Snapshot A 20-year-old college student returns home from a camping trip with her friends. They were camping by a freshwater lake, where they fished and canoed. Since then, she reports feeling tired and fatigued. On physical exam, she appears pale. Basic laboratory evaluation is sent, including a complete blood count. This reveals a megaloblastic anemia. Subsequent labs reveal vitamin B12 deficiency. She is started on praziquantel for suspected helminth infection for ingesting fish from the freshwater lake. (Diphyllobothrium latum infection) Introduction Helminths are macroscopic parasitic worms that are classified into three clinically relevant groups: cestodes (tapeworms) trematodes (flukes) nematodes (roundworms) General features of helminths macroscopic (though the parasite’s eggs are usually microscopic) multicellular have 3 main life-cycle stages eggs larvae adults Helminths Tapeworms (Cestodes) Helminths Transmission Disease Treatment Taenia solium (pork) Ingestion of larvae in undercooked pork Ingestion of eggs in food contaminated with human feces Intestinal tapeworm (ingestion of larvae) Neurocysticercosis (ingestion of eggs) Praziquantel Albendazole (for neurocysticercosis) Taenia saginata (beef) Ingestion of larvae in undercooked beef Intestinal tapeworm Praziquantel Diphyllobothrium latum (fish) Ingestion of larvae in raw freshwater fish Megaloblastic anemia due to vitamin B12 deficiency Praziquantel Echinococcus granulosus/multilocularis Ingestion of eggs in food contaminated with dog feces Hydatid cyst disease (liver cysts) Albendazole Flukes (Trematodes) Helminths Transmission Disease Treatment Schistosoma Penetration of skin by cercariae, usually in contaminated fresh water (snails are intermediate host) Hepatosplenomegaly Portal hypertension Squamous cell carcinoma of the bladder (chronic infection with S. haematobium) Praziquantel Clonorchis sinensis (Chinese liver fluke) Ingestion of undercooked fish Clonorchiasis (biliary tract inflammation) Cholangiosarcoma Praziquantel Paragoniums westermani (lung fluke) Ingestion of undercooked crab or crayfish Mimics pulmonary TB (hemoptysis) Praziquantel Roundworms (Nematodes) Transmitted by the Ingestion of Eggs ("EATT") Helminths Transmission Disease Treatment Enterobius vermicularis (pinworm) Fecal-oral Anal pruritis Albendazole Pyrantel pamoate Ascaris lumbricoides (giant roundworm) Fecal-oral Colonic obstruction Biliary obstruction Intestinal perforation Albendazole Trichuris trichiura (whipworm) Fecal-oral Diarrhea Rectal prolapse (with heavy infection Albendazole Toxocara canis Fecal-oral Visceral larva migrans Albendazole Transmitted by the Invasion of Larvae through Skin ("SANd") Helminths Transmission Disease Treatment Strongyloides stercoralis (threadworm) Penetration of the skin by larvae Gastrointestinal upset Albendazole Ivermectin Ancylostoma braziliense Necator americanus (hookworm) Penetration of the skin by larvae Microcytic anemia Albendazole Pyrantel pamoate Transmitted by the Ingestion of Larvae Helminths Transmission Disease Treatment Trichinella spiralis Ingestion of larvae in undercooked pork Myalgia Albendazole Transmitted by Arthropods Helminths Transmission Disease Treatment Wucheria bancrofti Arthropod vector (mosquito) Lymphatic filariasis Diethylcarbamazine Loa loa (African eye worm) Arthropod vector (Deer, horse, or mango fly) Skin swelling Worm in conjunctiva Diethylcarbamazine Onchocerca volvulus Arthropod vector (blackfly) River blindness Ivermectin Dracunculus medinensis (Guinea worm) Ingested copepod in contaminated freshwater Skin inflammation and ulceration Worm eruption from skin Niridazole