55th AASV Annual Meeting summary: Vaccines and biosecurity

Vaccines

Vaccine platforms: What’s currently available? Amy Gill. USDA

Industry pressure to find solutions to emerging pathologies is increasing. The options are grouped under four headings:

1. traditional licensed vaccines (require only a similar serological response and safety tests are not very stringent),
2. conditionally licensed,
3. autogenous, platform-based (VSM 800.213), and
4. prescribed platform-based (VSM 800.214).

The platform products are classified as initial products, made by an expression vector system and genes of interest (GOI). To be allowed, they must be stable. There can be no changes except in the defined variant. For example, in the influenza vaccine, H1 is added to N1 or N2 instead of N3. The prescription of veterinary biological products will be prepared on an individual animal basis, prescribed by veterinarians, and tested for safety, purity, and absence of side effects. Species, age, dose volume, route, mixtures, storage, and maximum antigen content are limited in the first approved product. To prescribe the product veterinarians and producers must start bt pathogen isolation at the farm level. Its production must have documented references and demonstrate efficacy. The differences between the VSM 800.213 Platform and VSM 800.214 Prescription registrations are centered on the fact that the former does not require a veterinary prescription and the latter does not allow the creation of products with new variants. It also has certain limitations for agents and species. Administrating vaccines in practice requires knowledge of how they can be excreted, the age at application, their impact on maternal immunity and its duration, and maintaining flexibility in administration over time. Platform and prescription products cannot be live, like autogenous vaccines, but they are safe, unlike the latter.Their potential must be tested and safety studies must be conducted. As for efficacy studies, platform vaccines require them, but prescription vaccines do not.

Commercial vaccine development and considerations of vaccine use under field conditions. M Roof. Iowa State University

He worked for 25 years developing vaccines based on four pillars: safety, efficacy, potency, and purity. Efficacy is carried out through animal testing that demonstrates the statistical significance of disease reduction, focusing on reducing clinical signs, but not so much on the impact on productive parameters. In terms of efficacy, the focus is on the minimum immunizing dose (MID), as the dose required to reduce clinical signs. The conditions of use in practice are not always very clear in the presented scientific studies. The route of administration, dose, number of doses, and the age of the animals are critical factors in defining the data sheets and transferring them to the labels. We often find controversial information on labels that make us doubt the indications are correct (do not vaccinate pregnant animals, seropositivity has not been demonstrated in piglets, the duration of immunity has not been established, etc.). In some cases, it is a matter of avoiding making recommendations due to negative impacts or lack of information.

The timing of vaccination is highly dependent on numerous factors such as exposure to the pathogen, display of clinical signs, maternal immunity status, days required to induce the necessary immunity, ability to vaccinate in the presence of field virus, presence of other concomitant infectious agents (Salmonella, PCV, PRRS), and infection pressure.

Sows are the source of pathogens for suckling piglets and the benefits of vaccination are evident in reducing clinical signs or modifying the degree of immunity of the population. Vaccinating dams has economic advantages over vaccinating piglets, especially in preventing problems at early ages, with the potential to reduce or eliminate pathogens transmitted from sows to offspring. One should consider how long maternal immunity lasts and whether it interferes with generating immunity to subsequent vaccines.

The best option is to vaccinate negative animals to reduce the risk of future field virus infections. Waiting for maternal antibodies to decrease and piglets to become negative poses a high health risk. The level and duration of maternal immunity tend to vary greatly between sows and their litter. Vaccinating outside the age range recommended on the label has potential risks and consequences concerning efficacy and safety, especially with live vaccines. Off-label use has risks when combining live and inactivated vaccines, associated with different adjuvants (some incompatible - aqueous, oil, liposomes), reduction of their antigenic potential, greater number of reactions at the point of inoculation (reactivity), doubts in the cut-off point of the effective dose, and reduction of immunogenicity. In some cases, partial doses are used to reduce cost or improve immunity but, we must bear in mind that the recommended dose is the one shown to be effective, that they have been tested in healthy animals under optimum conditions, that their handling and stability decrease with time, and that companies work based on profits.

Vaccine-generated antibodies and concurrent infections generate changes in immunity, such that different doses or timing of administration may alter adequate immunity. Combining vaccines helps reduce the labor needed to administer them, and they must be cost-efficient, assessing antigenic interference, the optimal time to administer for all agents, and reactions at the point of inoculation. Companies need 2-6 years and a large investment to approve a product.

Vaccines and maternal antibody. P. Piñeyro. Iowa State University

Colostrum is rich in proteins - immunoglobulins (IgG) and essential nutrients (lipids and carbohydrates, as well as important non-nutritional components such as minerals, vitamins, exosomes, leukocytes, hormones, and oligosaccharides). In addition to immunoglobulins, colostrum contains leukocytes (neutrophils 40%), T lymphocytes 30%, B lymphocytes 13-16%, macrophages 7-11%), and proinflammatory cytokines (IL1B, il-6, TNF alpha, IL-10). Maternal antibodies are transferred via the placenta through chorionic and endometrial epithelial cells starting at day 20 of gestation. Fetal immune cell development takes place between 30-45 days of gestation. The axis digestive system - lymph nodes - mammary gland - immunity, determines the transfer and duration of maternal antibodies. The interference of maternal antibodies, particularly IgG, can neutralize vaccine antigens causing a change in piglet immunity which can obstruct the vaccine antigens and the circulation of antibodies and other components. The piglet vaccination program must be established based on the duration of maternal immunity. Vaccination strategies involve selecting the right vaccine, the right infectious agent, and critically balancing vaccination timing between mother and piglets as it is crucial to ensure that maternal antibodies reach the piglets until they can develop their own immunity. To do this we must monitor management practices that contribute to improved transfer of maternal immunity.

The dynamics of maternal antibodies and those of the pathogen are critical in defining the right time to administer each vaccine. This won't be the same from one farm to the next, nor will it be the same over time on the same farm. The level of antibodies in sows prior to farrowing has no effect on sow viremia status. The immune status of sows prior to farrowing also has no correlation with maternal antibody values. The window of immunity varies across infectious agents and vaccines. Interference with vaccine antibodies can affect seroconversion and production parameters (average daily gain).

Vaccine immunology and expectations. M. Rahe. NC University

The innate immune response is rapid and non-specific. It is focused on eliminating or controlling the infection before adaptive immunity acts. The adaptive immune response is slow, but antigen-specific. The main antibodies are the effector B-cell molecules, immunoglobulins G (protect against systemic infections and somewhat protect the airways), and A (protect mucosal surfaces - intestine and trachea). The function of antibodies is neutralization (prevent infections), agglutination (improves the efficiency of pathogen elimination), opsonization (mark antigens for phagocytosis), complement fixation (IgM is the best and build to attack membrane complexes for the destruction of the first bacteria, as well as cytotoxic cell-mediated antibodies). T cells are CD4 (helper T cells) that have an effect on intracellular pathogens and influence the primary effect of cytokine production and CD8 (cytotoxic T cells) that focus on target cells and induce apoptosis, which is important for infection control.

Nonstructural viral proteins are proteins made by the virus after cell infection that are not part of the virion and are important in viral replication. Antibodies degrade over time, while memory lymphocytes are sentinels of new infections. These proliferate rapidly in case of new infection, T cells increase the levels of CTLs and T cells to clear the infection, and B cells rapidly generate new antibody titers.

Vaccines can be divided into infectious (modified live virus, avirulent live culture) and non-infectious (killed, inactivated) vaccines. Non-infectious vaccines do not infect or replicate because they do not express non-structural proteins. The basis of immune protection is centered on pathogenic and defensive mechanisms (neutralizing antibodies, cytotoxic T cells, interferon 2). The vaccination route conditions the immune response. IM and subcutaneous - ID have an IgG response and systemic immunity. Oral vaccines have an IgA response with mucosal immunity.

There are numerous cases of vaccine failures, derived from misdiagnosis or insufficient time for the immune response to develop, vaccine administration - handling - storage problems, host-associated problems due to immunosuppression by other pathogens, incorrect administration of recommended doses, or inadequate duration of immunity before infection occurs.

Futuristic vaccines: mRNA. D. Verhoeven. Iowa State University

mRNA vaccines were discovered in 1960. There are two critical parts and numerous steps in their production (in vitro transcription, purification, processing, and formulation). Their main advantages are that they are developed rapidly and do not require prior immunity to have a potentiating effect. Their disadvantages are cost, thermostability, and finding the RNA inside the cells. Two types of mRNA vaccines have been tested: conventional and self-amplified. A third generation is coming, the most specific for developing vaccines against bacteria. Their efficacy is not necessarily better than traditional vaccines, but they are of interest in controlling cross-border diseases since they can be effective against viruses, bacteria, and cancer, with thermostability being their critical point. RNA degrades >30% at 37ºC in only 7 days. The alternative of expression vectors can reduce its cost, which is essential in animals.

Futuristic vaccines: DNA vaccines. H. Vu. University of Nebraska

Viruses must enter the host cell to replicate (viruses contain only a genome and a protective coat protein). Thus there are two types of adaptive immunity. Antibodies and T cells. Not all viruses are culturable to generate both inactivated and live attenuated vaccines. The target proteins of different viruses are variable: influenza is HA protein, PCV2 is capsid protein. Protein-based vaccines are DNA vaccines and those based on their vectors are mRNA vaccines. The advantages of the former are their safety, ease of production, high stability, and low risk of biological contamination with limitations being their poor immunogenicity and need for multiple immunizations. Risks include the possibility of carrying antibiotic resistance genes and interfering with maternal antibodies. Lipid-encapsulated DNA nanoparticle vaccine technology can protect the nucleic acid from degradation, increasing its protein expression. In tests of this technology against the influenza virus it generated a high immune response, conferring complete protection against the disease.

Next generation nanovaccine platforms for animal health. B. Narasimhan. Iowa State University

The new vaccine platform focuses on a base of polymers, lipids, vesicles, or inorganic products. The use of polyanhydrides is under study as they are hydrophobic, easy to metabolize, and stable to antigens and room temperature. The production and synthesis of nanoparticles with a size of 1-10 microns is done by dry aerosol techniques. They are easy to encapsulate, stable to proteins, and low cost. The objectives of the new generation of vaccines are to reduce manufacturing time, deliver a single dose, be easy to administer, stable at room temperature, safe, non-reactive at the point of inoculation, and generate a very rapid immune response. Intranasal nanovaccines are better distributed through the respiratory tract and transferred to lymph nodes, generating mucosal and systemic immunity, and quickly and easily immunize a large population of animals in a short period. They have carried out trials against influenza (encapsulated inactivated H1N2) generating cross-protection against other virus strains, as well as current studies against epidemic diarrhea with encouraging results. (www.nanovaccine.iastate.edu).

Biosecurity and sustainability

A standardized outbreak investigation: A new approach for identifying and prioritizing biosecurity hazards. D. Holtkamp

The high persistence of infectious pathologies on farms, especially PRRSV and PED, which are introduced laterally both on sow farms and finishing farms, causing high mortality and economic losses, together with the spread of African swine fever virus in Asia and Europe, highlight the deficiencies in the biosecurity measures carried out on farms in practice. The great changes in the swine industry in the last 30 years have led to the assumption of numerous risk factors for the dissemination of certain infectious agents, with an increase in the frequency of infectious agents entering farms through equipment, vehicles, semen, people, feed, and maintenance personnel. Therefore, it is necessary to implement new biosecurity resources to make production sustainable. In 2021 the Swine Health Information Center (SHIC) founded the standardized outbreak investigation program. The working group consists of 40 trained veterinarians based on hazard analysis and critical control point methodology (HACCP), which originated at NASA in the 1960s and was developed to ensure that the food astronauts took with them on their space missions was not contaminated by analyzing their production processes rather than the production itself. The critical concept for identifying biosecurity hazards centers on three failures:

1. The first is preventing carriers from being contaminated or infected with infectious pathogens.
2. The second is to mitigate contamination or infection in said carrier.
3. The third failure is preventing pigs on the farm from becoming infected with pathogens that other pigs have carried.

Carrier pathogens are any agent that can become infected or contaminated with a pathogen and carry the agent from one farm to another. Each entry of any possible carrier and their frequency determine biosecurity risks. Therefore analysis of the circumstances, activities, and steps within the production processes connected with each event (including all relevant details) are required to perform a critical point analysis. Epidemiological information should be incorporated with the hazard analysis so that the standardized investigation program should be carried out immediately after a disease outbreak or prospectively at any time as a biosecurity problem analysis, under the slogan "never let a good crisis go to waste." It is an opportunity to learn and not to repeat failures in biosecurity measures, implementing the parts of the measures that were somehow problematic and putting them into protocols in the daily practice of the farms.

Outbreak investigation of a gilt developer unit. M. Ackerman

When a disease enters a production system we know there will be negative repercussions and we must act. To make progress we must learn from our mistakes and take corrective actions. They have us consider the recurrence of a PRRSV case in a gilt development unit as an example. Reviewing all risk factors for virus entry into the unit focused on eight areas:

• Movement of pigs
• Movement of people
• Vehicles and tools
• Other animals
• Slurry removal
• Entry of food with pork products
• Air intake
• Feed/water

They conclude that all the theoretical measures reviewed by different means (video conferences, emails, and phone conversations) did not fully coincide with the farm veterinarian's assessments, revealing it is always necessary to work with the veterinarian to complete the on-farm investigation, taking time to visit the farms to find out if the biosecurity practices that are in the theoretical plan are being implemented. In this case, failures centered on improper carcass disposal procedures and animal loading processes.

Biosecurity ideas from the egg industry. C. Rowles

The laying hen industry has many similarities to the swine industry in preventing the entry of serious infectious agents, such as the case of the highly pathogenic strains of avian influenza that involved the culling of millions of birds between 2015 and 2022. The first risk prevention method is investing time, effort, and money in biosecurity measures. Biosecurity procedures include both structural and operational components. Structural biosecurity refers to the physical construction, design, and maintenance of facilities to prevent the entry of vectors and facilitate practical compliance with measures. Operational biosecurity includes the associated risks and risk mitigation derived from management practices, including the implementation of and compliance with standard operating procedures to prevent the entry of infectious agents into the farm. The most important thing is to keep the principles in line with what should be done and what we actually do. In poultry farming, measures to control migratory birds on farms are more important than in pig farming, which emphasizes that it is essential that both structural and operational measures are systematically reviewed and that gaps that are not being filled in practice are filled.

Building design and processes for new builds and remodels. K. Coleman. Iowa Select Farm

Biosecurity measures reach their maximum expression in areas with high swine density, which contributes significantly to sanitary changes. In these regions, biosecurity failures have more serious consequences, which is why three significant failures regarding farm design are considered responsible for infectious conditions especially focused on PRRSV bio-exclusion. These failures originate when carrier agents are exposed to infectious agents (pigs, trucks, people, air, or other elements), when we do not mitigate contagion or infection, and the transmission of the virus from the carrier agent to the pigs on the farm. We should always consider the natural flow of people, pigs, and actions on the farm to help us comply with biosecurity protocols to do the right things easily. One example is to have floors and surfaces that are easy to clean, with convenient entry access from the outside and good demarcation for crossing from dirty to clean areas, as well as ample changing areas - showers, as well as areas for daily laundry. Have a transition area between animal loading and unloading areas with a drainage surface between the two and a design that avoids the exchange of people from outside and inside the farm. These areas should be cleaned and disinfected immediately after use, and especially footwear should be changed.

State-of-the-art swine facility designs for biosecurity. A. Romagosa. PIC

Depending on the country, region, and continent, constructing new farms is not an easy matter for many reasons including safety plans, legal regulations, and implementing numerous biosecurity measures to preserve animal health and productivity. Investing in biosecurity infrastructures increases construction costs, although these are crucial to prevent diseases. The veterinarian's role before and during farm design and construction is essential to analyze biosecurity proposals that may impact the future of production. This requires close cooperation between all those involved (engineers, builders, owners, integrators).

Implementing structural building measures for biosecurity involves understanding the control of both involuntary (aerosols, insects, wild animals) and voluntary movements (vehicles, people, equipment, animals). In this sense, we can divide farms into three sections: surfaces, barriers, and enclosures.

To increase safety, biosecurity surfaces should not only be protected by a single barrier but by several layers of barriers with progressive biosecurity standards. Thus, biosecurity in construction should facilitate compliance and consistency of operational biosecurity to enable measures to be implemented on the farm. Good knowledge of the geographic and production conditions and type of production company gives us primary information on the biosecurity elements and control measures considered important for the design of new farms, such as location (air filters), surface needed, site climatology, farm size (number of people and qualification), type of production system, production pyramid of the company, and time dedicated to implementing biosecurity measures (balance between: necessary personnel - simple and intuitive application - rigor in their daily implementation).

Expectations of “baking” livestock trailers. M. Oberreuter

In 2005 Automated Production (AP) began marketing the Bio-Dri System for cleaning and disinfecting pig transport trucks. Air lines at 121ºC are used with two centrifugal fans and sensors that determine when the different compartments complete the cycle and then apply the gas with maximum effectiveness against pathogens. Between 45 and 50 liters of gas are used per cycle. The floor of the trucks reaches the desired temperature after the doors and side dividers. In some trucks, depending on the design, the lower floor and corners need more time to reach these temperatures. They recommend removing the cab from the trailer during treatment for safety reasons. Many variables determine the effectiveness of reaching the target of 30-80 minutes in each cleaning cycle: outside temperature, truck design, materials, cycles per day, and fixed points of the sensors.

Biosecurity for supply entry. B. Heitkamp

Cooper Farms conducted a study on six sow farms with severe PRRSV symptoms from new strains. They specifically analyzed the entry of materials into the farms and their sanitization by UV in rooms during the three days prior to their introduction. The amount of UV used was 124 and 335 UW/cm² rotating both for 15 minutes each. They emphasize the importance of the absence of organic matter on the materials in order for proper chemical disinfection, as well as the possible risk to some electronic equipment. They recommend that the room temperature be at 23ºC and that decontamination be programmed at night, without people present.

Conducting effective outbreak investigations using the new web-based outbreak investigation instrument. K. Dion

Biosecurity problems result in disease outbreaks on farms that are often associated with errors and gaps in biosecurity protocols, which presents an immense opportunity for learning and improvement. The standardized infectious disease investigation programs were only available in Microsoft Word (https://www.swinehealth.org/rrc-resources/) until November 2023. Now, thanks to the Swine Health Information Center, they are also available in a web-based application for easy use by veterinarians who can identify biosecurity issues confidentially. The program stores all data from all farms to identify the major biosecurity errors in the U.S. swine industry as an aggregate.

The zombie apocalypse approach to biosecurity, biocontainment, and disease control and elimination. L. Dufresne

Often, infectious cases of epidemic diarrhea and PRRS virus are traumatic, which can be compared to the social collapse depicted in zombie movies that makes us question reality. We get the feeling that the experiment went wrong, that the administrations have an inadequate response in handling the situation, that the problem is spinning out of control, that we are isolated on our own farm without any solutions, and that our morale is at rock bottom. The main issues at the origin of these infectious cases derived from biosecurity problems are centered in six areas:

1. Incorrect acclimation of future breeding sows entering the farms
2. Trucks contaminated picking up animals: for slaughter, piglets to other farms, carcasses collection
3. Contamination of contaminated pork products or infected feed as in the case of PED
4. Contact with wild animals (including wild boar) on commercial farms
5. Movement of animals between clean and contaminated areas infecting shared equipment
6. People's inappropriate non-compliance with biosecurity standards due to ignorance, laziness, lack of mental preparedness, greed, or sheer stupidity.

Antonio Palomo Yagüe