THE SPOTTED FEVER AND OTHER ALBERTAN TICKS

Abstract

The Rocky Mountain spotted fever tick, Dermacentor andersoni Stiles, is present in large numbers throughout the greater part of southern Alberta. Since 1938 a total of 58,534 drag ticks and 3851 host ticks have been collected. These ticks were taken in 412 separate collections made in 18 different districts. Two collections, one made at Manyberries and the other at Lethbridge, showed that the ticks in those areas were infected with Dermacentroxenus rickettsi Wolbach, the causative organism of Rocky Mountain spotted fever. Sixteen collections made in various districts in southern Alberta were positive for Pasteurella tularensis McCoy and Chapin, the causative organism of tularaemia.The known range of the spotted fever tick extends from the Montana border on the south to Township 33 on the north, and from the Saskatchewan boundary on the east to the British Columbia boundary on the west. The area of greatest abundance is the semiarid rangeland region lying south of the Canadian Pacific Railway from Walsh to the Crow's Nest Pass. Within this region the density of the tick population varied with the district but the highest population was found along the river valleys and in the coulees.It was observed that ticks were more plentiful in small coulees and draws that were well covered with vegetation and possessed numerous cattle paths. The majority of the ticks were usually found on the western and southern slopes of such coulees.The importance of the spotted fever tick cannot be overrated for it is a known transmitter of Rocky Mountain spotted fever, tularaemia, and human and animal tick paralysis in this province. During the course of the survey a new disease of man, believed to be transmitted by this tick, was located in the Eastend district of Saskatchewan.Nine other species of tick are known to be present in Alberta but they were not studied in detail. Two of these, the rabbit tick, Haemaphysalis leporis-palustris Packard, and the bird tick, Haemaphysalis cinnabarina Koch, are known disease vectors.