Endoparasitic infestations

Adverse hygienic conditions favor human infestation with multicellular organisms (referred to here as parasites). Skin and hair are colonization sites for arthropod ectoparasites, such as insects (lice, fleas) and arachnids (mites). Against these, insecticidal or arachnici-dal agents, respectively, can be used. Endoparasites invade the intestines or even internal organs, and are mostly members of the phyla of flatworms and roundworms. They are combated with anthelmintics. 

Taylor Q) found the endoparasitic dinoflagellate Amoebophrya ceratii in phytoplankton samples taken in 1965 from Sequim Bay, Washington (Figure 1). He reported that 30-40% of the G. catenella cells in 3 samples taken at intervals over 4 months were infested by this parasite. He suggested that the parasite offered a remote possibility of biological control of catenella, the causative organism of many of the outbreaks of paralytic shellfish poisoning (PSP) on both sides of the North Pacific (2, 3, 4, and in the Southern Hemisphere (j6). 

Ectoparasites such as ticks, mites and haematophagous flies together with certain endoparasites may be "managed" by use of avermectins (macrocyclic lactones) or hormone analogues and by Immunization of the hosts with antigens derived from the vectors or parasites themselves. Recently this combined approach has been used most effectively against helminth infestations as well as against ticks and flies. Use of components of host odors and pheromones to trap, sterilize or kill tsetse flies is described as well as inexpensive methods of crop and livestock protection, such as oils and plant extracts, used traditionally in less developed countries. 

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