Preventive medicine strategies for pigs on commercial units

The UK has a long history of quality pig production, due partly to the high welfare standards set as well as closely monitored breeding and preventive disease programmes.

Approximately 30,000 UK premises house pigs (including as pets) alongside 10,000 commercial pig farms. These farms use a variety of production and housing systems. Nearly half of the UK pig herd is housed outdoors, differing significantly to other parts of the world. In the UK, 97% of pigs are finished indoors – 39% of them on fully slatted floors, 30% on partly slatted floors and 31% on solid floors with bedding.

Although 10,000 commercial units are in existence, the majority of pig production is from only 1,600 assured farms. A total of 35 companies account for half the UK breeding herd, and of these only 10 corporate firms account for a third of all breeding sows.

The structure of the UK pig industry comprises:

Commercial production herds

• Farrow-to-finish (three-week batch production or weekly)
• Multi-site production. Site one: breeding herd. Site two: weaners (7kg to 35kg). Site three: growers and finishers (35kg to 100kg)
• Rearing pig production (continuous flow or all-in, all-out)

Companies producing replacement breeding stock.

• Genetic nucleus herd
• Multiplication units
• Boar studs

Preventive medicine

Due to the nature of the UK pig industry, disease prevention and control is of utmost importance when designing management and herd health plans. For a commercial unit, biosecurity and quarantine protocols should be strictly adhered to, and this is also advisable for any pig-keeping system.

Biosecurity is important to limit disease spread, not only within a unit, but also between farms and from other sources. By implementing good biosecurity protocols, high health status within a unit can be maintained, costs associated with disease reduced and, most importantly, good levels of productivity can be maintained.

The position of any commercial pig unit is important, as maximum distance from other pigs or a site that may be a potential source of infection (for example, an abattoir) must be ensured. Once established, it is rarely possible to change the location of a farm to reduce any risk of infection. Therefore, potential risks must be fully considered and management steps implemented to minimise these risks.

Disease transmission most commonly occurs by direct pig-to-pig contact. The introduction of infected stock provides the highest risk to animals on any farm. Quarantine and isolation protocols are, therefore, extremely important in minimising risk from these sources.

Aside from direct contact, transmission can also occur through other routes, some easier to protect against than others.

These alternative routes include airborne, mechanical, workers and visitors, other animals or contaminated material (for example, bedding, feed or semen).
The route of transmission depends on
the individual disease, and, for any disease to establish, enough infective organisms must come into contact with the pig. Reducing the risk or amount of contact with infective material is the key to successful biosecurity, with hygiene, cleaning and disinfection protocols being integral to success.

Risk factors should be regularly reassessed so any biosecurity programme can be updated accordingly.

General biosecurity

Good biosecurity management guidelines should consider the following:

• Source incoming stock from herds with known disease status
• Isolate all incoming stock (see quarantine/isolation section later)
• Control all access on to the unit
• Define “clean” and “dirty” areas and ensure these are clearly signposted
• Keep external vehicles outside the unit; only allow own vehicles and machinery to enter. Own vehicles should be cleaned and disinfected when they have been off site. If external vehicle access is required (for instance, for feed delivery), restrict these to as far from livestock buildings as possible
• Visitors should arrange their visit in advance. A visitor book must be completed by all visitors before entry, which also confirms they understand the requirements of visiting the unit. Visitor entry should be through a single point, and clean boots and overalls must be provided.
• Staff should be fully trained in hygiene and biosecurity standards. Provide staff with boots and overalls and ensure they are only to be used on the unit. Ensure staff are aware of risks if they have contact with pigs outside of the unit
• Use active pest control strategies
• Ensure no pets are allowed on the unit
• Empty and clean feed bins and water storage regularly
• Purchase bedding from a safe source and store it securely
• Dispose of dead stock promptly, adhering to disposal regulations
• Thoroughly clean and disinfect any machinery or equipment coming on to the unit

Quarantine or isolation of incoming stock

Any incoming pigs should be isolated for a period of 30 to 60 days (Figure 1). The specific duration will depend on the advice of the veterinarian and the diseases of concern. The isolation period allows time for veterinary examination, samples to be taken, submitted and results reported, clinical signs of incubating diseases to become apparent and vaccination of new stock prior to entering the herd. Isolation also acts as a period of acclimatisation for new stock, allowing them to recover from transportation and adapt to their new environment. Important points to consider for an isolation facility are:

1. Biosecurity must be as good as for the main herd.
2. Direct contact with other pigs, livestock and wildlife should be prevented.
3. It should be located far from other pigs; distance will be dictated by management, testing and biosecurity protocols.
4. Air, feed and water must be separate from all other pigs and livestock.
5. Facility should have own manure-handling facility.
6. A suitable environment for the pigs must be provided.
7. It should operate on an all-in, all-out system.
8. Ideally use separate equipment and personnel for the isolation facility. Note: If the provision of dedicated personnel is not feasible, then the isolation facility should be dealt with at the end of the day, adopting strict biosecurity protocols.
9. Adequate handling and examination facilities to be in place.
10. Regular monitoring of isolated stock.
11. Veterinarian visits as needed; paired blood samples may be required.
12. Protocol for acclimatisation of new stock to endemic diseases.
13. Isolation facility must be easy to fully clean and disinfect. It must be allowed to dry completely before new stock are housed.

Vaccination strategies

Vaccination is a significant weapon in the prevention of disease in any animal species. In the pig production system, the strategic use of vaccinations can play an important role in minimising disease and improving productivity.

Table 1 details the diseases UK pigs can be vaccinated for, alongside the licensed protocols.

Vaccination programmes should comply with manufacturer recommendations and be on the advice of a veterinary surgeon. Multiple vaccines should only be administered at the same time if proven to be safe to do so.

A huge range of vaccines is available for pigs, and the list in Table 1 is not exhaustive. Combined vaccines are also available for use in control strategies.

Parasite control

A number of parasites (both internal and external) can affect pigs on commercial units. Not only are these highly infective, but they can also have significant effects on productivity and carcase quality. Zoonotic risks are associated with some parasitic diseases. Table 2 details the common parasites of pigs, the clinical signs and suggested treatment options.

Good housing and pasture management can reduce the necessity for treatment of parasites in pig herds (Figures 2 and 3).

Although resistance is not currently a problem, prudent use of anthelmintics should be implemented.

Quarantine and sourcing stock can play an important role in preventing new parasites from entering a herd.

Notifiable diseases

It is important staff working on pig units are made aware of the notifiable diseases that may be seen in pigs and they should be aware of the main clinical signs of the following diseases so their potentially devastating effects within the UK can be minimised: foot-and-mouth disease, classical swine fever, African swine fever, swine vesicular disease, Aujeszky’s disease, vesicular stomatitis, Teschen disease, bovine tuberculosis and anthrax.

Although not notifiable, porcine epidemic diarrhoea virus (PEDv) is an emerging disease of concern to the UK pig industry. It has been identified in eastern Europe and is having devastating effects across Canada and the northern US.