~I ~ ~ ~ -~ 'PA~fc lf~fc. ~ g.&~ e.s . . i 'i ~ . ,.., 'j VlifHJ_ I , cl. c xZJO D I ;.200 I_J <( z V') X 50 r X 50 XIOO H E. X200 V') 1- z <( _J a. u :::> kLL::L_v S. r;J_ 0 a: w i X :00 j Figure 11-3. Larval forms of Fasciola hepatica. A. !mmature egg. B. Miracidium in egg shell. C. Miracidium ready to enter snail. D. A very young sporocyst, immediately after completion of metamorphosis. E. Young sporocyst undergoing transverse fission. f. Adult sporc>cyst wit~1 rediae. G. Immature redia. H. Redia with developing cercariae and one daughter redia: 1. Cercaria. J. Body of cercaria. K. Encysted metacercaria. L. Excysted metacercaria. ap.::ap- pendages; b=excretory bladder; b.p.=birth pore; c=ceca; c.c.=cystogenous cells; c:l=dtia: col.=collar; e=esophagus; e.s.=eye spots; f.c.=flame cells; g.a.=germ_ifl'ill a~ea; ----- •• l...- . .n.~-~1~ • I ---- -
~·~ ~ ~ NERVOUS SYSTEM INTE.GUME:NT AND SUCKERS DIGESTIVE SYSTEM EXCRUORY SY)TEJ,: MALE REPRODUCTiVE SYSTEM !FEt-JALE REPRODUCTIVE SYSTEM e. c. (kivA I \rM ffM:: I . . !\ ,:4' : ; . 1 jCIP.RAL5AC AND GENITAL ATRIW I F LA \IE. CELL FEMALE RE.PRODUCTIVE. ORGANS u lc. v. !\ v.e. 1 e.c. ' Figure 11-2. Schematic representation of morphology of a typical trematode. b=bladder; c= ceca; c.g.=eephalic ganglia; cl.=eilia; cr.=cirrus; cr.s.=eirral sac; c.t.=collecting tube; d.n.=dorsal nerve' trunk; e=esophagus; e.c.=excretory capillary; e.p.=excretory pore; f.c.=flame cell; g.a.=genital atrium; g.o.=genital opening; l.c.=Laurer's canal; l.n.=lateral nerve trunk; m.g.=Mehlis' gland; n=nucleus; oot=ootype; o.s.=oral sucker; ov.=ovary; p=pharynx; p.g.=prostate gland; s=spines; s.r.=Seminal receptacle; s.v.=seminal vesicle; t=testis; u=uterus; v.d.==vas. deferens; v.e.==vas efferens; v.n.=ventral nerve trunk; v.s.=ventral sucker; vt.=vitellaria; vt.d.=vitelline duct. '\ 1 I j
r~ ~0.~ \~I~ ~._, v.~ ~. .;1~ies; ~- "~-\'.$ \T-v.~. ~r-v SCHISTOSOMA HltMATOBIUM SCHISTOSOMA MAtl~ONI SCHISTOSOMA JAPONICUM v..s. b xs •5 I xs I e\g e-lf- o s. I l·· I b. c. n-eg Iff\\ 1 '7/(S' !i i-< il I' 1 .J-uc ,f . I \\ "' \ I -e5 x5 v.s b. c. u oot-;J __ 0 d w ..J <t L t.J .... xs XS Figure 13-1. Schematic representation of important schistosomes of humans. b.c.~bifurca tion of ceca; c=ceca; e=esophagus; e.g.=esophageal glands; g.c.=gynecq~c canal; g.o.=genital orifice; o=eggs; o.d.==aviduct; oot==aotype; o.s.==aral sucker$~:)·~-~ u=uterus; u.c.=union of ceca; v=vulva; v.s.=ventral sucker;·" ""';h>ll· ..::.;:_· __ :~:.~XE2~
~- [~ ~ ~ ~ ~ Blood Flukes of Human Beings 247 People infected by contact with cercariae in water t 1-!.any cercariae released Miracidia infect ' from infectt;d snails sm:i::> Schistosomulae Q ...., _____ __ migrate in liver S. hematobium c: hematobium (f) ----- G-U system S. mansoni S. mansoni @ mainly in colon S. japonicum Fieure 13-2. Life cycle of three main species of human schistosomes (5. mansoni, 5. haema- (";\ ...,...___. .....------- ...,...___. -y----
~S:! 248 lD lD w 2 :::J Ci u ~ a 2 :::; <{::l <t:Z uo ere. w« u' vi Figure 13-3. Egg, miracidium, and cercaria of the schistosome' of humans. a.s.=anterior sucker; c=cecum; c.e.c.=caudal excretory canal; e.g., g.g. 1, c.g. 2 =cephalic glands; d.s.=duct spines; e.p.=excretory pore; e.t.=excretory tubule; e.v.=excretory vesicle; f.c.=flarne ce!l; g=gut; g.c.=germinal cells; g.d.=gland ducts; h.g.=head gland; i=island of Cort; l.d.=lateri!l duct; l.g.=lateral gl<!nd; l.t.=lobe of tail; m=mouth; n=nervous system; n.t.=nerve trunk;. r.g.=refractile globule; s.t.=stem of tail; v.s.=ventral sucker; vt.m.=vitelline membrane.
~ .-:l<i.t~vw~-;~:._~_-:-· !\ 1 Blood flukes of Humans : I Schistosomes : S. haematobium inhabits veins of the genitourinary system. S. mansoni and S. japonicum inhabit the veins of the large and small bowel. They differ from other trematodes in they are rounded and the sexes are different, eggs are not operculated and possess a terminal spine (haematobium), lateml spine (mansoni) and rudemintaory lateral spine Gaponicum). The integument is smooth or tuberculated depending on the species. The adult worms are 0.5-2.5 em long and reside in pairs in the terminal venules, they do not normally evoke an immune response as they are covered by host own antigenic molecules. The eggs are produced and may lodge in the walls of smaller venules producing an intense inflammatory reaction and rupture through the wall and gain access to the lumen of the bladder or intestine, and are passed out with the faeces or urine. Some eggs may 1 be swept centrally into the liver or the lungs. The cercariae have forked tails. The intermediate host is a fresh water snail. The I cercariae penetrate the skin on swimming or exposure to water, they reach the circulation, squeeze through the pulmonary capillaries into the systemic circulation, reach the liver where they develop into adolescent worms which migrate against the portal blood flow to settle in the vesical and intestinal veins, where they become adults and may Jive up to 30 years. Symptoms and pathology : An itch and a rash may develop on entry of the cercariae. A general syndrome of malaise and fever and urticaria may occur during the development to the adult. This may be severe and is called Katayama fever. Pathology produced by the eggs may lead to abdominal pain, diarrhoea, haematuria and dysuria. !\ Periportal fibrosis in the liver around eggs leading to portal hypertension and oesaphageal varices. Yet the function ofhepatocytes is well preserved. Obstruction of ureters, predispose to bladder carcinoma. Male and female pelvic organs may be affected. 1 Pulmonary involvement may lead to cor pulmonale. Either through vesical veins into systemic circulation or shunting of blood that occurs with portal hypertension, Brain and spinal cord may be involved. · Katayama fever is more associated with S. japonicum because the female produces 10 times the output of eggs of S. mansoni. It is also associated with cerebral affection probably because of the large number of eggs and the smaller size of the egg. Diagnosis: Demonstrating eggs in urine, faeces, prostatic fluid after massage, rectal biopsy. Liver biopsy is not justified as the possibility of finding an egg is slim. Wedge biopsy is more reliable in the diagnosis ofliver fibrosis. Treatment: Praziquental for all three species of Schistosoma. !" 1 I 3 ... /·-· ·
.:._-~ Schistosoma dermatitis : This is swimmers' itch, due to the entry of cercariae of birds and animals that cannot infect Man. The The cercariae are destroyed in the skin and go no further but produce a sensitization reaction at the site of entry and destruction. Thorough rubbing and drying of the skin after bathing may prevent the cercariae from entering the skin. 4 .. ·. -~
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