Environmental Issues Animal diseases cause heavy economic losses both for individual farmers and at national or regional levels. The prevention and control of diseases aims to permanently or temporarily reduce these losses and, as far as the major animal epidemics are concerned, to prevent the economic and social catastrophes which accompany them. The control of animal health presents three categories of possible repercussions on the environment : Chemical substances (e.g. antibiotics) and pesticides (against parasites and vectors of disease) can have direct effects on the environment by affecting unintended target organisms and animals, thus disturbing the functioning of ecosystems. These aspects are dealt with on the page Environmental impact using chemicals and medicines in animal health control. Some ecological, biological and mechanical methods replace the use of pesticides, particularly against external parasites. Environmental effects of non-chemical control methods are generally considered to be much lower. Reduction of livestock morbidity and mortality promotes increase in human and animal populations and consequently pressure on the environment. These indirect consequences are shown on the page Environmental issues of livestock protection.

Environmental Issues Description Techniques Costs Targeted Livestock Systems Consequences Context of Application Monitoring: EIA, Indicators References & Further Reading  Environmental Impact:  Using Chemicals and Medicines in Animal Health Control     Non-Chemical Methods of Combating External Parasites of Livestock Animal Health Care: Summary Examples Use of Pour-on Technology to Control Ectoparasites

Description

Disease can be defined as a disturbance of all or part of the biological functioning of the animal. Factors causing disease can be grouped into two large categories:

• Living agents such as viruses, bacteria, protozoa, helminths, arthropods, etc. In this case there are two types of transmission:
• direct contact,
• indirect, through the intermediary of vectors or intermediary hosts.
• Physical agents such as heat and cold, or chemicals or toxic substances in water, or food, and also insecticides, disinfectants, etc.

• Sporadic (isolated cases).
• Enzootic (limited to a herd or a fairly small area).
• Epizootic (spreading quickly and capable of covering a wide area).

Techniques

Eradication of disease normally uses one or more of the following methods.

To reduce the prevalence of animal diseases, two main types of action are implemented :

a) Preventive and therapeutic measures:

• Treatment of the disease : it remains necessary, as long as the disease is present in the concerned population. Many kind of medicine are used, including antibiotics to control infection. The most common methods of application are by injection (subcutaneous, intra-muscular or intravenous), or orally.

• Medical prophylaxis, including vaccination: repeated at specific intervals, once the population to protect has been identified. Chemoprophylaxis can be used to control animal diseases : for instance, monthly intra-muscular injections of an antibiotic can control bovine anaplasmosis. A delay should be respected before consuming the meat because of the persistence of the medicine.

• Use of animals tolerant to disease (e.g. trypanotolerant livestock breeds).

• These are daily preventive activities taken within an animal production framework. For example, the cleanliness of  livestock housing, the supply of appropriate feed. It also comprises sanitary prophylaxis, including the fight against vectors, which can be repeated at determined intervals. These measures can be implemented at the level of a region or a country (for example by the control of cattle movement at the border).

c) Chemical methods (e.g. insecticides, acaricides).

For instance, the various methods to apply chemicals to protect livestock against external parasites and more specifically ticks are the following :
• Dip: by immergis animals completely in a dipping vat.
• Spray race: by spraying acaricides onto animals with a permanently fixed spray.
• Spray-dip: the machine can be moved from place to place.
• Hand spray: the hand-power spray is carried on the back of the livestock's owner.
• Ear-tags or tail tags impregnated with acaricides can also be used to control certain species of ticks.
• Pour-on an spot-on methods consist of applying acaricides only to the back or the sides of animals.


The same methods and sometimes the same products are used to control various species of flies e.g. tsetse flies, tabanids, stomoxes.

These include:

Ecological approaches (biotope modification of the vectors or of the intermediates hosts).

Biological control measures (predators, parasites, growth regulators).

Genetic measures (release of sterile males).

Mechanical measures (trapping and repelling techniques.  See Non-Chemical Methods for methods of trapping tsetse flies).

For further information see the individual sections on:
Environmental impact using chemicals and medicines in animal health control, and
Non-chemical methods against external parasites of livestock

The Pan African Rinderpest Campaign is an example of a large scale vaccination campaign to control rinderpest in Africa. The campaign has succeeded in eradicating the disease from most countries and rinderpest remains present only in a few areas. The second step in diseases-free countries consists of sero-surveillance and more globally in an epidemic-surveillance activity.

Total eradication can be both very expensive and almost impossible. Therefore, in such cases, the aim is not eradication, but diminution of infection to a reasonable level at which economic and/or social consequences are minimal. Hence, the acaricid treatments now aim at maintaining a minimum load for ticks on cattle. In this case, a minimum load is necessary to keep a natural immunity, which is useful in cases where cessation of treatment occurs. For these control programs to be optimised, an acceptable maximum load must also be determined, above which the negative effects on animal production are considered too heavy.

Costs

Evaluating the costs of animal health control has to take into account the methods and the technologies applied, the strategy of prevention or treatment, as well as the country where the progrmmme is to be implemented (cost of services, of salary, cost of products etc).

The costs include equipment, products, transport, infrastructures and labour.

Targeted Livestock Systems

The control of animal health is relevant to all animal production systems.

Consequences for Livestock Production and Human Welfare

The control of zoonoses in animals has a positive impact on human health because animals can be a source of infection for human: for instance the control of rabies, of anthrax, of tuberculosis, of Rift Valley Fever, etc.

Diseases are a major constraint to livestock development. Alleviating disease impacts on livestock is an important condition for increasing animal population; productivity and animal production (milk, meat, energy..).

Context

• Favourable factors:
• Progress in research in pharmaceuticals and veterinary medicine.
• Increasing knowledge on diseases, their causes, their epidemiology treatment.
• Good national and regional networks of veterinary services, public and private.
• Quality of infrastructures (road, paddocks for vaccination).
• Existing methods of prevention or treatment of the major diseases.
• Increase of demand of animal products.
• Market oriented livestock systems.
• High disease pressure.
• Unfavourable factors:
• Weakness of veterinary services, insufficient number of rural veterinary surgeons.
• Weak strategy and insufficient budget for prevention and cure of livestock diseases.
• Inaccurate statistical data on diseases, lack of animal identification.
• Mobility of herds in nomadic and transhumant systems, helping transmission and broadcasting of pathogens.
• Weakness of certain countries in implementing sanitary programmes for financial reason.
• Competition between human and animals for resources.

Monitoring: EIA, Indicators

• Prevalence or incidence rate of the diseases.
• Animal mortality rate.
• Lost reduction rate.
• Degree of coverage of the prophylaxis operations.
• Animal production indices.
• Animal health data (e.g. national statistics).

References / Further Reading

FAO, 1984. Ticks and tick-borne disease control. A practical field manual. Rome, FAO, pp. 621.

Bussieras, J., Chermette, R. 1991. Abrégé de Parasitologie vétérinaire- Fascicule 4- Entomologie. Ecole Nationale Vétérinaire, Maisons Alfort, pp. 163.

Douthwaite, R.J. 1992. Non targets effects of insecticides used in tsetse control operations. FAO World Animal Review.  70-71: 8-14.

Koeman, J.H. 1979. Chemicals in the environment and their effects on ecosystems. In: GEISSBÜHLER H. Edit.; Advances in Pesticide Science. Part 1. World Food Production- Environment- Pesticides, Pergamon Press, Oxford, 25-38.

Müller P. 1988. Effects of pesticides on fauna and flora. In: IAEA ed.: Pesticides: Food and Environmental Implications. IAEA-SM-297-40, 11-27.

Nagel, P. 1995. Environmental monitoring handbook for tsetse control operations. CTA/RTTCP, Scientific Environmental Monitoring Group, pp. 323.

Nagel, P. 1994. The effects of tsetse control on natural resources. FAO Animal Production and Health paper , 121:104-119

OIE. 1994. Ectoparasites des animaux et méthodes de lutte. Revue scientifique et technique de l'OIE, 13(4), pp. 1430.

Reid R., Wilson C.J., Kruska R.L., Mulatu W. 1997. Impacts of tsetse control and land-use on vegetative structure and tree species composition in south-western Ethiopia. Journal of Applied Ecology, 34: 731-747.

Rodhain et Perez C. 1985. Précis d'entomologie médicale et vétérinaire,.Maloine S.A. pp. 458.

Uilenberg G., 1998. A field guidefor the diagnosis, treatment and prevention of African animal trypanosomosis. Rome, FAO, pp. 158.

Wilson C.J., Reid R., Stanton N.L., Perry B.D. 1997. Effects of land use and tsetse fly control on bird species richness in southwestern Ethiopia. Conservation Biology, 11(2): 435-447.

WHO. 1984. Chemical methods for the control of arthropod vectors and pests of public health importance. WHO, Geneva, pp. 108.

WHO. Safe use of pesticides. Ninth report of the WHO expert Committee on vector biology and control. WHO Technical Report Series 720, 60 pages.

WHO. 1989. DDT and its derivatives. Environmental aspects. International Programme on Chemical Safety (IPCS), Environmental Health criteria, N° 83,  pp. 98.

WHO. 1989. Deltamethrin health and safety guide. International Programme on Chemical Safety (IPCS), N° 30, 31 pages.

Environmental Impact:
Using Chemicals and Medicines in Animal Health Control

Background

Medical and chemical treatments should strictly follow the instructions for use: quantity of product, frequency of application, duration of treatment, as well as delay before eating meat or milk. People who apply the treatment should be specially trained in those aspects and in the correct use of the medicines.Incorrect usage may lead to ticks resistant to acaricides, and diseases resistant to treatment.

To control ticks, acaricides are regularly applied also, weekly, fortnightly or monthly, according to tick species and tick infestation rate. The use of organophosphates as acaricides requires a delay before consuming the meat. Other acaricides, e.g. pyrethroids need a shorter delay but are more toxic for fish.

Positive Environmental Impact

• Reduction of infectious and parasitic zoonotic diseases ( human transmissible diseases).
• Control of diseases allows human activity and livestock presence in infested areas.
• Epizootic control of livestock also contributes to wildlife preservation.
• Realise efficient use of resources for same level of productivity.

• Disease treatment.
• Inconsiderate and  excessive use of drugs for animals, principally antibiotics, can select resistant pathogen agents leading to the continued need to identify new compounds. It is worth noting that the induced resistance can be transmitted to bacteria affecting human health (eg. tuberculosis).
• Excessive use of drug use causes modification of microbial ecology (i.e. soil microbiology) - with potentially serious impacts on the environmetal functions of ecosystems.
• Insecticide and acaricide treatments against parasites and vectors of parasites. These can have an impact on the non-targeted animals, especially:
• Induce water pollution by residues or washes.
• Poison fish and shellfish living in polluted waters.
• Reach other beings of the ecosystem, for example the boozers which are necessary to incorporate faeces in the ground, or pollinator insects.
• Increased population of resistant insect or acrid strains, leading to an inefficiency of treatments.


Insecticide treatments have been used for a long time against biting diptera, on the ground or by air (Spraying of the resting or reproduction places). The ground spraying of pen is quite easy, while the vast eradication campaigns with ground treatment of the big carriers' biotopes (glossines, mosquitoes ...) require significant labour as well as financial means and a great capacity for organisation. They are only applicable during the dry seasons. Helicopters and planes are used according to the situations.

The helicopter is very efficient in uneven areas with dense vegetation for it can act swiftly on large surfaces, but it is expensive and has an impact on the non-targeted fauna. (Sprays applied in areas with rich biodiversity, especially on the banks of surface waters; large doses used in ultra-low-volume-sprays). The plane is very efficient and quick against diptera from scarcely wooded Savannah in flat regions with light and regular winds.

Persistent treatments on the ground or by helicopter with DDT or dieldrin have short term sharp effects on the terrestrial (Hymenoptera) and aquatic entomofauna and maybe on vertebrates (carnivorous and insectivorous birds ; some small mammals), fish, with accumulation in the food chains (animal fat, maternal milk) ; the endosulfan reveals a strong and immediate effect on fish and terrestrial as well as aquatic arthropoda with a risk of intoxication for consumers of the fish affected. In persistent doses, the action of pyrethroids is strong on crustaceans (shrimps ...) and terrestrial as well as aquatic arthropoda (ephemera, ants, wasps, spiders).

Treatments with non persistent doses with endosulfan (14-24 g/ha) by plane still have a strong but very transient effect on fish and insect. Organochlorines are scarcely used nowadays because they are prohibited in many countries. They are replaced by pyrethroids. Deltamethrine in non-persistent doses (0.25 g/ha) has a passing knock-down effect on insects (Ephemera, Coleoptera, Hermiptera) and transient lethal effect on fish from waters that are not very deep. In the mid and long term, the effects of most of these products die down because tropical ecosystems have a strong capacity for regeneration (Generally after a year) and anti-vector treatments are in general unique compared to agricultural treaments that are repeated, multiproduced and used in high doses.

One must note that in environmental follow-ups, the tendency is to entrust rural populations with the monitoring of some biotic parameters well perceived by themselves (dynamics of some vegetal and animal species) or abiotic parameters (quality of soils, water, etc) in their living surroundings.
 
 





[Livestock & Environment Toolbox Home]



 
 

 

Biconical trap Chalier-Laveissière for tsetse fly: Cage  Tulle net plasticized cone  Four internal screens in black material Windows in the material Black material inside Metallic peg.
Pyramidal trap for tsetse fly of Gouteux and Le Gall, (adapted from Gouteux et al.).  Plastic bottle transformed in cage Tulle screen pyramid Three internal black screens Stick Opening Blue plastic.
Mobile screen of Mérot-Filledier  (adapted from Mérot et al.).  Metallic frame Blue material Black material Mosquitos net tulle Small bottle with aceton, other with octenol Metallic peg.
Monoconical trap "Vavoua" of Laveissière for tsetse fly. (Laveissière - Les glossines, guide de formation et d'information. Série Lutte antivectorielle, 1988).  Mosquito net tulle cone Cotton ball Metallic peg Iron circle Blue screen in cotton-polyester Black polyamid screen.

 

Endectocides (e.g. avermectines, milbémycines), easily applied by injection or pour-on are efficient against endoparasites (gastro-intestinal and pulmonar worms, hypodermes, microfilaria) and certain ectoparasites (biting flies, lice, mite, scabies).  Their relatively high cost limits their use to the richer farmers. See Also: Use of Pour-on Technology to Control Ectoparasites   Tsetse fly

"Pour on" application on the back of an animal with a measuring bottle (adapted from Cuisance).

• Use of a limited quantity of pesticide.
• Parasite well targeted.
• Efficiency of the method to decrease vector and parasite population.

• Land clearing destroys native vegetation and exposes soil to erosion. (This technique almost has been abandonned).
• Indirect effect of pesticides on non-target insects (pollinators) or birds.
• Problem in  wildlife habitats with traps and screens.

• A sufficient awareness of farmers either to apply  these techniques correctly, or to allow advisory services to use them.
• A participatory approach to organize and facilitate the use of these techniques at a sufficient scale.

 

 
 




[Livestock & Environment Toolbox Home]



 
 

Health care and disease prevention for livestock has a positive effect on the animal populations. Basically they allow other livestock improvement technologies as :

• Breeding for improved livestock varieties (which itself has negative impacts resulting in loss of agro-biodiversity).
• Intensification of livestock production systems (which may have a negative social impact from loss of traditional methods and loss of systems diversity).
• Minimizing economic losses linked to low productivity and low reproduction rate due to diseases.

• Increase of animal pressure on soil, grassland and pastures, feed resources and water.
• Extension of areas grazed by animals, leading changes of ecosystems.
• Extension of cultivated crops for feed production.
• Increase of animal waste.
• Competition with wildlife.

 



[Livestock & Environment Toolbox Home]