Studies on the reactions of animals to infestation with ticks. I. Tick anaemia

Abstract

Tick anaemia appears to be caused mainly by loss of the blood ingested by the engorging ticks. It is possible that some toxic effects of the salivary secretion may help to account for the slow recovery of heavily infested animals in poor condition, even after the infestation has been removed and an adequate supply of feed provided. Animals in poor condition showed a marked fall in red blood cell concentration and haemoglobin content following heavy infestation with Boophilus microplus (Canestrini), whereas animals in moderate to good condition showed a much smaller and more temporary reduction in these components. When submitted to very heavy infestations, even animals in good condition showed a considerable reduction in these components and in serum protein, all of which, however, soon returned to normal following cessation of the infestation. Many of the heavily infested animals, especially those in poor condition, carried large numbers of translucent adult female ticks, which were filled with a clear fluid similar to bovine plasma, instead of normal ticks, which were dark in colour owing to the ingested blood.