Helminthes The helminthes or worms unlike the protozoa are macroscopic and multicellular,they have digestive,excretory, reproductive and nervous systems, through these may be lacking or highly modified in some species.like the protozoa the worms can be categorized according to their habitat in the host,there are intestinal round worms,liver,flukes, blood parasite as well as many free living species.helminthes have an outer protective covering "cuticle" the month may be provided with teeth or cutting plates many helminthes possess suckers or hook for attachment to host tissues they don't possess organ locomotion,but in some species the suckers assist in movement (locomotion is generally by muscular contraction and relaxation. Helminthes do not possess body cavity. have a primitive nervous system The excretory system is better developed The greatest development is seen the reproductive system may be 1-diecious (with two distinct male and female sexes) separate,the male being smaller than the female) 2-Hermaphroditic helminthes,both male and female reproductive system are present in the same worm and self- fertilization The eggs or larvae are produced in enormous numbers Survival and development are further complicated by the fact Many helminthes require more than one intermediate host for completion of their life cycle. Classification Based on their shape and other characteristics helminthes are classified into two broad groups 1- The cylindrical worm belonging to the phylum nematheliminthes(class nematode) name-thread. 2- Flat worms belonging to the phylum platy helminthes-platys flat.
Nematodes The flat worms in turn are classified into two categories the leaf-like( class treamatoda )and tape-like (class cestoda) or tape worms Are elongated cylindrical worms with an segmented body.they possess relatively well developed alimentary canal,complete with the anus,the head does not have either suckers or hooks, but may have a buccal capsule with teeth or cutting plates "the sexes are separate" Trematodes Have flat or leaf-like unsegmented bodies the alimentary canal is present,but in complete,without anus, they posses suckers but no hooks the sexes are separate in schistosomes,while the other flukes are hermaphroditic. Cestodes Have tape-like segmented bodies,they do not possess an alimentary system.the head carries suckers and some also have hooks, they are mosnoecious. Trematodes :fluke Trematodes are unsegmented helminthes which are flat and broad. resembling the leaf of a tree,they vary in size from the species just visible to the naked eye, like heterophyes to the large fleshy flukes like fasciala and fasciolopsis. Medically important members of the class treatment belong to the subclass diagenea, diagentic (require two hosts) - The definitive hosts in which they pass the sexual or adult stage are mammals (ex. amen) - Intermediate hosts in which they pass their asexual or larval stage are fresh mollusks,snails. Flukes are hermaphroditic (monoecious) except for schistosomes in which the sex are separate. - Presence of two muscular cup-shaped suckers the oral sucker surrounding the mouth at the anterior end and the ventral sucker in the middle ventrally
- They have no body cavity & circulatory or respiratory organs. - The alimentary system consists of month surrounded by the oral suckers,a muscular pharynx and the esophagus which bifurcates anterior to the ventral sucker to form two blind caeca..(which reunite schistosomes) the anus absent. - The reproductive system is well developed,the hermaphroditic flukes have both male and female structure so that self fertilization take place.in the shistosomes the sexes are separate but the male and female live in close apposition (in copula). - Immature stages of flukes: 1- The egg : operculated or spined it is agrem cell or miraciduim enclosed in a shell 2- The miracidium: a ciliated larva which may be free swimming or may hatch inside a shell. 3- Sporocyt :intromolluscan,non ciliated suc-like containing germ balls. 4- Redia :intra molluscan and develops from the gram balls of the sporocyst ; from it the cercaria emerges. 5- Metacercaria. encysted cercaria,with out a tail,but with resisent cyst wall.it is usually formed on plants fish or other animals. Trematodes infecting man can be classified as follows. a- Diecious blood flukes or schistosomes which live inside veins in various location 1- In the vesicle and pelvic venous plexuses,schistosoma haematobium. 2- In the inferior mesenteric vein--- s.mansoni 3- In the supeeior mesentricvein ----s.japanicum b- Hermaphroditic flukes which live in the lumen of various tracts- 1-biliary tract (liver flukes ---- fasciola hepatica, clonochis sinensis, opisthrochis sp.) 2- gastrointestinal tract (intestinal flukes) a- Small intestine fasicolopis, heterophyes heterophyes, metagonimmus yokogawai. b- Large intestine Gastrodiscoides homins 4- Respitary tract (lung fluke) Parayonimus westermani
** blood flukes: schistosomes: Human schimstosomiasis (bilharzias ) schistosomes are diecious treatment in which the sexes are separate the male is broader than female,and its lateral borders are rolled ventrally into cylindrical shape,producing a long groove called gynaecophoric canal, in which the female is held. all schistosomes live in venous plexuses in the body of the definitive host.the location varying with the species. Schistosomes Differ from the Hermaphroditic trematodes in many Respects They lack a muscular pharynx Their intestinal caeca reunite after bifurcation to from a single canal They produce non- operulate eggs They have no redial stage in larval development The cercariae have forked tails and infected by penetrating the unbroken skin of definitive hosts Schistosomiasis (bilharzias is) is a water borne disease constituting animportant public health problem Morphology The male is covered by finely tuberculated cuticle,it has two muscular suckers and prominent.the oral sucker being small and the ventral sucker large and prominent. beginning immediately behind the ventral sucker and extending to the caudal and is the gynoecophric canal in which the female worm is held. The adult female with the cuticular tubercles confined to the two Eds.
life cycle: It is basically similar in the all species. Eggs of haemotobium pass with urine which of mansoni pass with faeces.in water egg hatches giving miracidium which seeks about the intermediate host which is a snail Bulinus Biomphalaria for Haematobium for mansoni Inside the snail miracidium develops into sporocyts then to cercaria ( radial stage absent) cercaria seeks about body of man and is attracted to it by its warmth after losing its tail it finds its way into a capillary to reach the systemic circulation and finds its way into a capillary to reach the systemic circulation and finally the liver and portal circulation after
maturation in the liver and hepatic branches of the portal veins, haematobium select the venous plexuses of urinary tract, while mansoni migrates to branches of the inferior mesenteric veins related to the colon due to states within the venules,piercing action of spine and the lytic action of an enzyme secreted by the miracidium inside the ova the eggs breaks through the wall of vessels and escape into the lumen of the bladder (haematobium ) or the colon (mansoni ) together with blood.
Pathogenicity and clinical features 1- The invasion stage extending from the period of exposure to cercariae till formation of adult and beginning of egg laying generalized and localized reaction occurs due to metabolites of growing and mature worms 2- The stage of egg deposition and extrusion. the period between egg deposition and their appearances in the urine or faces.. trauma and hemorrhage as eggs pass from the venules are the main pathogenic feature 3- The stages of tissue proliferation and repair it is a late stages initiated after egg deposition in tissue and their extrusion is progressing.the present of eggs in tissue ---- tissue reaction producing formation of local tubercles or granulomatus lesion with deposition of histocytes,plasma cells and fibroblastic proliferation and development of scar tissue which may lead to strictures chronic ulcers and other pathological changes
Diagnosis: 1- Direct A. The most important diagnosis method to find living eggs : Urine for s.hamatobium,eggs with characteristic terminal spines can be demonstrated by microscopic examination Specimens collected between midday and 2 pm are most likely to contain eggs sedimentation 2- Indirect method Filtration Stool for mansoni,lateral spin Best egg. concentration technique formal - ether TIF (Thiomersal, iodine formal) glycerol sedimentation. B-rectal biopsy for all schistosomes asmall pieces of rectal mucosa is removed by biopsy forceps.it is placed on slide under a cover slip and examined with x10 power S.hamemotobium eggs are often trapped in the rectal mucosa. S.mansoni more often look As intradermal test(fairley's test) Compliment fixation test EliSA Although the better ones correlate well with the results of direct diagnostic methods. Treatment Metriphonate is the drug of choice in schistosomiasis to haematobum Prazignatel is effective against all schistosomes prevention and control Eradication of the intermediate hosts (copper sulphate 10 p.pm) Prevention of environmental pollution with urine and faces Effective treatment of infected persons.
Fasciola Fasciloa hepatica: the sheep liver fluke cause disease primarily in sheep and other domestic animals humans are infected by eating watercress ( aquatic plants) contaminated by larvae (metacecariae ) that excyst in the duodenum,penetrate the gut wall and reach the liver where the mature into adults.hermaphroditic adult in the bile ducts produce eggs which are excreted in the feces.the eggs hatch in fresh water and miracidia enter the snails.miracidia develop into cercariae, which then encyst on aguatic vegetation.sheep and humans eat the plants thus completing the life cycle.
Symptoms :are due primarily to the presence of the adult Worm in the biliary tract in early infection,right upper guardant pain, fever and heapatomegaly can occur,but most infections are asymptomatic Months or years later obstructive jaundice can occur. Pathogenesis: In invasion stage symptoms are caused by penetration of the intestinal wall,migration across the peritoneal cavity and entry into the liver. Small nectotic foci and micro-abscess have been describe. f.hepatica is large and so causes more mechanical damages so it causes parenchymal injury. Patients present initially with fever Eosinophilia and tender hepatomegaly. later they develop acute epigastric pain, obstructive jaundice and anemia. Halzoun (meaning suffocation) and is a painful pharyngitis caused by the presence of adult flukes on the posterior pharyngeal wall phyaryngeal wall. the adult flukes are acquired by eating raw sheep liver Diagnosis : is made by identification of eggs in the feces. eosinophilia is constanly present Treatment by praziguantel and bithonal are effective drugs oral bithionol - Intramuscular emetine has been used successfully adult flukes in the pharynx and larynx can be removed surgically prevention involves not eating wild aguntic vegetables or raw sheep liver. Halzoun : is particularly common in Lebanon and other parts of the middle east and north Africa Diagnosis: demonstration of eggs infaeces or aspirated bile is the best method of diagnosis. Diagnosis is made by identifying the large ovale,golden brown operculated eggs in the feces of an infected animal.the identification can be made by sedimentalue techniges.
The fluk eggs will often not be present in the feces during acut stages of disease. Others oriental liver flukes Opisthorchis spp: Clonorchis sinensis Opisthorchis felinens, opisthorchis viverrini Lung flukes Paragonimus westermani :