In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Delayed anemia after treatment with injectable artesunate in the Democratic Republic of the Congo : a manageable issue .
### Output Text:
Delayed anemia after treatment with injectable <span class="chemical">artesunate</span> in the Democratic Republic of the Congo : a manageable issue . 