When incorporated directly into cattle dung, a formulation of moxidectin was less toxic to larvae of the dung beetle Onthophagus gazella and the buffalo fly, Haemafobia irritans exigua, than an abamectin formulation. Concentrations of moxidectin @-fold greater than abamectin concentrations were required to produce equivalent toxicities. Neither moxidectin nor abamectin reduced oviposition by 0. gazella. Moxidectin may consequently be less likely than abamectin to affect the decomposition of cattle dung but may have less effect on buffalo fly infestations.
This review describes 4 species of parasites in Australia generally regarded as Theileria. The physiological and epidemiological characteristics of the species that occurs in cattle are discussed. Confusion still surrounds the relationship of this species with benign species of Theileria in other countries. Arguments are presented to support the proposal that the bovine species in Australia is correctly designated Theileria buffeli and that this name should apply to all the benign species of Theileria of cattle in Eurasia. The other 3 species considered in the review are proposed species from marsupials. Of these, only Theileria tachyglossi can confidently be included in the genus Theileria, because schizonts have yet to be detected in the other 2 species.
SUMMARY
The distribution and prevalence of Theileria buffeli in Queensland cattle were investigated using serum samples and blood films collected primarily for brucellosis surveillance and tick fever diagnosis. Serums from 8654 cattle from 357 farms throughout Queensland were examined by an indirect fluorescent antibody test for antibody to T buffeli. In addition, 347 peripheral blood films collected from 147 farms in south‐eastern Queensland were examined for plroplasms of T buffeli.
The overall herd and animal prevalences for T buffeli were 75% and 41%, respectively. There was significant variation among regions in both herd and animal prevalences (P <0.001). Herd and animal prevalences were highest in the north and east decreasing westward. The results indicate that T buffeli is more widespread in Queensland than previously thought.
Cloned lines of Babesia bovis were prepared from the avirulent vaccine strain, Ka, by an in vivo limiting dilution procedure. The virulence of these clones for adult Bos taurus cattle varied from completely avirulent to highly virulent. This suggests that the parent strain, Ka, is composed of a mixture of subpopulations of varied virulence. Passage of the avirulent clone K-19-47 in intact (nonsplenectomized) cattle resulted in its full reversion to virulence. This suggests that two mechanisms are operating to enable virulence to be a readily modified characteristic in this parasite: differential gene expression and phenotypic selection of subpopulations. A series of experiments demonstrated that all clones were non-tick transmissible. This lack of vector transmission was a stable characteristic and could not be altered by the passage of K-19-47 in intact cattle, despite the fact that passage in intact animals caused this clone to revert to the fully virulent phenotype. A mechanism is suggested for the virulence and vector transmission variations observed in B. bovis.
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