Although most of the causes of heart disease observed in the first quarter of the 20th century are still present, their relative proportions have changed considerably, and some causes that were mentioned only occasionally or not at all at that time are considered common today. This is especially true of the virus infections. In some parts of the world the diagnosis of "heart disease of unknown origin" is a common one. In the United States such a diagnosis exists but is uncommon, and a few kinds of heart disease that are common in certain disease states other countries are rare or nonexistent in the United States. For example, Chagas' disease (myocardial trypanosomiasis) is a parasitic infestation of the heart common in South America.
Infectious Types of Heart Disease. During the early 1900's infectious types of heart disease were the greatest scourge, making up much more than half of all the cardiac cases. Today they account for less than a fourth of all cases in the United States and other countries that are equally prosperous and equally able to control infectious diseases. The two major infectious heart diseases in the United States are rheumatic heart disease and syphilitic heart disease.
In modern poultry production, thousands o chickens are raised in close proximity to eacl other. Under these circumstances, the spread o disease can be extremely rapid, and losses fron disease can be serious. The monetary loss in thf United States each year from chicken disease: has been estimated to be as high as $300 million Disease control requires measures aimed at the prevention of outbreaks as well as the proper diagnosis and treatment of diseases. The most generally encountered diseases of poultry are the following:
Although most of the causes of heart disease observed in the first quarter of the 20th century are still present, their relative proportions have changed considerably, and some causes that were mentioned only occasionally or not at all at that time are considered common today. This is especially true of the virus infections. In some parts of the world the diagnosis of "heart disease of unknown origin" is a common one. In the United States such a diagnosis exists but is uncommon, and a few kinds of heart disease that are common in certain disease states other countries are rare or nonexistent in the United States. For example, Chagas' disease (myocardial trypanosomiasis) is a parasitic infestation of the heart common in South America.