Unit 4. Chapter 5. ch 5.2. Eukaryotes. section 2. Helminths(1).pptx

Eukaryotes of Microbiology Section 3. Helminths Chapter 5.2 Helminths • Parasitic worms that cause disease in humans • Among world’s most common animal parasites • Includes roundworms and flatworms • Some are monoecious, having both male and female reproductive organs in a single individual, while...

Eukaryotes of Microbiology Section 3. Helminths Chapter 5.2 Helminths • Parasitic worms that cause disease in humans • Among world’s most common animal parasites • Includes roundworms and flatworms • Some are monoecious, having both male and female reproductive organs in a single individual, while others are dioecious, each having either male or female reproductive organs. Characteristics Phylum Classes Roundworm Nematoda shape Threadlike: cylindrical bodies, tapered toward ends Separate sexes Male and female organs on one worm Complete No digestive tract: digestive tract gut consists of sac with single opening gender Digestive system Flatworm Platyhelminthes Cestoda(tapewor ms), Trematoda(flukes) Flat bodies Phylum Nematoda (roundworms) © R.F. Ashley/Visuals Unlimited Roundworms. Phylum Nematoda • Ascaris lumbricoides ( giant roundworm) • Is the largest nematode intestinal parasite found in humans; males 20cm females 30cm long • Second most prevalent multicellular parasite in the US • Female Ascaris: prolific producer of eggs: 200,000 per day • Ascariasis: perforation in small intestine, pneumonia if infects lungs • Host: human • Location: gastrointestinal, respiratory tract • Transmission: food-borne, water-borne • Treatment: mebendazole Phylum Nematoda • Enterobius vermicularis (pinworm) • Female 10mm Male 5mm • Pinworm disease is most prevalent helminthic infection • Host: humans • Location: small intestine, large intestine( where symptoms include diarrhea and perianal itching) • Transmission: nail biting, poor hygiene, or inadequate hand-washing, fomites Figure • A micrograph of the nematode Enterobius vermicularis, also known as the pinworm. (credit: modification of work by Centers for Disease Control and Prevention) 5.19 Diagnosing Pinworm Disease. Phylum Nematoda • Necator americanus ( hookworm) • Necatoriasis: skin lesions, blood loss, anemia, ulcer-like symptoms • Host: humans • Location: gastrointestinal ,integumentary • Transmission: walking barefoot in human feces • Reach intestines, suck blood from ruptures capillaries • Single host life cycle • Treatment: mebendazole A Hookworm. © Dennis Kunkel Microscopy, Inc./Phototake/Alamy Images The Life Cycle of the Hookworms Phylum Nematoda • Trichinella spiralis • Trichinellosis: intestinal pain, vomiting, nausea, constipation • Host: pig • Location: intestines of pigs • Transmission: eating undercooked pork • Migrate from intestines to muscle, where they remain in cysts • Treatment: mebendazole to kill larvae Trichinella spiralis. Courtesy of CDC Phylum Nematoda • Wuchereria bancrofti( filarial worm) • Female roundworm is 100mm long • Elephantiasis: gross swelling of lymphatic tissues • Host: humans • Location: lymphatic system • Transmission: through flight of mosquito Elephantiasis. © John Greim/Photo Researchers, Inc. Phylum Platyhelminthes ( flatworms) Figure 5.20 • Phylum Platyhelminthes is divided into four classes. (a) Class Turbellaria includes the Bedford’s flatworm (Pseudobiceros bedfordi), which is about 8–10 cm long. (b) The parasitic class Monogenea includes Dactylogyrus spp. Worms in this genus are commonly called gill flukes. The specimen pictured here is about 0.2 mm long and has two anchors, indicated by arrows, that it uses to latch onto the gills of host fish. (c) The Trematoda class includes the common liver fluke Fasciola hepatica and the giant liver fluke Fascioloides magna (right). The F. magna specimen shown here is about 7 cm long. (d) Class Cestoda includes tapeworms such as Taenia saginata, which infects both cattle and humans and can reach lengths of 4–10 meters; the specimen shown here is about 4 meters long. (credit c: modification of work by “Flukeman”/Wikimedia Commons) Platyhelminthes: Class trematoda (flukes) • Bilateral symmetry • Nonsegmented • Oral sucker • Complex life cycle that may include encysted egg stages and temporary larval forms • In the human host, the parasite produces fertilizes eggs generally released in the feces. • When the eggs reach water, they hatch and develop into tiny larvae called miracidia. • Use mimicry to evade host’s immune system Clonorchis sinensis, Chinese liver fluke Light micrograph of a sheep liver fluke, Fasciola hepatica © Sinclair Stammers/Photo Researchers, Inc. Figure 5.21a Southeast Asian liver fluke Platyhelminthes: Class Trematoda • Schistosoma mansoni (blood fluke) • 10mm in length • Schistosomiasis/bilharziasis: chronic illness, damage to internal organs, ulceration, diarrhea, bloody urine • Major effects due to eggs • Host: human • Location in body: Gastrointestinal, liver, bladder • Transmission: Swimming, walking in infected water • Treatment: praziquantel Figure 5.22 • The life cycle of Schistosoma spp. includes several species of water snails, which serve as secondary hosts. The parasite is transmitted to humans through contact with contaminated water and takes up residence in the veins of the digestive system. Eggs escape the host in the urine or feces and infect a snail to complete the life cycle. (credit “illustration”: modification of work by Centers for Disease Control and Prevention; credit “step 3 photo”: modification of work by Fred A. Lewis, Yung-san Liang, Nithya Raghavan & Matty Knight) Platyhelminthes: Class Cestoda (tapeworms) • Segmented • Head region called scolex and body segments referred to as proglottids • Generally live in intestines of host organism. • Humans usually become infected by eating undercooked meat containing tapeworm cysts, which then develop into mature adult worms. Platyhelminthes: Class Cestoda • Taenia saginata ( beef tapeworm) 10 meters in length • Taenia solium (pork tapeworm) 2-8 meters in length • Few symptoms • Host: humans • Transmission: Eating poorly cooked meat Figure 18BC: (B) Photograph of a coiled beef tapeworm, Taenia saginata (C) T. saginata showing the suckers and hooks B. © Medical-on-Line/Alamy Images C. © Dennis Kunkel Microscopy, Inc./Phototake/Alamy Images Figure 5.21b (b) This micrograph shows the scolex of the cestode Taenia solium, also known as the pork tapeworm. The visible suckers and hooks allow the worm to attach itself to the inner wall of the intestine. (credit a: modification of work by Sripa B, Kaewkes S, Sithithaworn P, Mairiang E, Laha T, and Smout M; credit b: modification of work by Centers for Disease Control and Prevention) Figure 5.23 • Life cycle of a tapeworm. (credit “illustration”: modification of work by Centers for Disease Control and Prevention; credit “step 3 micrographs”: modification of work by American Society for Microbiology) A Summary of Human Helminthic Diseases Antihelminthic • Target nondividing organisms • Examples: • Praziquantel • Mebendazole • Avermectins • Ivermectin