5 Parasite1 × Parasite2„Parasite1“ (an organism performing parasitism – a type of non mutual relationship between organisms): the term may include viruses, bacteria etc.„Parasite2“ (object of interest of medical parasitology): the term is mostly used for eucaryotic, sometimes multicelullar organisms other than fungi.Historically they were considered microscopical „animals“ (protozoans and worms), but today unicelullar parasites are no more considered animals and they belong to taxonomically very distinct groups
6 Parasites classification The most typical groups (not necessarilly taxonomic groups) of medically important parasites are:Unicellullar parasitesAmoebae (taxonomically close to animals and fungi)Flagellates and other unicellullar parasites (rather related with plants, especially apicomplexa/sporozoa)Multicellullar parasitesFlat worms (Platyhelminthes)Flukes (liver fluke and other flukes, schistosomas etc.)Tapeworms (swine tapeworm, beef tapeworm, fish tapeworm, dwarf tapeworm, tissue tapeworms – ecchinococci and others)Roundworms (pinworm, common roundworm, Trichuris, dog and cat roundworm and other roundworms)Arthropods (insects and acarids)
7 Historical term „worms“ The term „worms“, or its latin equivalent „helmints“ was historically used for organisms with prolonged shape of bodyFor practical reasons, we use this term sometimes even now, although we know already for a long time that they are not a taxonomic unitMajority of them are visible by a naked eye or a simple lens. Some of them are quite large (e. g. 10 m in common tapeworm). Their eggs are microscopic
8 Another parasites classification It is also common to classify parasites according to the most typical localisation:EndoparasitesIntestinal parasites (from Giardia to tapeworms)Blood parasites (intra- and extraerytrocytal)Urogenital parasites (e. g. Trichomonas)Tissue parasites (e. g. Toxoplasma)Other parasites (e. g. eye parasites)Ectoparasites (mostly arthropodes)This classification is important also for diagnostics. For example, we prefer indirect diagnostics in tissue parasite diagnostics, as we are usually unable to find a suitable specimen for direct diagnostics.
10 Story oneLittle Nicol all the time scraped her buttocks, and it was evident to parents and teachers that something is wrong. She was also inquiet and unconcentrated. So they placed a translucent scotch-tape on her anus and sent to the laboratory. And the result did not surprise anybody. Nicol started to use drugs and in a short time everything was in order again…
11 Causative agent wasEnterobius vermicularis or threadworm (UK) or pinworm (US). It is a tiny roundworm (♂: 2–5 mm, ♀: 8–13 mm) that is present in the intestine. The eggs are present in perianal area. It is present mostly in children collectives. In small children autoinfections often occur.Another related roundworm is common (or „giant“) roundworm – Ascaris lumbricoides. It is much longer (♀: 20–35 cm, ♂: 15–30 cm). It is a little similar to earthworm (Lumbricus terestris), but still slightly different (roundworms have no band – citellum). Roundworms may cause various problems, from allergic problems to mechanical obliteration of orifices of bile bladder and pancreas.
17 Intestinal parasitesIntestinal parasites are the most common ones. They may belong to any of endoparasital group. Some of them result in diarrheic diseases, some of them produce rather non-specific problems (dyspepsia, pruritus, tiredness…)Most common ones: Flagellates: (Giardia intestinalis = Lamblia), Amoebae: (Entamoeba histolytica), Nematoda: Pinworm, common roundworm and others. Trematoda: e. g. Fasciolopsis buski. Cestoda: common (swine and beef) tapeworm and other tapeworms
18 Non-pathogenous amoebae in the bowel Not allways presence of parasites, especially amoebae, is a reason for treatment. There are many species, that are considered to be rather non-pathogenic.The most important non-pathogenous amoebas are: Entamoea dispar (very similar to pathogenous E. histolytica!), Entamoeba coli, Entamoeba hartmanni, Endolimax nana, Iodamoeba buetschlii and others.
19 Story twoBianca, who took care of several cats, had enlarged lymphonodes for some time, and long time it was a question, what is the reason. The throat swabs showed nothing, and also results or other investigations were resultless.Bianca planned to have a child, and so she was afraid. And it was shown, that it is really so: the causative agent responsible for her lymphonode syndrome is really sometimes dangerous for pregnant women…
20 The causative agent was Toxoplasma gondii, a coccidium, that is transmitted by cats, although people say that people with dogs are in risk more than people with cats (they can wear the particles of cat faeces in their fur)In immunocompetent persons, majority of infections is asymptomatical, or only with mild symptomas (enlarged lymphonodes). Rarely, ocular form may occurIn pregnant women toxoplasmosis may lead to abortion or embryonic organ defectsEven asymptomatic cases may lead to carriership of cysts, that is also asymptomatic. Toxoplasma may only reactivate in case of immunity problems (HIV+), especially in decrease of CD4+ lymphocyte count
21 Rare, but important: toxoplasma retinitis may occur… Rare, but important: toxoplasma retinitis may occur…
22 Down: toxoplasma cyst in brain Toxoplasma life cycleDown: toxoplasma cyst in brainwebdb.dmsc.moph.go.th
25 Tissue parasites Some parasites may live inside the organism. Some unicelullar parasites, like toxoplasma, produce parasital cysts (formations containing living parasital cells)Some nematodes may be present in tissue, e. g. Toxocara canis or T. catiSome cestodes (e. g. swine tapeworm) may produce cysticercs in the tissueSymptomatology is variable. In toxoplasmosis, cysts are clicinally quite mute. Cysticercs of tapeworms may be dangerous e. g. by pressing to important organsDiagnostics is difficult, because it is usually nothig to take for direct diagnostics.
26 LeishmaniasisOne of worldwide important tissue parasitosis is leishmaniosis. It occurs in the whole tropical and subtropical band. It is caused by a unicelullar organism LeishmaniaVector is a tiny blood sucking insect (mothfly) of genera Phlebotomus or LutzomyiaThere exist some twenty important species, that may be classified into “Old world“ leishmaniae and „New world“ leishmaniae, and also to skin, skin-mucosal and visceralThey may cause diseases from skin mutilation to inner organ damage, often lethalThere are no cases of leishmaniosis in Central Europe (except imported ones)
29 Story threeJoddie had again gynecological problems. It was quite common in her, but this time bacteriological examination was of no help. So, C. A. T. swab was sent for examination, and so the result was found.Foto: Ondřej Zahradníček
30 Causative agent wasTrichomonas vaginalis, a flagellate, that is transmitted sexually, although exceptionally other ways of transmission are possible, tooDischarge of typical smell and colour is typicalIn men, the disease is usually asymptomaticAs treatment for anaerobic infections (metronidazol) is effective for trichomonosis, too, the number of trichomonad disease decreases in recent times.
32 So called „strawberry cervix“ webmedia.unmc.eduSo called „strawberry cervix“
33 Urogenital parasitesAmong sexually transmitted parasital diseases, trichomonosis is the only really important (if not discussing the pubic louse).Usually its diagnostic is done together with bacteriology examination, as the ethiology is rarely clear at the first momentIn the urinary tract, most important parasites are some flukes (schistosomas), i. e. Trematodes. Diagnostic is partially microbiological, partially histological.
34 Story fourMr. Hiker used to travel throughout the world. After coming back from the last trip he started to have some problems, he caugth fever, then it finished, but during two days it started again. The GP sent him to infection department. They took his blood and made a smear to two slides, using two various methods. And really the causative agent was…
35 Causative agent wasPlasmodium vivax, one of four species of malaric plasmodiaMalaria is worldwide one of the most serious diseases. It causes illness of many persons every day, including many coming from Europe.The worst course is in „tropical malaria“ or „malignant tertiana“, caused by P. falciparum. Fever mostly does not decrease.Milder are both „benign tertianas“, caused by P. vivax and P. ovale. Fever comes in 48 h interval here (day 1, 3, 5, 7… „malaria tertiana“). P. vivax is more common, P. ovale occurs in western Africa.The malaria quartana, caused by P. malariae, is rare. Fever comes in 72 interval here (day 1, 4, 7…)
37 Bloostream parasitesAmong bloodstream parasites, of course, malarial plasmodia are the most important, but not the only ones.A flagellate, Trypanosoma brucei lives in bloodsteam, causing sleeping disease. Trypanosoma cruzi lives there too, producing Chagas diseaseNematodes – filariae may live in bloodstream, too (in tropical countries). Nevertheless, filariae may also occur in lymphatic vessels, eye, skin etc.Symptomatology: in all of them fever appeares, other symptomas are related to the agent
41 SamplingFor intestinal parasites rectal swab is not sufficient, a bit of stool is needed (see more )For Trichomonas either a slide for Giemsa staining is sent (alone or in pair with another one for Gram staining), or a C. A. T. swabFor Acantamoeba used contact lenses are sent in their own fluid, eventually corneal scraping might be performedFor tissue parasites serum is sent usuallyIn other parasites we sample according to the situation (urine, content of a cyst)
42 Sampling for intestinal parasites To send stool for parasitological sampling (usually using Kato and Faust methods), we need sample of stool sized like a hazelnut. A vessel for sampling need not be sterile. Unlike virologic examination the sample does not need low transport temperatureCoconut-sized specimens (as sometimes students use to say) are not recommended
43 Sampling for blood parasites For blood parasites, it is recommended to send a thick smear and a thin smear. Thick smear is just a drop mixed by a corner of another slide, thin smear is spread to the slide by special movement. Thick smear is not fixated.Pictures taken from CD-ROM „Parasite-Tutor“ – Department of Laboratory Medicine, University of Washington, Seatle, WA
44 Some more sampling methods Search forUsed sampling proceduretoxoplasmosisserum (for antibodies)trichomonosisC. A. T. swab, or smearurinary schistosomosishistological examinationgiardiasisduodenal juice (or stool)acanthamoebiasisused contact lens
45 C. A. T. swab for urethral and vaginal sampling for Candida (yeast) and Trichomonas Here the swab is broken to fit into the test tubeFoto: Ondřej Zahradníček
47 Parasites: diagnostic methods in general Microscopy is important, either wet mount, or staining (trichrom, Giemsa stain, Ziehl Neelsen for intestinal coccidia)Culture is rarely used, in practice only in Trichomonas and Acantamoeba.Among other direct methods PCR is used recentlyIndirect detection is used in tissue parasitoses, mostly toxoplasmosis, larval toxocarosis etc.
48 Intestinal parasites diagnostics As a basis, we use methods based on modified wet mount:In Kato method counterstain with malachite green is used, to make parasites better visibleFaust method is a concentration one (see later)Graham method is used in pinworms only (see later)Wet mount „sensu stricto“ and stained preparations (e. g. trichrom) are used in increased suspicion for intestinal protozoa (either primarilly, or after seeing Faust and Kato)
49 In the second halft, Kato is already prepared Faust methodIn the second halft, Kato is already preparedPrinciple: stool is repeatedly mixed with ZnSO4 solution, centrifuged and supernatant taken for the next step. Finally, the solution is filled up to the top of the test-tube and covered by a coverslip. The parasites adhere to the coverslip from below. Then coverslip is removed onto the slide with allready prepared Kato method.
50 Methods for diagnostics of intestinal protozoa Helmint eggs are found directly in Faust and Kato methods. When something resembling cysts (of trophozoites) of protozoa is found, more methods are used. We use hereWet mount, just stool mixed with a drop of saline, eventually a drop of Lugol solution is added after first observation to see better some structuresTrichrom staining. Fixation using alcohol-sublimate and further 70% alkohol, proper trichrom, 96% alcohol and carbolxylene. Or haematoxylin stain.for intestinal coccidia eventually Ziehl Neelsen, or , in Czechia, Miláček staining (Mr. Miláček was a laboratory, assistant in parasitology in České Budějovice)
51 Graham method in pinworm/threadworm diagnostics The patient bends forward, stretches his/her buttocks, and now a special transparent scotch-tape is placed on his/her anus and mostly perianal rugae. Then the tape is removed again and placed to a slide.Transparency of the tape is crucial, otherwise it is not possible to microscopy. (Nevertheless, some „experts“ send a non-translucent tape, or cover all the tape by a label with patient name)It is easier and more effective than stool examination. It is still used rather in children – adults use to have to hairy anus, so the method would be too painful and difficult.
52 Practical microscopy in Faust, Kato and Graham methods In all three methods we use no immersion, objectives 10×, 20×, 40×.Faust and Kato methods are usually observed together, on the same slide (the coverslip from Faust method is moved to the free half of the slide with already prepared Kato preparation)Graham method result is microscopied just in the form how it comes to the laboratory, no preparation is needed.
53 Morphology of eggs of intestinal parasites You should know at least these shapes to the examinationPinwormEnterobiusTrichurisRoundwormAscarisTapewormTaeniaPictures taken from CD-ROM „Parasite-Tutor“ – Department of Laboratory Medicine, University of Washington, Seatle, WA. Tapeworm picture origin:
54 Evaluation of protozoan diagnostics Gomori trichrom or Heidenheim haematoxylin is used. Size of the protozoon, number of nuclei, in Entamoeba genus also central and peripherial chromatineUnlike Entamoeba coli, E. histolytica has maximally four nuclei. Usually you cannot see all nuclei together, they appear and disappear during focusing.Entamoeba histolytica/dispar cannot be differentiated microscopically, in reference laboratory PCR discrimination is performed
55 Diagnostics of blood parasites: thin smear and thick drop In diagnostics of blood parasites it is important to perform a smear using special methods of thin smear and thick drop.For both methods, fresh blood is used, of non-clotted blood, if the smear is not performed immediately. The thin smear is fixated, the thick drop is not. Both of them are Giemsa stained.Look at following pictures.
56 Pictures taken from CD-ROM „Parasite-Tutor“ – Department of Laboratory Medicine, University of Washington, Seatle, WAThin smear Thick drop
57 Microscopy of blood parasites – an example of a result We use immersion system, 100× objective. The preparation is usually Giemsa stained. On the picture below, we can see erythrocytes and young trophozoites of Plasmodium falciparum.a plateletRBCellsmalarial trophozoites (ring form)a WBC
58 Erythrocytal stages of parasite, observable in the smears web.indstate.edu(Reduced to human erythocytal stages only, i. e. not liver stages and not mosquito stages)Merozoites
59 Erythrocytar stages of plasmodia Pictures from CD-ROM „Parasite-Tutor“ – Department of Laboratory Medicine, University of Washington, Seatle, WAmerozoites„ring-form“gametocyteschizontolder trophozoiteErythrocytar stages of plasmodiamosquito stages
60 Trichomonas diagnostics Trichomonads are recently diagnosed mostly using culture-microscopical:A C. A. T. swab is performedThe medium is cultured overnightA drop of medium is microscopied as a wet mount.The preparations cannot be preservedTherefore in our practical we have the second possible way of diagnostics – Giemsa stained smear on a slide. When it is a part of „Microscopical appearance of vaginal microflora“ (MAVM), it is described as MAVM V.Other ways (e. g. fluorescence staining, see picture) are used rarelly
62 Microscopical preparations of Trichomonas in MAVM (Giemsa) We use immersion microscopy (objective 100×, immersion oil)In some preparations we can see yeasts, tooThe pictures on Internet are usually ideal cases, often specially stained of computer adapted.TrichomonasLeucocytes
64 Diagnostics of other parasital diseases In ectoparasites majority of diagnostics is non-microbiological (everything can be observed by a laik, eventually a dermatologist in case of Sacroptes scabiei)In tissue parasites serum for indirect diagnostics is sent usually (CFT, ELISA)In some cases, mostly tropical parasitioses, it is better to consult sampling technique with a laboratoryIn some filarioses the sampling is recomended to perform during night only, or during day only.
66 Diagnostics of Toxoplasma gondii using serological tests In toxoplaxmosis, we often combine two tests.Complement fixing test (CFT). It is performed like other complement fixing tests, see J08 practicalELISA, too, is like other ELISA reactions. One specific feature is that instead of IgM + IgG we mostly search for IgA + IgG antibodies. IgA antibodies are typical for recent infections, IgG for „status after“ an infection. Paradoxically, pregnant women with IgG + are in a better situation than IgG – (they are protected).
89 Filariae A – Wuchereria bancrofti B – Brugia malayi C – Loa loa Pictures taken from CD-ROM „Parasite-Tutor“ – Department of Laboratory Medicine, University of Washington, Seatle, WAFilariaeA – Wuchereria bancroftiB – Brugia malayiC – Loa loaD – Mansonella perstansE – Mansonella ozardi
92 Head louse with an egg www.museum.vic.gov.au/bugs/image.aspx?ID=96.
93 The End Picture on this page – toxoplasmosis in artistic view The EndPicture on this page – toxoplasmosis in artistic view
94 Check-up questions1. What diseases are caused by protozoa of genus Leishmania?2. What are bloodstream parasites other than malaric plasmodia?3. What are staining methods for diagnostics of Giardia and intestinal amoebae?4. What staining method can be used for diagnostics of Cyclospora cayetanensis and Cryptosporidium parvum?5. Which non-pathogenic intestinal amoeba cannot be distinguished microscopically from Entemoeba histolytica?6. What are diseases transmitted by Glossina fly, Anopheles mosquito, Aëdes mosquito, Ixodes ricinus tick, Phlebotomus gnat?7. What is the name of the artificial (iatrogenous) myiase used for treatment? (It is a method, where larva of Lucillia serricata fly are administered to the wound to eat diseased, but not healthy tissue.)8. What is the most common sampling method for intestinal parasites?9. What is the most common sampling method for Trichomonas vaginalis?10. What are the sizes of common parasital eggs or cysts?11. And one more secret question ;-)