PRRS, PED PCV2, and SIV: How can we improve our support to the swine industry?

“Insanity: doing the same thing over and over again and expecting different results.” Albert Einstein

Globalization, the increased movement of people, swine, supplies, and food pose growing risks to the swine industry. An example of the above are the economic losses and social impact caused by the worldwide spread of porcine epidemic diarrhea (PED), porcine reproductive and respiratory syndrome (PRRS), swine influenza (SIV), and porcine circovirus (PCV2). These losses include, among others, the financial impact caused by increased mortality, decreased reproductive and productive performance, and a significant augmentation in secondary diseases, the purchase of drugs and vaccines, as well as enlarged cost of diagnosis and changes and/or improvements in biosecurity. This dealings have challenged our profession and made us reflect on how we can improve our support to our pork producers and in general, to the swine industry. It is imperative that we ensure that everyone involved in this industry understands how:

a. Disease enters to a farm?

b. A farm develops a plan/ tools to reduce the risk of disease contamination

c. Owners and veterinarian rapidly responds to an important health issue

d. Can promptly diagnose a new disease

e. Can communicate its presence to neighbours, veterinarians and authorities

f. Develop tools/plan to contain the disease from spreading to its neighbourhood/area and country

g. What is an emerging disease?

h. What is food safety?

Travelling around the world and consulting in different countries that before 2013, where and few still remain free of some of the above mentioned diseases, has made me reflect on what would be my “non-negotiables” to avoid continuous chaos in our industry. To my surprise, and in my advice, today, not much has to be invented. I believe that we as an industry have failed in applying the tools that have been provided to us in ensuring a healthier and more productive industry.

So where have we failed as practitioners to apply existing research and technology in order to support our producers? 

Preventing the spread between and within pig populations is a critical component of a farm’s disease control program. Biosecurity can be termed as: “The set of measures taken to protect herds from the introduction of any new infectious pathogen”. Without totally eliminating the risks, a good biosecurity and management program can drastically help the herd to protect its health status. This of course includes external and internal routes of transmission for pathogens, as well as some biosecurity and management measures to stop its transmission. Keeping viruses out of the farm represents a challenging task for modern swine production. Therefore, enforcing a standard application of strong biosecurity protocols to limit vertical, horizontal, mechanical and aerosol transfer of pathogens is imminent. Steps involved comprise creating a biosecurity checklists for farms that include, among others:

a. Risk identification

b. Application of protocols/plans,

c. Training, and continuous education

d. As well as audits and testing of farm personnel

This is easily said, but very difficult to constantly respect and maintain; especially in certain production systems and cultural approaches.

To prevent mechanical transmission, disease prevention focuses on incoming materials and people. Personnel and inanimate objects like shoes, clothes, materials and equipment can act as mechanical carriers and transmitters of viruses. It is therefore vital to implement a biosecurity protocol for personnel entry to the farm. More and more new and retrofitted swine facilities include a disinfection room allowing fumigation of incoming materials. Wearing disposable coveralls and plastic boots and applying the “bag-in-a-box” shipping method efficiently prevents pathogen transmission.

Strategies to reduce virus circulation are:

a. Adequate gilt acclimation

b. Good colostrum immunity

c. Use of Mc Rebel™ in the farrowing area

d. Wean negative piglets

e. Reduction/elimination of viral challenge to piglets and nursery animals

f. Use of area specific tools and equipment

g. Unidirectional flow in all the farm

h. Strict all in/all out in all areas of the farm

i. Monitoring farm stability when specific and effective test is available

j. Creating a solid population immunity, when an effective vaccine is available

k. Constant risk analysis to find opportunity areas.

l. Continuous personnel training

m. Biosecurity audits

Likewise, older pigs and their secretions can be a source of infection to younger pigs on premises where biosecurity between groups is lacking. Therefore, subpopulation of infected and non-infected pigs play a very important role in the persistence of the infection in the farms and areas.

Vehicles, as well can carry many pathogens. Most viruses are only moderately resistant to environmental degradation. Researchers have demonstrated that a transport vehicle contaminated with certain viruses can transmit infection to naïve pigs. Effective treatment eliminating viruses from a vehicle has been described as a combination of litter removal, washing, disinfection, and drying, so why have we not implemented this in all farms and abattoirs? Also, one should put up a recovery container for dead pigs at a good distance from the farm, in order to prevent carcass collection trucks from getting too close to the farm. For the same reason, vehicles coming to a farm for picking up live pigs should be empty, clean and disinfected. 

Figure 1. Example of pig movement in a swine production area (Mondaca et al., 2010)

 

The possibility of aerosol transmission of several of these viruses has also risen controversy during a number of years, nonetheless, several of them are now recognized to be spread through aerosol. Several filtration systems have been developed to protect swine farms against this mode of transmission, and we should consider them more seriously as an option to protect our farm. 

While veterinarians have developed a variety of strategies to control and eliminate the disease from pig herds, the risk of re-infection remains high even with the best current practices of management and biosecurity. It has been shown over and over that the repeated failures of non-coordinated control and elimination efforts and the ease with which the disease is transmitted from one herd to another strongly suggest that a regional approach is necessary. Therefore, understanding the patterns, causes, and effects of these diseases would certainly reduce their impact. A basic requirement to understand changing local, regional, or global distributions of disease and/or disease risks is the real time access to current information providing alertness of factors potentially associated with disease risk. Developing and/or using more surveillance systems to control disease at a regional level is critical for the swine industry. This information would allow control in areas of high prevalence and high pig density, while elimination would be feasible in areas of low prevalence and low pig density.

In order for this approach to be successful, we need to changes several paradigms:

a. First and foremost, learn to work together, as a team in order to achieve a common goal…

b. Identify all swine premises in an area

c. Identify pig-related facilities in the area

d. Classify pig sites according to their disease status

e. Design control plans/strategies, and

f. Focus individual projects to combine with existing regional projects 

Figure 2. Example of identification of swine sites in a disease surveillance program (Mondaca et al., 2010)

 

Continuous disease monitoring, diagnosis and surveillance is necessary to achieve:

a. Early detection of disease outbreaks

b. Ratification of the presence or absence of a specific disease in farm/region

c. Definition of subpopulations

d. Definition of risk factors associated with the spread of disease

e. Planning and setting priorities

f. Evaluation of interventions

g. Resource allocation

Active surveillance has largely been criticized for its cost and labour intensiveness. However, it should be highlighted that it allows for early detection of outbreaks permitting for estimates of spread to farm/areas and permitting the establishment of early and effective control strategies. Surveillance can assist by providing information to make intelligent and more economical decisions rather than waiting until the disease has already spread in the area/region/country.

Essentials components of a monitoring program are:

a. Sample size, always dependent on prevalence, confidence interval and error margin.

b. Type of samples to be collected (i.e. sera, oral fluids, environmental samples, aerosol, etc.)

c. Analysis of all the collected data to gain information of the area under control

d. Establish reporting mechanisms to all the participants of a group

e. Action plans to improve the established working plan and therefore the control of the targeted disease

However the advancement of these programs will not be successful if clarification of the reason(s) for collecting information/different samples types, the use, management and analysis of the data (continuous and the confidentiality) are maintained. Finally, direct benefits such as, health/production improvements and return on investment, and indirect benefits (reduction of lateral infection, improved area knowledge to reduce infection risks, improvement of employees moral, industry perception and enhanced communication among the working group) should occur.

Two final considerations, a good diagnostic laboratory and an excellent diagnostician, with exceptional communication skills, are mandatory to the success of this diagnostic program. 

Please read the following statement:

“Today the variation in clinical signs and apparent emergence of new syndromes in these viral diseases is due in part to changes in PRRSV genome. Therefore, the appearance of PRRSV variants with new genetic compositions increases the likelihood of increased variation in the virus and in the diseases it causes, including disease characteristics, modes, and ease of transmission, changes in cell permissiveness, and species specificity, capability of persistence and escape from vaccinal immunity”. ¹¹

Then, please analyze and explain the following dendrogram: 

(Murtaugh, 2010) I think I made my point very clear!

Networks around the swine veterinary community should be as common as Facebook, Twitter or Linkedin, however they are not. These networks should combine practice data with communications amongst swine veterinarians which would help manage swine health issue around the world. Some of these networks already exist (i.e. http://www.swinehealth.ca/CSHIN.php, http://bioportal.ucdavis.edu/ ). How do they work?

a. They collect data about swine health

b. Data is collected daily and analyzed

c. Information is added by veterinarians and swine experts

d. Information about the diseases and how to control them is produced

e. Information is shared among veterinarians

f. Veterinarians and industry associations use the information to help producers deal with disease

g. Swine veterinarians and specialists hold regular web-based meetings to review and identify new health challenges

h. Participating veterinarian fill a form describing problems they have recently encountered

i. Reports from these meetings are sent to all swine veterinarians, keeping everyone informed about changes to swine health and ways of managing it.

j. The network is also a way to quickly communicate whenever something unusual and important is observed by a veterinarian or laboratory

k. Real time maps of disease surveillance are produced

l. Alerts can be sent on a real time basis

m. All information is kept confidential

In my point of view, PED has shown us that if we do not break status quo and existing paradigms, it will become almost impossible to protect swine herds from emerging disease, help veterinarians solve disease problems, and help the pork industry to maintain current markets and access new markets. 

There is no single successful strategy for control of all these viral and emerging diseases. However, we have many answers and options, that for some reason, we have chosen not to use. Recently, experienced has proved that area regional control programs are the answer to future control and possible elimination. Virus control strategies and specific farm and region situations are so variable, it is imperative that experienced practitioners, producers, diagnosticians and research workers continue to objectively expand their knowledge, communicate and network to better control and eventually eliminate these financially impacting diseases.