Respiratory disease in pigs

Question 1

Why are respiratory diseases such a major problem to the pig industry?

Answer 1

Animal welfare
Performance & production
Mortality
Meat quality

Question 2

How does respiratory disease impact production in pigs?

Answer 2

Morbidity and mortality.
Treatment/veterinary costs/need for vaccination.
Reduced growth rates/increased days to slaughter.
Reduced FCE (energy into immune system).
Variation in supply – growth rates, back fat.
Penalties at abattoir – slow line, increased trimming.
Assurance schemes/market (multiplier).
Environmental impact- more food, slurry, antibiotics.

Question 3

What pathogens are involved in respiratory disease of pigs?

Answer 3

-Bacterial/mycoplasmal
-Viral
-Parasitic
Secondary bacterial infection of lung tissue already compromised by primary pathogens frequently occurs.
Often more than one agent involved.
Often highly contagious.
Spread by direct or aerosol contact.
Or indirect via birds and vehicles.

Question 4

What defence mechanisms in the pig are present against respiratory infection?

Answer 4

Nasal chambers
- Turbinates create turbulence. 
- Changing airway diameters alter speed
Mucociliary apparatus.
Cough reflex.
Pulmonary alveolar macrophages.
Neutrophil invasion.
Antibody production (airway IgA, alveolar IgG).

Question 5

Respiratory disease in pigs is multifactorial…

Answer 5

Environment
Management
Breed and age
Exposure to pathogens

Question 6

What clinical signs are seen in pig respiratory disease?

Answer 6

Coughing (often 1st thing noticed). 
Dyspnoea +/- hyperpnoea.
Snuffling sounds (nasal obstruction).
Heart failure and cor pulmonale (severe/chronic).
Pleurisy.
Anorexia.
Ocular discharge.
Sudden death.

Question 7

How would you diagnose respiratory disease in pigs?

Answer 7

History and CE/observation may provide tentative diagnosis.
Clinical examination often limited.
-Brief auscultation may be possible and increased lung sounds may be evident:
-Wheezing – narrowed airways
-Bubbling sounds – blocking of bronchioles
-Squeaking sounds – pleuritic
-Harsh rubbing sounds – pleurisy
This must be confirmed with lab tests/PME.
Abattoir surveillance data may indicate current diseases.
Remember mixed infections!

Question 8

What sort of respiratory diseases do you see in pre-weaned pigs?

Answer 8

Progressive atrophic rhinitis.
Bordetella bronchisepticum.
Inclusion body rhinitis (pig CMV).
PRRSv (reproductive and respiratory syndrome virus).
Enzootic pneumonia (Mycoplasma sp).
Glassers disease (Haemophilus parasuis).

Question 9

What sort of respiratory diseases do you see in weaners, growers and fatteners?

Answer 9

Bordetella bronchiseptica
Glassers disease
Actinobacillus pleuropneumonia
Pasteurella multocida
Mycoplasma hyopneumonia (EP) / hyorrhinis
PRRSV
Porcine respiratory coronavirus (PRCV)
Influenza
PMWS?/PCVAD
(Aujeszky’s disease (pig herpesvirus 1))

Question 10

What are some examples of significant respiratory disease in non-immune adult pigs?

Answer 10

Glassers disease
Actinobacillus pleuropneumoniae
Pasteurellosis
Enzootic pneumonia
PRRSV
Influenza

Question 11

What is progressive atrophic rhinitis?

Answer 11

Toxigenic Pasteurella multocida in association with Bordetella bronchiseptica.
Colonisation of nasal mucosa by B.b with production of cytotoxin – allowing P.m to invade.
PM damages osteoblasts with osteolytic toxin and enhances osteoclast activity.
CS usually seen at 3-9 wks age – sneezing, nasal discharge/h+, facial deformity - later.
Reduced growth rates and increased risk of pneumonia.

Question 12

How to diagnose progressive atrophic rhinitis?

Answer 12

Causal organisms can be cultured from nasal swabs, serology for B. bronchiseptica.
PME – Section snout at level of 2nd premolar – damage to turbinates assessed on 0 (no damage) -5 (severe) scale

Question 13

How to treat and control progressive atrophic rhinitis?

Answer 13

Antibiotics may help if early
Vacc: sows 2-6wks before farrowing
Control: Depop-repop with AR-free stock, strategic medication if CS, screening herds with ELISA for B. bronchiseptica

Question 14

Bordetella bronchisepticum in pigs…

Answer 14

Found in most pig populations.
Generally mild, self-limiting rhinitis (non-progressing).
Therefore, clinically and economically of little importance.
Only a problem when in combination with toxigenic Pasteurella multocida.

Question 15

What is inclusion body rhinitis in pigs?

Answer 15

Porcine Cytomegalovirus (herpesvirus)
>90% UK herds affected
Transmission pig-pig or aerosol
Mostly young pigs but outbreak in naive herd may affect all ages
CS: sneezing, serous nasal discharge and brown ocular discharge, high morbidity, low mortality.

Question 16

How to diagnose and control inclusion body rhinitis in pigs?

Answer 16

Diagnosis: ELISA, inclusion bodies from nasal swabs.
Control: Maintain closed herd, protect suckling pigs from exposure.

Question 17

What is PRRS?

Answer 17

PRRS virus – Arterivirus.
Virus replicates in and destroys macrophages and endothelial cells →vasculitis.
Mixed infections with other resp pathogens very common.
Clinical signs – weaned pigs, mild coughing, sneezing, tachypnoea, innapetence, increased mortality.

Question 18

How to treat PRRS?

Answer 18

In-feed/water antibiotics to cover period at risk – to reduce 2o bacterial infections (usually 6-8 wks).

Question 19

How to control PRRS?

Answer 19

Early weaning off-site to break cycle, review pig flow, consider partial dep-pop of 1st and 2nd stage housing, vaccination @ weaning and breeding stock.
- Vaccination:
Modified live (avoid in pregnant)
Killed (breeders)
Use in breeders and growers.
- Stabilise infection:
Expose gilts / vaccinate prior to breeding.
Stream grower pigs in separate airspaces.
- Eradication:
Stabilise sow/gilt infection and then depopulate all exc sows. Wean off-site to rest buildings for period.
- Depop-repop:
Infection transmits up to 3km.
Purchase uninfected stock and quarantine / test at isolation.
Purchase uninfected semen.

Question 20

What is enzootic pneumonia?

Answer 20

30-80% pigs have lesions at slaughter.
Mostly caused by Mycoplasma hyopneumoniae with frequent superimposed infection, esp. Pasteurella multocida.
Spread pig-pig mostly, also aerosol and wind (2 miles).
Multifactorial – housing, temperature, humidity, mixing different ages/sources, overcrowding, continuous throughput systems.
Immunity short-lived, no colostral transfer.

Question 21

What is the typical clinical picture of M.hyopneumoniae (that causes enzootic pneumonia)?

Answer 21

Weaned pigs
↑coughing – non-productive, worsened by exercise
↓FCE - <14%
Variance in growth - 17% reduction in DLWG
2º infection

Question 22

How to diagnose M.hyopneumoniae (enzootic pneumonia)?

Answer 22

Herd history
Clinical signs
Lung lesions at slaughter/PME
Culture (difficult) /PCR
Histology
Serology

Question 23

How to treat M.hyopneumoniae (enzootic pneumonia)?

Answer 23

Acute cases may respond to antibiotics but only if early.

Strategic dosing of growing pigs may be necessary on some farms.

Question 24

Control of M.hyopneumoniae (enzootic pneumonia)…

Answer 24

Improve environment & management...
-ventilation, groupings, husbandry. 
All-in, all-out management of growers. 
De-pop, re-pop infected herd. 
Partial de-pop and tx – original breeding stock retained and treated (10d), all other pigs removed
Medicated early weaning (removed at 5d)
Vaccination (1 and 3wks).

Question 25

What is Glässer’s Disease?

Answer 25

Haemophilus parasuis – found in the nasal cavity of many pigs
Usually a 2ry invader but can also be a primary pathogen (so usually relies on other pathogens to take effect first).
Associated with polyserositis, arthritis and meningitis. Resp. signs usually in weaners - 4 months of age as piglets have colostral immunity
CS: acute onset pyrexia, cough, dyspnoea, lameness, swollen joints, CNS signs.

Question 26

How to diagnose Glässer’s Disease?

Answer 26

History, cs, PCR, ELISA, PME

Question 27

How to treat and control Glässer’s Disease?

Answer 27

Tx: Antibiotic injections to sick pigs, in-feed/water Abs to contacts. Early tx essential.

Control: Avoid stress, strategic medication at times of high risk, Vaccination <10 wks of age

Question 28

What is APP?

Answer 28

Actinobacilus pleuropneumoniae.
12 capsular subtypes but cross reactions occur
Produces toxins that kill macrophages and neutrophils
Explosive outbreaks of pneumonia with high morbidity and mortality – to - seroconversion with few clinical signs
CS: sudden onset, sudden deaths, pyrexia, dyspnoea (jerky), coughing, blood-stained foamy mucus from mouth and nose.

Question 29

How to diagnose APP?

Answer 29

ELISA, culture from nasal swabs/lung tissue, PCR, PME- fibrinous pleuritis and firm lung infarcts.

Question 30

How to treat and control APP?

Answer 30

Tx: Parenteral Abs, Isolation, NSAIDs.

Control: Closed herd, eradicate with de-pop, re-pop, wean piglets at 10d and move to separate unit.

Question 31

What is pasteurellosis?

Answer 31

Pasteurella multocida –important as secondary invaders – EP, AR, APP
Can also act as a primary pathogen – resulting in pneumonic pasteurellosis or pasteurella septicaemia
CS: mostly sporadic dz of 10-20wk old growers, pyrexia, dyspnoea, open-mouth breathing, coughing, sudden death.

Question 32

How to treat and control Pasteurellosis?

Answer 32

Tx: Parenteral Abs.

Control: improve management, segregated early weaning.

Question 33

What is Aujesky’s disease?

Answer 33

Pseudorabies.
Swine herpesvirus type 1 (SHV1)
Notifiable and not present in UK (present in NI until 2012).
Clinical presentation is age and strain specific:
- <4 wks: neurological, mortality <100%.
- 4 wks – 5 months: neurological + pneumonia, mortality <15%
- Adult: few clinical signs
–Abortion and mummification
–URT coughing
–Rare neurological signs
Slaughter policy in UK, targeted vaccination in NI, Ireland, Spain.

Question 34

What is swine influenza?

Answer 34

Influenza A virus, orthomyxovirus
Direct pig-pig transmission, also airborne
Mostly young pigs but rapid involvement of up to 100% pigs
CS: Pyrexia, lethargic, prostrate, skin erythema, anorexia, severe cough sneezing, dyspnoea, conjunctivitis, pregnant sows may abort
Recovery equally rapid (5 days).

Question 35

How to diagnose swine influenza?

Answer 35

ELISA, PCR, PME – severe congestion of upper resp. tract, enlarged LNs, necrotising bronchiolitis.

Question 36

How to treat and control swine influenza?

Answer 36

Tx: Abs to prevent 2o bacterial infection.

Control: Closed herd.

Question 37

What is PRCV?

Answer 37

Porcine respiratory coronavirus.
May be subclinical, usually mild disease.
PME: Interstitial pneumonia, hyperplasia of bronchial epithelium, virus in macrophages
The exact role of the virus is unknown but it is thought to predispose to other respiratory diseases

Question 38

What are the clinical signs of PRCV?

Answer 38

Coughing:
- In growers and finishers (endemic).
- Across all age groups (epizootic)
Absence of other causes:
- Occasional pasteurellosis.
Not usually a significant problem but:
- Contributes to multifactorial pneumonia.
- Indicates biosecurity issue on high health herd.

Question 39

What is PMWS?

Answer 39

PCV-2 associated disease – respiratory component is very important. 
Immunosuppressive.
90% UK pigs seropositive.
Involved in many disease syndromes.
Can cause respiratory signs in growers.

Question 40

What are some examples of parasites found in pigs?

Answer 40

Metastrongylus:

• Relatively uncommon
• Earth worm as intermediate host
• Most likely in outdoor units
• Worms found in lungs 20-24d after the pig consumes the egg containing L1
• Coughing and dyspnoea in piglets or growers.

Ascaris suum:
- Milk spot liver most common symptom but coughing may be observed due to migrating larvae 1 wk after infestation.

Question 41

What is PRDC?

Answer 41

Porcine Respiratory Disease Complex.
PRDC results from a combination of infectious agents and environmental stressors.
Results in reduced performance, increased medication costs and increased mortality.
Typically 30-70% of pigs will be affected, with a mortality rate of 4-6 %.
Usually seen in pigs 14-20wks old.
CS: Lethargy, anorexia, fever, nasal discharge, ocular discharge, coughing, laboured breathing, purple discolouration of skin, especially of ear-tips – variable CS, depending on pathogens involved and baseline level of immunity.

Question 42

What agents are involved in PRDC?

Answer 42

Viral agents often involved include:
PRRS*
Coronavirus
Swine Influenza virus
Circovirus (PCV2)*

The bacterial agents often involved, which may act alone or together, are primarily:
Mycoplasma hyopneumoniae*
Haemophilus parasuis
Streptococcus suis
Bordetella bronchiseptica
Actinobacillus suis
Actinobacillus pleuropneumoniae

*Considered most important.

Question 43

What is the epidemiology of PRDC?

Answer 43

A new-born pig receives colostral protection from its mother – dependent upon her immunity.
This immunity will decline over time, with young pigs becoming susceptible to challenge.
As they become exposed, infection follows the usual pattern of colonisation, replication, excretion and immune development.
Disease may occur following replication and excretion phases and duration will depend upon the level of replication and the agents involved.
In the typical continual production system of, say, weekly farrowings, older pigs are a source of infection for younger pigs, maintaining a cycle of infection
However, it should also be realised that this source of infection is also relevant to the breeding herd. A trickle of challenge to immune sows will maintain their immunity and help maximise colostral protection
Conversely excessive challenge may override their immunity, rendering them a source of infection for their own and other litters.

Question 44

How would you diagnose PRDC?

Answer 44

• Detailed clinical history, including age of onset, morbidity and mortality estimates, response to treatment, and the most current vaccination status of the sows and pigs.
• On-farm/laboratory post-mortem examination of affected pigs with appropriate diagnostic sampling.
• Cross-sectional blood sampling of the herd to establish epidemiological pictures of suspected pathogens.
• Use of abattoir data for slaughter pigs to indicate levels of lung consolidation and pleurisy and the involvement of other pathogens (e.g. Actinobacillus pleuropneumonieae- Acpp) (BPHS).

Question 45

How can PRDC be controlled?

Answer 45

Medication and vaccination are fundamental to the long-term control of PRDC but are no substitute for sound management principles.
- Even the best and most extensive programmes will not overcome extreme disease where pig-flow and management have not been corrected.
Vaccines should only be used with full diagnostic knowledge, including targeting the timing of vaccination. Vaccines againstMycoplasmaand PCV2 are probably the most widely used vaccines in young piglets, but strategies are also needed to identify additional pathogens for which vaccine can be introduced.

Question 46

How can PRDC be controlled?

Answer 46

Medication and vaccination are fundamental to the long-term control of PRDC but are no substitute for sound management principles.
- Even the best and most extensive programmes will not overcome extreme disease where pig-flow and management have not been corrected.
Vaccines should only be used with full diagnostic knowledge, including targeting the timing of vaccination. Vaccines againstMycoplasmaand PCV2 are probably the most widely used vaccines in young piglets, but strategies are also needed to identify additional pathogens for which vaccine can be introduced.

Question 47

What medication is administered for PRDC?

Answer 47

• Where bacterial involvement is identified, strategic medication can be used to supplement vaccination programmes.
• Prophylactic or metaphylactic use may be appropriate where the timing of disease is readily identifiable.
• Parenteral or oral medication (via water or in feed) can be appropriate. In high disease-level situations, where bacteria play a significant role, long-term suppressant medication – usually via the feed – is still widely used.
• However, in such situations a full herd analysis with attention to pig-flow and management and preventative vaccination should be made in order to reduce such dependency on antibiotic use.

Question 48

What is the gold standard for trying to control the respiratory diseases involved in PRDC?

Answer 48

All-in-all-out.

• The first rule of control must be separation of age groups by building or room and application of hygiene controls between occupations by the use of ‘all-in-all-out’ (AIAO) principles.
• Washing, disinfecting, drying and resting are fundamental requirements.
• To achieve AIAO production, the pig-flow through the buildings must be established and maintained.

Question 49

PRDC - Buildings…

Answer 49

Match production to suit building provision, identifying bottlenecks
Where necessary alter buildings (by divisions, new buildings, etc.)
Consider what the correct stocking rates are for the buildings.
Ensure buildings are adequately ventilated – to remove polluted air and excess heat without draughts or over-ventilation.

Question 50

PRDC - Production…

Answer 50

Review productivity in light of building availability and, where appropriate, consider batch production, i.e. produce a larger number of pigs less often to enable filling and emptying of buildings.
Ensure evenness of production from the breeding herd. This will avoid overstocking or under-stocking and will reduce the temptation to mix ages.
Avoid back-mixing slow-growing pigs to younger groups. If thinning is necessary, forward mixing of the best pigs in a group is less hazardous.

Question 51

PRDC - Sick pigs

Answer 51

Deal with sick pigs correctly. Not only is the sick pig a welfare concern in its own right, it is a threat to healthy pigs.
Therefore:
Hospitalise sick pigs.
Never return recovered pigs to the mainstream system, especially by mixing with younger groups.
Hospital pens should be clean and cleanable, isolated but well attended by stockmen. Washing hands and changing boots/overalls after attending hospitals should be standard.

Question 52

PRDC - Partial depopulation

Answer 52

It may be appropriate to apply partial depopulation strategies in which older infected animals are removed from the farm, creating a break in production
Such actions should be combined with attention to disease control in the younger pigs to prevent the situation rapidly repeating itself once re-stocking has taken place. This may in itself involve an increase in vaccine use in sows or piglets, or the administration of medication to sows and/or piglets, either to eliminate or severely suppress specific pathogens.
The actual programme needed will depend on each farm situation but any potential depopulation should allow refurbishment, alteration and review of accommodation with respect to pig-flow and building quality.

Question 53

PRDC - Full depopulation…

Answer 53

In the extreme case, full herd depopulation may be appropriate, particularly where major rebuilding is needed and disease levels are unsustainable
Herd depopulation and repopulation requires meticulous advance planning to minimise loss of production whilst achieving the necessary cleaning
A minimum unoccupied period is needed (generally 6 weeks), with thorough cleaning and disinfection, aided by timing the programme such that the empty period is in mid-summer – June provides the highest intensity of sunlight which aids cleaning and drying.

Question 54

PRDC - Biosecurity…

Answer 54

To limit the spread and occurrence of disease
To improve overall herd health
To increase the growth and efficiency of the herd
-Airborne eg windborne spread from neighbouring unit
-Mechanical eg vehicles, machinery and equipment
-People, footwear and clothing
-Birds, rats, mice, insects and other animals
(domestic, farm and wildlife)
-Contaminated feed, water, semen, bedding etc.

Question 55

What is the British Pig Health Scheme?

Answer 55

Voluntary scheme run by AHDB pork
Team of specialist Pig Vets who visit abattoirs and examine 50 pigs from each slap mark killed that day
They record Enzootic Pneumonia like lesions, Pleuropneumonia (APP-like lesions), Viral Pneumonia, Pleurisy, Pericarditis, Peritonitis, Pyaemia, Milk spot, Abscesses, Liver Scarring, Papular Dermatitis (Mange-like lesions) and Tail Bites
This helps to monitor overall health, and can give an early identification of emerging disease problems or outbreaks.

Question 56

What is the British Pig Health Scheme?

Answer 56

Voluntary scheme run by AHDB pork.
Team of specialist Pig Vets who visit abattoirs and examine 50 pigs from each slap mark killed that day.
They record Enzootic Pneumonia like lesions, Pleuropneumonia (APP-like lesions), Viral Pneumonia, Pleurisy, Pericarditis, Peritonitis, Pyaemia, Milk spot, Abscesses, Liver Scarring, Papular Dermatitis (Mange-like lesions) and Tail Bites.
This helps to monitor overall health, and can give an early identification of emerging disease problems or outbreaks.