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Animal health and ecological implications
Use of veterinary products
Use of pesticides
Presence of toxic residues in animal products
The objective of animal health services is to contribute to improved levels of livestock production. In developing countries, the first stage is very often the control of major diseases to enable increase of animal production. While pursuing these objectives, the activities could result in environmental degradation and pollution, due to increases of livestock population, through mismanagement and overutilization of the available natural resources and veterinary products.
The intensification of livestock production as part of the development process may, if not properly carried out, contribute to land degradation through overgrazing, reduced soil fertility, erosion and desertification. This is particularly true in marginal areas unsuitable for agriculture, where most extensively managed ruminants are kept. Major animal health activities, such as vaccination campaigns or parasite (e.g. tsetse or ticks) control programmes, have positive impacts on productivity and size of animal populations that lead to increased animal population pressure and may contribute to land degradation unless correct land-use planning is implemented.
Proper land-use planning and utilization, taking into account the diverse agricultural, topographical and geographical aspects involved, is essential to reducing the risk of adverse ecological developments while increasing productivity and animal disease control. Therefore it requires a multidisciplinary approach to ensure the correct planning and utilization of the land.
In a similar way, the intensification of livestock production results in increased use of veterinary products, such as pesticides, and the production of different types of waste, like manure from feedlots. The pollution or contamination of the environment, especially water supplies, due to animal wastes (manure and liquid manure) is an increasing problem and must be foreseen when planning new animal housing, especially in the industrial production systems. Proper action has to be taken for the careful use or safe disposal of the slaughterhouse waste. These can be valuable by-products if appropriately processed. This should involve sterilization or rendering of ail condemned or contaminated material before further processing and release for use. Improper disposal of this type of waste can lead to an increase of predatory animal species (e.g. hyenas, rural dogs, etc., on land and sharks with disposal to sea).
As well, waste food from international sea and air traffic must be sterilized to avoid dissemination of animal disease through contaminated animal products.
Environmentally friendly methods of applying insecticides (targets and traps for tsetse control) and acaricides (pour on) are becoming available. These have the potential for reducing possibilities of contamination of the environment and should be utilized where practical. The use of pesticides may be minimized by using breeds or their crosses that are resistant to parasitic species, e.g. trypanotolerant cattle or tick-resistant breeds.
Changing ecological equilibrium
Frequently the reduction of the population of one species in an area has unexpected consequences for the environment through its impact on non-target species. Occasionally the application of disease-control measures may have unpredicted consequences for the environment.
The widespread and disproportionate use of antibiotics and parasiticides, such as anthelmintics and acaricides, has lead to the development of strains of pathogens that are resistant to the drug employed, thus complicating control.
Poisoning coyotes (predators) to control rabies in Mexico resulted in such a dramatic increase in the jackrabbit population that it became a pest in agriculture.
Game parks in Africa may constitute a reservoir of infection of certain livestock pathogens, e.g. foot-and-mouth disease and trypanosomiasis.
These examples serve to emphasize
the need for comprehensive planning of animal health interventions to take fully into
account the possible ecological consequences.
With the increased use of veterinary products for the treatment of disease, control of parasites and enhancement of production levels, it is essential that all those concerned with the handling and administration of such products be made aware of their potential danger to the environment.
Veterinary products are generally
supplied with explicit details on their use, disposal, possible side-effects and, in the
case of pesticides, their toxicity rating and recommendations for neutralization in case
of accident. This information should be in an appropriate language. The details included
on the packaging may, however, vary from country to country depending on national
regulations governing registration. To ensure an adequate standard of packaging and
instructions on use, close cooperation should be established and maintained between animal
health services and registration authorities. Products destined for use and administration
by untrained personnel, such as livestock owners, should be supplied with instructions in
the appropriate language. Labels proposed by manufacturers for new products should be
submitted to registration authorities for prior approval.
Strict control over the importation,
registration, distribution and use of pesticides should be exercised, while users should
be adequately trained in their handling and methods of application. Recommendations on
this aspect are contained in the FAO/WHO Guidelines for pesticide use.
Following the administration of veterinary drugs, their residues may be present in edible products of treated animals. Potential health hazards emanating from residues in food can be divided into toxicology, immunopathology and microbiology. This last aspect is a consequence of use in feed of antimicrobial substances at subtherapeutic levels.
Other chemicals are used in animal husbandry. These include additions such as antioxidants or antifungal agents used to preserve the quality of the feed, colourants, disinfectants and pesticides. These are also a cause of public health concern.
Control over the presence of residues of pesticides, drugs and hormones in meat, milk, eggs and other animal products is not yet common in developing countries, but it is advisable to reinforce the control of these products.
To avoid these problems, dissemination of information, seminars and training activities on the presence of residues in animal products should be carried out.
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