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Major Health Problems in the Livestock Production Sector Caused by Infectious Agents

 

 

Prof. Dr. Jos. P. Noordhuizen,
Ruminant Health Unit, Dept. of Farm Animal Health,
Faculty of Veterinary Medicine,
Utrecht University,
The Netherlands.

Introduction

There is a large variation in animal health status between the different EU member states. This variation refers to both highly contagious diseases and endemic infections.

Moreover, certain infections in livestock appear to be of increasing public health concern.

Many factors appear to be involved in the phenomenon of prevalence differences.

In-depth insight into such factors may help in designing appropriate disease combat or eradication programmes.

In this presentation emphasis will be on the various factors contributing to the major health problems in the livestock sector.

Highly contagious infections.

Such infections refer to e.g. foot-and-mouth disease (cattle; swine); classical swine fever; New Castle disease (poultry); avian influenza (poultry); brucellosis and tuberculosis (cattle)

Factors contributing to the repeatedly occurring outbreaks of highly contagious diseases are animal population densities; introduction of agents through wildlife; the EU non-vaccination strategy; the open internal EU borders; the intensive live animal transportation network over the EU; increased mobility of man, animals and feed commodities; on-going genetic selection for productivity traits; increased disease susceptibility of animals.

In certain areas of the EU the animal population, e.g. pigs, is so high that once an agent is introduced it spreads so rapidly that large populations are affected and losses are tremendous. Area examples (e.g. pigs) are Po-river area (Italy), Brittany (France), West Flandres (Belgium), Holland and Nordrhein Westfalen (Germany).

Areas to which the aforenamed conditions apply need to develop new tactics to be safeguarded from most disease disasters.

Tactical manoeuvres in such areas may refer to clustering of herds within that area coupled to the creation of buffer zones between clusters. And to restriction of transportation separated from external transportation. Uniform health status within clusters, standardised hygiene procedures within clusters, fixed relationship between breeder multiplies and fattener.

A cluster might thus be considered a closed participatory business unit. Once an infection is introduced in an area, a few affected clusters are closed and stamped out, while other clusters can take preventive or protection measures (e.g. ring vaccination) and again other clusters are safeguarded.

The question that remains to be solved at the local level is whether this industrial type of approach is politically, socially and economically acceptable and feasible.

Endemic diseases

Endemic disease prevalence differences between countries, regions and farms are even larger than in the case of highly contagious diseases.

Factors contributing to this phenomenon are the prevailing differences in husbandry systems, marked differences in management quality levels, the highly intensified production and the physiologically marginal potential of food animals to cope with all kind of stresses including infectious agents, the largely monotrait focussed genetic selection programmes.

Special attention may be given to food animals affected by metabolic stress. This is a relative problem, largely provoked by one-sided genetic selection on productivity mainly. One to this metabolic stress (e.g. after calving or around piglet weaning), endocrinological, neurological and immunological functions are impaired. This impairment may ultimately result in increased disease susceptibility and or reduced reproductive performance.

It is obvious that particularly exporting countries need to focus on this kind of infectious diseases too in order to retain market access for live animals or their products.

Emphasis may be a disease eradication e.g.IBR; Aujeszky disease) and or on disease risk management (e.g. after eradication to prevent (re-) introduction of agents; or to safeguard herds from becoming infected).

Disease risk management is an underestimated instrument in disease combat programmes while emphasis has been on vaccination and medication. Disease risk management requires a qualitative and quantitative approach. The latter not in the least to set priorities in a more justified manner.

Public health issues

The most commonly known zoonoses such as brucellosis and tuberculosis are largely eradicated from the EU but have not disappeared. They still pose a threat.

One should rather be aware of the fact that modern livestock production carries implicitly the risk of presence of carriers or infected animals, representing a potential risk for man, sometimes even without causing overt disease in animals.

Examples of such infections are salmonellosis, vtec, Str. suis II.

Various voluntary and compulsory disease combat programmes are operational. These programmes aim at eradication of the agent from the food animal herds and or reduction of prevalence.

It would be worthwhile to apply quality risk control programmes at farm level in order to control the prevalence of such disease, or rather the risks of such disease to be introduced and spread. An example of such an approach is the HACCP concept which focuses on hazard identification, risk assessment and definition of critical control points, as well as of critical management points, the latter as elements of a Good Farming Practice code.

Concluding remark

Sustainable animal production can be enhanced when more emphasis is put on better managerial qualities, and on disease risk management instead of on disease control alone.

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