Circular Volume 101-173

Circular Volume 101-173

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1908 edition. Excerpt: ...ROCKY MOUNTAIN SPOTTED-FEVER TICK. (Dcrmacentor verwstus Banks.) By F. C. BISHOPP, Agent and Erpert. The demonstration of the fact that Rocky Mountain spotted fever, an important disease of man, is conveyed by the common wood tick of the Rocky Mountains, has naturally attracted considerable attention. In the year 1902 Drs. Wilson and Chowning advanced the theory that the "wood tick" acts as a carrier of the disease. In 1906 the late Dr. H. T. Ricketts began a series of admirably planned and executed experiments which showed that the tick Dermacentor venustus Banks is principally, if not entirely, responsible for the transmission of this disease to man. While the disease appears in its most virulent form in the Bitter Root Valley in western Montana, it is known definitely to occur in a less severe form in parts of Idaho, Wyoming, Utah, and Nevada. Although no authentic records to that effect are to be found, there is little doubt that it occurs occasionally in certain sections of Colorado and Oregon. In the Bitter Root Valley from 70 to 80 per cent of the cases terminate fatally, while in southern Idaho there is a mortality of about 5 per cent. The cases of the disease which have appeared in the other States mentioned seem to be of this less virulent type. Since it has been determined that a tick is the transmitter of this disease, the importance of ascertaining the distribution of the species concerned is at once apparent. In 1909 Prof. R. A. Cooley, as Entomologist of the Montana Agricultural Experiment Stat-ion, undertook the determination of the distribution of this tick in the State of Montana. He accumulated 172 lots of ticks, including 142 lots of Dernuzcentor venustus, from 49 localities. During the same season Mr. more

Product details

  • Paperback
  • 189 x 246 x 15mm | 517g
  • United States
  • English
  • black & white illustrations
  • 1236960211
  • 9781236960214