INFLUENCE OF PARASITEMIA LEVEL AT FEEDING ON DEVELOPMENT OF ANAPLASMA-MARGINALE THEILER IN DERMACENTOR-ANDERSONI STILES

  • 1 January 1983
    • journal article
    • research article
    • Vol. 44  (4) , 554-557
Abstract
Four splenectomized dairy calves were inoculated with a Virginia isolate of A. marginale Theiler and served as an infective source (donor) for laboratory-reared D. andersoni Stiles nymphs. Two donor calves developed higher parasitemias during tick feeding than did the 2 other donor calves. One month after molting, adult ticks were incubated at 37.degree. C for 2.5 days to stimulate development of colonies of A. marginale; homogenates of gut were made from ticks fed on each donor calf. Eight susceptible, splenectomized dairy calves (2/donor calf) were inoculated i.v. with the gut homogenates collected from 50 adult ticks and were monitored for patent A. marginale infection. Gut tissues from these same groups of ticks were processed for histologic studies. Homgenates from ticks infected on donor calves with lower parasitemias caused infections with longer prepatent periods (average, 43.25 days) than did similar homogenates made from ticks infected by feeding on donor calves with higher parasitemias (average, 31.0 days). Sections of gut tissues from ticks infected at the lower parasitemias contained fewer (average, 0.65) colonies/0.001 mm2 of tissue examined than did those from ticks infected at higher parasitemias (average, 6.31). The results are relevant to the infectivity of the tick vector in A. marginale epidemics in cattle.