A PREVENTIVE APPROACH
TO INFECTIOUS DISEASE CONTROL

ECONOMIC IMPLICATIONS OF INFECTIOUS LIVESTOCK DISEASES

Infectious diseases in intensively reared livestock have been very much in the forefront of international events recently, and continue to extract a devastating toll on regional economies. The 2001 UK Foot & Mouth outbreak is estimated to have knocked 1-1.5% off GDP growth, based on losses in meat exports alone.

The poultry industry has historically been volatile, and particularly susceptible to infectious diseases. The 2003 avian flu pandemic has resulted in a billion birds having been lost to infection or culling in South East Asia. Losses in the region of $12 billion have been sustained by the poultry industry in China alone. Thailand's poultry industry lies shattered the wake of the flu epidemic. Bans imposed on exports of raw meat to Europe and other countries are not likely to be relaxed in the near future. Infectious organisms such as H5N1 and other pathogenic viruses can have additional indirect consequences on national economies through restrictions on travel and tourism, and other long-term implications.

Even in the absence of epidemics on this scale, infection-related livestock mortality routinely ranges from 10-20%, in spite of a better understanding of the epidemiology of infectious poultry diseases, and improved technology in disease management (improved vaccines, automated vaccination and in ovo vaccination equipment). Losses are primarily due to the astoundingly rapid onset of common infectious poultry diseases, which can cause mortality overnight. The final outcome of infectious disease outbreaks within animal housing units is generally dependent on the level of staff vigilance, speed of management response and on early diagnosis.
 

IMMUNOSUPPRESSION & INFECTIOUS LIVESTOCK DISEASES
 
A group of diseases loosely termed ‘Complex Disorders' has been on the increase in intensively reared livestock in recent years, frequently causing widespread immuno-suppression. Multiple infective pathogens are implicated, causing a ‘blurring' of symptoms and difficulty in diagnosis. Vaccines frequently fail to control such disorders as they tend to be targeted very specifically against single pathogens, and can often prove ineffective even against variants of the same virus. Furthermore, vaccines rely heavily on a healthy immune system for their protective action, as their effectiveness relies on stimulating the animal's own immune system to mount a defense against pathogens. The benefits of expensive immunisation programs are therefore greatly limited or lost on immuno-suppressed animals.
Immuno-suppression is unfortunately very common in intensively reared livestock; it can be virally induced following exposure to Mareks, Gumboro (Infectious Bursal Disease) or Chick Anaemia viruses, or simply stress-related due to congestive housing conditions. As a result, susceptibility of livestock to opportunistic secondary bacterial, fungal and other trivial infections is greatly heightened.
 
Immuno-suppressed animals are thus rendered highly susceptible to environmental pathogens, even to micro-organisms that might not normally present a threat to healthy animals, or those present in sub-infective levels. It is therefore essential to reduce the populations of ALL types of micro-organisms in the animal housing environment to minimal levels in order to prevent outbreaks of infectious diseases.
 
Although vaccines have been shown to be effective in controlling certain livestock diseases, the variation in quality varies considerably between sources. Furthermore, its use in the control of certain diseases, such as the highly pathogenic H5N1 responsible for bird flu, is highly controversial. While vaccination might improve bird survival, it does not necessarily rule out the birds' carrier status (the ability to shed infective viral particles). Hence the European Union has imposed a 3-year ban on poultry from areas where birds have been vaccinated.
 

ANTIBIOTIC USAGE IN LIVESTOCK AGRICULTURE
 
Antibiotics usage in meat production for human consumption is of growing concern to consumers and health & regulatory agencies internationally. While they were once routinely used as growth promoters in animal feed, their use in meat production is now heavily regulated in response to consumer concerns about antibiotic residues in meat and dairy products. Risks to the consumer include development of hypersensitivity reactions following drug residues ingested in food products of animal origin over long periods of time. The most serious health concern is that repeated exposure to low-level antibiotics encourages the emergence of antibiotic-resistance in human intestinal microflora, which can limit the range of antibiotics available for treatment of human bacterial diseases.
 
As in human health practices, the tendency to misuse/overuse antibiotics in livestock disease control is common. It is essential to bear in mind that antibiotics are a remedial rather than a preventive measure, and useful for diseases of bacterial origin only. Most diseases of economic concern in the livestock agriculture tend to be virally induced, and thus not responsive to antibiotics.
 
The main justification for antibiotic usage in meat production was the manipulation of enteric microbial populations to improve intestinal absorption of nutrients, hence achieve a higher feed conversion ratio. Secondly, the lower microbial content of faecal matter reduced the sub-clinical infections that can significantly lower productivity.

Reducing the dependency of meat producing industries on antibiotics has led to safer food products that meet with consumer approval. It has also resulted in a more sustainable, long-term solution of implementing infectious disease management programs.

THE NEW APPROACH TO DISEASE MANAGEMENT IN LIVESTOCK AGRICULTURE IS STRONGLY PRO-ACTIVE, WITH A FOCUS ON DISEASE PREVENTION THROUGH IMPROVED HYGIENE IN ANIMAL HOUSING ENVIRONMENT.
 

A PREVENTIVE APPROACH TO INFECTIOUS DISEASE CONTROL
 
The success of any disease control program therefore hinges essentially on adopting a two-pronged approach to prevent exposure of animals to pathogens. Microbial challenge encountered by livestock can be minimised by preventing Importation of pathogens onto the farm through management techniques, ie. the use of reputable stockists, limiting movement of vehicles, equipment and personnel through the housing areas, etc.

Secondly, heightened on-site vigilance of animals, prompt diagnosis and isolation, rapid removal of carcasses and frequent clearing of animal waste helps minimise the horizontal spread of infectious disease.

The Immunological status and general health of the animals greatly determines the extent to which birds can withstand exposure to virulent pathogens. Provision of comfortable housing conditions (timed lighting, good ventilation, temperature control, adequate space) can result in healthier, stress-free livestock, better able to resist infection.
 

THE IMPORTANCE OF GOOD HYGIENE

A Good Hygiene Routine comprising Cleaning and Disinfection is the most powerful and cost-effective approach to disease control. It serves to reduce pathogenic microbial populations to safe, non-infective levels within livestock housing environments. Persistence and Proliferation of pathogens in animal housing environments can be extremely problematic, particularly as a result of high levels of Humidity, Warm conditions and the presence of high levels of Organic matter.

Any disease control regime, whether it is based on Immunisation or Medication, can be rapidly undermined by poor hygiene conditions. Maintenance of Good Hygiene Practices through Regular Cleaning and Disinfection is Fundamental to any Disease Prevention Program.

+ Dirt and Organic matter can harbour infinite numbers of disease causing organisms, and act as a nutritional base for microbial proliferation. Cleaning dissolves and rinses away organic matter and associated pathogens.
 
+ Disinfection reduces any remaining pathogens to safe, non-infective levels by killing them outright at the Recommended Use-dilutions and Contact Periods.
 

THE ROLE OF DISINFECTION IN INFECTIOUS DISEASE CONTROL
 
QUATCHEM Encourages a Preventive Approach to Infectious Disease Management. A high level of sanitation throughout the growth period is critical in breaking the cycle of infection, and reducing the frequency of disease outbreaks under intensive animal rearing conditions.
 
Disinfectants act at a fundamental level in infectious disease control, by eradicating pathogens responsible for both clinical and sub-clinical infectious diseases from livestock housing environment. Disinfection has proven to be the most Cost-effective and Versatile approach to Infectious Disease Control, and can be readily adapted to any Infectious Disease challenge in any environment. Disinfectants offer a much broader spectrum of protection relative to antibiotics and vaccines, without the likelihood of leaving harmful chemical residues in the meat. While both are useful adjuncts to Infectious Disease Control, Disinfection allows their use and associated costs to be minimized.
 
Disinfectants offer a very broad spectrum of protection against pathogenic organisms that includes bacteria, viruses, fungi and yeasts. A wide choice of Chemo-disinfectants is available, with diverse properties suitable for any Livestock Agricultural application.
 
Actives such as quaternary ammonium compounds possess both cleaning (highly effective in dirt penetration and removal) and powerful disinfection properties thus allowing a single-step sanitisation. They are highly recommended for use in poultry production due to their non-corrosive and non-toxic properties, which allow their use around young animals and on a variety of surfaces.
 
Other actives include Phenolics, Iodophores, Oxidative Peroxygens, Aldehydes, each with its own characteristic Biocidal Spectral Range and Properties.
 
Disinfection thus safeguards Meat Quality and ensures Maximum Productivity under Livestock Friendly conditions, without the use of Systemic drugs and chemicals.
 

*All Quatchem Disinfectants are independently tested to stringent British & European Standards. This requires achievement of a Minimum 5-log (99.999%) kill at Recommended dilutions, where the bacterial load can be reduced from One Million to less than 10 infective cells, within only 5 min contact time.
 
Quatchem Disinfectants are specially Formulated for Maximal Performance under practical Farmyard conditions. Testing is carried out under conditions of Hard Water and high levels of Organic Contamination.
 

Dr. R.K. Chowdhary,
Director Scientific Affairs, QUATCHEM