Helminths and Arthropods PDF

Dr.Sajini Souda  Learning Objective:  Give examples to indicate the range of conditions resulting from helminth infections, and the main types of organism responsible.  Describe the life cycle of medically important helminths in the region.  Summarize the role of arthropods as vectors of...

Dr.Sajini Souda  Learning Objective:  Give examples to indicate the range of conditions resulting from helminth infections, and the main types of organism responsible.  Describe the life cycle of medically important helminths in the region.  Summarize the role of arthropods as vectors of disease.  Summarize the pharmacological approaches to treatment of helminth infections.  Helminths The term “helminth ”is used for all groups of parasitic worms. Helminthic infections most common infectious agents of humans The highest prevalence occurs in tropical countries with  poor or inadequate food supplies  where insect, molluscs and other invertebrate vectors abound  sanitary conditions are poor. Helminths –general characters  No true coelomic or body cavity  Outer protective covering, the cuticle or integument  Mouth with teeth/cutting plates, suckers/hooks  Digestive system absent/rudimentary  Primitive nervous system  Excretory system better developed  Reproductive system most developed  Locomotion by muscular contraction and relaxation  Parthenogenic- produce fertile eggs or larvae without mating.  Unable to multiply in the body of the host  Require more than one intermediate host Transmission of helminths occurs in four distinct ways  Cestodes Taenia saginata Taenia solium Echinococcus granulosum- dog tapeworm Diphyllobothrium latum -fish tapeworm Hymenolepis nana –Dwarf tapeworm Hymenolepis dimunita  Taenia saginata/solium Most common tapeworm found worldwide. Definitive hosts- Humans Acquired from eating uncooked beef  The worm ≈ 10 meters in length  Each segment (proglottids) contain nervous, muscular, excretory , male and female genital systems,  The uterus having 15–30 lateral branches ( T. solium has 7–12). Taenia saginata adult worms. Symptoms: non-specific -intermittent pains or indigestion. The adult is approximately 4-10 mete Taenia solium –slightly smaller Tapeworm segments (proglottids) in stool Diagnosis: Stool examination for eggs or segments. Treatment: Praziquantel / Niclosamide Prevention: Sewage treatment; cook or freeze beef.  The scolex of T. saginata has four large suckers but lacks the rostellum and rostellar hooks. The scolex of T. solium contains four large suckers and a rostellum containing two rows of large and small hooks. There are usually 13 hooks of each size. Mature proglottid of T. saginata primary uterine branches >12. Mature proglottid of T. solium primary uterine branches