High incidence area of cattle cancer with a possible interaction between an environmental carcinogen and a papilloma virus.

Cattle in upland areas of Scotland and northern England are substantially more prone to alimentary cancer than those of the immediately neighbouring lowlands, and epidemiological evidence implicates a combination of papilloma virus and bracken in the aetiology of the disease. Here Professor Jarrett outlines the circumstantial case against these agents and discusses its implications.

An improved parasitological technique for the diagnosis of African trypanosomiasis.

Light microscopic examination of the buffy coat zone of a microhaematocrit capillary tube expressed on to a slide was found to be consistently more reliable than other standard techniques in detecting trypanosomes in the circulation of cattle. This method alaos allowed identification of different trypanosome species. Optimal results were obtained using darkground illumination.

Immunological studies on Dictyocaulus viviparus infection; active immunization with whole worm vaccine.

Experiments on the vaccination of calves against infection using whole worm antigen in Freund's adjuvant are described. A reduction in the number of worms developing from a challenge infection was sometimes obtained but the method seems to be of little practical value.

Immunological studies on Dictyocaulus viviparus infection; immunity produced by the administration of irradiated larvae.

Experiments are described on the immunity to infection produced by the administration of 3rd stage larvae partially inactivated by X-irradiation. A high degree of immunity was obtained by this method.

Immunological studies on Dictyocaulus viviparus infection: the immunity resulting from experimental infection.

It has been shown experimentally that infection of calves with confers a high degree of resistance to a subsequent reinfection. This acquired immunity can result from a single infection with a sub-lethal dose of larvae or from a series of repeated doses of small numbers of larvae. Animals immunized by a previous infection exhibit on challenge a rapid antibody response and a striking reduction (in some cases to zero) in the numbers of worms reaching the lungs, and in the numbers of larvae appearing in the faeces.