STUDIES ON THE ETIOLOGY OF HEARTWATER : II. RICKETTSIA RUMINANTIUM (N. SP.) IN THE TISSUES OF TICKS TRANSMITTING THE DISEASE.

The evidence offered in the first of these studies indicative of a causative relationship between Rickettsia ruminantium and heartwater is supplemented by the following observations concerning the ticks which carry the disease. When larvae, which had taken no food since hatching, were allowed to feed upon cases of heartwater, they acquired Rickettsioe which appeared to be identical with those in the tissues of animals suffering from heartwater, whereas control larvae hatched from eggs deposited by the same female and fed on normal animals remained free of Rickettsioe. After larvae presumably infective had moulted, the resultant nymphae containing Rickettsioe in their alimentary tracts, when fed upon susceptible animals produced in them typical attacks of heartwater, which the control nymphae, devoid of Rickettsioe, failed to do. The tissues of animals thus infected were found upon histological examination to contain typical Rickettsioelig;.