Rotary Minute: John Staddon

John Staddon delivered the following Rotary Minute about research he had participated in while in Africa. Coincidentally, in attendance were Rotarian Rebecca Johnson and her boss at FHI 360 and prospective Rotarian, Ted FitzGerald. FHI 360’s headquarters are visible across the field from the meeting room and was formed in 2011 when Family Health International joined forces with Academy for Educational Development. Among other things they do research in Africa and both were there during the Ebola crisis. What an interesting group we have.

John’s Minute:

An ecology lesson?

Some years ago I found myself, a college dropout, in Fort Rosebery (Mansa) in N. Rhodesia (Zambia) looking for a job.  Fort Rosebery was tiny: about 20 British families, a few hundred Bemba people, a handful of Indians and no electricity.

After many tries I got a job with something called the Health and Nutrition Scheme, run by the colonial government.  Health and Nutrition studied disease – malaria and bilharzia (schistosomiasis) especially – and nutrition, especially kwashiorkor a protein deficiency that stunts development and leaves kids with skinny limbs and bloated bellies.

The scheme had three study sites.  The main site was Fort Rosebery, which had a laboratory and a small hospital.  The other two sites were Bemba villages at Matanda on the Luapula River and Shikamushile on Lake Bangweulu – a river site and a lake site.  Each was a one-hour or so bone-rattling drive from FR on dirt roads.

The senior researcher on the scheme was Fergus McCullough, an Irish expert on tropical diseases.  The medical chap was a recently arrived Danish pediatrician, Bent Friis Hansen.  Both these guys were supported by WHO.

I worked both in the lab and as a note-taker for Friis Hansen as he examined children.

Malaria and bilharzia were the main diseases affecting the Bemba people.  I will talk just about one interesting thing about bilharzia that came up again recently.

Bilharzia is a nasty affliction with a bizarre life-cycle – not really an appropriate pre-prandial topic, but hey, this is Rotary!  It is caused by a parasitic trematode worm about 1 cm long that lives in your veins and subsists on red blood cells and other things essential to life.  The worms are monogamous.  They come in pairs and reproduce as busily as they can in the victim’s body.  Since the worms don’t multiply in the body, the amount of sickness depends on the patient’s fixed ‘worm load’.  The eggs, when they don’t get lodged in an organ and cause trouble that way, are excreted in urine and feces.

Lucky eggs end up in water – a river or lake – where they hatch into tiny larvae, which go looking for a particular kind of snail.  When they find the snail, they bore into it and after a few weeks produce sporocysts which each produce thousands of cercaria.  These little darlings then swim about looking for bathers into whose skin they can burrow. There they turn into the trematode worms and repeat their sorry cycle.  (How this strange life cycle evolved I leave to someone more imaginative than I.)

Fergus and Bent never understood why bilharzia was so much more common at the Luapula river site compared to lake Bangweulu: 

What is so different about the river compared to the lake?

A possible answer appeared just recently.  The African rift-valley lakes – Malawi, Kivu, Victoria, Bangweulu and many others – sport the world’s most varied set of freshwater fish, hundreds of species, each adapted to its own special niche.  A tasty cichlid Trematocranus placodon, was once common in Lake Malawi.  The incidence of bilharzia was then also relatively low, just as it was in Lake Bangweulu.

The reason for the low incidence in Malawi was that T. placodon  feeds on the snails that transmit the disease.  More placodon means fewer snails, hence less bilharzia.   BUT, when overfishing caused a decline in the Malawi placodon population, snail numbers increased and so did bilharzia.

Possibly, therefore, it was the relative lack of snail-eating cichlids in the little Luapula streams that allowed the snails, and thus the bilharzia, to flourish in Zambia’s Northern Province.

I wonder if anyone has tested this hypothesis in modern Zambia?

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