# What is Hymenolepiasis?

There are two types of tapeworms that causes this disease.

1. Hymenolepis nana
    
2. Hymenolepis dimunata
    

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<div data-node-type="callout-text">Hymenolepis nana is the smallest cestode known to infect man but in Sri Lanka the title goes to Bartiella struderi. H. nana is also the commonest cestode infection.</div>
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Hymenolepis is a zoonotic infection, infection happens as a result of humans and rodents ingesting cysticercoid infected arthropods. This worm does not leave the intestine and H. nana can cause both internal and external autoinfection but H. dimunata does not cause autoinfection.  

## Morphology

### Hymenolepis nana

1. Has a refractile rostellum with a single row of hooks.
    
2. Four suckers.
    
3. Proglottid are broader than the length.
    

### Hymenolepis dimunata

1. Has no hooks on the rostellum.
    
2. Four suckers.
    

Cestodes are 15-60mm in length.

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<div data-node-type="callout-text">H. dimunata looks like a penis under the microscope :p</div>
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<div data-node-type="callout-text">This is also the only cestode which completes it’s lifecycle in one host.</div>
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## Morphology of the Egg

The egg has two membranes, the inner membrane and the outer membrane. There are yolk granules and thread like polar filaments between the two membranes.

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<div data-node-type="callout-text">How to differentiate <strong><em>Hymenolepis dimunata</em></strong> and <strong><em>Hymenolepis nana</em></strong> by the egg? H. dimunata has a prominent clear space between the inner and outer membranes of the egg while H. nana has prominent polar filaments visible under the microscope, instead of the clear space.</div>
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The most important point is that both cysticercoid and the adult worm live in the intestine in Hymenolepis dimunata.