Studies on fascioliasis and ostertagiasis in cattle and sheep

The work described in this thesis is concerned with two parasitic helminths, Fasciola hepatica and Ostertagia ostertagi. Although the major part of the thesis describes investigation into fascioliasis in both cattle and sheep, the first section records a hitherto undescribed condition in cattle where both F. hepatica and O. ostertagi coexisted in significant numbers.Single experimental onfections of cattle and sheep with metacercariae of F. hepatica were studied, and these were followed by observations on the sequential development of an outbreak of fascioliasis in sheep grazing under natural conditions, a subject investigated in detail for the first time. The final section describes a method of control by use of a fasciolicide. The thesis is divided into five sections as follows: Section I Field Studies on Clinical Parasitism in Young Dairy Cattle in South-west Scotland. The first part of this section reviews a series of out breaks of ostertagiasis occurring during the course of the winter (Type II). This is followed by the description of a further series of outbreaks of parasitic disease in which both O. ostertagi and F. hepatica were present in significant numbers (the fascioliasis/ostertagiasis complex). The two conditions had different background histories, seasonal incidences, clinical signs and necropsy findings, and these differences are discussed in detail. Section II Experimental Fasciola hepatica Infections in Calves. Single oral inoculations of susceptible calves with 1000 or 2000 metacercariae of F. hepatica resulted in the establishment of an adult fluke burden capable of producing clinical signs and death. The haematological and blood biochemical values recorded at weekly intervals demonstrated the presense of a macrocytic, normochromic anaemia and a hypoalbuminaemia. At post-mortem all but two of the infected calves showed a percentage take (i.e. the percentage of the inoculation which became established) of between 16% and 37%; the two remaining cal