6OFIGURE 13-39 Clonorchis sinensis egg in a fecal specimen (X1000, D’Antoni’s iodine stain). The eggs are thick shelled and between 27 and 35 µm long. There is a distinctive operculum (O) (positioned to give the appearance of shoulders) and often a knob at the aboperular end (not visible in this specimen).
10FIGURE 13-45 Schistosoma mansoni egg in a fecal specimen (X1000, D’Antoni’s iodine stain). Schistosoma mansoni eggs are large (114 to 175 µm long by 45 to 70 µm wide) and contain a larva called a miracidium. They are thin-shelled, lack an operculum, and have a distinctive lateral spine (arrow).
11FIGURE 13-46 Schistosoma mansoni egg in a fecal specimen (X1000) FIGURE 13-46 Schistosoma mansoni egg in a fecal specimen (X1000). The lateral spine may be oriented in such a way as to be difficult to see. In this specimen, the spine (arrow) is above the egg and the egg may be misidentified as S. haematobium.
16FLAT WORMS Phylum Platyhelminthes = Flat worms Class Cestoda = Tape wormsScolex contained in eggholdfast structure with hooks and suckersProglottids major body of tapewormcontains both ovaries and testes = hermaphroditicEggs can penetrate intestine of host and form hydatid cysts in tissues
20FIGURE 13-55 Taenia spp. egg in feces (X1000) FIGURE 13-55 Taenia spp. egg in feces (X1000). Taeniid eggs are distinctive looking enough to identify to genus, but not distinctive enough to speciate. Eggs are spherical and approximately 40 µm in diameter with a striated shell. The oncosphere contains six hooks.
27HookwormsAncylostoma duodenali and Necator americanus Old world and new world hookworms differ only in their geographic location.Human phase of this worm begins with a filaform larvae penetrating the skin, enters circulation, carried to the lungs, coughed up and swallowed, develops to adulthood in small intestine. Adult worms lay between 10,000 and 20,000 eggs per day. Daily blood loss 0.2ml/adult/day. Microcytic hypochromic anemia develops.
31FIGURE 13-63 Hookworm egg in feces (X1000, D’Antoni’s iodine stain) FIGURE 13-63 Hookworm egg in feces (X1000, D’Antoni’s iodine stain). Hookworm eggs are 55 to 75 µm long and 36 to 40 µm wide. They have a thin shell and contain a developing embryo (seen here at about the 16 cell stage) that is separated from the shell when seen in fecal samples.
32Biblical wormTrichinella spiralis etiological agent of trichinosis. Infectious larva is present in the striated muscle of carnivorous and omnivorous mammals. Swine most common organism to transmit to humans. Encysted larvae live for many years. Polar bears and walruses are accounting for new human infestations in our Alaskan artic regions.
34FIGURE 13-68 Trichinella spiralis larva in skeletal muscle (W. M FIGURE 13-68 Trichinella spiralis larva in skeletal muscle (W.M., X260). The spiral juvenile and its nurse cell are visible in this preparation.
35FIGURE 13-69 Trichinella spiralis larvae in skeletal muscle (sec FIGURE 13-69 Trichinella spiralis larvae in skeletal muscle (sec., X260). Each larva has entered a different skeletal muscle cell and converted it into a nurse cell that sustains it with nourishment.
36Pin worms or Seat wormsEnterobius vermicularis most common helminthic infestation in America, 500 million cases annually globally second globally to Ascaris infestations.Eggs are ingested mainly fecal-oral.Egg laden dust can be inhaled. Autoinfection occurs frequently. “Scotch Tape Test” from perianal folds of diagnostic value.
39FIGURE 13-62 Enterobius vermicularis egg (X1000, D’Antoni’s iodine stain). The eggs of Enterobius vermicularis are 50 to 60 µm long and 20 to 40 µm wide with one side flattened (arrow). They are usually embryonated in typical preparations.
40Ascaris LumbricoidesLarge worms 25cm – 45cm in length. Most common helminth with over a billion infested a year. Prevalent in areas where sanitation is poor and human waste is used as fertilizer.Ingested egg releases a larva that penetrates the duodenal wall and carried to the liver and the heart, enters the pulmonary system, enters the alveoli where they molt and mature. They are coughed up, swallowed and returned to the small intestine. Adults can be passed out into the feces.
43Pathogenesis of Ascaris suum (Larvae) Damage associated with larval migrationLiverwithin 24 hr PIhemorrhage, inflammation, necrosis“milk spots” - fibrosisresolves after treatment30
44Pathogenesis of Ascaris suum (Adults) Interfere with digestion and absorptionpoor feed conversion, stuntingObstruction or rupture of intestineMigrate up bile ductobstructive jaundice32
45FIGURE 13-59 Fertile Ascaris lumbricoides egg in feces (X1000, D’Antoni’s iodine stain). Fertile Ascaris lumbricoides eggs are 55 to 75 µm long and 35 to 50 µm wide and are embryontated. Their surface is covered by small bumps called mammillations.
48SNFIGURE 13-71 Wuchereria bancrofti microfilaria in a blood sample (X960). The microfilariae of Wuchereria bancrofti can be distinguished from others in the blood by the sheath (S) and the single column of nuclei (N) not extending to the tip of the tail.