Abstract
This thesis brings together my published work in the field of investigation and control of animal diseases and
infections, including zoonoses. It was undertaken between 1980 and 2011 whilst employed by the former Veterinary
Investigation Service and Veterinary Laboratories Agency (VLA), firstly based in Norwich, Norfolk and
subsequently in Bury St Edmunds, Suffolk. Part 1 covers a broad spectrum of predominantly novel and emerging
conditions, or unusual manifestations of known diseases, and is subdivided into separate sections for pigs, sheep,
cattle, goats and birds. These investigations used clinical field work, diagnostic necropsies and currently available or
newly introduced laboratory tests, and relied heavily on initial referrals from local veterinary practitioners and
extensive subsequent cooperation from farm managers or owners. Part 2 covers zoonotic diseases and infections,
including separate sections on Escherichia coli (mainly verocytotoxigenic serogroup 0157), cryptosporidiosis and Q
fever. Most of the work on zoonoses was undertaken during the period from 2004 onwards when I was VLA project
leader for non-statutory zoonoses and it includes investigations into human outbreaks of zoonotic disease initiated at
the request of public health professionals. In both parts of the thesis the publications have been grouped within their
respective sections to demonstrate progression of ideas and activities, including relevant test development.
In the early 1980s, pig producers in East Anglia and elsewhere experienced devastating piglet losses from
transmissible gastroenteritis (TGE). The subsequent history of TGE in Britain until its eventual demise by the end of
the 20th century is charted in the pig disease section. Other pig topics include swine influenza, a previously
undescribed zinc induced copper deficiency anaemia in swill fed pigs and farm biosecurity Although sheep are a
minor species in East Anglia, a number of new and emerging conditions were recognised, often before being seen in
other regions. The foremost is maedi-visna which was first identified in indigenous sheep in Norfolk in 1983 and
soon became strongly associated with the area. Other conditions recorded include a high morbidity ovine vulvitis
outbreak and the Dandy-Walker syndrome. Despite a relatively small cattle industry, the region has exhibited many
unusual bovine diseases including probably the most severe outbreak of acute bovine virus diarrhoea (BVD) ever
recorded in Britain. The emergence of fascioliasis in East Anglia is also detailed. Close involvement with the former
MAFF Cattle Health Scheme in the late 1980s led to an interest in herd biosecurity, abortion and the development of
milk antibody tests for Leptospira Hardjo, and BVD and IBR virus infections. These tests were subsequently
introduced within the VLA and used for assessing and monitoring herd disease status. Regular bulk milk antibody
screening of a high health status dairy herd led to the detection of novel high morbidity non-pathogenic IBR virus
infection. Publications on several new or emerging diseases of goats and birds are also included in Part 1.
Cattle are the principal reservoir of VTEC 0157 and the primary source of most human infection. A number of
outbreak investigations, particularly on farms open to the public, revealed the extent of infection in a diverse range
of other animal species including sheep, pigs, horses, goats and camelids. An outbreak amongst visitors to a wildlife
gardens in Norfolk was linked to contact with wild rabbits co-grazing with infected cattle. Cryptosporidium parvum
infection is prevalent in young ruminants and has led to zoonotic outbreaks amongst visitors to farms. A series of
investigations used a newly adopted sensitive fluorescent antibody test to define the extent of sub-clinical infection
in pigs, calves and lambs, including orphan lambs being bottle-fed by visitors to an open farm. 0 fever emerged as a
zoonosis of increased importance following human outbreaks in Britain and a massive outbreak in the Netherlands.
My participation in a multi-disciplinary outbreak control team for a Q fever outbreak in Cheltenham in 2007 led to
the development of improved diagnostic tests (PCR and ELISA) which were subsequently used for farm outbreak
investigations and surveys in Britain. Other zoonoses featured include Leptospira Icterohaemorrhagicae infection
acquired from pet rats and zoonotically acquired Corynebacterium ulcerans diphtheria.
