Strategic and tactic control of parasitic diseases
The reduced performance of the animals in terms of decreased milk yield, draught power, breeding performance, poor body weight gain, and higher susceptibility to other diseases, mortality and condemnation of affected organs are the attributes used for estimating the economic impacts of parasitism. Many a times, estimates gets underestimated when concurrent problems associated with reduced performance and the costs involved for control and treatment of parasitism are not taken into account. Years of research has brought about endemicity of specific parasite in a particular locality. The strategic control of parasitism refers to use of anthelmentic for control of parasites depending on the environmental conditions such as climate and possible increase in infective stages of the parasites. Those are fixed in a particular geographical area based on monsoon and other regular influencing factors. However, unexpected change in climatic conditions resulting in change in parasitic burden can be controlled through tactic use of anthelmetics. Use of drugs in tactic and strategic manner has resulted in reduced losses due to external and internal parasites leading to higher productivity, at least in organized system of livestock rearing.
The present day concept of parasite control strategies suggests that animals may live with worms, but worm burden should not be allowed to rise to a level that hampers the productivity. Therefore, the conventional concept of frequent deworming of animals in line with the eradication of parasites may not be much useful as premune status of the host gets disturbed with repeated and non-judicious use of anthelmintics. The concept of economic threshold for parasitism dictates that parasite control measures must provide an economic advantage that exceeds the total cost of the intervention to make the programme cost-beneficial. However, reliable economic thresholds of subclinical parasitism are difficult to determine as performance variables are affected by multitude of factors. Also, if we consider the comfort and well-being of animals that is achieved by parasitic control, the cost involved in deworming and other control measures cannot be equated in terms of enhanced performance and economic benefits.