Herbal Immunomodulatory and Therapeutic Approaches to Control Parasitic Infections in Livestock

Parasitic diseases are a major constraint in the animal health and production throughout the tropical and subtropical countries of the world. Allopathic parasiticides are currently in operation as the most effective means for their control. But these have serious limitations, such as their non -availability in some developing countries, risk of misuse leading to drug resistance, environmental pollution and food residues. Naturally produced medicinal plant products offer as an alternate immunomodulatory and therapeutic agents so as to overcome some of these hazards and subsequently may be sustainable and environmentally acceptable. Networking and interactions within the immune system are so complex that modulation of the immune system to achieve designed therapeutic success is still in the realm of philosophical editorials rather than of definite efficacy studies (Benson, 1993). The use of immunostimulants, particularly as an adjunct to chemotherapy for control and prevention of infection (Chatterjee et al, 1988) holds great promise but has not yet received the attention that it deserves. Immunomodulator may be defined as a substance biological or synthetic which can stimulate, suppress or modulate any of the components of the immune system. The basic function of the immune system is to protect the individual against infectious agents and potential pathogens which puts the immune system in a vital position between a healthy and diseased state of a host. One of the starting points in the field of immunomodulation has been the search for agents that could be used for the treatment of residual cancer (Yamamoto, 1996). The results with intralesional application of BCG (Patard et al, 1998) and systemic use of levamisole (Kurman, 1993)) have been quite promising. Further, we have experimentally observed that a haemoprotozoan infection caused by Trypanosoma evansi causes impairment of blood brain barrier status and increases Ig biosynthesis in cow-calves. Levamisole @ 2.5 mg.kg as an immunomodulator produced marked improvement in the status of blood brain barrier (Singla et al, 1998). Most significant progress in the field of immunomodulators is represented by the discovery of cyclosporine (Walsh et al, 1992). It is a potent immunosuppressant that has proved to be boon for the prevention of graft rejection. The drug is also gaining ground for the treatment of several auto immune diseases. Chemical non-specific immunomodulator levamisole has been found to improve the development of resistance to caecal coccidiosis as there was no mortality in such treated birds