Brucellosis of Cattle (Bang's Disease)

No disease of livestock has received greater attention from the standpoint of control measures than brucellosis of cattle, or Bang's disease, as it is commonly called. Years of research have been spent in developing methods of control, and these have been applied in practical field studies. The studies have definitely established that no one system of control is applicable to all herds, but that the choice of method depends on conditions such as size of herd, degree of infection, environment, and whether the herd is for dairy or beef.

As a consequence, the Department has approved the use of four methods of control in the Federal-State program for the control of Bang's disease, namely: Blood test and slaughter of all reacting animals; blood test and slaughter, accompanied by the vaccination of calves; blood test to determine the amount of infection, but retention of reactors until vaccinated replacements are available; whole-herd vaccination.

The first plan is the method of choice in small herds and in herds in which brucellosis has been of long standing, that is, where the storm of abortions has passed and the disease has taken on a chronic form. In herds from which certified milk is sold there is no alternative than test-and-slaughter, and this method also is used in the area-plan of control.

The second method adds calf vaccination to the first. It has the extra advantage of building a herd that eventually will be more resistant to reinfection, should it occur. Calf vaccination has proved to be a most desirable practice in all herds in which infection is present.

The third plan is a good one for herds in which such a large proportion of animals is shown on test to be reactors that their immediate removal, in the absence of suitable replacements, would work an extreme hardship on the owner. Calf vaccination is necessary in this plan and some owners prefer to vaccinate all animals up to breeding age. This plan applies especially to dairy herds in which the milk is pasteurized or sold to creameries, and in purebred herds where the preservation of valuable blood lines is involved. The retention of reactors should be considered only as a temporary expedient, to tide the owner over a period until vaccinated replacements can be raised and added to the herd. When replacements become available, the least desirable or profitable reactors should be removed from the herd first and this process continued until the herd is free of brucellosis. Three or four years should be enough to establish a negative herd.

The fourth plan, whole-herd vaccination, is one of last resort. There are a few herds, called problem herds, in which the infection is of so severe a type, or the animals are so susceptible, that the removal of reactors following repeated tests cannot check the infection. In such herds, vaccination of the whole herd has had some success. In some herds the procedure has stopped abortions abruptly, but in others no improvement is evident for 6 to 8 months. Whole-herd vaccination has its main advantage in infected beef herds, where a calf crop is a prime requisite.

There are several undesirable consequences of the vaccination of adult animals. The vaccinal blood titer, which cannot be told from that of actual infection, may persist for indefinite periods and thus interfere with sales or interstate shipment; in cows more than 4 months advanced in pregnancy it may cause abortion; and if practiced in dairy cows, a marked drop in milk production may be expected from 10 to 14 days following vaccination.

There is little reason to vaccinate all cows in a negative herd. The owner has little to gain, especially in view of the undesirable after-results. On the other hand, calf vaccination, preferably at 6 months of age, is good insurance in all types of herds, infected or negative, against the animal's subsequently becoming infected. The only drawback is that a small proportion of calves may be slow in losing the vaccinal blood titer, which may thus interfere with their interherd movement.

The rapidity with which brucellosis in cattle may be eradicated in an infected herd under any of the four plans depends largely on herd management and sanitation.