CHAPTER ONE
INTRODUCTION
1.1 Background of the study
Intestinal parasites are parasites that inhabit, live off and can infect the gastrointestinal tract of humans and other animals. They are divided broadly into two groups which are protozoan such as Blastocystis sp, Balantidium coli, Cryptosporidium sp, Cyclospora cayetenensis, Dientamoeba fragilis, Entamoeba histolytica, Giardia lamblia, Isospora belli, etc and parasitic worms (helminths) such as Taenia sp, Diphyllobothrium latum, Bertiella sp, Fasciolopsis buski, Schistosoma sp, Strongyloides stercoralis, Ascaris lumbricoides, Trichuris trichuria, etc.
Intestinal protozoan parasites are unicellular and microscopic organisms. They could be flagellated, ciliated or in amoebiform including intestinal coccidian protozoan parasites. Most of them reproduce asexually by binary fission or schizogony or sexually by conjugation, process of sporogony (Cheesbrough, 2009). They usually have cysts and trophozoites as their life stages of which in most cases, the cyst is the infective stage (Cheesbrough, 2009)
Intestinal helminths on the otherhand, are multicellular organisms which can be seen with the naked eye. They may be hermaphroditic (such as seen in Taenia sp) or have separate sexes (such as seen in roundworms). These intestinal helminths have varying developmental stages, depending on the species. However, some species such as Ascaris lumbricoides and Trichuris trichuria have the egg as the infective stage while in some others like Hookworm; it is the infective larva stage. Their lengths also vary depending on the species and/or the sex (Cheesbrough 2009).
1.1.1 Life cycle and transmission of intestinal parasites
Intestinal parasites such as Entamoeba histolytica, Giardia lamblia, Trichuris trichuria etc exhibit direct life cycle whereby only one host is required to complete the life cycle while some others such as Taenia sp and Schistosoma sp exhibit indirect life cycle, in this case two or more hosts is required for the completion of their life cycle. Transmission is by ingestion of cysts and eggs through contaminated food and water as well as skin penetration by active larva of helminths (Cheesbrough, 2009).
