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    The epidemiology of Yersinia infections in goat flocks : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy at Massey University
    (Massey University, 1990) Lañada, Eugene Baticados
    Due to the increasing frequency of yersiniosis in goats, it was considered necessary to study the behaviour of Yersinia species in goat flocks. The aim of this study, carried out in several phases among goat farms in the Manawatu, was to identify factors involved in the epidemiology of Yersinia infections, which might eventually lead to the formulation of effective control measures. The first phase of the study was the screening of goat flocks for the presence or absence of Yersinia species infections. This phase was considered necessary, since prior to the study the prevalence of such infections among apparently healthy goats were unknown. The results of this phase showed that 18 of the 30 farms screened (60%) were positive for the infection. Concurrent with the screening phase, a postal survey was undertaken involving the farmers of the thirty goat farms. This survey gave an indication of the production and health management practices implemented on goat farms in the region, and how these related to the presence of Yersinia species infections in the goat flocks. The results of the survey (97% response rate) showed that farmers generally managed goats in the same manner as sheep, and that the farmers' knowledge of the presence of gastrointestinal bacterial infections such as yersiniosis was almost nonexistent. Stress-related management practices which might be associated with the presence of Yersinia species infections were also identified in this phase of the study. The farms found positive during screening were included in the next phase of the study, the prevalence survey. This phase involved the sampling of three age groups from each flock: kids (less than one year old), hoggets (one to two years old), and adults (two to five years old). The results of this phase showed that the mean level of Yersinia prevalence of all the combined age groups from the 18 farms was 15%. In kids, the prevalence was 24.7%, in hoggets 11.8%, and in adults 9.6%. The predominant Yersinia species recovered from kids was Y. enterocolitica biotype 5, comprising 94.5% of all the isolates. Among hoggets, Y. enterocolitica biotype 5 and the environmental strains (Y. frederiksenii, Y. kristensenii and Y. intermedia) were about equal in prevalence, while among the adults, the environmental strains predominated, comprising 92.7% of all the isolates in that group. The prevalence survey also revealed that infection levels among ihe different goat flocks were extremely variable, and since sampling was conducted only once, the results were obviously only minimum estimates of flock infection levels. In order to explain the inherent drawbacks associated with a single sampling event, it was decided to carry out repeated samplings on the same group of animals over time, particularly as Yersinia species infections had been reported in the past to be commonest during the colder months of the year. Thus a cohort study was implemented, where selected groups of goats stratified into three age groups (kids, hoggets and adults) were subjected to repeated monthly samplings for at least 12 months. Several key points were brought to light by the cohort study. It was shown that the incidence of potentially pathogenic Yersinia species (Y. pseudotuberculosis and Y. enterocolitica biotypes 2, 3 and 5) appeared to have a distinct seasonal variation, a characteristic which was absent in the incidence of the majority of the environmental strains (Y. enterocolitica biotype 1A, Y. frederiksenii, Y. kristensenii, Y. intermedia and Y. rohdei). Of the climatic factors studied, low daily minimum temperatures were particularly influential on the incidence of the potentially pathogenic strains, while increased monthly precipitation levels were highly influential on the incidence of the environmental strains. Age was also an important factor in the incidence of the infections, with the younger age groups showing a higher incidence of the potentially pathogenic strains and the older age groups showing a higher incidence of the environmental strains. The ability of the animals to develop apparent immunity against subsequent reinfection by the potentially pathogenic Yersinia species was another finding of the cohort study. The numerous strains of Yersinia isolated throughout the study exhibited heterogeneity in their reactions to biochemical testing, even among strains within the same species. An attempt was therefore made to classify these strains using numerical taxonomy. This procedure indicated that the pathogenic and environmental Yersinia strains were quite different, as shown by a number of distinct clusters.
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    Effects of Yersinia enterocolitica infection on the development of the small intestine in newborn piglets : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physiology at Massey University
    (Massey University, 1993) Shu, Dairu; Shu, Dairu
    A model of bacterial gastroenteritis has been developed in which the effects of Yersinia enterocolitica infection on the structural and biochemical development of the small intestine have been examined in neonatal piglets both during the infection period (3 and 5 days postinfection) and during the subsequent recovery period after antibiotic therapy (at 14 days). The potential of oral bovine lactoferrin and another bovine milk protein for preventing or reducing the effects of Y. enterocolitica gastroenteritis have been evaluated in these piglets. Newborn, colostrum-deprived piglets were inoculated orogastrically with a high dose (about 3 x 1010 colony forming units/ml) of Y. enterocolitica serotype 0:3, biotype 4. Diarrhoea began between 40 hours and 4 days after inoculation in 18 of the 19 animals and microabscesses, the typical lesions of Yersiniosis, were present in the mucosa of the small intestine in all infected piglets. At 5 days postinfection, microabscesses also were present in the liver of 7 of 8 piglets, and in the mucosa of the stomach in 2 animals. The mucosal damage and resulting malabsorption were reflected in the lower plasma glucose, Na+ and Cl- concentrations. Yersinia enterocolitica infection reduced the body weight but not body length, but did not significantly affect the gastrointestinal tract length or weight or the growth of non-intestinal organs except the liver. There were markedly lower lactase and sucrase, but not maltase and Na+-K+-ATPase, activities in the small intestine. The mucosal protein and DNA contents and the ratio of RNA to DNA in the small intestine were not significantly different in infected animals. Rapid proliferation of crypt cells resulted in crypt enlargement in the entire small intestine, but reduced vacuolation of the epithelium of the distal small intestine. Following institution of effective antibiotic therapy, gastrointestinal lesions were absent. Compared with controls, the piglets gained body weight at the same rate, although remaining lighter in weight, and organ weights and concentrations of plasma Na+ and Cl-, but not glucose, were no different. Previously-infected piglets retained an altered profile of disaccharidase activity with a lower lactase activity, higher maltase and sucrase activities and early appearance of sucrase activity in the ileum. There were fewer vacuoles in the epithelium of the distal ileum. A bovine milk fraction, but not bovine lactoferrin, appeared to reduce the severity of the infection due to Y. enterocolitica, there being shorter crypts, fewer proliferating crypt cells and higher lactase activity. The group means for the lesion number were also much lower although not significantly different. Oral supplementation with bovine lactoferrin in the milk formula did not have any beneficial effects in the infected piglets. In non-infected piglets, lactoferrin appeared to have trophic effects on the kidney and the small intestinal crypts, increased the lactase activity and caused an unexplained reduction in plasma glucose concentration and liver weight. Yersinia enterocolitica enteritis in newborn, colostrum-deprived piglets accelerated the maturation of the epithelium of the small intestine, indicated by reduced enterocyte vacuolation and an altered disaccharidase profile.
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    Enhanced surveillance of potentially foodborne enteric disease within a New Zealand public health service : thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies in Public Health at Massey University, Palmerston North, New Zealand
    (Massey University, 2009) Shadbolt, Tui Louise
    An enhanced notified enteric disease surveillance trial began on 1 July 2007 and continued until 30 June 2008. The aim of the trial was to measure the quality, timeliness and completeness of data collected and submitted by a regional Public Health Service (PHS) to the Institute of Environmental Science and Research Limited (ESR), via the national disease database (EpiSurv) for notified cases of enteric diseases. The trial evaluated two different methods of data collection: postal questionnaires and telephone interviews. Telephone interview techniques were used to improve the contact rate, timeliness and completeness of data gathered from all notified cases of campylobacteriosis in the Manawatu, Horowhenua and Tararua regions. The target set for the project was to achieve a 95% contact rate with 90% full completion of all EpiSurv data fields. For all notified cases of campylobacteriosis a 97% contact rate was achieved in a time frame of between zero to 20 days (three day median) and completeness of all the EpiSurv case report fields ranged between 96 – 100% in the final data. Prior to the commencement of the study, between 1 July 2004 to 30 June 2005, MidCentral PHS (MCPHS) made contact with around 58% of all notified cases of campylobacteriosis and 77% of all other notified enteric disease cases1 . A short pre-screen mail questionnaire, with reply-paid envelope, was sent to all notified cases of cryptosporidiosis, giardiasis, salmonellosis and yersiniosis in the MCPHS regions. EpiSurv case report fields were completed using information supplied in the returned questionnaires. Return rate, timeliness, and completeness were compared with the telephone interview group. Fifty three percent of cases we attempted to contact via mail questionnaire responded within two to 63 days (six day median) and completeness of all the EpiSurv case report fields ranged between 81 – 100%. In addition, we monitored the newly introduced ESR Early Aberration Reporting System (EARS) flags for increased levels of disease compared to historical disease rates, and assessed its usefulness as a tool to identify potential outbreaks in the region. While no outbreaks that had not already been identified by PHS staff were found by monitoring the EARS system, EARS has become an important tool in the MCPHS for comparing our rates of disease with bordering PHSs. EARS also provided a good quick reference tool for media enquiries and the graphs produced in EARS have been well utilised as visual aids for training and seminars presented during the trial period. The results of the surveillance trial initiatives were compared to the rest of New Zealand (NZ) over the same time frame and with a comparable, medium-sized, PHS. While the results of the telephone interviews from the MCPHS trial were close to the comparable PHS, they were significantly higher than for the rest of NZ. The postal questionnaires achieved a lower contact rate than the comparable PHS but similar to the rest of NZ. However, the quality of data gathered in the returned MCPHS postal questionnaire was significantly higher in most fields. Additional analysis was undertaken which indicated that those cases living in higher deprivation and rural areas were less likely to respond to a postal questionnaire. An over-representation of common enteric disease notifications from rural areas in the MCPHS was also highlighted by our research. This trial has shown the effectiveness of utilising telephone interviews and telemarketing techniques for gathering timely and complete data for human enteric disease surveillance within the MCPHS. It has also demonstrated that a short pre-screen questionnaire can be effective in collecting good quality data needed to complete the standard EpiSurv case report form.