Those who are upset at seeing barefoot people will sometimes say that we are just setting ourselves up for hookworm. The danger of that is highly (and I do mean highly) exaggerated, particularly in the United States and Europe.
Here is some information for you on Hookworm. Maybe it will help you next time you are challenged.
Much of this information is from “Hookworm Disease – Its Distribution Biology, Epidemiology, Pathology, Diagnosis, Treatment and Control” by Asa C. Chandler (New York: The Macmillan Company, 1929). While the work is pretty darn old, it presents many scientific findings that ought to have held up over time (with the exception of, I suspect, treatment for hookworm). It also provides a historical perspective on a time when hookworm infestation was endemic.
Hookworm is a parasitic nematode that attaches itself to the intestinal wall of its host, feeding from there, and weakening the resistance and vitality of the host. Before 1930, hookworm was so prevalent in the Southeastern United States that the so-called “laziness” of many blacks or white crackers was probably due to the negative effects (including severe anemia from iron deficiency) of hookworm infestations.
The hookworm nematode requires warm, moist conditions. It was practically unheard of in areas that receive less than 40 inches per year of rain. In the United States, only the Southeastern US had problems. It went north only as far as Virginia and southern Kentucky. It only occurred as far west as Arkansas, and an eastern strip of Texas. Any other place in the United States is either too cold, or too dry for the hookworm to survive. [Note: I am discussing human hookworm here, Necator americanus and Ancylostoma duodenale. Canine hookworm, Anclyostoma caninum is able to survive somewhat colder temperatures than human hookworm.]
Here is a map from the book showing its distribution back then on the North American continent:
The various shadings represent the degree of infestation, with the obviously lighter shading being lower infestation (and you can see it getting lighter the farther north you get).
Hookworms lay their eggs while attached to the intestines of their hosts. These eggs pass out of the body with defecation. It takes about 5 days for the eggs to develop into larvae that start looking for a new host. During this time, the larvae feed on material in the feces.
The larvae invade a new host by burrowing into the skin. They can enter either through breaks in the skin, or through pores. The book references a bunch of studies that clearly have shown that their main mode of entry is through the skin. (In fact, before 1898, it was thought that their only way of entry was through the mouth—while still possible, it was shown in that year that it penetrates the skin, and it was later shown that skin penetration is the main mode of infection.) If you are a regular barefooter, the skin on your soles is probably too thick for them to get through; it’s between the toes that you have to look out for.
The hookworms penetrate by twisting about and by using the surface tension of water to provide them with something to push against as they enter. Once in the body, they enter a vein, where they are taken through a ventrical of the heart and into the lung area, where they burrow through the arteries into the lungs. From there, they are coughed up to the mouth, swallowed (interestingly, people who regularly spit have lowers rates of infestation than those who do not), and then passed through the stomach to the intestines, where they attach to the intestine walls, allowing the cycle to begin again.
Hookworms can live about a year or two, though 5-6 months seems to be more typical. Among those infested, it appears that the hookworm population reaches an equilibrium where reinfestation occurs at about the same rate hookworms die off.
There are a number of spots where this cycle can be interrupted. One of them is by wearing shoes. The book had an interesting plot of number of hookworms harbored by age, taken in Alabama.
As children get older, they got more exposure, and harbored more hookworms. However, around age 15, the number starts dropping, and pretty much disappeared by around age 20. Dr. Chandler attributes this to “the custom of beginning the constant use of shoes at about fourteen years of age.” At that point, with no (or few) new reinfestations, eventually the older hookworms die out and the person is finally rid of the infestation.
However, there are other habits that are much more important for controlling hookworm. Sanitation is primary, since the eggs are passed in the feces. During the period of the book, people in the south often didn’t even use privies(!). They would end up standing where they had defecated before (this would not always be obvious, since dung beetles would have removed the feces, but not the hookworm larvae). Even a primitive outhouse prevents people from standing where the larvae might be.
Other facts about the larvae prevent them from becoming an issue today. As already mentioned, the larvae must be kept moist. If they dry out, they die. Outdoors, they can dry out during the daytime. They are able to move a bit, and use their stores of energy for moving up when it is moist in the morning, and down to where it is wetter during late day. However, if they are not “picked up” soon enough, they soon exhaust their stores of energy, and die. Also, if it gets too cold, they die (winter pretty much takes care of them).
Studies have also shown that the larvae do not move laterally much at all. That means that, to pick one up, you have to stand almost right on top of where an infested person defecated after the eggs have developed into larvae but before the larvae have died off due to dryness or exhausting their energy stores. The larvae can be spread slightly by water runoff, but that dilutes them so much that the odds of getting one within the necessary period is miniscule.
I already mentioned how they need moisture (water tension) to burrow into the skin. They also need some time to get started. That means that simply walking on a place with hookworm larvae is not sufficient to get one. You must stand there (or, step in some mud with larvae that stays on the foot). The primary mode of infection is to stand (or squat) on older infected feces. That gives them the purchase and time to start burrowing.
By the way, people getting infected with hookworms can often feel it happening. It was given the name “ground itch”, “dew itch”, “water sore”, and “mazamorra.”
It’s fairly easy to see why modern sanitary conditions have eliminated human hookworm (and why barefooters need not worry about it). Even if an infected person used a modern toilet and missed, such that feces containing eggs got on the floor, it takes at least 5 days for the eggs to develop into larvae. The toilet (and floor) would have been cleaned before there was any chance for the eggs to develop. I just don’t see how human hookworms can be considered any sort of a threat today in the United States.
For those of you in other parts of the world, pay attention that you don’t stand in places of regular defecation, or temporarily put something on your feet when you do. (Note: even flip-flops may not provide total protection if you get infected mud on top of your feet). Well-meaning attempts to donate shoes to such places miss the real problem—lack of sanitation. Directing that money to providing real sanitation would not only take care of hookworm, but a host of other endemic health problems.
An additional tidbit: there are a few quite northerly places that had hookworm infestations: mines. Even as far north as England mines would get infected (they were nice and damp, and never got too cold). And I guess the miners would just go into a side tunnel to relieve themselves. If you look at that map of North American, above, you can see that big dot in West Virginia where they are lots of coal mines. Again, the hookworm can survive in the even-temperatured mines where they cannot survive outside.
Let me also say a few words on canine hookworm (which the book just barely touched upon). First, canine hookworm does seem to be able to tolerate colder conditions than human hookworm, so it can be a concern farther north. However, they just are not very good at penetrating human skin (it appears that hookworm target specific proteins to know which way to go). What can happen is that the hookworms get lost burrowing in and can give something called “creeping eruption.” But even then they don’t make it into the bloodstream. Again, just walking through a mine field doesn’t give the larvae the opportunity to get started—you have to stand in the stuff (or step in it and not wipe it off). And, given today’s sanitary conditions, you are not going to pass it to anybody else.
Hookworm is treated these days with drugs called benzimidazoles. Since the Chandler book was written we’ve been able to get much more selective in finding drugs that can kill the hookworms with minimal toxicity to ourselves.. Back when the book was written, the favored treatment was carbon tetrachloride (yoicks!).
Finally, there has been some research that suggests that maybe a light infestation of hookworms may not be so bad for us (NOT that I am suggesting you ought to go out and get one!). It seems that it may prime the immune system, and also that the presence of hookworm calms overactive immune systems, providing help in allergies and auto-immune diseases.
Hookworm is really not something that we need to be concerned about.
How many times I have read on the internet in response to either mentioning someone going barefoot in a city, or a picture of someone barefoot in a city, “what?? barefoot in the city?? maybe in the country, but in the city?” , ” they must never have heard of hookworm – idiots” – yet in the past people got hookworm from the country, not the city. Urban and suburban paved areas are some of the safest places to go barefoot, yet perception is stronger than reality. You are probably more likely to get hookworm by walking on a tropical beach than in a city.
I wonder how miners got hookworm. They did not work barefoot, did they?
Yes, back then many miners worked barefoot. Quite a difference from today!
Let me edit in some more information, and correct myself. As I try to research this further, it seems that most did not work barefooted, except in places like India. So, how did the miners get the hookworm? I cannot find anything that specifies how.
I did see that infested mines had something like 72% to 90% of the miners infested. Instituting controls (like defecating into buckets that were then brought to the top) made a big difference.
Don’t forget that the larvae can dig through any skin, so it is likely that they got in from handling material that had been defecated on previously, and got in through the hands, or maybe on bare arms. There were also various controls used to keep down coal dust (like spraying water). I wonder if that water had gotten contaminated and then the spraying spread eggs and larva to where the mining was happening.
But that’s my best guess from what I’ve found so far.
If the miners did not work barefoot, can we assume that the larvae can be inhaled?
I haven’t seen anything that suggests that hookworm can be inhaled. The larvae are about 1/2 a millimeter long, which suggests to me that they are too large to be easily lifted into the air to be breathed.
However, looking into it further, I’ve found papers that refer to just how muddy the miners get, on their clothes and hands. If the larvae are in the mud, and the mud gets on clothing, they can both penetrate the clothing or enter through the hands when the clothing is touched.
I found one other reference that said that miners actually could get hookworm through their shoes if the shoes were not kept in good repair. According to this, at one California mine, 40% of the miners shoes were in sufficiently bad repair as to allow hookworm to penetrate through the shoes.
Amazing, eh?
[…] written about hookworm before, but I thought I’d take this opportunity to say a few more words about […]
Returning to the earth – barefoot – after moving to the country in northern US state has been great. Until I picked up hookworm…again. Had it when I was living in the city and gardening barefoot where pets might have been popping. Tested, diagnosed, and treated (with steroid foam) by a dermatologist. Now I have it again. This old farm had livestock for more than 100 years, but I guess they don’t live that long. Maybe the dogs? Bear scat? Deer scat? (Honestly, I think from research this could be roundworm, also transmission possible through feet.) Going in to my PCP this week. But after treatment, any ideas how to be barefoot and worm-free? Will try to report what the doc says.
Odd. Northern US states are generally hookworm free, since the hookworm cannot survive the winter (though climate change may be messing that up).
Was it human hookworm, or dog hookworm?
I’ve been going barefoot for over 20 years in Ohio and have never had a problem.
Dogs take ivermectin. It’s not particularly approved for humans, but I’d sure be tempted if I kept getting hookworm.