Study of parasites Hymenolepis nana, Taenia Echinococcus(), & Pneumocystis carinii Treatment Morphology Life cycle Pathogenesis Laboratory diagnosis Parasites Hymenolepis nana – Cestode (Dwarf Tapeworm) Taenia Echinococcus – Cestode (Dog Tapeworm) Pneumocystis carinii - Sporozoan parasite Hymenolepis nana Geographical Distribution Habitat Morphology of Hymenolepis nana Adult Worm Eggs Larva Life cycle of Hymenolepis nana Direct Cycle Indirect Cycle Hymenolepis nana - Life cycle Life cycle of Hymenolepis nana Pathogenesis of Hymenolepis nana Laboratory diagnosis of Hymenolepis nana Treatment of Hymenolepis nana Prevention (Prophylaxis) of H. nana Taenia Echinococcus Echinococcus Genus: Tapeworm with carnivorous and herbivorous hosts. Morphology of Taenia Echinococcus Life Cycle of Taenia Echinococcus

1. Hymenolepis nana, Taenia Echinococcus
&
Pneumocystis carinii
By SANDEEP KUMAR
Master of Science in Medical Laboratory Science
Delhi Skill and Entrepreneurship University, Dwarka Sec-9, New Delhi

2. Study of parasites
Hymenolepis nana,
Taenia Echinococcus, &
Pneumocystis carinii
Treatment
Morphology
Life cycle
Pathogenesis
Laboratory diagnosis

3. Parasites
Hymenolepis nana – Cestode (Dwarf Tapeworm)
Taenia Echinococcus – Cestode (Dog Tapeworm)
Pneumocystis carinii - Sporozoan parasite
The taxonomic status of P.carinii has been uncertain. While it was generally considered as a sporozoan
parasite, analysis of its chromosomal and mitochondria genes indicates its closer relationship to fungi
than to protozoa.

4. Hymenolepis nana

5. Hymenolepis nana (also known as the Dwarf Tapeworm)
• Geographical Distribution
• Hymenolepis nana is cosmopolitan, meaning it is found worldwide.
However, it is more common in warm climates.
• Habitat
• This tapeworm lives in the proximal ileum, which is part of the small
intestine, in both humans and rodents.

6. Morphology of Hymenolepis nana
• Adult Worm
o Hymenolepis nana is one of the smallest intestinal cestodes (tapeworms) that
infect humans.
o It measures between 5 to 45 mm in length and is less than 1 mm thick.
o The scolex, or head of the worm, has 4 suckers and a retractile rostellum with a
single row of hooklets.
o The worm consists of around 200 proglottids, or body segments.
• Eggs:
o The eggs of Hymenolepis nana are spherical or ovoid and measure between 30 to
40 μm.
o They have a thin colorless outer membrane and an inner embryophore that
encloses a hexacanth oncosphere, which is the larval stage of the tapeworm.

7. Morphology of H.nana Continued…….
• Larva
o The larval form is called cysticercoids.
o It is solid except the proximal part which is vesicular and contains the scolex.
Cysticeroid larva of Hymenolepis nana with the invaginated
scolex housed within an anterior vesicle.

8. Life cycle of Hymenolepis nana
Two life cycles - direct and indirect cycle.
Direct Cycle
Host: Man is the only host. There is no intermediate host. Rodents (rat
and mice) are the other hosts.
Infective form: Eggs
Mode of transmission:
1. Ingestion of food and water contaminated with eggs
2. Autoinfection with their own eggs released in the small intestine.
3. In the small intestine, eggs hatch out, penetrate the intestinal wall
and develops into cysticercoid larvae in 4–5 days.

9. Life cycle of H. nana Continued……..
4. Thereafter, the intestinal villi rupture and cysticercoids larvae
become free in the gut lumen and transform into the adult worms
in 10–12 weeks
5. Adult worm, when fully mature undergoes fertilization to produce
eggs
6. Eggs are passed in the feces which are infective to man
7. Though the adult worm lives only about 4–10 weeks, the infection
persists due to autoinfection.

10. Life cycle of H. nana Continued……..
Indirect Cycle
Host: Man is the definitive host. Insects act as intermediate host such
as rat fleas like Pulex irritans and Xenopsylla cheopis.
Mode of transmission: Men acquire the infection rarely, by accidental
ingestion of insects containing the cysticercoid larva.
• In human intestine: Th e larva develops into adult worm in human
small intestine which then produces eggs that are passed in the feces.
• In rat fleas: Eggs are ingested by the insects, embryo hatches out,
penetrate the intestine and develop into the larval stage cysticercoid
larva in the insect’s body cavity. Th is stage is infective to men.

11. Hymenolepis nana - Life cycle
Life cycle of Hymenolepis nana

12. Pathogenesis of Hymenolepis nana
1. Infection: Humans, especially children, get infected by ingesting eggs from infected
fecal matter.
2. Incubation and Development: Ingested eggs incubate in the duodenum, releasing
oncospheres that penetrate the mucosa and transform into cysticercoids.
3. Maturation: Cysticercoids return to the intestinal lumen, attach to the mucosa, and
develop into adults in the ileal portion of the small intestine.
4. Reproduction: Adult worms produce gravid proglottids. Eggs are passed in the stool.
5. Autoinfection: An alternate mode of infection where the eggs release their hexacanth
embryo, which penetrates the villus continuing the infective cycle internally.
6. Symptoms: Often asymptomatic, but heavy infections can cause nausea, anorexia,
abdominal pain, diarrhea, irritability, and anal pruritus (itching around the anus due to
an allergic response).
Note: The lifespan of adult worms is 4 to 6 weeks, but internal autoinfection allows the
infection to persist for years. Prompt treatment is recommended, especially in children.

13. Laboratory diagnosis of Hymenolepis nana
• Stool examination - detects non bile stained eggs with polar filaments
between the shell membranes. It observed wet mount method.
• Some patients have eosinophilia of 5% or more.
Saline mount—three pairs of
hooklets are seen clearly.
Iodine mount

14. Treatment of Hymenolepis nana
Praziquantel (single dose of 25
mg/kg) is the drug of choice, since
it acts both against the adult
worms and the cysticercoids in
the intestinal villi.
Nitazoxanide 500 mg BD
for 3 days may be used
as alternative.

15. Prevention (Prophylaxis) of H. nana
Prevention strategies include:-
• Maintaining good personal hygiene,
• Improving sanitation,
• Avoiding consumption of contaminated food and water, and
• Controlling rodent populations.

16. Taenia Echinococcus

17. Taenia Echinococcus
Echinococcus granulosus, the dog tapeworm or the hydatid worm, formerly
called Taenia echinococcus.
Echinococcus Genus: Tapeworm with carnivorous and herbivorous hosts.
Hosts: Dogs, sheep, and humans involved.
Human Disease: Causes unilocular echinococcosis or hydatid disease.
Historical Context: Hydatid cysts known since Hippocrates.
Scientific Discovery: Goeze linked cysts to tapeworms in 1782.
Global Prevalence: Widespread, especially in sheep/cattle-raising areas.
Regional Prevalence: Common in Europe, China, Middle East, India.
Climate and Disease Occurrence: The disease is seen more often in
temperate than in tropical regions.

18. Morphology of Taenia Echinococcus
• Size of the Worm: The adult worm is small, measuring only 3-6 mm in
length.
• Structure of the Worm: It consists of a scolex (head), a short neck,
and a trunk composed of 3 proglottides (segments).
• Features of the Scolex: The scolex has 4 suckers and a prominent
rostellum (beak-like structure) with two circular rows of hooklets.
• Characteristics of the Terminal Proglottid: The terminal proglottid
(segment) is longer and wider than the rest of the worm and contains
a branched uterus filled with eggs.

19. Morphology of Taenia Echinococcus
Echinococcus granulosus: Adult worm.
Adults of this species are small (this
specimen is 5 mm in length) and
usually consist of 3–4 segments
(proglottids).
Note the presence of a rostellum at the
tip of the scolex. The rostellum is
armed with two rows of hooks.
Continued ……….

20. Morphology of Taenia Echinococcus
Continued ……….

21. Life Cycle of Taenia Echinococcus
• Definitive Host: The dog is the principal definitive host where the adult worm
lives.
• Egg Release: The eggs are passed in dog feces and ingested by sheep and cattle
while grazing.
• Embryo Release: The eggs hatch in the duodenum, releasing hexacanth embryos
which penetrate the intestinal wall and enter the portal circulation.
• Embryo Filtration: The liver and lungs act as filters, trapping the embryos which
then develop into hydatid cysts in various organs and tissues.
• Cyst Growth: The cysts grow slowly, often taking 20 years or more to become big
enough to cause clinical illness.
• Cyst Reproduction: Inside mature hydatid cysts, further generations of cysts may
develop (daughter cysts and granddaughter cysts).
• Completion of Life Cycle: When sheep or cattle harbouring hydatid cysts die or
are slaughtered, dogs may feed on the carcass or offal. Inside the intestine of
dogs, the scolices develop into the adult worms that mature in about 6 to 7
weeks and produce eggs to repeat the life cycle.

22. Life Cycle of Taenia Echinococcus Continued……….

23. Pathogenesis of Taenia Echinococcus
Infection Source: Human infection follows ingestion of the eggs passed by
infected dogs.
Infection Timing: Infection is often acquired during childhood when intimate
contact with pet dogs is more likely.
Disease Cause: Disease results mainly from pressure effects caused by the
enlarging cysts.
Hypersensitivity: A second pathogenic mechanism in hydatid disease is
hypersensitivity to the echinococcal antigen. Hypersensitivity may cause
urticaria.
Anaphylaxis: If a hydatid cyst ruptures spontaneously or during surgical
interference, massive release of hydatid fluid may cause severe, even fatal
anaphylaxis.

24. Laboratory Diagnosis of Taenia Echinococcus
Radiological Exams for Diagnosis: Radiological examinations, such as ultrasonography and
CT scans, are commonly used to diagnose hydatid disease. These imaging techniques allow
visualization of cysts in organs like the liver or lungs.
Blood Eosinophilia: Blood eosinophilia (an increase in eosinophils, a type of white blood
cell) may be present in hydatid disease cases, but it is not a definitive diagnostic criterion.
Exploratory Puncture and Hydatid Fluid: Exploratory puncture of the cyst can yield hydatid
fluid. If scolices (small hook-like structures) are observed in the hydatid sand, it confirms
the diagnosis.
However, this procedure is risky and not recommended due to the risk of anaphylaxis
caused by the escape of hydatid fluid.
Casoni’s Intradermal Test: The Casoni’s intradermal test, although less common nowadays,
involves injecting hydatid fluid intradermally (under the skin). If a hypersensitivity reaction
occurs (a large wheal with pseudopodial projections), it suggests hydatid disease.
Note that false-positive reactions can occur in other conditions.

25. Laboratory Diagnosis of Taenia Echinococcus
Serological Tests:
Serological tests are more widely used. They include:
• Complement Fixation Test (CFT): Detects antibodies against hydatid
antigens. Not very sensitive but useful after surgical removal.
• Indirect Hemagglutination Assay (IHA): Another antibody-based test.
• Latex Agglutination: Uses hydatid fluid antigen for detection.
• Enzyme-Linked Immunosorbent Assay (ELISA): Helpful in demonstrating
circulating hydatid antigen.
Antibody levels increase with an active cyst and decline after surgical
removal.
Continued ……….

26. Treatment of Taenia Echinococcus
Surgical Removal
• Surgical removal is the preferred treatment if cysts are accessible.
However, recurrence after surgery is common.
Drug Treatment:
• Drug treatment options include mebendazole, albendazole, and
praziquantel.
• Unfortunately, drug therapy has limited effectiveness in treating
hydatid disease.

27. Prevention of Taenia Echinococcus
Avoid Animal Carcasses or Offal:
• Ensure that dogs do not eat animal carcasses or offal, as these can be
sources of infection.
Periodically Deworm Pet Dogs:
• Regular deworming of pet dogs helps prevent infection.
Practice Good Hygiene:
• Wash hands thoroughly after touching dogs.
• Discourage kissing of pet dogs to minimize the risk of transmission.

28. Pneumocystis carinii

29. Morphology of Pneumocystis carinii
• Habitat: P.carinii is a microorganism that lives in the lungs.
• Forms: It has two forms: trophozoite and cyst.
• Trophozoite: The trophozoite is 1 to 5 μm in size, amoeboid in shape,
and has a central nucleus.
• Encystation: Some trophozoites become encysted and produce eight
daughter trophozoites within the cyst.
• Cyst: The mature cyst is thick-walled and measures up to 10 μm in
diameter.

30. Life Cycle of Pneumocystis carinii
• Binary Fission: The trophozoite
divides by binary fission.
• Encystation: Some trophozoites
become encysted and produce
eight daughter trophozoites within
the cyst.
• Cyst Collapse: The cyst collapses,
releasing trophozoites which
initiate another cycle of
multiplication.

31. Life Cycle of Pneumocystis carinii

32. Pathogenesis of Pneumocystis carinii
• Commensalism: P.carinii is normally a commensal in the lung, spread
by respiratory droplets.
• Disease Occurrence: It causes disease only when the host’s resistance
is very low, as in premature and malnourished infants and in AIDS and
other immunodeficiencies.
• Immune Response: The multiplication of the parasite in the lungs
induces a hyaline or foamy alveolar exudate containing numerous
lymphocytes, macrophages and plasma cells.

33. Laboratory Diagnosis of Pneumocystis carinii:
• Sample Collection: Diagnosis may be made by demonstrating the
parasite in sputum, tracheobronchial lavage or transbronchial biopsy
specimens.
• Staining: The cysts can be stained by Giemsa or methanamine-silver
techniques.
• Immunofluorescence: Immunofluorescence has been used for
demonstrating cysts.
• ELISA: P.carinii antigen can be demonstrated by ELISA.

34. Laboratory Diagnosis of Pneumocystis carinii:
P. carinii cyst
(methanamine silver stain)

35. Treatment of Pneumocystis carinii
• Medication: Cotrimoxazole and pentamidine have been used in
treatment.
• Prognosis: However, the prognosis is poor in pneumocystis
pneumonia in the immunodeficient subjects.

36. Prevention of Pneumocystis carinii
• Immune Status: As P.carinii is an opportunistic infection, prevention
strategies primarily involve improving the immune status of at-risk
individuals.
• Preventive Measures: This can include proper nutrition, avoiding
exposure to known sources of infection, and in some cases,
prophylactic medication.

37. Thank You