Methodical instruction for students of the I course
Medical Faculty
LESSON № 10
THEME: PHYLLUM NEMATHELMINTHES. CLASS NEMATODA. LABORATORY DIAGNOSTICS OF GEIMINTHIC INFECTIONS.
6 hours
Aim: to know morphological peculiarities, life cycles and pathogenic significance of Ascaris lumbricoides, Enterobius vermicularis, Trichuris trichiura; Trichinellaspiralis, Ancylostoma duodenale, Necator americanus, Wuchereria bancrofti and Brugia malayi, Onchocerca volvulus, Loa loa, Dracunculus medinensis; be able to determine their reference to species, to ground the methods of laboratory diagnostics and prophylactics of ascariasis, enterobiasis, trichuriasis, trichinosis,ancylostomiasis, wuchereriasis, brugiasis, onchocercosis, loaosis, dracunculiasis.
Professional orientation of students: Ascariasis has a world-wide distribution and is particularly common in regions with poor or no sanitation. Enterobiasis is the most common helminthiasis in the world. More than 500 million people are affected by whipworm infection (trichuriasis). Hookworm is found worldwide, especially in tropical areas. The global prevalence of hookworm infections probably is greater than the past estimate of nearly 500 million
There are 9 known filarial nematodes which use humans as their definitive host. These are divided into 3 groups according to the niche within the body that they occupy: ‘lymphatic filariasis’, ‘subcutaneous filariasis’, and ‘serous cavity filariasis’. Lymphatic filariasis is caused by the worms Wuchereria bancrofti, Brugia malayi, and Brugia timori. These worms occupy the lymphatic system, including the lymph nodes, and in chronic cases these worms lead to the disease elephantiasis. Subcutaneous filariasis is caused by loa loa (the African eye worm), Mansonella streptocerca, Onchocerca volvulus, and Dracunculus medinensis (the guinea worm). CDC estimated that at the end of 2007, there were about 10,000 reported guinea worm disease cases in five nations in Africa: Sudan, Ghana, Nigeria, Niger, and Mali. Guinea worm disease is expected to be the next disease after smallpox to be eradicated and presently there may be as few as 1000 cases worldwide.
Filariasis is “considered” endemic in tropical and sub-tropical regions of Asia, Africa, Central, South America and Pacific Island nations, with more than 120 million people infected and one billion people at risk for infection.
In communities where lymphatic filariasis is endemic, as many as 10 percent of women can be afflicted with swollen limbs, and 50 percent of men can suffer from mutilating genital symptoms.
Methodology of Practical Class: (900 – 1200).
Work 1. Ascaris lumbricoides – the causative agent of Ascariasis.
Examine the display of adult Ascaris lumbricoides. Pay attention on sexual dimorphism: a male (15-25 cm) is smaller than a female (45 cm); male has a hook-like back end of the body, female – straight and narrow.
Learn morphology of adult worms (a chart). Pay attention on internal structure: lips, peripharyngeal nervous ring, intestine, excretory channels, two ovaries, oviducts, two uteri, vagina.
Examine the slide of Ascaris lumbricoides eggs under a microscope (7 x 40). They are brown, oval or round form, covered by membranes. An external membrane is tuberous. Sketch.
Life cycle. Examine a life cycle of Ascaris lumbricoides (a chart). Sketch .
Work 2. Ancylostoma duodenale (hookworm) – the causative agent of ancylostomiasis
Examine the slide of Ancylostoma duodenale. Learn the structure of hookworm. The anterior end is bent dosally. Examine buccal capsule (mouth cavity)ofAncylostoma duodenale (a chart). Sketch buccal capsule. Mark 2 anterior pairs of teeth.
Egg. Learn the eggs of Ancylostoma duodenale (a chart). Their form and size are similar to Ascaris lumbricoides eggs, but the membrane is thin, smooth and transparent. An egg is on the stage of four blastomeres. Sketch.
Work 3. Strongyloides stercoralis (thread worm) – the causative agent of strongyloidiasis.
Examine the structure of male and female Strongyloides stercoralis (a chart). Study the life-cycle of Strongyloides stercoralis. Note stage of parasite development
Work 4. Trichuris trichiura (whip worm) – the causative agent of Trichuriasis
Learn a structure of adult worms (a chart). Sketch. The front end of the body is thread-like extend (a long esophagus is situated in it). The back end is evidencing. Male has a hook-like back end of the body, female – straight and narrow.
Examine the slide of Trichuris trichiura eggs under a microscope (7 x 40). The typical eggs are brown, barrel-shaped with a plug at each end. Sketch.
Work 5. Trichinella spiralis – the causative agent of trichinosis
Examine the slide of encapsulated Trichinella spiralis larvae in cross-striated muscles of the rat under a microscope (7×8; 7×40). Sketch. Mark: capsules, musclesfibers,Trichinella larvae.
Life cycle. Learn a life cycle of Trichinella spiralis (a chart). Sketch. Mark the stages of the development, location of Trichinella spiralis adults and larvae in human body.
Work 6. Enterobius vermicularis (pinworm) – the causative agent of Enterobiasis.
Learn morphology of adult Enterobius vermicularis (a chart). Pay attention on internal structure: mouth, vesicle (a cuticle in the front part of body), esophagus, bulbous (an esophagus dilatation), intestine, two ovaries, oviducts, uterus, vagina.
Examine the slide of Enterobius vermicularis eggs under microscope (7 x 40). They are transparent and colorless, asymmetrical The membrane is thin and smooth up to 40-60 micro;m. Sketch.
Work 7. Dracunculus medinensis – the causative agent of Dracunculiasis
Study the life-cycle of Dracunculus medinensis. Note stage of parasite development.
Work 8. Family Filariida
Several nematodes belonging to the superfamily Filarioidea are responsible for filariasis. Perhaps 10 times that number live in areas where these parasites are endemic and are therefore at risk of infection (northern Australia, South America, West and Central Africa, Asia, Pacific Islands). There are recognized species for which man is the normal definitive host.
Wuchereria bancrofti – the causative agent of wuchereriasis.
Brugia malayi – the causative agent of brugiasis.
Onchocerca volvulus – the causative agent of onchocercosis.
Loa loa – the causative agent of loaosis.
Work 9. Features of medically important nematodes.
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Primary location |
Species |
Commoame or disease |
Mode of transmission |
Endemic areas |
Diagnosis |
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Intestines |
Enterobiusvermicularis(pinworm) |
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Ascarislumbricoides |
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Trichuristrichiura(whipworm) |
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Ancylostomaduodenale(hookworm) |
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Strongyloidesstercoralis (thread worm) |
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Trichinellaspiralis |
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Tissue |
Dracunculusmedinensis |
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Wuchereriabancrofti |
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Onchocercavolvulus |
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Loa loa |
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Trichinellaspiralis larvae |
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Work 10. Laboratory diagnostics of helminthic infections.
Fill the table by laboratory diagnostics of helminthic disorders
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Laboratory diagnostics of helminthic disorders |
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№ |
Helminthosis |
Worm |
Material for examination |
What be find out |
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1 |
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2… |
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According to practical skills of modules of content 5 and 6 “Medical protosoology” and “Medical helminthology” be able to determine the slides of
– Lamblia intestinalis
– Trichomonas vaginalis
– Entamoeba histolytica
– Malaria parasites
– Toxoplasma gondii
– Fasciola hepatica
– Opishorchis felineus
– Gravid proglottid of Taenia solium
– Gravid proglottid of Taenia saginata
– Cysticerc of Taenia solium
– Cysticerc of Taenia saginata
– Hymenolepis nana (dwarf tapeworm)
– Hydatid cyst of Echinococcus granulosus
– Gravid proglottid of Dihyllobotrium latum
– Ascaris lumbricoides
– Enterobius vermicularis
– Trichuris trichiuria
– Ancylostomas duodenale
– Encysted larvae of Trichinella spiralis
Seminar discussion of theoretical issues: (1230 – 1400).
1.General characteristics of Nematodes.
2.Medical importance of Nematodes.
3.Ascaris lumbricoides: morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
4.Enterobius vermicularis (pinworm): morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
5.Trichuris trichiura (whipworm): morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
6.Trichinella spiralis: morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
7.Ancylostoma duodenale and Necator americanus (hookworms): morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
8.Laboratory diagnostic of ascariasis, enterobiasis, trichuriasis, trichinosis, ancylostomiasis.
9.Prevention of ascariasis, enterobiasis, trichuriasis,c trichinosis, ancylostomiasis.
10.General characteristics of Family Filariida.
11.Wuchereria bancrofti: morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
12.Brugia malayi: morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
13.Onchocerca volvulus: morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
14.Dracunculus medinensis: morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
Seminar discussion of theoretical issues.
1.General characteristics of Nematodes.
2.Ascaris lumbricoides: morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
3.Enterobius vermicularis (pinworm): morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
4.Trichuris trichiura (whipworm): morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
5.Trichinella spiralis: morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
6.Ancylostoma duodenale and Necator americanus (hookworms): morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
7.Laboratory diagnostic of ascariasis, enterobiasis, trichuriasis, trichinosis, ancylostomiasis.
8.Prevention of ascariasis, enterobiasis, trichuriasis,c trichinosis, ancylostomiasis.
9.General characteristics of Family Filariida.
10.Wuchereria bancrofti and Brugia malayi: morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
11.Onchocerca volvulus: morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
12.Dracunculus medinensis: morphological peculiarities, distribution, life cycle, transmission, pathogenic significance.
Individual Students Program: (1415 – 1500).
Test evaluation and situational tasks.
1.What is infective stage of Enterobius vermicularis?
A.miracidium
B.cercaria
C.redia
D.egg
E.cystisercus
2. What are the main organs through over the Ascaris lumbricoides migrate?
A.muscles
B.brain
C.liver
D.heart
E.lungs
3.What is the diagnostic stage of Trichuris trichiura?
A.miracidium
B.cercaria
C.redia
D.egg
E.cystisercus
4. Indicate the diseases, which can be treated by drugs:
A.Ascariasis
B.Enterobiasis
C.Trichuriasis
D.Cysticercosis
5. In what time Ascaris lumbricoides eggs become invasive?
A.24 days
B.4 – 6 hours
C.7 days
D.an hour
6. What species of Nematodes is biohelminth?
A.Trichinella spiralis
B.Ancylostomas duodenale
C.Strongyloides stercoralis
D.Necator americanus
E.Ascariasis lumbricoides
7. Indicate the helminth of class Nematoda which life cycle does not have migration of larvae?
A.Ascaris lumbricoides
B.Strongyloides stercoralis
C.Ancylostoma duodenale
D.Trichuris trichiura
8. Which stage of Ancylostoma duodenale is invasive for humans?
A.an egg
B.filariform larva
C.rhabditiform larva
D.adult worm
E.encapsulated larva
9. Enterobiasis often can cause repeated contamination by the eggs (autoreinvasion – repeated ingestion of the eggs). What physiological peculiarity of Enterobiusvermicularis does promote the patient reinfection?
10. Ascariasis was diagnosed in 8-years old child. Is this child epidemically dangerous for other members of the family? Why?
11. The larvae were found during the sputum microscopy of one patient with pneumonia, blood analysis had shown an eosinophilia. Indicate the most probable diagnosis?
12. In hookworm infection, what is the mode of transmission and how is the laboratory diagnosis made?
13. What is the pathogenesis of anemia caused by hookworms?
14. Why are humans end-stage hosts for Trichinella?
15. A patient was admitted to the hospital and complained of muscle pain, fever, periorbital edema. This patient ate an undercooked pork some time before illness. Blood analysis had shown an eosiniphilia. What is the most probable diagnosis? How you can confirm the diagnosis?
Student should know: morphological peculiarities, life cycles and pathogenic significance of Ascaris lumbricoides, Enterobius vermicularis, Trichuris trichiura;Trichinella spiralis, Ancylostoma duodenale, Necator americanus, Wuchereria bancrofti and Brugia malayi, Onchocerca volvulus, Loa loa, Dracunculus medinensis
Student should be able to: to determine their reference to species, to ground the methods of laboratory diagnostics and prophylactics of ascariasis, enterobiasis,trichuriasis, trichinosis, ancylostomiasis, wuchereriasis brugiasis, onchocercosis, loaosis, dracunculosis.
Correct answers of test evaluations and situational tasks:
1. D. 2. C, D, E. 3. D. 4. A, B, C. 5. A. 6. A. 7. D. 8. B.
9. Within 6 hours, eggs of E. vermicularis develop into larvae and become infectious. Reinfection can occur if they are carried to the mouth by fingers after scratching of the itching skin. 10. No. Because child spreads only unembryonated eggs, they become infectious in 24 days in warm, moist soil. 11. Ascariasis. 12. Mode of transmission of hookworm infection is penetration of skin by filariform larva; laboratory diagnosis: eggs in the stool. 13. Hookworms feed blood and cause blood loss. 14. Humans are end-stage hosts of Trichinella spiralis, because the infected flesh is not consumed by other animals. 15. Trichinosis, muscle biopsy revealslarvae within striated muscle; serologic test (become positive 3 weeks after infection).
References:
А – Basic:
1.Biology. – Sylvia S. Mader, Wm. C. Brown Publishers: Dubuque, Lowa – Melbourne, Australia – Oxford, England, IV edition. – 850 p.
2.Biology. Art notebook – Sylvia S.Mader, Wm. C. Brown Publishers: Dubuque, Lowa – Melbourne, Australia,1995. – Oxford, England, IV edition. – 205 p.
3.Romanenko O.V., Golovchenko O.V., Kravchuk M.G., Grinkevych V.M. Medical biology: The study guide of the practical classes course. Еdited by O.V.Romanenko. – K.: Medicine, 2008. – 304 р.
4.Lazarev K.V. Medical biology.- Simferopol: IAD CSMU, 2002 – 350 p.
5.Bihunyak T.V. Medical biology. – Ternopil: Ukrmedknyha, 2010 – 214 p.
6. Practical classes materials
В – Additional:
1. Karp S. G. Cell and molecular biology.-NY.Willey, 1996. – 773 p.
2. Biological Science. – William T. Keeton, James L Could, Fourth edition-1986.- 1175 p.
3. Hunter’s Tropical Medicine – G. Thomas Strickland, VI-th edition – 1057 p.
Methodical instruction has been worked out by Bihunyak Tatyana
Methodical instruction was discussed and adopted at the Department sitting
13.01.2014 Minute № 6
