TRANSMISSION OF THEILERIA-PARVA TO CATTLE BY RHIPICEPHALUS-APPENDICULATUS ADULTS FED AS NYMPHAE IN-VITRO ON INFECTED BLOOD THROUGH AN ARTIFICIAL MEMBRANE

A technique is described for the efficient feeding of Phipicephalus ap pendiculatus nymphae on cattle blood through an artificial membrane be aring tactile and olfactory stimuli. The effect of four anticoagulatio n methods on the feeding of nymphae was compared and heparinized blood was found to be the most efficacious, followed by defibrinated blood. Blood treated with acid citrate dextrose (ACD) or ethylenediamine tet raacetate (EDTA) inhibited nymphal feeding. Nymphae fed on heparinized and defibrinated blood obtained engorgement weights within the range of ticks fed on mammalian hosts and they subsequently moulted and fed normally as adults and produced viable eggs. Nymphae fed on membranes using either defibrinated or heparinized blood infected with Theileria parva piroplasms developed salivary gland infections as adult ticks a nd transmitted East Coast fever (ECF) to susceptible cattle. There wer e indications that T. parva-infected defibrinated blood was not as inf ective to the feeding nymphae as the infected heparinized blood. When T. parva-infected heparinized blood was used to feed nymphae through m embranes in two experiments, it was found that the infections in the r esultant adult ticks could be comparable to those of nymphae fed on do nor cattle, but were usually lower. The membrane feeding technique wil l enable the study of factors affecting the tick and T. parva transmis sion without the complication of host/T. parva interactions and could be useful for both tick maintenance and Theileria parasite isolation a nd maintenance.