelial degeneration and desquamation, exudation, mottled liver, with giant and round cells and amœbæ, degeneration, necrosis, caseation, no abscess. Diagnosis from bacteridian typhlitis or diphtheria. Treatment: Intestinal antisepsis. Prevention: Disinfection of buildings, yards, manure, seclude from other flocks, birds, flies, breed new flock on fresh ground from eggs of affected or other flock, set in incubator or under hens.
Synonym: Blackhead.
Definition. An infectious disease of turkeys, especially destructive to the young, due to a protozoön (amœba meleagridis), and characterized by inflammatory thickening of the walls of the cæca, diarrhœa, brownish, yellowish or greenish areas of degeneration of the liver, and congestion with blackish discoloration of those portions of the head which are uncovered by down or feathers.
Microbiology. The microörganism (amœba meleagridis) is found in the thickened walls of the cæca, in the exudate, in the lumen, and in the degenerating patches of the liver. The most common and simple form is that of a rounded body, varying slightly in form, and containing a group of very minute granules situated somewhat eccentrically. They may be enclosed in lymph spaces or less frequently in giant cells, or have portions of broken up cells adherent. Their size varies from 10 to 15μ. They may be stained by the following process: Harden in 95 per cent. alcohol saturated with mercuric chloride, then in the same with an equal amount of a 5 per cent. solution of bichromate of potash, and finally in Hemming’s solution. After a day in these solutions they are washed for a day in running water, then treated with ascending strengths of alcohol, dried by passing through alcohol and chloroform, imbedded in paraffin, sectioned dry, and stained in Delafield’s hæmatoxylin and eosin. The spherical or slightly oval amœbæ have a homogeneous, bluish red tint, feebler and therefore distinct from the tissue nuclei. Near the centre in most a blue circular line shows the outlines of the nucleus.
Th. Smith compares this affection with the amœbic dysentery affecting the large intestine and liver of man, and notes these differences, that amœbic movements have not been observed in amœba meleagridis, and that hepatic abscess does not occur in the turkey. The indisposition of the bird to suppuration may perhaps account for the latter distinction. Smith found rounded organisms in the tubules of the cæca and flagellates in the lumen of the gut, but did not attach any importance to their presence. Bacteria were only found in the lesions in the solid tissues where the subject had not been killed and immediately examined, but left over night for examination in the morning. There was no constancy in their species as in the case of the amœbæ, all indicating that their invasion was post mortem.
Symptoms. The disease is most frequent and fatal in the young (1 to 4 months, exceptionally 6 to 10 months), and the symptoms vary much in different cases, according to the intensity of the disease and the relatively extensive implication of the different organs. Among the general symptoms are those of general suffering and ill health, dulness, spiritlessness, drooping of the head between the wings, a pendent condition of wings and tail, erection of down or feathers, separation from the flock, the bird moping alone and sitting much of the time. The more characteristic phenomena which are rarely sufficient to identify the disease unless it is known to be prevalent, are loss of appetite, a greenish diarrhœa, yellowish or brownish discoloration of mucosæ, emaciation which becomes extreme if the subject survives long enough, and more or less blackish discoloration of the gobble and bare portions of the skin covering the head.
Lesions. These are characteristic, the cæca being greatly enlarged, the walls thickened by a yellowish submucous exudate, the epithelium disintegrated and desquamating, and the mucosa covered by a solid yellowish gelatinoid exudate arranged in superposed layers, while the contents are soft, pasty or of a greenish liquid appearance. The comparative stagnation of the contents as in the appendix of man appears to favor microbian infection. Amœbæ are especially abundant in the exudate into the submucosa and in the lymph spaces. The liver changes show infective inflammation in the spots of mottling, followed by degeneration, and necrosis, the liver cells disappearing under the compression of the giant and round cells and the amœbæ, the surface over the affected parts is depressed, and the mottling may show a variety of colors, as brown, brownish red, or yellow, pale yellow, grayish or dirty white. The degenerating tissue may become caseated, but abscess appears to be unknown, though so common in amœbic dysentery of man. In the skin of the head the blackish color predominates; there is more or less congestion, capillary embolism, and tissue degeneration.
Diagnosis. Th. Smith notes three cases of diseased cæcæ without great thickening of their walls, and an exudate in the lumen having the general appearance of that seen in the amœba disease but with no amœbæ, only the bacillus coli communis. The odor was strongly feculent. In all three cases the liver was healthy. In one there was an abundance of tapeworms in the bowels. Manifestly the absence of liver lesions may be held to indicate the absence of the protozoan disease. VonRatz (Budapest) gives two similar cases, with many nematodes, those in the exudate being 8 to 14 mm. long.
Zurn describes the presence of the diphtheria of fowls in the intestines of hens, turkeys and palmipeds and sometimes confined to the cæca. It is characterized by great prostration and debility, and an offensively smelling diarrhœa at first pultaceous and mucous, later bloody, and followed by constipation, in which case the cæca and rectum are ulcerated and blocked with the yellow croupous exudate. It lasts 2 to 3 weeks or even months, is subject to relapse, and sometimes occurs as a sequel to the diphtheritic affection of the head and throat. The absence of marked thickening of the cæcal wall, and of the protozoön, the presence of the diphtheritic exudate in the lumen, and the croupous condition or congested appearance of the head and throat are distinctive. Th. Smith, however, refers to two cases, supposed to be of this kind, in which the walls of the cæca were greatly thickened, the result of reparatory inflammation following a slough of the mucosa. Siedamgrotzky also describes thickening of the walls of both cæca in a hen, the mucosa being covered with a thin pseudo-membranous exudation, without ulceration.