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Investigation of Leptospira serovars in pigs in the UK; transmission factors and control - OD0214

Description
Results from passive surveillance of pigs indicates that there is an increasing incidence of Leptospira in the national herd. The potential economic impact of leptospirosis (e.g. infertility and reduced production, reduced exports, transmission to other farmed animals, zoonotic hazards) requires an understanding of those factors that influence this apparent increase. These factors may include changes to husbandry practices and use of antimicrobial medications, for example. In order to provide policy advice on the control of leptospirosis in pigs, studies aimed at establishing (1) the strains endemic to the UK pig herds, (2) validating current diagnostic procedures by use of endemic antigens, (3) determining the seroprevalence and geographic distribution of letpospires in pigs, (4) risk factors at herd level that will include husbandary practices and use of antimicrobials, (5) factors influencing transmission including wild life reservoirs will be undertaken. This study will result in peer reveiwed publications of findings and a report to DEFRA that is aimed at providing scientific evidence to inform policy.
Objective
Objective 01
To isolate endemic leptospira serotypes endemic in the national pig herd
Subobjective 1; identify farms with history of poor reproduction associated with leptospira
Subobjective 2; collect aborted foetuses and culture from kidney, urine and blood
Subobjective: achieve pure culture of leptospira
Objective 02
To identify endemic leptospira serotypes endemic in the national pig herd
Subobjective 1; complete sequence analysis of the gene encoding the 16S RNA
Subobjective 2; compile sequences and compare with database entries to provide preliminary identification
Subobjective 3; compare genotype with other leptospira seotypes by IS-RFLP methods developed in the previous DEFRA funded leptospirosis study, OD0212.
Objective 03
To apply endemic leptospira serotypes to retrospective and prospective serolgical analysis of the national pig herd
Subobjective 1; complete development of culture methodology and confirm QA
Subobjective 2; apply endemic strains to MAT tests of stored serum, from routine submissions and from sera arising from the epidemiological survey within this project
Subobjective 3; compare outcomes of MAT between endemic and reference antigens
Objective 04
To develop a PCR for the specific detection of endemic pig associated leptospira serotype(s)
Subobjective 1; use sequence analysis of the gene encoding the 16S RNA to define possible serotype specific PCR primers
Subobjective 2; utlise ligated mediated PCR to identify unique IS-chromosomal junction sequences
Subobjective 3; use IS-chromosomal junction sequence to design specific PCR
Subobjective 4: apply PCR to stored tissue samples from 01/02 above
Subobjective 5; apply PCR(s) to support prospective epidemiological studies; urines and aborted foetuses will be the primary target specimens for analysis.
Objective 05
To analyse and use existing leptospiorsis diagnostic databases
Subobjective 1; Identify trends in private requests for diagnostic testing
Subobjective 2; Identify trends in pig associated serotypes arising from diagnostic data
Subobjective 3; Utilise current database and local knowledge to identify probable high prevalence or at risk farms; establish these as probable case study farms for longitudinal analysis (Objective 8).
Subobjective 4; Assess validity of existing passive surveillance system as a method of monitoring porcine leptospirosis in the future by comparing existing leptospirosis data to results from cross-sectional survey (Objective 6).
Objective 06
To implement a cross-sectional prevalence survey
Subobjective 01; Collect blood, tissue (kidney) and urine samples from sows and gilts slaughtered at participating abattoirs
Subobjective 02; traceback and recruit farms and their associated veterinary practices to obtain questionnaire information and for serum/urine collection from remaining gilts and sows in herd
Subobjective 03; complete serological analysis using current leptospira reference strains ensuring coverage of all representative leptospira
Subobjective 04; collate data from recruited farms and associated veterinary practices and report on comparison of prevalence in slaughtered pigs with retained pigs and comparison of these prevalences with predictions from trend studies (objective 05)
Subobjective 05; Identify serotype-specific trends in affected regions and by management types, pig age and breeds.
Objective 07
To define risk factors that affect likelihood of a herd being infected with Leptospira serotypes
Subobjective 1; Devise questionaire for study
Subobjective 2; Use data collected from infected and leptospirosis-free herds (Objective 6), descriptively analyse farmers’ use of antibiotics, awareness of leptospirosis and use of other control measures to prevent losses due to leptospirosis
Subobjective 3; Apply logistic regression analysis to identify herd-level risk factors for leptospirosis
Objective 08
To define transmission dynamics of leptospira serotypes within endemically infected herds
Subobjective 1; Routinely monitor serostatus of gilts on endemically infected herds to detect seroconversion and to identify serotypes
Subobjective 2; Routinely collect information from herd owner regarding herd biosecurity practice and management and disease events occurring on the farm.
Subobjective 3; Describe and analyse spread of infection within herd and any association with events affecting herd
Subobjective 4; Using linear regression, determine impact of leptospirosis on gilt productivity

Project Documents
• Final Report : Investigation of Leptospira serovars in pigs in the UK; definition and detection of infecting agents   (446k)
Time-Scale and Cost
From: 2003

To: 2006

Cost: £190,581
Contractor / Funded Organisations
Veterinary Laboratories Agency
Keywords
Animal Diseases              
Animal Health              
Biotechnology              
Control              
Leptospirsis              
Pigs              
Plants and Animals              
Transmission              
Fields of Study
Animal Health