Biosecurity is frequently understood as prevention of entrance of infection into a pig farm, but true biosecurity includes this plus controlling the spread of disease within the farm. The importance of this has been brought home by the changes in the epidemiological pattern of pig disease. Previously the Pig Veterinarian was mainly concerned with mycoplasmal and bacterial diseases, most of which responded well to antibiotics and some managemental changes. The few viral diseases which existed were discrete entities. This pattern has been changed by PRRS and Swine Influenza. These immunosuppressing diseases are primarily spread by respiratory or fomite means. They have a high morbidity and quickly allow other pathogens to cause many more problems than previously. Multiple resistance and decreased efficacy have increased costs of medication to unsustainable levels. At the same time pressure for reduced medication from supermarket buyers and consumers is becoming more apparent. How are we to break this new cycle of disease? The answer lies in combining management such as (segregated early weaning, segregated rearing systems and production breaks) with true biosecurity. All the new systems are based around all-in-all-out utilisation of buildings or whole farms. We must aim to prevent spread of infection between different batches of pigs to enable these systems to work. Spread of disease between batches occurs in three main ways, Static Vectors, Mobile Vectors, and, Nutrient Vectors. Static vectors are those which remain on a site or in a house following removal of the pigs. Mobile vectors are those which carry infection to a site or house. Nutrient vectors are a special form of mobile vector. Table 1 lists these vectors:
DISEASE VECTORS
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For any system of Disease Control on a pig farm to be successful we must involve three aspects:
Biosecurity Disinfection programs play an important part in this process. Terminal disinfection, at the end of a batch is used to control static vectors, while continuous disinfection can be used to control mobile vectors and nutrient vectors. Terminal Disinfection depends on complete removal of all animals from the building or site. Removable equipment should be taken out and cleaned separately. Gross organic waste should be removed as this contains a high level of contamination and interferes with cleaning and disinfection. The next phase is pre-cleansing and sanitising. The aim of this is to remove further organic waste and start killing infected material. Water systems should be drained, gross dirt removed, refilled and disinfected using Virkon S. Following this we are ready for the disinfection stage. Here use a broad spectrum product to reduce the residual infectious burden. With modern disease patterns it is essential to use a product with a proven virucidal activity . Finally allow the house to dry, a last phase can be to apply a phase of aerial disinfection or fogging . For a program of continuous disinfection to be effective it is essential to prevent or reduce pathogen introduction with pigs entering the building. While this mainly depends on control of intrinsic infection within the pig, mechanical carriage can be reduced by washing or spraying with a disinfectant prior to entry. This is especially important in the farrowing house. Control of spread of infection by human vectors is based around control of visitors and movement around a unit, clothes worn and cleaning between rooms or departments. Foot dips containing disinfection solutions should be regularly used and replenished as contaminated. Hand disinfection is overlooked on most units. Hands should be washed and sanitised between houses or even more often. Work patterns should encourage movement only from clean areas to more dirty areas. Equipment should ideally be moved around a unit as little as possible. When it is moved it should be washed and disinfected. Tractors and scrapers are two real problem areas that need special attention, but also remember their operator. Vehicles entering the unit or its surrounds can introduce disease, and need control. Pig deliveries should be into a separate isolation facility. A proper loading bay should be provided and loading bay discipline maintained. Bulk delivery hoses are a special hazard and ideally every farm should have its own. A well constructed wheel dip can even be sited between the unit and the road. Drivers should change into unit overalls and boots if they must enter the unit. Control of rodents can be especially important. Here regular and correct baiting will provide good control, but also consider house design and work practices which can be utilised to reduce problems. Flies can spread pathogens and control is by a combination of good hygiene, insecticide usage and possibly dung active agents. Reduction of aerial spread is one of the more difficult areas. Geographical considerations such as siting of unit are obvious, but more local factors such as positioning of buildings in a unit, position of ventilation outlets and inlets, and pig movement routes all play a part. Filtration of air entering a building is being investigated, but is not practicable on most units. The main control of spread is be fogging and aerial Disinfection. This can be used to reduce spread of infection between buildings and within buildings. Buildings can be fogged daily or even more frequently in problem times. A good distribution system such as a mechanical fogger is essential. Reduction of nutritional vectors is two phased. Water system Disinfection has been covered above. Control of disease spread by food is more complexed. Purchase food or raw materials from a reputable store. This source should routinely monitor materials for pathogens, especially Salmonella. The source should not be able to be infected by pigs in its immediate area. Material or containers which have been on another pig unit should never be accepted. Movement of these within a pig unit should also be controlled. Delivery vehicles should be kept outside the unit. To summarize, modern diseases have brought new challenges to the pig industry. These can only be controlled by the application of modern production systems coupled with an extensive system of true Biosecurity including Disinfection using proven broad spectrum biocides which include a virucidal activity.
ELEMENTS OF A DISINFECTION PROGRAMME
REMOVAL OF EQUIPMENT
CLEAR GROSS ORGANIC MATTER
PRE-CLEANING & SANITISING
SANITISE WATER SYSTEM
DISINFECTION
FOGGING & AERIAL DISINFECTION
PREVENT OR REDUCE REINTRODUCTION OF PATHOGENS