Studies on the interaction between an irradiated bovine lungworm vaccine and a morantel sustained release bolus

Antibody responses to natural Dictyocaulus viviparus exposure in first year grazing cattle using vaccination or different kinds of anthelmintic treatment

In two field trials vaccination or different anthelmintic treatments against Dictyocaulus viviparus infections were used in 6 groups of first year grazing cattle. The antibody response to lungworm infections was determined using an ELISA. Cattle treated once or repeatedly at long intervals with levamisole developed clinical signs of dictyocaulosis. The detection of anti-D. viviparus antibodies at the end of the grazing season confirmed that these anthelmintic treatments were not able to prevent lungworm infections. Cattle that received strategically administered treatments with ivermectin remained clinically healthy. These cattle were seronegative until the end of the trial which proved the efficacy of the strategic control. Cattle that received an intraruminal slow release bolus did not develop clinical disease. However one animal shed lungworm larvae and the herd became seropositive at the end of the grazing season indicating a history of infection. The serological examination of a cattle herd at the end of the grazing season is able to demonstrate a history of lungworm infections and to determine the efficacy of anthelmintic control measures.

The influence of host immunity on the epidemiology of trichostrongyle infections in cattle

The acquisition of immunity to the important trichostrongyles of cattle is reviewed and the subsequent effect on the epidemiology of trichostrongylosis is discussed. Examples of factors which can delay or impair the development of immunity to these nematode infections are presented. These include the interactions with anthelmintic prophylactic programmes, nutrition, intercurrent infections, pregnancy and lactation.

Parasitological, serological and clinical effects of continuous graded levels of Dictyocaulus viviparus inoculations in calves

To investigate the parasitological, serological, clinical and growth effects of continuous graded levels of Dictyocaulus viviparus inoculations in calves an experiment was carried out with 10 groups of 5 calves each. Calves were inoculated twice a week during a period of ten weeks. The range of the doses was 10-2560 infective larvae (L3) per inoculation. The results were analysed by linear and curvilinear regression of various traits on infection level. It is concluded that: A continuous exposure of calves to L3 of D. viviparus was followed by a continuous larval excretion at all levels; Results of the ELISA technique gave a very good reflection of the level of infection; Clinical signs and weight loss were evident before the parasitological and serological results were positive; The serological parameter and the parasitological parameters were mainly linearly related to the level of infection. The clinical parameters were mainly cubically related to the level of infection.