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.
It would seem that the cæca of birds, like the vermiform appendix of man
is very subject to invasion microbes, bacterian and protozoan, and
should always be carefully examined in case of intestinal or hepatic
disorder.
_Treatment_ would be in the line of intestinal antisepsis with carbolic
acid, salol, sulphurous acid, or the sulphites, with a laxative of
castor oil, to carry these agents unchanged to the cæca, but no success
has attended attempts in this direction, and the danger that comes from
preservation of the infected animal, and consequent multiplication of
the microbe would as a rule far more than counterbalance any probable
recoveries.
_Prevention._ Moore has shown that the amœbæ, passed with the fæces,
contaminate the food and water and thus actively propagate the disease,
so that preventive measures must be mainly directed toward the
purification of these infecting media. To be thorough new ground must be
secured on which no diseased turkeys have been, and through which no
water from contaminated or suspected land can flow; if necessary this
must be closely fenced to prevent all ingress or egress, and on this
ground we can place, as soon as they leave the shell, young turkeys
hatched from eggs obtained in noninfected localities, or the eggs
carefully washed of the turkeys living on infected ground. In this way
the heredity and quality of the flock can be preserved without risk of
contamination from the parents. The amœba is not known as a parasite of
other birds, but if it should eventually be found to be so or to occupy
any other animal body as an intermediate host, the local extermination
of such host will become a necessary precaution.
When a new flock has been started in this way, the birds of the old
flock may be fattened, killed and marketed, and as suggested by Cooper
Curtice the grounds they have occupied may be secluded by fencing for
one or two years, in the hope that the amœba will perish by this break
in the chain of its life history. If this should prove successful with
the land, the infection might be easily exterminated in the whole
infected district or state.
The poultry buildings will require thorough disinfection. All manure and
droppings must be carefully removed and the building whitewashed, using
freshly burned quicklime and ¼ lb. of chloride of lime to the gallon of
the mixture. The litter should be burned, and all nests, roosts,
drinking vessels and troughs soaked with a mixture of sulphuric acid ½
gallon, carbolic acid ½ gallon, and water 20 gallons, (Th. Smith). The
agents are mixed slowly in a vessel set in cold water. The same may be
liberally applied on the surface, fences, etc., of the yards. Or
quicklime, freshly burned, may be used freely on the yards holding the
infected flocks (Moore). Mercuric chloride is dangerous. When the
infected flock has been finally disposed of, the buildings and yards
should be again thoroughly disinfected, and together with the field
runs, abandoned for at least one year.