Can Hookworm Cause Anaemia in Therapeutic Numbers?

I have asked each of the PhDs who work for Autoimmune Therapies to write articles and reviews of scientific papers on the subject of helminthic therapy, the Hygiene Hypothesis and Old Friends Hypothesis, etc.

I have done this because so much of what is discussed online regarding helminthic therapy is uninformed or based on folk-knowledge, much of it being flat wrong.

Of course a great deal of the research and what is known is very difficult to find, and even harder to understand.

I and those of us who work at Autoimmune Therapies have been studying the subject for years.

I have been reading about the life-cycle of hookworms and whipworms, the Hygiene Hypothesis, and Old Friends Hypothesis, as well as the impact of infection with either hookworm or whipworm on the human immune system, since June, 2004. That was when I first encountered the concept of the Hygiene Hypothesis and the work of Dr. David Pritchard, and others, thanks to my aunt.

One of the most misunderstood aspects of hookworm is their potential to cause anaemia. I have read on someone’s blog for instance that a single hookworm can take up to six pints of blood per day. The person writing the post apparently is not aware that we each have roughly only 8 pints of blood. Or that an adult hookworm is only about one centimetre long and a half a millimetre wide. It is hard to imagine how so much blood could be consumed by such a small organism.

But how much blood does a single hookworm consume in a day?

That depends on which species of hookworm we are talking about. Here we are discussing Necator americanus, the kind that Autoimmune Therapies uses. We selected N. americanus instead of Ancylostoma duodenale because N. americanus draws much less blood, and lives far, far longer than A. duodenale.

According the various parasitology texts and papers I have read that examine this subject the most commonly quoted figure is 0.01ml/day per adult hookworm. Which works out to be 0.3ml/month, if the month has 30 days.

To put that amount in perspective a teaspoon contains about 5.0ml of liquid if filled to the top.

The second most commonly quoted figure for daily blood loss per adult hookworm is 0.03ml per day. Which gives a monthly amount, for a thirty day month, of 0.9ml/month.

The respective amount of blood lost to an infection with 50 hookworm each 30 days then must be between 15ml – 45ml.

In comparison the range quoted on Wikipedia for blood lost each month to menstruation is 10ml – 80ml being considered normal, and 35ml/month considered average.

So clearly, unless you have some disease that leads to blood loss or can cause anaemia, a therapeutic number of hookworm do not represent any risk of anaemia, because clearly the body can cope with a monthly blood loss of at least 100ml without problems.

But how much blood loss per month can humans tolerate, after all a menstruating woman with hookworm might be a risk of anaemia.

Marc wrote the following discussion of the body’s ability to replace lost blood in reply to a thread on the Yahoo Forum on this subject. If you are interested the thread is here.

“Just a note on blood loss, depending on the source the upper limit of average blood loss due to menstruation is 80-100 ml per month. Assuming the highest level of blood loss per worm is 0.03 mL/day which is the most commonly reported higher amount for N. americanus, this equates to 63 ml/month for 70 hookworms (note that AIT provides 35 hookworm as the most common therapeutic dose, although up to 100 will be provided if necessary).

To put this into context, a woman donating blood will give (in the UK) 470 ml of blood per donation without any adverse consequence. The average adult can lose up to 15% (approximately 800 mL) of their blood suddenly without clinical symptoms. So even if we assume 126 mL of blood loss per month to hookworm, double the known amount taken by hookworm, the body is easily of capable of replacing this.

To demonstrate the ability of the body to cope with chronic blood loss, the following calculation may be useful, I have used a blood loss that is double the maximum expected from 70 hookworm which allows for extra blood loss as they move around, at the same time I have assumed the lowest values pertaining to our bodies’ ability to produce Red Blood Cells (RBC).

Therefore, in reality the following calculation underestimates the ability of the human body to replace blood loss from helminths by somewhere between 2 and 5 fold.

We like to be conservative at AIT.

The use of RBC is more appropriate than the use of the total blood volume when evaluating the impact of hookworm on the body’s iron status. It is the RBC that transport oxygen, and it is a decrease in RBC or in haemoglobin in the RBC, that is by definition anaemia. Total blood volume is independent of RBC, and maintained at a fairly constant level at the expense of all other factors.

Assuming there is no reason why normal red blood cell (RBC) production can not be achieved (such as dietary iron deficiency, the normal RBC production in an average male is 18 ml/day. The body can increase production of RBCs by up to six times this value when needed. The average adult male has a haematocrit of 48% (that is each litre, 1,000ml, of blood contains 480 mL of RBC, i.e. 48%). Assuming 126 ml per month of whole blood loss due to hookworm(0.03x70x30x2), this equates to the loss of 60 ml of RBC per month (126×48%).

the human body in that same time produces 540 mL (18×30) of RBC, and can if required produce at least 3240 mL of RBC per month (540×6). Therefore using this worst case scenario, there is an approximate 54 fold excess in the volume of RBC’s that can be produced by the body (3240/60) compared to the amount that are lost to hookworm. For women the calculation is slightly different as the average haematocrit  and the production of RBC per day will be slightly different.

This means that unless there is a significant factor already causing iron deficiency, such as poor dietary intake (malnutrition), or poor absorption of iron, due to dysfunction of the small intestine (or surgical removal as is common with Crohn’s Disease), hookworm on their own in appropriate therapeutic numbers, like those provided by AIT, cannot cause iron deficiency and subsequent anaemia.

Bottom line: There is no risk of developing anaemia if you are provided hookworms by AIT, or know what you are doing and use the appropriate number of hookworm

For the record, I infected myself with a total of 300 N.Americanus and show no signs of anaemia about six months later.

Jasper Lawrence