We get a whole lot of bizarre questions in our inbox about parasites. Most of them, we will’t reply as a result of doing so would quantity to giving medical recommendation…however now and again we get a query fully out of left area. Like this one:
Can a nematomorph from the stomach of a preying mantis infect a canine or cat that assaults and chews the insect? My cat retains killing mantises on my deck; it’s mortifying as a result of I really like them. Numerous them appear to be contaminated with nematomorphs. May it get into my cats digestive system and do hurt?
In the case of medical doctors and invertebrates, I’m notoriously skeptical as a result of there’s an extended historical past of medical doctors misdiagnosing brown recuse bites. Rick Vetter-one of my private heroes-made an extended profession out of merely mentioning that analysis of brown recluse bites don’t correlate with the recognized vary of the critters…a collection of errors which probably masked the rise of group acquired antibiotic resistant flesh-eating micro organism.
It’s not usually that I hear a brand new medical declare, so this was completely one thing I needed to take a look at.
Gordian worms, or nematomorphs, are parasitoid nematode-like critters which have sophisticated lifecycles, often revolving round water.
They sometimes have two hosts. After they hatch, their larvae search out an preliminary insect host. Particularly, they search for insect larvae…often a fly of some kind. They want a primary host which can depart the water as an grownup, as a result of it must be eaten by an insect on land. As soon as it’s eaten, it develops into an grownup which takes up your complete physique cavity of the insect.
The adults aren’t parasitic, so they should discover water to deliver concerning the subsequent technology, and so they accomplish this by way of thoughts management.
That is in all probability their greatest recognized, and in addition most misunderstood function. As soon as the insect turns into an grownup, it begins to wander and doesn’t actually appear to acknowledge environmental risks anymore. As soon as the insect encounters a physique of water, it often makes an attempt to cross it by jummping in.
I really feel like their potential to govern hosts has all the time been a bit exaggerated. A standard false impression is that these parasites trigger the host to hunt out water, which doesn’t appear to be the case. They only tend to go away their habitats and simply stroll round, which implies they’ll often discover a pool of water someplace close by.
Both method, this can be a reputable type of thoughts management, and that’s what makes them compelling parasites. There may be, in any case, an extended historical past of mind-controlling parasites being antagonists in sci-fi literature.
When first wanting into stuff like this, my first cease is all the time Wikipedia, as a result of I can often rely on stuff like this to be mentioned…and positive sufficient:
So I dug up each article I may discover (most of them are cited under, though there’s some I can’t entry some experiences from the early 1900s which aren’t digitized, and many others), and it seems like there are literally fairly just a few case experiences of those worms being present in vertebrates. Roughly 40 of those are related to people.
So, I suppose case closed…proper?
Properly, it seems that this isn’t fairly correct. There may be apparently some literature which claims these items can infect family pets and folks, however these guys merely aren’t able to parasitizing family pets.
This can be a case of one thing known as pseudoparasitism.
Nematomorphs depend on just a few comparatively uncommon occasions to finish their lifecycle, so that they make up for this by having an insane reproductive fee. Should you want one host to get eaten, and one other host to stumble round lengthy sufficient to seek out some water whereas not getting eaten, you’re gonna must have a whole lot of infants so as to make that occur. As a result of their hosts are simply type of drunkenly stumbling round, a whole lot of them are going to get eaten and these worms want a backup plan to outlive.
This stuff aren’t tremendous nicely studied, however my impression is that the adults in all probability take care of being an sudden meal by being tremendous powerful. As soon as the insect is eaten, the adults are in a physique of liquid and let the host dissolve round them. From right here, there’s precisely two exit factors…which is why we see a whole lot of case experiences of those worms being present in vomit or poop.
Youngsters and family pets get their palms on a whole lot of issues, and eat a whole lot of issues they shouldn’t. So it is smart that in the event that they eat a random bug, they’re going to often eat one with a gordian worm inside. A few of these circumstances are related to individuals ingesting unfiltered nicely water, as nicely. I’m undecided if the worms would be capable of make a predator vomit-again this isn’t nicely studied-but it’s not unusual for different animals to make this occur. So it wouldn’t shock me if in addition they had some type of chemical protection simply in case.
I do know the unique query was about family pets, however I felt that one case out of China was value a dialogue as a result of it demonstrates fairly nicely not solely how these myths get began, but in addition why they will’t stay inside individuals or pets:
I don’t wish to get an excessive amount of into the graphic particulars, however a whole lot of these worms had been introduced in by individuals who had grabbed them after urinating and introduced them in. So the medical doctors didn’t really witness them passing the animal, and there’s an extended historical past of individuals falsely believing they’re contaminated with parasites bringing in random arthropods to physician workplaces.
The problem with these case experiences is that they don’t really line up with the biology of the worms very nicely. Grownup Gordian worms don’t really eat, and the hosts they develop in usually don’t stay longer than just a few months even when they’re not contaminated. Gordian worms spend just a few months creating inside hosts, and the adults solely stay just a few weeks outdoors of the hosts. Their complete lifecycle takes lower than a 12 months, and so they (presumably) overwinter as eggs.
So as a result of these worms stay lower than a 12 months, it’s probably not attainable for them to stay inside one other animal for 3-4 years. In circumstances the place different parasites do discover their method inside hosts, they’ve appreciable issue navigating the unfamiliar biology of those unintended hosts.
What occurs when parasites get into the improper hosts?
We are able to fairly simply examine this to the rat lung roundworm Angiostrongylus. Usually, the nematode larvae get into rats after they eat a snail. They navigate to the lungs, the place they trigger the rat to provide a whole lot of mucus, which they then swallow. The rat poops them out, and the entire thing is comparatively innocent.
Once they get right into a human, nevertheless, the biochemical cues they should discover the lungs aren’t there. In order that they wander by way of the physique, ultimately ending up within the mind, the place they trigger intensive harm which often ends in dying. So whereas these worms are innocent to the rats, they’re just about all the time deadly to people.
That is fairly frequent with nematodes, and though Gordian worms are a very completely different phylum, their biology is very related. If Gordian worms had been able to inflicting these sorts of infections, we’d count on to see an analogous illness related to these circumstances. We simply don’t see that, although.
So not solely are these case experiences not in step with the biology of the Gordian worm, they’re additionally not in step with what we’d count on to see with other forms of unintended parasitism from related animals.
There’s a whole lot of myths about animals that are considered parasites of individuals, and these are fairly exhausting to quash as soon as they get began. It’s not all that completely different than what we’ve seen with the brown recluse, and even the candiru*.
Numerous these myths get began due to the sorts of observations I described above, and these even have a reputation…it’s known as pseudoparasitism and it means precisely what it appears like: faux parasitism.
Pseudoparasitism occurs when a critter finds itself in a spot (nicely, orifice actually) they shouldn’t be and occurs to outlive the ordeal. It’s a testomony to how powerful a few of these critters actually are, however as a result of they’re not dwelling and feeding inside the opposite animal as a behavior, it’s not really parasitism.
Nonetheless fairly cool, although.
I wish to warning in opposition to circumstances like this being interpeted as malicious, as a result of they’re often not. Within the circumstances above the sufferers had been clearly mistaken, and the medical doctors had been in all probability a bit extra desperate to interpret these circumstances as actual parasitism than they need to have been. The human circumstances I described had been practically half a century previous (therefore the inappropriate language at some factors), and none appeared to seek the advice of with specialists on the biology of those animals. Therefore, they probably weren’t able to understand how inconsistent these circumstances are with the biology of the animals.
Finally, although, on the finish of the day, the thought of the Gordian worm as a parasite can actually simply be chalked as much as a collection of errors.
Ali-Khan, F. E. A., & Ali-Khan, Z. (1977). Paragordius varius (Leidy)(Nematomorpha) an infection in man: a case report from Quebec (Canada). The Journal of parasitology, 63(1), 174-176.
Anaya, C., Hanelt, B., & Bolek, M. G. (2021). Subject and laboratory observations on the life historical past of Gordius terrestris (Phylum Nematomorpha), a terrestrial nematomorph. The Journal of Parasitology, 107(1), 48-58.
Dexiang, W., & Wenyuan, Y. (1981). Parachordodes sp.(Nematomorpha) human infestation of the decrease urinary tract: the primary case report in China. Acta Academiae Medicinae Wuhan, 1(2), 40-45.
Hanelt, B., Bolek, M. G., & Schmidt-Rhaesa, A. (2012). Going solo: discovery of the primary parthenogenetic gordiid (Nematomorpha: Gordiida). PLoS One, 7(4), e34472.
Herter, C. D., & Nesse, R. E. (1989). Pseudoparasitism with Gordius robustus. American household doctor, 39(3), 139-142.
Hinkle, N. C. (2000). Delusory parasitosis. American Entomologist, 46(1), 17-25.
Hong, E. J., Sim, C., Chae, J. S., Kim, H. C., Park, J., Choi, Ok. S., … & Park, B. Ok. (2015). A horsehair worm, Gordius sp.(Nematomorpha: Gordiida), handed in a canine feces. The Korean journal of parasitology, 53(6), 719.
Lee, Ok. J., Bae, Y. T., Kim, D. H., Deung, Y. Ok., Ryang, Y. S., Im, Ok. I., & Yong, T. S. (2003). Gordius worm present in a 3 12 months previous lady’s vomitus. Yonsei medical journal, 44(3), 557-560.
斉藤康秀, 井上巖, 林文夫, & 板垣博. (1987). A hairworm, Gordius sp., vomited by a home cat. 日本獸醫學雜誌 (The Japanese Journal of Veterinary Science), 49(6), 1035-1037.
Son, H. Y., Chae, J. S., Kim, H. C., & Park, B. Ok. (2009). Morphological research of the horsehair worm, Chordodes koreensis (Nematomorpha: Gordiida), remoted in canine vomitus. Journal of Veterinary Clinics, 26(4), 348-352.
Thomas, F., Schmidt‐Rhaesa, A., Martin, G., Manu, C., Durand, P., & Renaud, F. (2002). Do hairworms (Nematomorpha) manipulate the water searching for behaviour of their terrestrial hosts?. Journal of Evolutionary Biology, 15(3), 356-361.
Vetter, R. S. (2008). Spiders of the genus Loxosceles (Araneae, Sicariidae): a evaluation of organic, medical and psychological points relating to envenomations. The Journal of Arachnology, 36(1), 150-163.
Yamada, M., Tegoshi, T., Abe, N., & Urabe, M. (2012). Two Human Instances Contaminated by the Horsehair Worm, Parachordodes sp.(Nematomorpha: Chordodidae), in Japan. The Korean journal of parasitology, 50(3), 263.
*Notice from Joe:
The Candiru is a small catfish which is rumored to wedge itself into human penises and feed on blood. There’s really no proof it does this, and the one “confirmed” case report is sketchy to the purpose of violating the legal guidelines of each physics and biology. Within the biology sphere, it’s largely considered certainly one of many myths began by colonialist explorers.
I used to be going to make use of that for example of how these parasite myths get began, however it seems that Candirus do sometimes assault individuals. There are case experiences of bigger species attacking youngsters, though that is considered extraordinarily uncommon.
Nevertheless, in 2013, there was really a new species described which was really found whereas feeding on a human. Nevertheless, it feeds extra like a leech and the penis isn’t really concerned as a result of it simply can’t…match inside there. They can feed on individuals, however by no means just like the rumors declare they do. There’s photographic proof in each these hyperlinks, and they’re a bit graphic…so content material/set off warning there.
This is a little more of an advanced one, and your complete story about this delusion could possibly be a submit in and of itself. Nevertheless, because it’s essentially the most well-known and pervasive human parasite delusion on the market, I assumed I’d give it a shout-out.