Ans: Apicomplexan parasites are widely using in different fields. This plays an important role in veterinary medicine and agriculture. Plasmodium species that cause malaria comes under obligate intracellular parasites.  Toxoplasma gondii and Cryptosporidium parvum come under opportunistic pathogens as they act as immunocompromise the individuals. Eimeria species and Theileria species are considered important parasites for agriculture.