A study of some endemic viruses of cattle, with particular reference to enteric viruses : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science at Massey University, New Zealand
This investigation was undertaken to isolate and characterise a number of viruses from diarrhoeic cattle faeces, as a preliminary step in the systematic investigation of viruses as possible causes of diarrhoea in cattle, and more particularly calves. A further and important aim was to gain further experience in a number of virological procedures. Using 3 passages of inocula in each of secondary foetal bovine kidney and lung cells, and monkey kidney (Vero) cells, 7 viruses were isolated from 56 faeces, 2 intestinal samples, and 1 spleen, all from scouring animals. Five of the isolates were found to produce a rapid and complete cytopathic effect in a variety of cell cultures, and their biological and physicechemical properties were subsequently studied in some depth. One of these isolates was also studied with the immunofluorescent technique, and its buoyant density was determined in a caesium chloride gradient. These isolates were concluded to be bovine enteroviruses, and were found in further studies to be separable into 2 types on the basis of cross-neutralisation tests, fluorescent antibody tests, and behaviour in the presence of low concentrations of hydroxybenzyl benzimidazole. These 2 serotypes on further cross-neutralisation tests were found to be serologically distinct from the 7 U.S. standard serotypes that were available. Another of the isolates was found to cause a slow growing and relatively nonprogressive type of cytopathic effect in only Vero cells, and was consequently harder to study. On the basis of limited studies of this isolate, it was concluded to be probably a member of the diplornavirus group, possibly having some affinity with the "reo-like" viruses. Further more precise studies will be needed to confirm or refute this relationship. The remaining virus, which was isolated from the spleen, was identified as being bovine viral diarrhoea (BVD) virus on the basis of its cytopathic effect and neutralisation by standard BVD antiserum. A limited survey for neutralising antibodies to infectious bovine rhinotracheitis and BVD viruses, and haemgglutinating-inhibiting antibodies to parainfluenza 3 virus and reoviruses 1, 2, and 3 was undertaken. It showed that antibody to all the viruses was present in a considerable proportion of the North Island cattle population. This work can only be regarded as a preliminary study, as it is probable on the basis of overseas work that a number of other viruses remain to be isolated from diarrhoeic cattle faeces. It is hoped to continue this investigation and to eventually establish a better understanding of the relationships between viruses and bovine gastrointestinal disease, and more particularly to establish their possible economic significance.