OTHER FOOD STUFFS AS ROUTES OF INFECTION We will now give a brief consideration to the other food-stuffs, exclusive of water and milk. In this connection it is apparent that some, such as meat, may serve both as a source as well as a route of infection.
i. Meat as a Vehicle of Infection.—The muscular tissue and certain viscera of cattle, sheep, swine, horses, dogs, and goats are largely consumed as food and constitute what we designate as meat. The animals slaughtered for this purpose may be diseased, in which event their meat may be unsuited for food for the following reasons: (a) Infective agents to which man is susceptible may be present.
(b) The meat has an abnormal appearance and hence is repulsive.
(c) As a result of the illness the food value of the meat is lowered.
Furthermore careless methods of slaughtering may result in the contamination of the meat with micro-organisms from the intestinal tract, as a consequence of which decomposition takes place more rapidly.
Danger from such causes may be eliminated by a careful ante mortem inspection of the animals and a similar inspection of the carcass following slaughter. The presence of diseased tissue does not necessarily justify the condemnation of the entire carcass. Condemnation should be based upon an accu rate diagnosis of the diseased conditions detected, and the extent of its distribution. Many diseased caracasses can be safely used in part as food. In the United States but little progress in meat inspection has been made. The Federal system of meat inspection is only for meats designed for interstate shipment and export. Meats slaughtered for local consumption can only be supervised by local authorities and very little has been undertaken in this direction.
(a) Diseases of animals which may be transmitted through meat: 1. Meat Poisoning.—By this term is meant a group of infec tions and intoxications due to the activity of several different organisms. The conditions are all highly acute and occur after a very brief incubation period, so that clinically they do not resemble typical infections. Bacterially we find the organisms
concerned are B. enteritidis, B. proteus, B. paratyphosus B. and closely related forms, and also B. botulinus, whose action is due to highly potent soluble exotoxin. These outbreaks have usually been associated with the consumption of prepared meat foods (sausages, etc.) and pork has been the meat most com monly involved. These organisms are present in the gastro intestinal tract of the domestic animals and their presence in the meat is probably due to its contamination with the intes tinal contents and feces after slaughter. The organisms of the enteritidis group are all killed by low degrees of heating (6o degrees for 3o min.), but they possess poisonous endotoxins which withstand a higher temperature.
2. Verminous Parasites.—Several cestodes and one nemotode are of considerable importance, the latter particularly. The beef tape worm, the pork tape worm and the fish tape worm all pass their larval stage in the flesh of the indicated animal and human infection with all is primarily derived from the consump tion of parasitized meat. The pork tape worm possesses greater importance than the others, since an individual once infected can reinfect himself, as man can also serve as inter mediate host. The most important parasite is the nematode worm, Trichinella spiralis, whose larval stage is commonly passed in swine. Human infection is derived from raw pork. It is undoubtedly the most common and the most important of all infections derived from meat.
3. Other Infections.—Tuberculosis, anthrax, rabies, glanders, tetanus and foot and mouth disease are all diseases of the food producing animals, transmissible to man, yet so far as we know, no cases are on record where human infection was contracted from the consumption of infected meat. Man is susceptible to all of these, but his infection is derived from different routes than meat.