The 23rd IPVS Congress - a focus on trans boundary diseases

Friday, December 5, 2014

What are the major trans boundary and emerging diseases confronting producers and who is accountable for them? In the first of a two-part report on June's IPVS conference in Cancun, Mexico, the author summarizes the remarks of a leading Canadian veterinarian on this subject

by ERNEST SANFORD

The 23rd International Pig Veterinary Society (IPVS) Congress was held in Cancun, Mexico, last June with 2,714 registrants from 60 countries in attendance.

The conference was led off with a stirring lecture by Dr. John Harding, Canadian swine veterinarian and professor at the Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon. Dr. Harding focused his lecture, entitled "Accountabilities in the age of trans boundary and emerging diseases," on three key areas:

• A review of current trans boundary diseases.
• A summary of expert opinion on control of catastrophic swine diseases.
• An assessment of what should be done and who is accountable.

He informed us that over the last 30 years, about 90 novel pathogens (an average of three per year) have emerged to threaten pigs and people worldwide. Eighty per cent of these new pathogens are RNA viruses and most are zoonotic or potentially zoonotic (disease that can be transmitted between animals and humans). He noted that the predictors of zoonotic viruses are a high mutation rate of the virus and replication in the host's cytoplasm (not the nucleus).

These properties favour RNA viruses and single-stranded DNA viruses, both of which have a small genome, rapid rate of replication and polymerase enzymes with poor proofreading capabilities, prone to errors. They also feature production of swarms of slightly different genomes (called quasispecies) in the same host, which facilitate recombination, re-assortment and interspecies transmission.

With this background, there are many potentially pathogenic viruses that can affect commercial swine that are already lurking and ready to emerge almost anywhere in the world, including:

–    Torque teno sus viruses 1 & 2 (TTSu 1 & 2)
–     Menangle porcine virus (MenPV)
–     Nipah virus (NiV)
–     Ebola virus (EBOV)/Ebola Reston virus (EBOReV)
–     Novel parvoviruses – five genera including porcine parvovirus (PPV) and Porcine Bocavirus (PBoV)
–     Porcine Astrovirus (PAstV)
–     Porcine Torovirus (PToV)
–     Aichivirus (AiV-C), formerly Porcine Kobuvirus
–     Porcine Lymphotropic Herpesvirus (PLHV)
–     Picobirnavirus (PBV)

In addition, there are several emerging diseases and syndromes with potential to affect our swine industry, which include New Neonatal Porcine Diarrhea (NNPD), Peri-Weaning Failure to Thrive syndrome (PFTS) and Brachyspira hampsonii.

Dr. Harding emailed a short questionnaire to about 300 swine veterinarians in the Americas, Europe, Australia, New Zealand, Asia and South Africa and received 162 replies. The first question asked was "List the three most significant diseases or pathogens currently threatening the global swine industry." The three diseases that stood out in the answers were PRRS, Porcine epidemic diarrhea (PED) and African swine fever (ASF)

The second and third questions were: "What should we 'stop' or 'start' doing to substantially decrease the risk of catastrophic emerging, trans boundary and/or foreign animal diseases at home and globally?" This question generated more than 930 responses.

Responses on things to "stop" doing were heavily oriented towards feed and biosecurity. There was great support for stopping the importation of feed and feed ingredients from high-risk countries, implementing minimum quality control standards and eliminating swill feeding in countries that still permit or condone it.

For biosecurity, respondents also suggested stopping direct and indirect contact between commercial pigs and wildlife, including wild boars, and ceasing ignoring widely accepted biosecurity guidelines. Stopping introducing live animals into production units without quarantine and stopping live pig exhibitions were high on the list.

Biosecurity was also at the top of the list of things to "start" doing. Implementing accepted biosecurity principles and more education of producers and staff were the things most cited to start doing. There were calls for more collaboration and transparency among governments, laboratories, universities and producers to enable a more cohesive response to infectious disease threats.

Accountabilities. Dr. Harding highlighted 10 "accountabilities." The accountabilities were assigned to federal governments and various sections of the swine industry, locally and globally, and were specifically for global control of emerging and trans boundary diseases (like PED). Here are four examples:

Accountability #1 – national governments
What can we expect government responses will be to exotic diseases listed by the OIE (World Organization for Animal Health)?

Accountability #2 – swine industry globally
Develop realistic expectations regarding government's responses to exotic diseases versus non-exotic, trans boundary diseases.  Expect "too little, too late" unless it affects trade or public health.

Accountability #5 – feed industry globally
Discontinue the importation of animal protein destined for livestock or pet food and find alternative sources of protein suitable for nursery pigs.

Accountability #6 – national governments
Ban feeding of rendered pigs and pig byproducts back to pigs. This one is particularly important to us in Canada as, after establishing exceptional biosecurity against importing PED Virus  (PEDV) from the United States for nearly a full year, the PEDV was introduced into Canada (Ontario) via spray-dried plasma in suckling pig feed.

As for major conference topics, the usual suspects took centre stage, including PCV2, PRRS, SIV, oral fluids, Brachyspira and, especially at this IPVS, PED. BP

S. Ernest Sanford, DVM, Dip Path, Diplomate ACVP, is a Swine Veterinary Consultant based in London.