PARASITOLOGY. The doctor will not go in details as we took them in the previous semester. the animal is an intermediate host

Transcription

1 PARASITOLOGY in this lecture we will talk abut parasites that affect the musclskeletal system,which will include mainly the skin, muscles and sme subcutaneus tissues and s n. The dctr will nt g in details as we tk them in the previus semester Trichinella spiralis The first parasite, a nematde, that we will talk abut is trichinella spiralis, it's called spiralis because it is spiral in shape as we will see later n, in fact it is a small nematde ( rund wrm ) usually measures abut 2 t 3 millimeters in length. when we tk the parasites last semester we talked abut primary and intermediate hsts, this wrm actually has tw stages f existence I.e ( it must have primary and intermediate hsts ), BUT What is unique abut this wrm is that the same animal serves bth as primary and intermediate hst, s this is really an exceptin because the nrmal parasites' hsts are different rganisms, fr example ( human r animal as a primary hst and vectr r anther animal as a secndary hst ). S the animals r even humans if they are infected with this wrm they will act as primary and secndary hsts, in ther wrds this wrm culd exist in the intestine f the animal as an adult wrm (nematde) and this stage is cnsidered as a primary hst but the intermediate stage which is the ( larvea r a cycted larvea ) actually happened t be in the tissues f that animal mainly the skeletal muscles. in the flesh f the animal r any tissue the animal is an intermediate hst larvea. wich culd be encycted in the late stages f the infectin in the intestines the animal acts as is a primary hst adult wrm (nematde)

2 this type f infectin ( in which the rganism is bth primary and secndary hsts ) is transmitted frm rganism t anther by : 1. cannibalism in the same species ( a bear eats his brther :P ) 2. eating flesh (meat) frm anther species ( when a human eats pig's r bear's meat ) frm the pints 1,2 we can cnclude that the transmissin f the infectin is by eating the flesh (tissues ) f the animals ((( eating the larvae ))) frm the secnd pint we can cnclude that trichinella spiralis is NOT very specific (it is ubiquities ) as it culd infect different animals r species ( rats, pigs, plar bears, seals ), and this is anther exceptin as ther parasites are cnfined t specific kind f animals r species THE LIFE CYCLE : The adult wrms are fund in the intestinal tract, and as they are nematdes they must have separate sexes, then there will be pairing between males and females t prduce fertilized eggs but again there is anther exceptin, in fact trichinella spiralis desn't frm eggs as ther nematdes d, they frm larvae immediately just like the micrfilaria (tremadtes) but it is nt classified as micrfilaria it is a nematde indeed. Then these larvae are depsited in the sub mucsa f the small intestine and the male usually disappears, (After fertilizing the females the males' jb is dne ), and they will be discarded with the faces, but the females stay in the sub mucsa f the intestine prducing larvae. These larvae will penetrate the wall f the small intestine and then get access t lymphatics and bld vessels, then they will disseminate t the whle bdy (heart, lungs, liver, etc). Althugh these larvae disseminate t the whle bdy they can't settle dwn, further develp, and prduce cysts except in the skeletal muscles (A kind f specializatin fr these wrms). The presence f the wrms in the intestine culd give GI symptms (diarrhea, vmiting,... ) but nce they actually g t the bld stream they can prduce cnstitutinal (generalized) symptms. PS: anything that reaches the bld as bacteria r viruses r even parasites cause what is called cnstitutinal symptms which can be manifested by malaise (feeling unwell), headache and smetimes fever. In general parasites specially wrms r helminthes dn't cause fever, the prtza d. s this is again anther exceptin as the trichinella spiralis is a wrm and des prduce fever ( larvae in the bld d that ). As these wrms reach different parts f the bdy they culd cause a wide variety f symptms fr example : encephalitis and meningitis in the brain pneumnia in the lungs

3 These symptms are usually mild because the number f the larvae isn't that high and they disappears n their wn, but if the lad (number) f the larvae was high these symptms culd becme sever and cause death. S what happens nw is that all the larvae that were settled in the rgans will dye except the nes that reach the skeletal muscles, in the muscles they will cause inflammatry reactin which will bring the macrphages, ther inflammatry cells and fibrblasts. Then after the end f the inflammatry reactin arund the larvae the fibrsis will take place then these lesins eventually after few mnths will becme calcified. s the fibrsed lesin in the skeletal muscle cntains the spiral encysted larvae, s this lesin will cause pain, tenderness, and swelling.then after few mnths it will calcify and the pain will disappear because the inflammatin had stpped and the calcificatin tk place ( culd be seen n X-ray in severe cases). s the main symptms appear at the beginning ( pain, tenderness, swelling in the muscles all ver the bdy ) and then the larvae will stay quiescent but alive fr several years. s as the dctr said : " if u ganna eat yur brther at least ck him t kill the larvae and prevent spreading f the infectin "O.. S if a human eats a plar bear's r seal's meat infected with larvae he/she will catch the infectin BUT!! u can kill the larvae befre eating the meat by cking it r als freeze it at -21 degrees centigrade DIAGNOSIS : There is n pint f examining feces cause yu will see nthing in them even the male wrm wn't be seen 1. Taking histry frm the patient culd give yu a clue especially in endemic regins, actually in ur cuntry the cases are rare and that apply n mst Muslim and jewish cuntries because mainly the infectin cmes frm pigs, s in USA and Eurpe u culd see sme cases. 2. Serlgy : because these wrms induce the frmatin f IgE Anti-bdies and smetimes IgG yu can measure the titer f these IgE anti-bdies against the wrm by serlgical tests, usually the cncentratin f IgE Abs remains high fr abut ne year s in the early stages f the disease yu can use management f specific IgE against the wrm fr diagnsing r even IgG titer. 3. Esinphilia : in fact this namatde is peculiar in that it prduces a high level f esiphilia frm 40% up t 50% ( in the initial stage f infectin ), s after ne year r after calcificatin yu wn't see high levels f esinphils 4. Muscle enzymes ( in initial stages ) : the injury f the muscles cause the elevatin f certain muscular enzymes that culd be measured fr the diagnsis such as : CPK (creatine phsphkinase ) and LDH ( lactic dehydrgenase ), these enzymes are specific

4 fr skeletal muscles nt cardiac nes. 5. Muscle bipsy: as they say seeing is believing. This is the best way f diagnsis, yu search fr swellings r lesins in the muscle then a bipsy is taken and the tests are made under the micrscpe t see the spiral larvae, if there is an inflammatry reactin arund it that means it's in the early stages if its calcified the infectin is ld then. LEISHMANIA The lesin is caused by a prtza called leishmania. This kind f prtza belngs t a family called (flagellates / r tissue flagellates / r hem flagellates). But why they are called hem r tissue flagellates???because they are tissue parasites and they are flagellated as will. The family itself is called Trypansmatidae with 2 grups (genera): Leishmania Trypansma : we will talk abut it later. This figure represents the leishmaina in its primary hst (the left part) and intermediate hst (the right part). s leishmaina is a tissue dimrphic parasite as it has tw different structures in the primary and intermediate hsts. The primary hst culd be a human, a dg r even a jerba s really this is a znsis as these animals wrk as reservirs fr this parasite. The intermediate hst is actually a vectr, the sand fly. The mrphlgical structure in the primary hst is called amastigte r dnvan bdies which is an intracellular structure measuring abut 3 micrns in diameter s the left picture in the figure is actually a macrphage with multiple amastigtes in it ( 5 particles ), this amastigte cntains nucleus and a kinetplast (small mitchndrial DNA ). The structure f the leishmania in the intermediate hst (prmastigte) is much bigger abut 20 micrns with an anterir flagellum, nucleus and kinetplast at the base f the flagellum.

5 Cnsidering the sand fly (the intermediate hst ), as u can see in the secnd figure it has: Hairy wings. When it is nt flying its wings prject upward unlike the ther kinds f flies which have hrizntal (dwnward) wings when they land. LIFE CYCLE : When the sand fly bites smene it's ging t pick up the lesins (amastigtes), then inside the bdy f the fly it will develp and frm ( prmastigte ). After that the fly ges and bites smene else and injects the prmastigtes int the skin. then these prmastigtes lse their flagellum and are taken by the macrphage by phagcytsis and becme incrprated with the phaglyssme, but they are very resistant t the acidity f the lyssmes and thats why they culd live fr a lng time in the macrphage as an amastigtes. the nly way t get rid f these amastigtes is by chrnic infectin by T helper-lymphcytes and mre macrphages t site f infectin, and that ges n and n fr a lng time. When the human is sticked by a sand fly the site f injectin will develp a lesin (usually a swelling) which becmes hard as it is made f inflammatry cells. s yu will get a hard ndule which will ulcerate then becme indurate chrnic ulcer and after abut ne year it will heals leaving a nasty scar and yu will get slid immunity. (Bagdad, Halab, Alepp, Pmmpe ) bils are the endemic areas. In Jrdan there are sme few cases in AL-gur and Ma'an. LEISHMAINA SPECIES They are identical in there mrphlgies s they can't be differentiated depending n their shapes, fr differentiatin we can use mlecular methds r by mnitring the pattern f diseases that they frm. In fact, the illness that we have talked abut is called cutaneus leishmanisis, and usually the leishmaina that causes it culd fund in the new wrld ( America ) r the ld

6 wrld (Asia, Africa) as, leishmania trpica, leishmania majr and leishmania aethipica,in the new wrld usually the leishmania mexicana cause the cutanus leishmaneusis The secnd type f leishmanisis is the diffuse cutaneus leshmanisis (mstly assciated with L.aethipica ), its named diffuse because there is a spreading f the lesins n the skin unlike the previus type. Actually the immune respnse is respnsible fr this disseminatin as it is humral immunity (ABs mediated immunity) which can't enter the cells (infected macrphages) and eradicate the parasite there, unlike the previus type which develps cell mediated immunity. leishmania aethipica culd cause tw types f leishmanisis The third type is the muc cutaneus leishmanisis, it usually present in America and caused by leishmania braziliensis. The stry ges as a fly bites a persn then he will get a lesin which will heal in ne r three mnths but after many mnths r even a year r tw he will get an activatin f lesins at muc-cutaneus areas (the muth, nse,... ). This type is cnsidered mre serius as it develps chrnic lesins which are vulnerable fr bacterial superinfectin and then bleeding and destructin f mucus areas, r by aspiratin it culd reach the lungs and cause pneumnia and death, s this type desn't develp slid immunity like the cutaneus type and thats why there is reccurrence f lesins. Type 1-3 are related t the skin, Type 4 is related t viscera The last type is visceral leishmanisis (r kala azar...means "black disease" because f the hyperpegmintatin f the skin that is ne f its symptms). species that lives in cld envirnments like skin C (L.trpica, L.aethipica) cause cutaneus leishmanisis. But ther species like L.denvani, L.chagasi, L.infantum can live in cld tempreture and are mre resistant t cidal actins f the serum, s they can live inside the macrphages in viscera ( liver, spleen, bne marrw) and cause visceral leishmanisis. s the disease is generalized ( cnstitutinal ). it ges like this, a fly bites then there is a small skin lesin ( maybe nt nticed ) after several mnths the patient will becme extremely sick having pyrexia(fever), cachexia, lss f weight, enlargement f spleen and liver, and hyperpigmentatin (black clr) f the skin then death in 1 r 2 years if nt treated. DIAGNOSIS 1. Bipsy frm skin ( types 1-3 ) r bne marrw ( type 4 )but nt frm spleen as it may cause bleeding 2. serlgy specially in kala azar

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