Page:Popular Science Monthly Volume 81.djvu/556

550 the Piroplasma through its eggs to the young ticks of the next generation. These may feed on healthy animals the next season, conveying to them the parasites that have been handed down from the mother tick.

Several similar diseases of cattle occur in other parts of the world. In Africa, related forms of Piroplasma carried by ticks are the cause of redwater, East Coast fever, Rhodesian fever, and in various parts of the world other piroplasmoses have been observed in many animals.

Spirochætosis in animals, due to organisms similar to those producing relapsing fever, is well known. The most familiar example is probably a disease of fowls which is carried by Argas miniatus, a common tick which infests these birds.

Trypanosomiasis is a general term for diseases like sleeping sickness due to trypanosomes and there are many diseases of this type, among which may be mentioned an old-world affection of horses known as Surra; an African one, Nagana, that attacks other domestic animals as well; and a South American type termed Mai de Caderas. Flies are the insects implicated in the transmission of these diseases, mainly the large tabanid horseflies and the smaller stable flies of the genus Stomoxys. Surra was recently introduced into the United States, but was successfully stamped out before it had become established.

Among bacterial diseases of animals, anthrax may be mentioned as one which is sometimes transmitted by biting flies, the insects acting as mechanical or contaminative carriers only.

The foregoing enumeration of insect-borne diseases is by no means complete. Indeed, it would be well-nigh impossible to make it so, in view of the rapid strides which are being made at the present time toward a knowledge of these many problems which bear on the question of public health. New discoveries are being rapidly announced in all parts of the world, and while it is difficult to see how the fundamentally important revelations of the past fifteen years can be equalled in the near future, we should be very unwise to predict that they will not be exceeded.