Prevention and control of parasitism in livestock
Contd from previous issue
The main proof-of-concept studies for the use of TST were conducted in South Africa, where the FAMACHA method was devised and evaluated. FAMACHA assesses the colour of the conjunctival mucosal membrane, on a five-point scale, to estimate the degree of anaemia present as caused by the blood-feeding nematode, H. contortus. Anaemic animals, scoring 4 or 5 on the FAMACHA scale, are at risk of disease and are treated.
Use of plant origin anthelmintic are increasing day by day in modern medication. These included various extracts from jallop, quassia, areca nut, cloves, aloes, garlic, cucurbit seeds, castor oil, male fern and Chenopodium. In general, these were hazardous concoctions with low anthelmintic efficacy, especially in ruminant species, and they rapidly disappeared from veterinary use with the synthetic anthelmintic compounds. Although there is a large and diverse range of herbal de-wormers used throughout the word, particularly in the Asian and African countries. The possible use of specialised crops to control nematode infections in grazing ruminants has attracted considerable research interest in recent years. Bioactive plats or forages with secondary metabolites, particu- larly legumes with a high content of proanthocyani-dins (condensed tannins) e.g. Hedysarum-coronarium and Lotus pedunculatus have been reported to reduce worm burdens in grazing lambs by up to 50%. An in vivo anthelmintic effect has also been observed using quebracho, a condensed tannins extract, a a single high dose against sheep nematodes and the capacity of purified condensed tannins from legumes grown in Denmark to kill nematode larvae in vitro has been demonstrated. However, in several field studies, it has been difficult to relate anti-parasitic effects to the actual amounts of condensed tannins. Tannins may have a direct anthelmintic effect on resident worm popula-tions in animals and thirdly, tannins and/or metabolites in dung may have a direct effect on the viability of the free-living stages. The enthno-veterinary and medicinal plant knowledge offers a range of plant materisl to be evaluated for their acaricidal properties. Plant materials are known to possess insecticidal, growth-inhibiting, anti-moulting and repellent activities. Number of reports are available on the effect of different plant materials on tick species such as Jatropha curcas; Annona squamosa; Polyalthialongi-folia, Ageratum conyzoides, Tageteserrecta, Tagetes-minuta, Cymbopogan spp., Mentha piperita, Ocimum sanctum, Dalbergiasisoo- Roxb., Azadirachtaindica, Eucalyptus maculate, Citrus spp., Ferroniaelephantum, Solanum nigrum Lantana camara. (To be contd)