The pathology of some diseases of young calves

The thesis consists of two parts. The first is an original description of the pathology of bovine Hydrops foetalis; the second is a study of the pathology of the diseases of young calves found in 100 consecutive necropsies. Bovine Hydrops foetalis is a disease, now known to be transmitted by double autosomal recessives in Mendelian fashion, which has received considerable attention in the last few years since the offspring of some of the best bulls in the country were affected and the numbers of affected calves had increased. In view of the advances in knowledge of the human disease since 1939, when it was found to be due to haemolytic disease of the foetus caused by iso-immunisation of the mother, it was considered worthwhile comparing the human and bovine conditions utilising the techniques employed in the diagnosis of the former. The animals studied were 15 parents which had given birth to hydropic calves and six hydropic calves. The serological tests used were the "saline" and "albumen" agglutination tests, "direct" and "indirect" Coombs' tests and a haemolytic test. Haematological examinations were made on the blood of some of the calves. It has' been proved conclusively that the pathogeneses of the two diseases are different since in the bovine there is no serological evidence of iso-immunisation of pregnancy and no haematological or pathological evidence of haemolytic anaemia; the latter are the two basic processes in the human disease. The only constant pathological findings, apart from oedema, were cardiac hypertrophy and a marked serum albumen deficiency. It is suggested that the pathogenesis of the disease might "be either of placental vascular origin (an obliterative process or an arteriovenous "shunt") or a congenital defect in albumen metabolism. Unfortunately no placentas were available for study. An experimental attempt to produce iso-immunisation of pregnancy in three cows failed. In Part S a detailed pathological description is given of 100 calves which died from natural causes. The three main diseases of calves in this area were found to be pneumonia, "white scour" and suppurative omphalophlebitis. The main part of the work is a study of calf pneumonia. This disease group is commonly regarded as one condition but detailed histo-pathological examination has shown that there are at least nine morphological types. Original descriptions are given of acute interstitial pneumonia, inclusion body pneumonia, epithelialising pneumonia, pulmonary aspergillosis and "cuffing" pneumonia. On the basis of morphological findings an original classification of calf pneumonias is given. Studies have been carried out on the transmission of some of these pneumonias to laboratory animals and to experimental calves. The pathenogenetical and etiological implications of the histological findings are discussed in relation to pneumonias of man and other animals. The pathology of 36 cases of "white scour" is described. The three most important findings were (l) the pathology of the disease is not "specific", (2) 15 of the cases showed concurrent pneumonia, and (3) 11 showed lesions of the central nervous system (meningitis and subarachnoid haemorrhage. As is the case in the human infant, the clinical syndrome of "gastro-enteritis" in the calf is not associated with inflammatory changes in the alimentary canal. Several other diseases are described of which two, a type of renal agenesis and a form of sulphonamide poisoning, have not been previously reported. The role of peptic ulcers in initiating pyaemia is described