Swine Erysipelas

Swine erysipelas is now recognized to be second only to hog cholera in economic importance to swine growers of the United States.

It is not a consistent killer of swine, as is hog cholera, but causes losses by preventing normal rates of growth, altering tissues and organs to an extent that excludes their use for human food, lowering resistance of infected swine so that they readily fall prey to other diseases, and, in certain outbreaks, by actually killing.

Prevention by immunization of swine, with the simultaneous administration of anti-swine-erysipelas serum and live-culture vaccine, has been a subject of experimental study by several of the State livestock sanitary authorities, the State experiment stations, and the Department. The study has been conducted on a cooperative basis under restricted conditions for more than 8 years in 14 States where the disease is known to exist. Strict control over the production of the vaccine and serum has assured standard products of high quality for use in the work. This protective vaccination has been given nearly 7 million head of swine in 100,000 herds. The results have been satisfactory so far, but sufficient time to allow for complete evaluation of the sero-vaccination under all cyclic variations of the disease has not yet elapsed.

The organism that causes swine erysipelas is also dangerous to man. In humans, the disease is known as erysipeloid, and occurs generally through wound infection. Although erysipeloid usually localizes, in some cases general infection and death have resulted. Care should be exercised, therefore, in handling infected swine and their products.

The disease has also gained considerable economic importance for turkey growers. It manifests itself suddenly in turkeys around market time. The birds become droopy, sleepy, and depressed. Death usually occurs in about a day. There is a copious diarrhea in most cases. The wattles and caruncles become swollen and dark. On birds that recover, the caruncles may dry and drop off. Mortality ranges up to 50 percent, and the disease seems to affect young toms oftener than young hen turkeys.

Our preliminary investigations indicate that 10 cubic centimeters of anti-swine erysipelas serum ( equine origin) introduced into the wattles of artificially infected turkeys will cure about 50 percent of birds so treated, but all untreated birds die. By repeated administration of oil suspension of penicillin into the wattles of similarly infected turkeys, mortality was reduced to 10 percent.

Rabies

Rabies as a disease of livestock has never ranked in economic importance with the other well known infectious diseases, but it is exceedingly serious because it may affect all warm blooded species, including man.

Although dogs are the main victims of rabies, human beings and many farm animals also die from it. From 1938 to 1945 rabies caused 70,201 deaths.

It is invariably fatal. Since 1938, the Department has gathered statistics on the incidence of the disease in the United States. In the 8 years from 1938 to 1945, a total of 70,201 cases was recorded, of which nearly 90 percent were in dogs and less than 7 percent in other farm animals.

Incidence of the disease gradually declined from 1938 to 1942, with a sharp rise during the following 2 years and a small decline in 1945. Even a slight increase in the spread of rabies in a community gives rise to grave concern among veterinarians, public health officials, and citizens. Consequently aggressive programs have been inaugurated in the past few years in certain affected areas. Particular emphasis was given to vaccination as a very helpful prophylactic measure. Large-scale vaccinations of dogs in a number of States and communities were carried out promptly. In Washington, D. C., approximately 35,000 dogs were vaccinated in about 2 weeks. The results of vaccination have been gratifying; in many instances the number of cases dropped sharply upon the completion of the vaccinations.

Each lot of commercial rabies vaccine must be subjected to the Habel test, an accepted method for determining its power to immunize, before being released for sale. In the test, white mice are vaccinated with some of the rabies vaccine and these animals, together with an equal number of unvaccinated mice, are inoculated with varying doses of rabies-fixed virus. The vaccine is not passed unless 50 percent of the vaccinated mice withstand at least a thousand fatal doses of the virus.

Despite the high quality of present-day rabies vaccine and the good results obtained through its use in many dogs, the control and ultimate eradication of rabies must include other recognized measures. In late years the fox has played an important role in the spread of rabies in some localities. Should the disease become established in these animals, a program of systematic reduction of the fox population will become necessary.

THE AUTHOR

L. T. Giltner is assistant chief of the Division of Pathology, in the Bureau of Animal Industry, where his work has included research on all of the animal diseases discussed in this article.