3. Shell Fish as a Vehicle of clams, cockels or mussels are frequently secured from beds in bays, inlets, etc., that are contaminated by the sewage of large com munities, or else floated in brackish water similarily contami nated (Figs. 65, 66). Thus opportunities are afforded for the shell fish to become contaminated with infective agents de rived from human excreta. A considerable number of typhoid epidemics have been ascertained to have been caused by the consumption of sewage contaminated oysters and clams. These observations have chiefly been made in England. The typhoid bacillus will survive in oysters for as long as six weeks, and as changes of decomposition set in, will increase in numbers.
4. Cooked and Canned Foods.—For the most part hygienists have looked upon cooking as a process of distinct hygienic value, entirely apart from its influence upon the digestibility of food, for the application of heat will have a distinctly dis infecting action. However it now appears that not all cooking operations can be considered sufficiently thorough to altogether eliminate danger in cooked foods.
The greatest danger appears to exist where large lots of food are cooked at one time, for here the bulk of the material is so great that the interior is insufficiently heated and hence not sterilized. Furthermore bacterial spores can survive cook ing or the canning process. Little positive epidemiological evidence is at present available concerning food as a route of infection.
Baked Spaghetti: An extensive outbreak of typhoid has been observed in California in which infection was derived from the consumption of a large dish of baked spaghetti prepared by a typhoid carrier. Experimentally it was found that in baking
such a large dish that the typhoid bacillus could survive even though the exterior was charred.
Fried Fish: Several outbreaks of typhoid fever in London appeared to be due to the consumption of fried fish secured from sewage contaminated waters.
Botulism: Recently considerable evidence has been brought forward from the Pacific coast to the effect that the spores of B. botulinus can survive the process or canning. Several out breaks of botulism due to the consumption of home canned vegetables have been reported. Outside of this area botulism is practically unknown in this country. The European out breaks have occurred in connection with the consumption of pork sausage.
On the other hand, commercially canned foods have not until recently been implicated in botulinus intoxication. A few in stances of cans of contaminated ripe olives which caused epidem ics, have been noted. It would appear that commercially canned food from cans that are not obviously spoiled (swollen, leaky) are as safe as any foods available.
5. Fresh Vegetables.—A few outbreaks of typhoid have occured as the result of the consumption of raw fresh vegetables grown in gardens heavily mannred with human excreta. In this connection celery, lettuce, radishes and watercress have been incriminated.