The occurrence of distinct variants with minor morphological differences is a common features in all parasitic groups. So, great efforts have been directed towards reliable ways to identify closely related strains of parasites.

Morphobiological, biochemical, biological and immunological approaches have been revealed varying degree of heterogenicity and may occur under the pressure of environmental changes. The efficacy of immunodiagnosis approach would be also restricted by limited time of antibodies survival and differences in the response of individual hosts, together with cross reactivity phenomenon.

The detection of DNA sequence represents one of the most significant development in molecular biology, which has helped to distinguish parasite interrelationship at the specific and subspecific levels. Polymerase chain reaction (PCR) has been developed. Many modifications of the original procedure have been also evaluated in parasite diagnosis or identification. Molecular techniques have proven to be useful for evaluating the taxonomic status of parasites especially where morphological characters are unreliable to distinguish between species. Application of such approaches may facilitate specific diagnostic probes, identify parasite antigens / or immunogens, determine parasite phylogenetic relationships and may simplify the identification and ordering of variants. This will not only aid practical diagnosis but also provide a better understanding of parasite epidemiology and help design more efficient for deworming and control measures.