|GATE - 3/91 - Impact - A Neglected Dimension of AT (GTZ GATE, 1991, 52 p.)|
by Uly Matzigkeit
In 1982, I started collecting natural methods of parasite control that were both useful and practicable. There is no specialized natural veterinary medicine database anywhere in the world which contains information on the use of herbal substances to control ectoparasites and endoparasites, to cure diseases or to heal wounds, for example. Worldwide searches in agricultural, chemical and medical databases, botanical institutes such as those in Geneva and Hamburg, and a difficult and time-consuming search for "grey literature" made it clear that even basic information is rare, widespread and difficult to obtain.
Numerous factors have been instrumental in changing all the known relationships between animals and ectoparasites/disease vectors. These factors include
· the intensification of tropical animal husbandry
· the introduction of European high breeds
· cross-breeding of European high breeds with local tropical/subtropical breeds;
· the expansion of pasture into previously avoided areas highly infested with ectoparasites/disease vectors.
Biological control of ectoparasites indispensable
An increase in the performance of the breeds obtained in the ways mentioned above goes hand in hand with a loss of resistance to ectoparasites and their vector diseases. This in turn results in major loss of production or even death. To avoid such losses, industrial societies introduced synthetic pesticides to combat the parasites and disease vectors, promising to completely eliminate all problems. However, intensive campaigns to eradicate the major parasites have not achieved their aims.
· Ectoparasites have developed a steadily increasing resistance to prophylactically applied synthetic pesticides, and sometimes even a transmitted cross-resistance to different pesticides. The phenomenon of resistance is even better known in human medicine- one typical example is malaria prophylaxis. It was known as early as the 1950s that ectoparasites are resistant to pesticides. Many of the pesticides used then are still in use today.
· Farmers, neither psychologically prepared for, nor trained in the proper use of (toxic) synthetic pesticides, jeopardize their health, for example by inhaling the spray dust.
· Toxic residues may remain in frequently-treated animals, constituting a hazard to human health.
· Tremendous sums of money have been unwittingly spent on creating detrimental environmental influences. Contamination of soil and groundwater by draining dips, or runoff while spraying are examples of obvious ecological hazards.
· Synthetic pesticides are often unavailable or simply too expensive.
Methods of biological control
The only way to break this vicious circle is for farmers to switch to nature adapted animal husbandry and veterinary medicine by using local, traditional sources. The basis, and the crucial factor for health, is a stock of animals in good condition and resistant to parasites and disease, and husbandry systems that avoid providing optimum living conditions for parasites. Encouragement of natural enemies to ectoparasites, such as birds, predators, microorganisms and fungi, is also often neglected.
More than 3,000 plants which contain anti-parasitic substances are known worldwide. Of these, several hundred are recommended in natural veterinary medicine to combat both ectoparasites and endoparasites. Moreover, numerous plants are highly effective in curing animal diseases or healing wounds, not to mention the additional benefits they offer, e.g. as sources of fruit, timber, firewood, dye, fibre for ropes, fodder for ruminants etc., and their suitability for green manure, nitrogen fixing or erosion control.
Natural herbal insecticides are not only cheap and successful, but also completely biodegradable. As a rule, any farmer can produce herbal pesticides without difficulty; and there is no ectoparasite which cannot be controlled by insecticides or repellents derived from plants.
Ideal plants for such purposes are those which
· grow large, abundantly and wild
· are perennials, and therefore available from year to year
· make low demands on soil quality
· contain high quantities of the antiparasitic substance, in particular in their leaves, branches or whole herbaceous parts
· can be stored for a long time without losing their insecticidal or repellent properties.
Insecticides and repellents obtained from plants should be used in particular in peak periods of ectoparasite infestation.
Tephrosia vogelii Hook f. (Transactions of the Linnean Society of London, vol. XXIX, plate 31 (1873), London).
Use of an insecticidal plant to control ticks
The fish poison bean, Tephrosia vogelii Hook. f., is just one of many natural, plant-derived substances that can be used to control ticks. Ticks and the diseases they transmit cause considerable damage in tropical regions. The active insecticidal substance is contained mainly in the leaves of Tephrosia. Even prolonged storage of the dried leaves does not seem to result in any major decrease in their toxicity.
Among others, T. M. Bertram OSB, of St Benedict's Abbey, Peramiho, Tanzania, has reported on the use of this shrub, which usually stands less than 3 m high:
"One litre of pounded fresh leaves of Tephrosia vogelii has to be infused in 1 litre of water for some while. The fiItrate is used locally in Tanzania as an insecticide for tick control, especially on cattle. It is brushed onto the infested parts of the animal's body."
Tephrosia vogelii is probably not indigenous to East Africa. It was formerly grown throughout West Africa and used to stupefy fish. Well known all over southern Africa, the shrub was planted in Northern Rhodesia (now Zambia) for wind-breaks on coffee estates, and in India. In Assam, especially, it was cultivated by tea planters as a green manure.
It has been reported that another species of Tephrosia is used as an insecticide in North America: this is Tephrosia leiocarpa A. Gray, whose roots are toxic to fleas, ticks and lice.