Summary:

Biosecurity is one of the tools used for the epidemiology control of the main poultry diseases, including Avian Influenza. The term "biosecurity" includes the set of measures and husbandry practices taken to prevent the introduction, replication and spread of infectious agents in a farm, flock or poultry operation, and its purpose is to reduce the risk of infection or disease. Before defining and establishing which these measures are, it's good to analyze which are the main infection and spread mechanisms of Avian Influenza, in order to establish actions that can decrease the risk of their introduction to free zones or to the contention of prevalent zones. We will analyze the minimum biosecurity measures to prevent infection according to the epizoothiology situation in the regions, the farm location and the susceptibility of the flocks being immunized or not.

In general, the way of avoiding that a catastrophic disease, such as Avian Influenza, could be introduced or spread in a zone, region or operation, is keeping an epidemiology surveillance system, a proper biosecurity procedure and a control system for the birds movements, their products and byproducts. Additionally, there has to be a massive vaccination program, in those regions or countries where the Avian Influenza virus has circulated recently or is prevalent.

The epidemiology surveillance system applied to Avian Influenza has to be capable of identifying the eventual presence and circulation of the Avian Influenza Virus (AIV) of any subtype in absence of clinical disease, because the early detection, focalization and implementation of contention measures and removal of affected animals, will allow its eventual eradication. Also, it has to be adequate according to the risk or country or region situation where it is going to be applied and to the susceptible avian populations at risk. For example, there are countries where the main risk could be the wild water fowl or the migratory birds. In the case of Mexico, where there are two zoosanitary status, (free and scarce prevalence) the surveillance system should focus in:

• Live bird movement control and live bird markets.

• The backyard bird populations and combat birds

• The sanitary management of poultry byproducts (Hen and chicken manure)

• The geographic situation and the weather conditions according to the seasons of the year.

Currently, according to the official dispositions published in the Agreement , in Mexico it's established that the epidemiology surveillance system should be operated by SENASICA , in passive and active way. In passive way there is the mandate of reporting any outbreak, suspicion and diagnosis of AIV by any player in the poultry sector and the Secretariat will be giving follow-up. The active surveillance consists in the search of the presence of the virus through continuous and permanent sampling throughout the year in poultry, both commercial as well backyard, combat and others. Thanks to the technology advance regarding diagnosis and the experience generated in the country, there is a surveillance system able to detect and control avian influenza outbreaks. However, it's not as easy to determine the real prevalence in certain zones and seasons of the year, which is a challenge to the prevention systems that will be established, including biosecurity.

Biosecurity is the procedure of all the sanitary and prophylactic measures used in a permanent way that prevent and avoid the entrance and exit of infectious agents to a poultry farm or any agro-livestock operation. The components of the biosecurity program are physical, of structure and operation, so before planning and implementing a biosecurity program, a situation risk analysis has to be done to define these factors.

A flat geography and without natural barriers or of scarce plants and with an arid and dry weather, will have more airborne and mechanic infection risk that in a humid forest zone with hills and rivers. The same will happen in dry and cold weather or with winds in contrast with the hot season, not so hot and with rain that are predominant during the summer and fall in Mexico. Another risk factor to asses will be the number of farms in the zone, size, population and density, as well as the share limits with neighbor operation, as well as population centers and backyard birds. It's not the same to have an isolated farm at 5 Kms of distance from any other operation with few houses and well limited, than large farms or multiple farms with high population of houses and chickens. Being close to towns or premises with backyard birds, feedlots or live bird markets or primary transit are factors that increase the disease risk.

Regarding structure, the limits of the farm have to be in relation with its environment. Characteristics and uses of the land where the farm is, material and kind of houses and other buildings in the farm, as well as pits or collecting systems for mortality and chicken manure treatment. The status of the internal roads and walkways, plants and eventual presence of trash or wastes. Conditions of the sanitary arches and modules, as well as the availability of other implements for disinfection, hot water, soap and farm clothes correctly identified and placed in the corresponding area in the sanitary module. Have restrooms and sewage system.

Also the number of houses, distance between them, the flooring material, structure, ceilings and curtains has to be assessed. The number of entrances and conditions of the foot baths, curbs and walkways. Type of feeders and drinkers, nets, water tanks and cisterns, water faucets in the farms. Presence of other facilities as dining rooms, warehouses, washing room for the farm's clothes and offices.

From the operation point of view the first priority to assess is the transit control and access to the farm. To prohibit the access to not necessary visitors or eventual, as well as the prevention of burglary and an orderly flow of corresponding in comings to the farm such as: chicks or birds delivery at the flock start, gas, feed and inputs. The vaccination crews and the collection of birds after finishing, collection of eggs if it´s the case, and the removal of mortality and wastes. It has to be tried that maintenance and the delivery of conditioning materials be done at the end of the flock.

Very important from the operation point of view are the down time between flocks, it has to be of a minimum of 14 to 16 days in short life birds and of 21 to 28 days for long life birds, considering the cleaning, washing and disinfections process of the houses and the external parts, as well as the total removal of chicken manure, feed and any other remaining material of the previous flock. Place emphasis in cleaning and the pest control procedure.

Every process has to be documented and there have to be journals and continuous supervision.

Is there a good biosecurity system? This is a difficult question to answer, because the best answer is the eventual presence or absence of diseases in the operation or zone at the same time that they are present in other places. The experience has shown that in spite of having biosecurity the big epizootics of Newcastle, Infectious Laringotracheitis have spread in many countries and regions and this has allowed evaluating the biosecurity of the movements control. In concrete, biosecurity could be assessed through audits and risk assessment. In Mexico, there is an official devise operated be SENASICA that evaluates the minimum biosecurity measures and issues a certificate, and only if there is an eventual presence of an outbreak or disease foci, the risk assessment is performed for the spread of the disease.

Biosecurity works when it is properly regulated by an operation process and it is constantly reviewed through audits, as well as being convinced in the company. Biosecurity, is limited by the big masses of poultry populations, as well as for the intensive flow of the birds and their products that is present in certain regions, mainly where there is transit of live birds or in a lack of control of byproducts like chicken or hen manure, as well as the presence of other bird populations or animals that work as reservoirs or potential carriers of the disease. The best way of containing a disease is trying to avoid its entrance through an early epidemiology surveillance system and immediate action and compensation mechanisms facing the disease. When a disease like Low Pathogenicity Avian Influenza or moderate forms of Newcastle Disease are present, it´s better to recognize the reality and then establish the contention mechanism and the prevalence evaluation with the purpose of being able to guarantee a better scenario for production, as well as for the birds and their products trade without sanitizing any procedure as it could be, for example, vaccination.