Advancements and Technologies in Pig and Poultry Bacterial Disease Control

By Ilias Kyriazakis and Paul Barrow

Advancements and Technologies in Pig and Poultry Bacterial Disease Control provides the most up-to-date knowledge on the tools and technologies used in the economics, prevention, monitoring and control of the most important bacterial diseases in these two important livestock species. Written by international experts in veterinary medicine, veterinary science, agricultural economics and environmental monitoring, this book provides state-of-the-art information regarding the application of technology to the prevention and control of bacterial disease in pigs and poultry. It presents the most up-to-date information on the major bacterial pathogens, why they are important, their epidemiology, pathogenesis and molecular basis of their virulence.

Additional sections examine how genomic sequencing addresses the development of disease biomarkers for faster and highly specific diagnosis and how next generation sequencing can identify good and bad microflora. This book will be a valuable resource for veterinarians, epidemiologists, animal scientists, technologists, and researchers studying precision livestock farming. Students in veterinary, animal science and bio-science courses will also find it useful for its coverage of diseases and monitoring tools.

• Highlights crossover technologies from human to veterinary medicine, including the use of bioinformatics and genomics for disease prevention
• Uses results from the EU FP7-funded ProHealth project, the largest of its type ever awarded by the EU
• Examines how genomic analysis via next generation sequencing and microarray platforms can be exploited to develop novel biomarkers of bacterial disease in animals
• Reports on novel environmental monitoring tools and their use in determining disease threshold levels within herds and flocks

• Language: English
• Publisher: Academic Press
• Release date: Aug 21, 2021
• ISBN: 9780128182383

Book preview

9780128182383_FC

Advancements and Technologies in Pig and Poultry Bacterial Disease Control

First Edition

Neil Foster

Department of Veterinary and Animal Science, Scotland’s Rural College, Aberdeen, United Kingdom

Ilias Kyriazakis

Institute for Global Food Security, Queen’s University, Belfast, United Kingdom

Paul Barrow

University of Surrey, Guildford, United Kingdom

Table of Contents

Cover image

Title page

Copyright

Contributors

Foreword

1: The economic cost of bacterial infections

Abstract

1: Introduction

2: A farm-level economic approach to the impact of bacterial infections

3: An approach to the sector-level economic impact of bacterial infections

4: Cost of bacterial infections in pigs

5: Cost of bacterial infections in poultry

6: Wider societal costs of bacterial infections

7: Concluding remarks

2: Bacterial diseases in pigs and poultry: Occurrence, epidemiology, and biosecurity measures

Abstract

1: Introduction

2: Occurrence of bacterial pathogens in pig and poultry farms

3: Epidemiology of bacterial pathogens in pig and poultry farms

4: Biosecurity scoring in pig and poultry farms

5: Conclusions

3: Major pathogens and pathogenesis

Abstract

1: Infectious disease as a biological phenomenon

2: Major production disease pathogens of poultry

3: Major production disease pathogens of pigs

4: Enteric infections

5: Conclusion

4: Immunity to bacterial pathogens of pigs and chickens

Abstract

1: Introduction

2: Immunity to bacterial pathogens of the respiratory tract of pigs

3: Immunity to bacterial pathogens of the digestive tract of pigs

4: Bacterial disease of poultry

5: Laboratory diagnosis of bacterial infections

Abstract

1: Introduction

2: Technologies which have driven molecular diagnosis

3: Microarray analysis

4: Next-generation sequencing

6: Environmental monitoring and disease prediction

Abstract

1: Introduction

2: Determination of the role of environmental factors on-farm on the temporal expression of multifactorial production disease in pigs and poultry

3: Detection and influence of environmental factors pertaining to swine disease outbreaks in grow-finish pigs

4: Conclusion

7: Control and prevention of bacterial diseases in swine

Abstract

1: Introduction

2: Bacterial respiratory disease

3: Bacterial gastrointestinal disease

4: Systemic disease due to bacteria

5: Conclusions

8: Bacterial diseases in poultry

Abstract

1: Introduction

2: Infections with Escherichia coli

3: Infections with Gram-positive cocci

4: Necrotic enteritis (Clostridium perfringens)

5: Erysipelas (Erysipelothrix rhusiopathiae)

6: Fowl cholera (Pasteurella multocida)

9: Antimicrobial resistance in farm environments

Abstract

1: Introduction

2: What is the difference between intrinsic or acquired AMR?

3: How bacteria become resistant to an antibiotic?

4: What are the expression mechanisms of antibiotic resistance?

5: How is AMR distributed?

6: What are the most important genetic elements facilitating the transmission of AMR among bacteria?

7: What antibiotic-resistant Gram-negative bacteria with zoonotic potential are of particular concern for public health?

8: What are the most important Gram-positive AMR bacteria in farm animals that are of high medical importance to humans?

9: Which farm animals are the most important sources of antibiotic-resistant bacteria?

10: Is there any dependence of abundance of AMR and antibiotic consumption?

11: Are the genes responsible for antibiotic resistance in gut microbiota of farm animals preferentially associated with particular taxa or do they spread freely among all bacteria colonising the intestinal tract?

12: Are there any environmental bacteria, which may act as reservoirs of ARGs for bacteria colonising the intestinal tract of farm animals?

13: How can AMR be transferred from the farm to the environment?

14: How can wildlife acquire and further disseminate AMR of animal origin?

15: Are there any other production systems with an even higher abundance of antibiotic resistance?

16: Antimicrobial resistance in the future

10: Monitoring microbiota in chickens and pigs

Abstract

1: Introduction

2: Gut microbiota composition

3: Gut microbiota along the intestinal tract

4: Gut microbiota as a function of age

5: Function of gut microbiota

6: Monitoring gut microbiota

7: Culture of gut microbiota members

8: Microbiota members commonly considered beneficial

Index

Copyright

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Contributors

María Aparicio     PigCHAMP Pro Europa S. L., Segovia, Spain

Paul Barrow     School of Veterinary Medicine, University of Surrey, Guildford, United Kingdom

Filip Boyen     Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium

Ilias Chantziaras     Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium

Jens-Peter Christensen     Faculty of Health and Medical Sciences, Department of Veterinary and Animal Sciences, University of Copenhagen, Copenhagen, Denmark

Monika Dolejska     University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic

Neil Foster     SRUC, Aberdeen, United Kingdom

Freddy Haesebrouck     Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium

Manuel Jiménez-Martín     PigCHAMP Pro Europa S. L., Segovia, Spain

Ilias Kyriazakis     Institute for Global Food Security, Queen's University, Belfast, United Kingdom

Tommy Van Limbergen     Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium

Dominiek Maes     Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium

Edgar Garcia Manzanilla     Pig Development Department, TEAGASC, The Irish Food and Agriculture Authority Moorepark, Co Cork, and School of Veterinary Medicine, University College, Dublin, Ireland

Gema Montalvo     PigCHAMP Pro Europa S. L., Segovia, Spain

Joaquín Morales     PigCHAMP Pro Europa S. L., Segovia, Spain

Jarkko K. Niemi     Natural Resources Institute Finland (Luke), Seinäjoki, Finland

Carlos Piñeiro     PigCHAMP Pro Europa S. L., Segovia, Spain

María Rodríguez     PigCHAMP Pro Europa S. L., Segovia, Spain

Pedro Rubio     Department of Animal Health, University of León, León, Spain

Ivan Rychlik     Veterinary Research Institute, Brno, Czech Republic

Ida Thøfner     Faculty of Health and Medical Sciences, Department of Veterinary and Animal Sciences, University of Copenhagen, Copenhagen, Denmark

Foreword

Neil Foster, Department of Veterinary and Animal Science (North Faculty), Aberdeen, United Kingdom

Ilias Kyriazakis, Institute for Global Food Security, School of Biological Sciences, Queen's University, Belfast, United Kingdom

Paul Barrow, School of Veterinary Medicine and Science, University of Surrey, Guildford, United Kingdom

Bacterial diseases have negative impact on animal welfare, reduce animal performance, cause significant economic losses, and pose a risk to human health when zoonotic pathogens enter the human food chain or water systems.

The pig and poultry industries are becoming increasingly global with economic and health impacts both for the livestock and as a potential source of zoonotic infections. The poultry industry particularly is already managed by a small number of breeding companies, and trade in poultry and poultry products is increasingly international. Although the pig industry is some way behind, it is heading towards this direction. It is clear that all diseases are transmissible within and between countries, whilst affecting productivity and welfare with considerable associated zoonotic risk.

For many years, bacterial diseases of pigs and poultry have been controlled by antibiotics which, until 2007, were permitted in animal feeds within the European Union. Following the ban on antibiotics in feed, their metaphylactic use continued at disease risk points, and this contributed to antimicrobial resistance (AMR) as a major existential risk to the livestock industry and human health as bacterial species evolved in response to the selective pressure. Antibiotic resistant bacteria have entered the human food chain and human communities, and in some cases, pathogens may be resistant to multiple antibiotics either within a given class or even within different classes of antibiotics. As antibiotics become less effective, a select number of these are regarded as a last line of defence or ‘critical’ antibiotics. These are also now under threat, with the chemotherapeutic agent colistin being recent example. This is a critically important antibiotic (CIC), and resistance was rare and chromosomally mediated. However, in 2015, plasmid-mediated resistance to colistin was reported initially in pigs, and since then it has become more widespread in chickens and humans involving the mcr-1 plasmid gene, plasmid-mediated and highly-transmissible.

The huge risk associated with this has resulted in considerable revision of antibiotic usage, beginning with a reduction in the metaphylactic use of antibiotics on farms. Cessation of use of antibiotics for growth promotion and restrictions on the metaphylactic use of antibiotics (and zinc) are recognised to increase the risk and prevalence of bacterial disease in high-intensity production systems and as such represent a potentially serious issue for animal welfare and the agricultural economy. There is, therefore, a great need for a more holistic approach in gaining a better understanding of how bacterial disease can be prevented (or at least reduced) at the farm level in a postantibiotic era. This will provide a scientific platform that will inform regarding a sustainable practice of high-intensity farming.

This book addresses these issues by providing current information on risk analysis and biosecurity, antimicrobial resistance, and the technological advances required to overcome bacterial disease in pigs and chickens in a reduced antibiotic environment. The technological advances discussed include how genomic analysis has been exploited to diagnose disease, the presence of AMR genes, and the formulation of protective microbiotas to prevent disease. However, the book also highlights novel environmental monitoring (precision management) technologies and how these have recently been used to determine disease threshold levels within herds and flocks. In addition, this book provides up-to-date information on the economic cost of bacterial disease to individual farm and the sector as a whole, which is a quite often neglected area of research. As such, the information provided within this book should be of interest to a variety of stakeholders within the livestock industry.

The chapters have been compiled by authors who collaborated on ‘Prohealth’ (2013–2018), the largest project awarded by the European Union to study production diseases of pigs and poultry. This consortium consisted of 22 academic and industrial partner groups with expertise in pig and poultry health and disease, and the partnership has generated highly impactful data used by stakeholders within the animal production sector and legislators across the EU. The project is a good example of what can be achieved by multi-national and interdisciplinary collaborations to tackle major issues that not only affect livestock, but also are of major concern to both consumers and citizens. For those who are interested to find out more about the outputs and the impact of the project, they can access the project’s website which is still active and updated regularly with new information (https://www.fp7-prohealth.eu/).

1: The economic cost of bacterial infections

Jarkko K. Niemi    Natural Resources Institute Finland (Luke), SeinÄjoki, Finland

Abstract

This chapter reviews the financial impacts of selected bacterial infections in pigs and chickens. Bacterial infections can result in substantial economic costs to farmers. Although the costs can arise for various reasons, the principal causes are due to (i) the changes in the inputs used on farms (e.g. veterinary inputs to treat ill animals), (ii) changes in the inputs used beyond the farm (e.g. extra labour to trim carcasses at slaughterline), (iii) changes in the quantity of outputs sold (e.g. reduced piglet sales because of the disease), and (iv) changes in the quality of outputs sold (e.g. increased share of class B eggs). In pigs, the financial costs of porcine respiratory disease complex, for example, are typically around €7 per fattening pig produced by an affected herd, and those of postweaning diarrhoea mostly range from €2 to €7 per piglet. In chickens, salpingoperitonitis can cause a loss of about €0.50 per bird, and loss due to necrotic enteritis can be up to €0.32 per bird. There are interventions which can mitigate the financial costs from bacterial infections in pigs and poultry, although not all costs can be avoided.

Keywords

Pigs; Poultry; Bacterial infection; Animal disease; Financial cost; Economic impact; Production economics; Animal health economics

Chapter outline

1Introduction

2A farm-level economic approach to the impact of bacterial infections

3An approach to the sector-level economic impact of bacterial infections

4Cost of bacterial infections in pigs

4.1Bacterial infections considered

4.2Respiratory disorders in pig production

4.3Enteric disorders in pig production

5Cost of bacterial infections in poultry

5.1Bacterial infections considered

5.2Digestive disorders

5.3Respiratory disorders

6Wider societal costs of bacterial infections

7Concluding remarks

References

1: Introduction

Bacterial infections can result in substantial economic costs in pig and poultry production which are called here as the costs of disease. Although the costs can arise for a variety of reasons, the principal causes are (i) changes in the input use on farms (e.g. veterinary inputs needed to treat sick animals), (ii) changes in the input use beyond the farm (e.g. extra labour needed to trim carcasses at slaughterline), (iii) changes in the quantity of outputs sold (e.g. reduced piglet sales because of disease), and (iv) changes in the quality of marketable outputs obtained from the production process (e.g. increased share of class B eggs). The last cause, the quality of outputs obtained, includes the impacts on the value of products for consumers. Bacterial diseases can impair the microbial quality of meat, eggs, and other products, and in some cases, this can also be harmful to human health, incurring public health costs. Examples of such cases include impaired food safety in the event of a zoonotic disease, such as Salmonella, and the contribution of animal antimicrobials usage to the risk of antimicrobial resistance. The quality aspect can also involve changes in the environmental impacts of animal production or the level of animal welfare which both can deteriorate the value the consumer perceives when consuming livestock products.

Bennett (2012) presented a conceptual understanding of how diseases affect production systems through:

1.Economic impacts internal to the farm:

•loss of capital (i.e. animal mortality);

•reduction in the level of marketable outputs;

•actual or perceived reduction in output quality; and

•waste of, or higher level of use of, inputs.

2.Economic impacts, both internal and external, to the farm:

•resource costs associated with disease detection, diagnosis, prevention, and control;

•negative animal welfare impacts (i.e. animal suffering) associated with disease;

•international trade restrictions due to disease and its control; and

•human health costs associated with diseases or disease control.

3.Economic impacts external to the farm such as effects on rural economies, tourism, or wider food value chain.

Bacterial diseases can impair the cost-competitiveness of pig and poultry production. While some diseases, such as highly contagious animal diseases, can result in substantial one-time costs should they occur (e.g. Halasa et al., 2016; Niemi, 2020a), bacterial infections often lead to a continuous cost burden, which increases production costs per unit of produce. Because bacterial infections can be common and affect productivity, their impact on farms can also be substantial. For example, Wallgren et al. (2010) reported that the costs of endemic diseases (including bacterial and other infections) in pig production in Sweden were approximately €38 per pig produced.

The aim of this chapter is to develop both farm- and sector-level approaches to the economic impact of bacterial infections and to apply this approach to estimate the economic impact of specific pig and poultry bacterial infections.

2: A farm-level economic approach to the impact of bacterial infections

Partial budgeting provides a simple, but intuitive, approach to understanding the financial impacts of bacterial infections or any other diseases. The economic impacts of an infection can be considered through four changes (Dijkhuizen and Morris, 1997; Rushton, 2009):

1.Revenues and production foregone, for example, resulting from reduced growth rates, elevated mortality, reduced fertility, or increased carcass condemnations at slaughter after an infection.

2.Additional production costs, for example, additional labour, medication, and extra feed required by the animal.

3.Saved production costs such as saved feed when an animal is slaughtered prematurely.

4.Additional revenues, if any, such as extra revenues gained from successful disease mitigation interventions or from heavier carcasses when an animal is slaughtered at a heavier weight than planned.

It is essential to note that the financial costs of disease include effects which emerge both before and after an infection has taken place. Hence, the effects also include the costs of preventive and mitigation measures which are taken irrespective of whether the infection occurs.

Applying production and cost theory, the basic element of production economics (see e.g. McFadden and Fuss, 1978; Rushton, 2009) in the context of bacterial diseases helps in understanding how changes in costs, revenue, profit, and productivity can influence decisions made by the farmer and the role of bacterial infections in the farm economy. Production and cost theory assumes that farms make choices which satisfy the objective of maximising profit. The optimal production decisions are determined by (i) exogenously given market prices of inputs and outputs and (ii) production technology which limits the production possibilities set. Production technology refers to how inputs are converted to outputs, and it is presented by the production function. It also includes the effects of disease on output. Hence, in this context, ‘technology’ does not refer to any technological device or solution. Moreover, such functional forms are typically used so that a decreasing marginal return applies.

Bacterial infections influence the quantity of outputs obtained per certain quantity of inputs used. Infections can affect the optimal production decision. The profit function can be used to examine the effects bacterial infections have on production choices. Fig. 1.1 presents an example of how a bacterial infection influences profit and the optimal quantity of production in two ways. Firstly, when a disease outbreak caused by a bacterial infection occurs, production output is reduced. This is because in the short term the infection itself may reduce the output obtained with a given set of inputs. Additional costs caused by disease control, mitigation, and other measures result in increased production costs per unit of output, meaning a higher price is needed to cover production costs. In other words, the curve presenting the cost function is altered because of a disease-induced change in the production technology. This change can be considered exogenous to the farmer.

Fig. 1.1

Fig. 1.1 Illustration of a hypothetical profit function and marginal cost curve under the cases of infection and no infection.

Secondly, the optimal production plan may also change. In the example of Fig. 1.1, the change in optimum is illustrated by red arrows. This is also because in the longer term, the optimal production quantity with an infection is lower than it would be without an infection. In other words, the risk of infection increases production costs per unit, and to obtain compensation for this risk, it becomes optimal for the farmers to reduce production quantity to some extent. This adjustment is endogenous because it is decided by the farmers when they optimise production according to the new disease situation. Although the long-term effects of disease can be economically important, studies often focus on the short-term economic impact of bacterial infections and ignore adjustments due to the optimisation of production. Besides the earlier-mentioned situation, other cases may also occur, especially in relation to alternatives for controlling the disease (see e.g. Niemi et al., 2020) or enhancing animal welfare (see e.g. Niemi, 2020b).

Risk of disease is a cost, and it influences the costs of production and production decisions. With standard microeconomics assumptions, risk costs will lead to a reduction in the quantity produced. Some risk management measures should be considered for diseases as a group and not by disease, because different bacterial infections may be combatted with similar preventive measures. Therefore, evaluating the economics of disease risk management may require holistic, multiple-disease approach.

3: An approach to the sector-level economic impact of bacterial infections

Bacterial infections can lead to a vicious circle: the infection reduces productivity and market income, incurring additional production costs. As a consequence, farms must ask for a higher price for the product to cover their costs. Higher prices can reduce consumer demand for the product. In addition, the resulting disease may reduce consumer willingness to pay for the quality attributes of food, because antimicrobial usage may be increased, or food safety and animal welfare may be reduced because of the infection, for example. As the farms are producing less than before the infection, they may have idle production capacity, the costs of which should also be covered by the remaining sales. This also reduces the competitiveness of farming.

Fig. 1.2 illustrates how a bacterial infection may influence the meat or egg markets when the problem becomes widespread in the market. A short-term market response to a bacterial infection may deviate from the case presented below. Fig. 1.2 presents demand and supply curves for a product (meat or eggs) before and after an infection. The demand curve illustrates the quantity of product that consumers are willing to purchase at different prices, and the supply curve presents the quantity of product producers are willing to supply at different prices. In the absence of bacterial infection, producers are able to supply quantity Q0 at price P0. Consumers are also willing to purchase quantity Q0 at price P0. A market clearing (i.e. combination of price and quantity such that all that is produced will be traded) occurs, and quantity Q0 is therefore traded at price P0.

Fig. 1.2

Fig. 1.2 Demand, supply, and market-clearing price and quantity before and after a bacterial infection, without a shift in the demand for product.

As indicated in the previous section, a bacterial infection is expected to increase production costs per unit of product supplied to the market. Hence, when the effect of bacterial infection is taken into account, producers will need to obtain a higher price for the product to cover their increased production costs. This implies that the supply curve shifts from the position ‘Supply (no infection)’ to the new position ‘Supply (infection)’. However, consumers are unwilling to purchase quantity Q0 at a price which is higher than P0, and a new market-clearing solution must therefore be sought. When consumer preferences remain unchanged, the market-clearing price-quantity shifts from the old position A to the new position B where the shifted supply curve and the demand curve intersect, and a lower quantity Q1 will be supplied at a higher price P1 than in the original market-clearing solution (P0, Q0). In practice, this means that some farms will either quit business or reduce their production quantity to maximise the profit.

Bacterial infections may also alter consumer preferences. A change in consumer preferences means consumers are willing to pay either a lower or higher price for a given quantity of product, and the demand curve therefore also shifts. For example, deteriorating animal welfare, use of antimicrobials, or concerns about product safety may be associated with bacterial infections (see Clark et al. (2019) for a discussion on the importance of these factors), and the demand curve may shift. For example, as Clark et al. (2017) indicated, consumers are willing to pay a price premium for higher animal welfare products. The consequence of such a willingness to pay would be a shift in the demand curve. Fig. 1.3 illustrates a case where bacterial infections reduce consumer willingness to pay for the product, and the demand curve therefore shifts from the original position to new position ‘(Demand (after shift))’. Consumers are willing to pay less for the product produced under high disease impact conditions because disease reduces the value they perceive from consuming the product. In considering the steps already explained in Fig. 1.2, the new market-clearing solution is sought and found at point C, where the shifted demand and supply curves intersect. The new market-clearing quantity is Q2, and the corresponding price is P2. While less product would be traded in the new equilibrium than in the original case, whether price P2 is lower or higher than P0 depends on the magnitude of changes in the supply and demand curves relative to each other.

Fig. 1.3

Fig. 1.3 Demand, supply, and market-clearing price and quantity before and after a bacterial infection which shifts both supply and demand curves.

Studies of different types of disease risks illustrate that the increased risk of disease farmers face can reduce the quantity they are willing to supply (e.g. Losinger, 2005; Niemi and Lehtonen, 2011) and that the economic incentives the producers face may influence how they respond to disease risks when applying biosecurity measures (e.g. Gramig and Horan, 2011; Niemi et al., 2016b).

The economic welfare costs that a bacterial infection causes to producers and consumers as groups can be estimated by using the original and shifted supply and demand curves. The calculation is illustrated in more detail by Niemi et al. (2020). They assessed interventions to control for production diseases in pigs, one of which was particularly relevant for the bacterial infections considered in the subsequent section. In their case study, an intervention scenario based on a pig-rearing trial (Chatelet et al., 2018) showed that dirty housing and inadequate biosecurity were risk factors for pig health, and that an intervention where hygiene practice was improved enhanced pig performance and health. Pigs kept in clean conditions were assumed to gain more weight than pigs kept in dirty housing and to produce about 22% more meat per pig space unit. The clean group also had less weight variation at slaughter than the dirty group and had fewer respiratory lesions. The occurrence of pleurisy and pericarditis was associated with the reduced performance of pigs. Based on Niemi et al. (2020), the dirty group suffered from additional costs which were equivalent to 16%–17% increase in the producer price of pig meat. The additional costs were estimated to increase the consumer price of pig meat by 3.7%–5.0%. The benefit of improved disease control to pig-fattening farms was around 50% of the gross margin. Hence, the study illustrated that production diseases can lead to substantial economic costs to producers, consumers, and society.

4: Cost of bacterial infections in pigs

4.1: Bacterial infections considered

Elicited views of supply-side stakeholders along the food supply chain from five EU countries suggest that for weaner, grower, and fattening pigs, respiratory disorders are ranked as the most important diseases economically (> 35% of responses). In particular, porcine respiratory disease complex was considered an economically important disease. Moreover, postweaning diarrhoea and porcine enteric disease complex, as well as neonatal and perinatal mortality, are particularly important production diseases especially in piglet production (PROHEALTH, 2018a).

Section 4 focuses on farm-level costs of selected economically important bacterial infections in pigs. At first, two bacteria causing respiratory disorders, namely Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae, are examined. These are economically important disorders especially in fattening pig production and cause lung lesions and pleurisy. In addition, this section focuses on three bacteria causing enteric disorders in pig production. Diarrhoea by contrast is one of the most common and most important health problems in piglets. It is often caused by Escherichia coli, but also other bacteria and viruses commonly cause diarrhoea. Another enteric bacterium considered in growing pigs is Brachyspira hyodysenteriae, which causes an inflammation and disease known as swine dysentery. Lawsonia intracellularis by contrast is the causative agent of porcine proliferative enteropathy, or ileitis, a disease that affects pigs.

4.2: Respiratory disorders in pig production

M. hyopneumoniae is one of the most prevalent and economically significant respiratory pathogens in the pig industry (Maes et al., 2008). M. hyopneumoniae is the primary aetiologic agent of enzootic pneumonia, a chronic respiratory disease in pigs characterised by a chronic, nonproductive cough (Mare and Switzer, 1965; Goodwin et al., 1965), resulting from mixed respiratory infections with M. hyopneumoniae and one or more secondary bacterial pathogens. In many countries, vaccination to control for M. hyopneumoniae is applied in more than 70% of pig herds (Maes et al., 2008). M. hyopneumoniae is also considered one of the primary agents involved in the porcine respiratory disease complex (PRDC), predisposing animals to secondary infections with other respiratory pathogens including bacteria, parasites, and viruses (Thacker and Minion, 2012).

M. hyopneumoniae is economically important particularly because it influences the key production parameters. It leads to decreased feed efficiency and feed intake, reduced average daily gain, and increased medication costs. Lung lesions also cause costs at slaughter (Maes et al., 2008). Some studies have reported 6%–16% reductions in the growth rate of M. hyopneumoniae-affected finishing pigs (Pointon et al., 1985; Rautiainen et al., 2000). Because the disease is widespread, the importance of subclinical disease may have been underestimated (Maes et al., 2018).

A. pleuropneumoniae is another bacterium which is associated with the porcine respiratory disease complex and which can cause substantial economic costs to the pig industry. A. pleuropneumoniae infection can reduce the weight gain and feed conversion efficiency of pigs (Straw et al., 1989: Bernardo et al., 1990; Christensen, 1995), increase mortality during fattening (Hunneman, 1986; Wilson et al., 1986), and increase medication and veterinary expenses (Hunneman, 1986). Both acute and chronic forms of the disease can result in pathological lung lesions being recorded at slaughter, and the carcasses may require trimming to remove condemned parts. This increases the staff input needed to operate a slaughterline. Some companies therefore apply a price reduction for trimmed carcasses.

A review of 30 peer-reviewed and nonpeer-reviewed studies which have reported costs for M. hyopneumoniae or porcine respiratory disease complex, and which were published between 1995 and 2019 (updated from Niemi et al., 2016a), suggests that M. hyopneumoniae and porcine respiratory disease complex typically cost €4.39a per pig (95% range 1.78–7.00). Studies which examined intervention measures reported an average cost of €5.39 per pig. Costs due to A. pleuropneumoniae ranged from €2.35 to €11.12 per pig, with an average of €6.62 per pig. Based on the reviewed studies, financial costs caused by porcine respiratory disease complex can be estimated to be an average of around €7.00 per fattening pig produced by an affected herd.

However, the incidence and the severity of diseases greatly affected costs in individual cases. Costs associated with these diseases are sensitive to contextual factors. For example, input prices, prices paid for piglets, and quality price discounts that may be applied for condemned carcasses influence the magnitude of costs farmers are likely to face. The severity of lesions also influences the effects, and the more severe the lesions, the larger the financial costs that can be expected. For example, Ferraz et al. (2020) estimated financial costs caused by M. hyopneumoniae to range from $1.63 (about €1.39) to $6.56 (about €5.59) per pig, depending on the severity of lung lesions. By comparing M. hyopneumoniae-positive and M. hyopneumoniae-negative herds, Calderón Díaz et al. (2020a) found that M. hyopneumoniae-positive herds’ lower net profit (difference €7.20 per pig) was mainly caused by increased feed costs per pig produced, although other variable and fixed costs also contributed to the loss.

The literature has identified several measures to control, mitigate, or eradicate M. hyopneumoniae. However, worldwide only a few countries in Europe have acted to eradicate the disease (Ruokavirasto, 2020). Some studies have estimated that systematic measures leading to the eradication of M. hyopneumoniae are profitable. Recently, Silva et al. (2019) simulated the benefit of M. hyopneumoniae elimination in the US at $7.00 (about €5.98) per pig marketed. They estimated that an eradication scheme was able to cover the costs of eradication in about 2 months, when applying a herd closure protocol and subsequent introduction of new animals, or the costs of a medication-based eradication approach in about 7 months.

The estimation of the economic burden of A. pleuropneumoniae is typically based on the occurrence of acute outbreaks characterised by high mortality, loss in production, and veterinary costs. Similar to M. hyopneumoniae, costs caused by A. pleuropneumoniae also depend on the severity of the disease. Calderón Díaz et al. (2020b) estimated on average €6.60 higher net profit for a farrow-to-finish farm with a low prevalence of pleurisy (< 25%) and lung scars (< 8%) when compared with a high prevalence of pleurisy (≥ 25%). Stygar et al. (2016) simulated a scenario in which pig growth rate stagnated, and the annual costs of A. pleuropneumoniae ranged up to €18.9 (approximately €5.64 per pig) when a 3% increase in mortality rate was assumed, and up to €24 (approximately €7.20 per pig) in the most severe case of the disease considered (a 7% mortality rate and stagnant pig growth). A low risk of infection among piglets and low impact of the infection on pig growth resulted in substantially lower costs. It was also suggested that inefficient cleaning of the house between batches led to elevated financial costs.

Controlling the A. pleuropneumoniae may involve cleaning, vaccination, and medication activities, and combinations thereof, and the severity of the disease may influence the extent of these costs and whether it is profitable to implement an eradication or control measure. Stygar et al. (2016) illustrated that the optimal strategy to control the risk of A. pleuropneumoniae can be case specific. For example, a cleaning and vaccination policy was considered more beneficial than cleaning-only policy when the risk of infection among piglets was high, and the infection resulted in high decreases in the growth rates and/or larger increases in mortality. For example, when 50% of piglets were initially infected, mortality rate was 7%, and when vaccine efficacy was considered high, the benefit of vaccination ranged from zero up to €7.80 per pig space unit per year depending on the severity of disease. When the disease became more severe, the benefits of