A man in Vietnam who fell sick last year was likely infected with a never-before-seen species of parasitic worm. Stranger still, the patient had never traveled to any parts of the world where you typically find these parasites’ relatives and the unknown species has notable similarities to other worms found in reptiles.
The curious case was detailed in a study published earlier this year in the International Journal of Infectious Diseases.
The case first came to light in July 2020 when public health authorities in Vietnam detected a 23-year-old patient who was hospitalized with fatigue, anorexia, muscle aches, abscesses, and — most startlingly — worms hanging out of the skin in the lower limb.
The man was given antiparasitic treatments, after which the worms and larvae were removed from the lesions. In total, five adult worms measuring 30 to 60 centimeters (12 to 24 inches) were removed from the patient’s arms and legs. An initial inspection of the worms under a microscope suggested they belonged to the genus of worms called Dracunculus, which the Guinea worm (D. medinensis) belongs to. However, these worms were too short to be Guinea worms.
Samples were sent to the headquarters of the US Centers for Disease Control and Prevention (CDC) in Atlanta, US, who subjected them to genetic testing. This confirmed that the worm was not a Guinea worm (D. medinensis), but a previously unknown species of Dracunculus.
Curiously, the researchers note that it bore many similarities to other species of Dracunculus found in reptiles, as opposed to humans or other mammals, indicating they might have something to do with the zoonotic origin of the parasite.
As for how this unusual worm infected the man, it remains unclear. The study notes: “this is the first report of Dracunculus infecting humans in Vietnam.” Its infamous relative, the Guinea worm (D. medinensis), is almost eradicated from much of the world. Once found in many parts of Asia and Africa, the species is now endemic to just five African countries and, in 2018, a total of 198 countries were certified as GW-free by the World Health Organization.
However, other species of Dracunculus have been identified in some Vietnamese snakes. Paired with the man’s rural lifestyle, the researchers believe he most likely contracted the parasite through his diet. He lived in the northern highlands of Vietnam, where there is a tradition of eating raw vegetables and fresh fish from local rivers. It’s speculated he consumed drinking water containing infected tiny crustaceans or ate fish carrying larvae, although this can not be definitively proven.
So, should we be freaking out in this case? At least for now, no.
In an accompanying editorial, two tropical disease experts discuss whether “Dracunculiasis X” should be considered an emerging public health threat or simply an “exotic gem.” They explain that too little is known about this one-off case to form any concrete opinions, although they appear to suspect this is likely a freak anomaly rather than the next big public health threat.
“It might be... too early for too-optimistic conclusions yet, as we know too little about the reservoir epidemiology behind the single case described here,” the editorial concludes. “However, it does not appear to be too far-fetched to propose that we might be dealing with one of nature’s curiosities rather than the advent of a novel emerging helminth pathogenic to humans.”