Ancylostoma duodenale
Intestinal Hookworm
This female Ancylostoma duodenale was found attached to the wall of the terminal ileum during screening colonoscopy. It was removed and sent to the parasitology laboratory for identification where it was cleared and mounted on a glass slide. It is approximately 1-cm long.
In humans, intestinal hookworm infection is predominantly caused by Ancylostoma duodenale, Necator americanus, and A. ceylanicum. Adult hookworms live in the small intestine (typically the distal jejunum) and use specially adapted mouthparts to attach to the intestinal mucosa and feast upon the host’s blood. Females release unembryonated eggs into the feces where they mature in the soil and then release larvae. These infectious larvae can pierce human skin and travel in the blood to the lungs where they can penetrate alveoli and make the ascent up the bronchial tree and into the pharynx. After being swallowed, they make their way to the small intestines where they attach. Chronic infection results in iron-deficiency anemia and malnutrition. Rarely, heavy infection can result in death, especially in infants.
The sizes and morphology of rhabditiform larvae, filariform larvae, and adults differ. For ease of comparison and reference, a table has been made for Ancylostoma duodenale.
Stage | Size | Morphology |
Rhabditiform (L1) larvae | 250-300 µm long | - Long buccal canal - Inconspicuous genital primordium - Can occasionally be seen in stool when there is a delay in processing (see COTW 757), and need to be distinguished from L1 Strongyloides stercoralis larvae. |
Filariform (L3) larvae | 500-700 µm long | - Ensheathed, pointed tail |
Adults | Females: 10-15 mm long Males: 8-12 mm long | - Sharp teeth - the male tail has a large fan-like copulatory bursa, while the female has a pointed tail. |
The buccal capsule shows the characteristic cutting teeth in this image of Ancylostoma duodenale, which differentiates it from Necator, which has cutting plates. The teeth of A. ceylanicum have a similar appearance to that of A. duodenale but have larger front teeth.
Images contributed by Heather Morris.
