Thesis (M.Sc.)--University of Adelaide, 1958. / Typewr. copy.

In this study, data collected in a survey of Scottish sheep farmers was used to corroborate and augment secondary data available in the literature on sheep ectoparasites and their control in 1999/2000.  The data was used to design and construct a decision tree model, which was used to determine probability weighted profit-maximising control strategies for six flock types/size groups that were representative of Scottish sheep farms.  Organophosphate (OP) based dips, applied in both the autumn and spring/summer, were found to be the profit-maximising control strategy for five flock types/size groups.  The exception was for small (100-ewe) lowground flocks, where two applications of cypermethrin in pour-on formulation maximised the avoidable disease losses. Each of these strategies can give rise to animal welfare, human health and /or environmental externalities.  OP dips can damage human health and the environment but minimise animal welfare losses, and cypermethrin pour-on, while non-damaging to human health and the environment, can result in some avoidable welfare losses, as ectoparasite control is less effective than for OP dips. Using multi-criteria analysis (MCA), the economics of sheep ectoparasite control from a social standpoint has also been examined.  Some profit-maximising control strategies do not necessary maximise social benefits.  A conflict can arise between the farmer and society.  The minimum cost that society would need to be willing to accept in order to finance possible incentives for sheep farmers to switch from the profit-maximising control strategy to strategies that provide different bundles of social benefits is estimated.

Two 16 mm color films were made to help fill a general need for instructional motion pictures in the area of Parasitology. One film "Haemonchus contortus, a Sheep Stomach Worm," deals with a nematode parasite of sheep, showing all stages of its external development and including a time-lapse sequence of the embryonation of the egg. The other film, "Some Parasites of Freshwater Fishes," shows six parasites; Ichthyophthirius multifiliis, Cotylurus erraticus, Dactylogyrus sp., Lernaea cyprinacea, Trichodina sp., and Diplostomum spathaceum for the first time in motion pictures. The films were photographed through a Wild dissecting scope and a Reichert Universal Camera Microscope, employing the techniques of brightfield, darkfield, phase contrast and Nomarski interference microscopy. The films are available from the Parasitology Laboratory of the Department of Zoology at Brigham Young University.

This study was undertaken to determine the effect of thiabendazole and haloxon on the free-living stages of Haemonchus contortus and to determine the suitability of the free-living stages for their use in primary drug evaluation for chemotherapy or for chemical control of free-living stages. Cleaned unembryonated ova, embryonated ova, first-, second-, third-, and exsheathed third-stage larvae were exposed to suspensions of 5.0%, 1.0%, 0.5%, 0.25%, 0.12%, 0.05%, and water soluble concentrations of each drug for exposure times of 0.25, 0.50, 1.0, 2.0, 4.0, 8.0, and 16.0 hours at pH 7.0 and 25° C. Survival was assessed by observing any subsequent development or motility. Thiabendazole was partially ovicidal to unembryonated ova at water soluble levels and after exposure of only 15 minutes. Exposure of longer than 4 hours was 100% lethal. No other stages were effected by thiabendazole. Haloxon was ineffective against all stages tested.