31 Mar

Dr. Ross and the cunning seed

In 1902 Ronald Ross received the second Nobel Prize for Medicine. Those who knew him while studying medicine in St. Bart’s in London twenty years previously would have been dumb-founded by his achievement.

He was a feckless student. Pushed into medicine by his doctor father and the need to earn money, he concentrated more on his bad poetry, and worse novel writing than on his studies.
On graduating he cast around for a career. His childhood spent in India, he happily took a position with the East India Company in Madras, convinced that this would provide a leisurely medical practice that would allow him to continue with his writing.

As the months passed in the dead heat and stifling humidity of the subcontinent his interest became piqued by the ongoing mystery of the transmission of malaria. Tending to the East India troops he noticed that of two battalions stationed by a swampy pool , the battalion camped on the windward side suffered far less fevers then the soldiers camped on the lee side.

It had long been held that malaria was transmitted to humans through air polluted by swampy ground. This was known as the miasmatic theory which gave us the misnomer by which we still know it, ‘Mal aria’: ‘Bad air’.

Until the late nineteenth century no one had proved that the mosquito was the vector for the transmission of the disease to humans. Very few scientists had even discussed it as a possibility.

A confluence of serendipities led Ross to question the received wisdom. Firstly his complex personality underwent a change while in India. His focus moved away from the arts to a vocational approach to his medical practice.
‘I was neglecting my duty in the medical profession. I was doing my current work, it was true; but what had I attempted towards bettering mankind by trying to discover the causes of those diseases which are perhaps mankind’s chief enemies?” he wrote of the time.

Secondly, returning to England on a furlough in 1894 he made contact with Dr. Patrick Manson, a senior clinician and a leader in malarial research. Manson held the view, incorrectly, that mosquito larvae deposited in water and the water then drunk by humans was the mode of transmission of malaria.

Manson suffered from chronic gout, a painful condition brought on by high-living, that prevented him from traveling to the tropics to prove his theses. In Ross he found his avatar. Ross was not brilliant, but he had an innate energy and a rigour and elegance in the construction of his experiments which Manson recognised.

The main difficulty in proving the link between mosquito, malaria and man lay in the bewildering array of varieties of mosquitoes that existed. Take the anopheles mosquito, the primary malaria carrier. Within its category there are many subcategories, some that do carry malaria, others that do not, their distinguishing feature often being a subtle difference in the colour of their tiny eggs.
Ross was not aware of this and so, catching thousands of mosquitoes and dissecting them without finding the malarial bug, the proof seemed to slip from his grasp like mercury on a mirror.

The breakthrough came on the 20th of August 1897. On dissecting a type of mosquito he poetically named ‘dapple-winged‘ he found malarial organisms in its stomach wall. He went on to find these organisms in other mosquitoes of similar type, in some swarming through the insects head to its proboscis. This led him to think, as opposed to Manson’s theory of humans drinking the larvae, could it be that the mosquito acted as a direct vector, puncturing our skin and introducing the bug directly?

Ross could not find human subjects willing to be stung by a dapple wing and then pricked to show the presence of the bug. His letters show an almost comic reluctance by the Calcutta street people he tried to enlist.

Instead he used birds. His experiment proved conclusive, mosquitoes directly introduced malaria to birds through their bite, the extrapolation being they did the same to humans.

The thousands of hours he had spent in a dark room in Calcutta in stifling heat peering through a rudimentary microscope as he carefully dissected mosquitoes had come to fruition. During these months as the menagerie of birds and vermin in cages surrounding him, brought from the treetops and sewers of Calcutta, chirped and hissed, his perspiration proved a greater boon than his inspiration, until at last, the moment of discovery.

In celebration he wrote these lines:

“This day relenting God
Hath placed within my hand
A wondrous thing; and God
Be praised. At His command,
Seeking His secret deeds
With tears and toiling breath,
I find thy cunning seeds,
O million-murdering Death.
I know this little thing
A myriad men will save.
O Death, where is thy sting?
Thy victory, O Grave?”

Author: Dr. Sam McManus

Sir Ronald Ross