TEXAS OR TICK FEVER.
—The earliest accounts that we have of this disease date back to 1814. It was found that cattle driven from a certain district in South Carolina to other parts of the state would infect others with the disease, while they themselves seemed to be in perfect health. The disease is known by various names in the different sections of the country. It is often called red water, Spanish fever, Australian tick fever, and murain.
A TYPICAL CASE OF FOOT AND MOUTH DISEASE
The disease shows itself about the mouth, the feet and the teats. When an outbreak occurs all affected animals should be destroyed and all quarters thoroughly disinfected.
This is a specific fever, and is characterized by the peculiarity among animal diseases that animals which scatter the infection are apparently in good health, while those which sicken and die from it do not, as a rule, infect others.
When the cattle are brought into the infected districts they usually contract the disease during the first of the summer, and if they are adult cattle, particularly milch cows or fat cattle, nearly all die; calves are more likely to survive. The disease is one from which immunity is acquired, and, therefore, calves which recover from the disease are not again attacked, as a rule, even after they become adult.
When the disease is prevalent or scattered beyond the infected district the roads, barns and pastures are dangerous until freezing weather, when the disease disappears and cattle can be kept in the grounds or driven over the roads without catching the disease. The midwinter months is the only time that cattle can be safely driven from an infected area to a non-infected area without spreading the disease.
The Cause.
—Texas fever is caused by an organism which lives within the red-blood corpuscles and breaks them up. It is not a bacteria, but a protozoa, and belongs to the lowest forms of the animal kingdom. How it gets into the blood corpuscles is not known. The fatality is due not so much to the loss of blood corpuscles as to the difficulty which the organs have in getting rid of the waste products arising from this wholesale destruction.
The Course of the Disease.
—After a period of exposure, which may vary from 13 to 90 days, the disease first shows itself in dullness, loss of appetite and a tendency to leave the herd and lie down alone. A few days before these symptoms appear the temperature rises from 103° to 107°. There is little change in temperature until death or recovery.
Pathological Changes Observable After Death.
—The presence of small ticks on the udder or escutcheon is a very important sign in herds north of the Texas fever line. The watery condition of the blood. The spleen or milt very much enlarged, and filled with a blackish pulp. Enlargement of the liver, and its color changed to a mahogany color. The distended gall-bladder, caused by an excessive amount of bile in it.
The Cattle Tick
(Boophilus bovis) is the carrier of this disease. Its life history is quite simple. It is unable to come to maturity and reproduce its kind unless it becomes attached to the skin of cattle, whence it may obtain its food. The eggs laid on the ground by the female tick after falling off the cattle begin to develop at once. The time required for hatching varies considerably, according to the temperature. In the heat of summer about 13 days, and in the fall, under the same conditions, from four to six weeks. On pastures these little creatures soon find their way on to cattle. They attach themselves, by preference, to the tender skin on the escutcheon, the inside of the thighs, and on the base of the udder. When very numerous they may be found on various parts of the body. They remain clinging to the cattle until mature, and then fall off and lay their eggs and hatch more new ticks.
How Prevention Is Possible.
—The spread of Texas fever can be prevented by two ways—sanitary arrangements and by vaccination. Where the cattle are infected with the tick, the ticks can be killed by smearing the animals with a solution capable of killing the ticks without harming the cattle. In large herds a large vat of crude petroleum is used to immerse the cattle in. In small herds smear the cattle with a mixture of equal parts of cottonseed oil and crude petroleum.
How to rid the pastures of the tick without killing the vegetation on them has for a long time been the problem. Divide the pasture in two parts by a double parallel line of fence with a 10-foot space between, to prevent ticks from crawling across. One of these pastures is then kept free of cattle for two winters and one summer. After the second winter it will be free of ticks and ready for tickless cattle, when the other pasture is abandoned for the same time.
Vaccination is for the purpose of immunizing cattle that are brought from a non-infected district to an infected district. Calves about six to eight months old should be used, as they are more immune than adult cattle. The immunity is caused by introducing the germ into the blood in a weakened form. This may be done in two ways—by placing virulent young ticks on the calves or by artificial vaccination. When this is practiced, it should be done in two or three inoculations, as it gives better results. The intervals should be about three weeks. The amount of virulent blood should be small the first time and increased in the following treatments.
The inoculation always results in a more or less serious attack of the fever upon the animal treated. Some may die, but the proportion of deaths resulting among animals taken directly into the infected district is large to the proportion of deaths resulting from vaccination. Medical treatment for this disease has proven unsatisfactory in the acute form, although in some chronic cases some good results may have been obtained by medical treatment.