It is not necessary that complete putrefaction should have taken place for meat to prove poisonous. In fact many of the severest cases are those in which it has not fully putrefied. The most poisonous toxins are present during the early stages of decomposition, and the changes are not recognisable by the senses—smell or taste—which would ensure the rejection of the meat as food.
The poisonous effects are rarely due to the ingestion of bacterial products alone; those cases in which no bacteriological investigation of the food has been made cannot be taken into consideration. The toxalbumoses are destroyed by a few minutes‘ exposure to a temperature at boiling-point, 212° F. (Durham, B. M. J., 1898, vol. ii. p. 797).
In reference to the toxic action of the alkaloids, these have been noted only from the results following subcutaneous injection; their effects when taken per orem have not been established by experiment. In all instances where the necessary bacteriological investigation has been properly carried out a true infection has been proved to have taken place.
In cases of meat poisoning the principal bacteria concerned are not the ordinary putrefactive organisms. The Bacillus enteritidis of Gärtner, which has been found associated with twelve epidemics, and the Bacillus botulinus of Ermengem are the most important causative agents.
The Bacillus enteritidis is killed by proper cooking. It is destroyed in one minute at a temperature of 180° F. At 41° F. it will not grow, but, in meat kept at 68° F. for seventy-two hours, it flourishes abundantly. Freezing will not kill it. In meat which has been infected with the bacilli post-mortem they do not penetrate the meat more than 1 cm. in ten days. Roasting or boiling will sterilise it. In those instances in which poisoning has taken place after cooking, the bacilli have either been present in the meat beforehand, and the temperature has not been sufficiently high or the cooking sufficiently prolonged, to ensure their destruction in the deepest portions; or the meat after cooking has become contaminated, and been insufficiently warmed up again after keeping it for a day or so. Exposure to sewer gas will not affect meat and contaminate it with the Bacillus enteritidis. The chief symptoms due to the Bacillus enteritidis are vomiting and diarrhœa, herpes labialis, rashes on the skin followed by desquamation in about fourteen days, jaundice, and great thirst. The onset is sudden, with nausea, headache, pains in the back and limbs, rigors, fever lasting a few days, general weakness, and, in cases which recover, convalescence extending over a period of from three to six weeks.
The symptoms of botulismus, due to the Bacillus botulinus of Ermengem, and associated with sausage poisoning, are, as a rule, dryness of the mouth, constriction of the fauces, nausea, vomiting, purgation, vertigo, dilatation of the pupils, with dimness of vision and diplopia, and a sense of suffocation. Marked muscular weakness and nervous prostration are prominent symptoms. In fatal cases there is weakness of the pulse and cyanosis, with coldness of the surface and perspiration. The temperature is raised at first and may reach 103° F., but ultimately falls below normal. Delirium comes on late, followed by coma and death.
In dangerous cases obstinate constipation may follow after a few hours of watery stools.
On post-mortem examination of the bodies in fatal cases the following appearances have been noted: a white, dried, parchment condition of the mouth, fauces, throat, and gullet; hyperæmia of the mucous membrane of the stomach and intestines with submucous extravasations of blood. The abdominal and thoracic viscera have been found engorged with blood, with enlargement of the spleen; the former are due to failure of the heart, and cannot be regarded as characteristic of sausage poisoning. Some stress has been laid on the observation that putrefaction is unusually delayed, but Müller has shown that no reliance can be placed upon it; he says that in forty-eight autopsies it has been noted that in eleven of them putrefaction had developed rapidly.
The symptoms of meat poisoning are grouped by Dixon Mann into two divisions: (1) those due to a true infection, (2) those due to simple poisoning.
In (1) the symptoms are those of an infectious disease—they include headache, anorexia, rigors, constipation followed by diarrhœa, pains in the back and limbs, photophobia, delirium, skin eruptions, meteorism, and enlargement of the spleen. The post-mortem appearances greatly resemble those of enterica—infiltration, ulceration, and sloughing of Peyer‘s patches; hæmorrhage into the bowels, enlargement of the spleen, with possibly some pus depots.