Hymenolepis spp 2025 PDF

Hymenolepis Spp/3rd stage Microbiology Department Dr.Ban Anas Medicine College University of Basrah Objectives Learning 1-Studying 2 species belong to genes Hymenolepis. 2–Studying morphology, biology, distribution life cycle , pathogenesis, diagnosis, treatment a...

Hymenolepis Spp/3rd stage Microbiology Department Dr.Ban Anas Medicine College University of Basrah Objectives Learning 1-Studying 2 species belong to genes Hymenolepis. 2–Studying morphology, biology, distribution life cycle , pathogenesis, diagnosis, treatment and control for these species. Cyclophyllidean Cestodes/ Hymenolepis spp Hymenolepis nana Common name :Dwarf tapeworm (It is the smallest adult of cestode infecting man, hence called as dwarf tapeworm). Common associated disease and condition names :Hymenolepiasis ,Dwarf Tapeworm Disease. Hymenolepis diminuta Common name: Rat tapeworm. Common associated disease and condition names: Hymenolepiasis, rat tapeworm disease. Hymenolepis nana Morphology Adult Worm The adult worm is small, 1–4 cm in length and consists of head, neck and strobila. Head/scolex: It is globular with four suckers and a rostellum and hook Neck: It is long Strobila: Consists of 200 segments (proglottids) which are much broader than long. Mature proglottids: Uterus has lobulated wall and there are only three testicular follicles. University of Basrah/Medicine College/Microbiology Department Page 1  Hymenolepis Spp/3rd stage Gravid Proglottids: their appearance is sac like uterus filled with eggs. Egg Eggs are the infective form as well as the diagnostic form of the parasite. Egg is round to slightly oval, 30–47 μm size.It has two membranes (outer egg shell and an inner embryophore) and an oncosphere with six hooklets. Space between the two membranes is filled with yolk granules Polar filaments: Both the poles of embryophore are thickened from which 4-8 polar filaments emerge. Larva The larval form is called cysticercoids.It is solid except the proximal part which is vesicular and contains the scolex. Life Cycle Two life cycles are noted. direct and indirect cycle. Direct Cycle Host: Man is the only host. There is no intermediate host. Infective form: Eggs Natural Habita:The adult worm lives in the ileum of human Mode of transmission: Man acquire the infection by: 1- Ingestion of food and water contaminated with eggs. 2-Autoinfection with their own eggs released in the small intestine. In the small intestine, eggs hatch out, penetrate the intestinal wall and develops into cysticercoid larvae. After, the intestinal villi rupture and cysticercoids larvae become free in the gut lumen and transform into the adult worms.Adult worm, when fully mature undergoes fertilization to produce eggs.Eggs are passed in the feces which are infective to man.Though the adult worm lives only about 4–10 weeks, the infection persists due to autoinfection. University of Basrah/Medicine College/Microbiology Department Page 2  Hymenolepis Spp/3rd stage Indirect Cycle Host: Man is the definitive host. intermediate host : Insects such as rat fleas like Pulex irritans and Xenopsylla cheopis. Mode of transmission: Men acquire the infection rarely, by accidental ingestion of insects containing the cysticercoid larva. In human intestine: The larva develops into adult worm in human small intestine which then produces eggs that are passed in the feces. In rat fleas: Eggs are ingested by the insects, embryo hatches out, penetrate the intestine and develop into the larval stage cysticercoids larva in the insect’s body cavity. This stage is infective to man. University of Basrah/Medicine College/Microbiology Department Page 3  Hymenolepis Spp/3rd stage Distribution It is cosmopolitan in distribution but is more common in tropical countries. Infection is most common in children. Pathogenesis and Clinical Features Asymptomatic:Light infections with H. nana typically remain asymptomatic. Hymenolepiasis, Dwarf Tapeworm Disease: Persons with heavy H. nana infections often develop gastrointestinal symptoms, such as abdominal pain, anorexia, diarrhea, dizziness and headache. Laboratory Diagnosis Laboratory diagnosis of H. nana is accomplished by examining stool samples for the characteristic eggs. {Note: Non bile stained (colorless in saline mount): It is the only cestode egg that is not stained by bile when passed through intestine} Treatment Praziquantel is considered to be the treatment of choice for infections with H. nana. Niclosamide is also known to be an effective alternative medication. Prevention and Control 1. Personal hygiene. 2. Proper sanitation. 3. Avoid consumption of contaminated food and water by flea or beetles. 4. Rodent control. University of Basrah/Medicine College/Microbiology Department Page 4  Hymenolepis Spp/3rd stage Hymenolepis diminuta Morphology H.diminutais similar to H.nana, except in some points : Scolices: A small rostellum bearing no hooks Proglottids: they are typically rectangle. Eggs: no polar filaments. Life Cycle H.diminuta life cycle resemble indirect life cycle of H. nana Definitive host :rat and man is accidental host Intermediate host : grain beetles or flea Natural habitat:the adult worm lives in small intestine of human. Mode of infection :ingestion of infected insect by cysticercoid larva University of Basrah/Medicine College/Microbiology Department Page 5  Hymenolepis Spp/3rd stage Epidemiology The distribution of H. diminuta is worldwide. Areas in which foodstuffs such as grain or cereal are not protected from rats and insects are at risk of transmitting the parasite. Clinical Symptoms Asymptomatic. Many patients infected with H. diminuta remain asymptomatic. Hymenolepiasis, Rat Tapeworm Disease. Persons infected with H. diminuta usually present with mild symptoms such as diarrhea, nausea, abdominal pains, and anorexia. Laboratory Diagnosis Laboratory diagnosis is based on the recovery of the characteristic eggs in stool specimens. {Note: that the proglottids are typically not found in stool because they usually disintegrate in the human gut} Treatment The treatment of choice against H. diminuta is praziquantel. Niclosamide is an effective alternative. Prevention and Control 1-Protection foods from both rat droppings and from intermediate host insects is critical to prevent consumption of contaminated food. 2- Thorough inspection of all potentially contaminated foodstuffs prior to human consumption is necessary to prevent transmission of the parasite to unsuspecting humans. University of Basrah/Medicine College/Microbiology Department Page 6