The lancet liver fluke, Dicrocoelium dendriticum, has a three-host lifecycle. Eggs in feces hatch and infect a snail. There, the larvae reproduce asexually to produce cercariae that get expelled by the snail in mucous to form slime balls. Ants feed on the slime balls and become infected. In the ant one parasite individual invades the brain, while the others encyst in the abdomen to become metacercariae. The brain larva compels the ant to cling to vegetation when temperatures are lower (at night), but loses control when temperatures rise (during the day). Grazing animals that consume an infected ant while eating get infected. The metacercariae finish their development into adults and reside in the bile ducts (1).
D. dendriticum is found throughout Europe, Asia, North America, and Africa (1). It infects terrestrial snails, ants of the genus Formica, and herbivores (1). Humans can become infected if they consume an infected ant (2, 3). This parasite is best known for the “zombie ant” phenotype it causes, where the brainworm causes infected ants to cling to vegetation all night. Micro-computed tomography (micro-CT) scanning of infected ant heads showed that the brainworm targets the suboesophageal ganglion - a major site of neuromodulation in the ant nervous system (4). GlobalPC’s founder Dr. Chenhua Li described hormonal changes and the gene expression changes that occur in infected ant brains to further investigate the mechanisms by which the brainworm controls this “zombie” behaviour.
1) 10.1016/j.pt.2022.09.002
2) https://www.cdc.gov/dpdx/dicrocoeliasis/index.html
3) 10.4269/ajtmh.16-0549
4) 10.1038/s41598-018-26977-2
5) https://prism.ucalgary.ca/items/4ed30da6-ecc3-4ef0-957b-619f251b0668
Parasite Comics Team:
Dr. Chenhua Li (Lead, Ideas), Dr. Þórey Jónsdóttir (Illustrator, Ideas), Dr. Stephen Pollo (Writer, Researcher), Yuanzhe Wang (Digital Consultant).