US - Two new papers indicate the most important biosecurity measures to control Porcine Epidemic Diarrhoea (PED) virus and how oral feedback of piglet faeces to the breeding herd may help protect vulnerable newborn litters from the infection. Jackie Linden summarises the main points of this latest research.
Most Effective Biosecurity Measures against PEDv
Preliminary results from the North Carolina Biosecurity Questionnaire indicate some of the most likely sources of infection with PED virus (PEDv).
Author, A. Beam of the USDA APHIS Centers for Epidemiology and Animal Health, stresses that the epidemiological study is not yet completed and that the results presented in the report - published by the University of Minnesota College of Veterinary Medicine - are based on incomplete data, and will change.
Over the previous two weeks, PEDv case farms had more visits from trucks delivering feed and collecting live pigs and dead haul/renderer than control farms that are clear of the infection.
Other factors that differ between the two groups of farms indicate that the following are risk factors:
- Using borrowed trailers from another swine site in previous two weeks
- Cull sows/gilts/boars/pigs removed in the previous two weeks
- Weaned pigs removed to nursery or wean-to-finish site in the previous two weeks
- Producer/family working off the farm in an abattoir or other swine farm
- Producer/family working off farm in another area of the swine industry, e.g. feed mill
- Visit from dead haul/rendering site to pick up dead pigs in previous two weeks
- Wild birds, rodents and other pests seen in pig/hog buildings in previous two weeks
- Moderate or severe problem with wild birds, e.g. buzzards, in previous two weeks.
Farms are advised to avoid or reduce the practices above and increase biosecurity practices relating to visitors.
This summary represents data from 53 sites (28 PEDv cases and 25 controls); although 93 per cent of the case farms have sows, only half of the control farms have sows.
Controlled Oral Exposure (Feedback) of PEDv
A paper provided recently to the American Association of Swine Veterinarians (AASV) describes a field-based strategy to enhance sow herd immunity to PEDv in herds suffering a recent outbreak.
In a philosophic preamble to the paper, Kent Schwartz, DVM, MS, of Iowa State University Veterinary Diagnostic Laboratory and co-authors from Abilene Animal Hospital PA and PFFJ, LLC write: “We believe, regardless of the following words offered, that no one knows or can accurately predict how present clinical responses to PEDv infections will manifest over time.
“There are no tested, objective protocols. There are, at best, vague indices which are often used to define ‘success’ or ‘failure’. Moreover, variation is a consistent feature of biology and swine production. Herd exposure to farrowing materials has evolved on farms to be a procedure that is commonly performed without consideration of context, clarity of objectives or process design. Based on our education and experience, we believe the following represents a logical, empirical, reasoned and balanced approach for herd exposure to PEDv."
Because PEDv is a mucosal (gut surface) pathogen, Schwartz and co-authors stress that it is important to understand that effective active immunity occurs at the level of the gut mucosa in the form of lactogenic immunity provided by IgA in milk.
This contrasts with many diseases, in which the IgG antibody in colostrum provides systemic protection for the piglet. PEDv is, therefore, unlike PRRSV, PCV2, SIV or PRV and the authors of this paper warn that any extrapolations from knowledge or experiences with other diseases should be made with care.
They go on to explain the concepts, science and experiences of controlled oral exposure as well as the specific strategies needed to achieve whole herd immunity.
In summary, Schwartz and his co-authors recommend feeding piglet faeces collected immediately after the onset of diarrhoea to sows and gilts within a short time-frame, and explain in the paper how this can be achieved in practice.
Find out more information on PED by clicking here.
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