Microbiology 9 - Parasitic Nematodes - Parasitic infections affect billions people in the world - Ascaris infection by ascaris worms - 2 billion people affected - Hookworm and whipworm - 1.3 billion - Enterobius vermicularis - 400 million Parasitic infections - Disease-causing organisms that depend on their infected host for survival - Can be divided in two groups o Protozoans Microscopic · Single-celled eukaryotes o Helminths · Macroscopic Multicellular worms · Three classes that can affect humans: · Trematodes · Cestodes · Nematodes (roundworms) o Divide them depending on where they localise in the humans o Gi tract - one host on their infection cycle Blood and tissue - multiple hosts Nematodes - Extremely abundant o 25000 described o 1000000 estimated - Not all harmful - Have adapted to all sorts of environments o Air, soli, water etc - Saprophytic o Feed on dead matter - Small predators o Can use them in our benefit such as pest control General features - Eukaryotic - Non segmented, cylindrical, tapering at both ends - Diecious or hermaphroditic Both sexes - 1mm to 3 feet (big range) o E.g. Pin worm Guinea worm - The big part of the nematodes body is the reproductive organ - If we cut through: o Different organ systems
o Epidermis (equivalent of skin) o Thick cuticle Protection layer · Exoskeleton · Gas exchange happens through here o Primitive nervous system · Dorsal nerve cord · Ventral nerve cord o Muscles o Excretory system o Gastrointestinal system o Reproductive system - The body is filled with a liquid - Nematodes undergo the cycle o Adult worms mate and produce eggs o Cells will divide in the egg Small worm will form and hatch into a larva (1st larva stage) . There are four stages overall At each stage, the larva will molt o . Shed the cuticle and grow a new one - L3 and L4 are capable of infection Infection Depends on whether they are intestinal or blood + tissue - Intestinal o Ingestion: " Contaminated food or drink with embryonated eggs · Get into GI system · Encysted embryos in infected pigs' flesh o Air born . Can inhale the eggs and enter the GI system - Blood + Tissue o Penetration of the skin o Vectors . Blood sucking insects Treatment - Seven different classes of drugs with different modes of actions such as: o Piperazine Neurotransmitters · Works on synapses Hyperactivates the muscle . And contracts the worms o Benzimidazoles · Thiabendazole · Work different receptors
. But principle of action is the same as piperazine . Normally compromise the cytoskeleton through a selective interaction with beta-tubulin o Imidazothiazole Classification for Tissue Nematodes - Lymphatic o Stops lymph's from flowing and swelling in legs occurs - Subcutaneous - Conjunctiva o E.g. loa loa - Can induce disease in tissue and blood and lymphoid system s - Four major types that use humans as a host - Can stay in they stay in the host