The Miraculous Fever-Tree Page 26

  Returning home after withdrawing a drop or two of blood from each bird, he slid the specimens under the glass of his microscope, and observed two parasitic forms he had never seen before: one was what he called a granular protoplasm, the other a clear form that put out waving arms, or flagella. Over a period of time he watched the flagella slowly detach themselves and begin swimming about, the same process that Laveran had observed in blood drawn from the soldier suffering from malaria in Algeria seventeen years earlier, to such mockery from the Italian Grassi, Sir William Osler and their colleagues. A number of the flagella quickly attached themselves to the granular protoplasm and, just like sperm, the strongest among them plunged its head into the sphere and finally wriggled its whole body into that organism.

  What MacCullum had just observed was the fertilisation process of the Halteridium parasite. Could this be the answer to the question of what happened to the malaria parasite within the mosquito’s stomach? Having been fertilised, the parasite multiplied, giving birth to new offspring. If this was the life cycle of Halteridium, could that of the malaria parasite really be different? Similarly, if it worked in this way in birds, was it not possible that the parasite operated in the same way in human beings? If so, then mosquitoes were essential not just to the transmission of malaria, but to the reproduction of the parasite.

  By chance, the zoological section of the British Association for the Advancement of Science happened to be holding its annual meeting in Toronto that year. MacCullum was given the chance to read his paper on the sexual reproduction of the Halteridium parasite to a distinguished audience of English doctors, which included Lord Lister. They listened carefully to his dramatic discovery, and were so impressed that at the end it was Lister himself who proposed the vote of thanks. One man who was not there was Major Ronald Ross. But thanks to Mrs Manson, who typed it out for him, he was soon able to read MacCullum’s paper in India, and begin adapting the experiment for himself.

  Ross’s own discovery of the pigmented cells within the mosquito had perhaps been announced too modestly. Whatever the reason, it had failed to have the impact he had hoped for. Before he could dwell for long on that, though, he received a telegram ordering him to proceed to Kherwara, a dry, empty spot in Rajputana, fifty-six miles from the nearest railway junction and reachable only by tonga, a two-wheeled horse-drawn carriage.

  The secondment threw him into despair, for although it had many other palpable hardships, Kherwara was free of malaria. If there was anything that epitomised the authorities’ disregard for and ignorance of the importance of Ross’s work, he felt, it was this posting to a place where his precious research simply could not proceed. ‘You must confess,’ he wrote to Manson in November 1897, ‘that it is trying to be snatched away just as one is on the point of proving a theory which one has been thinking of and working at for nearly three years; let alone being sent to a wretched place with two or three Europeans and a few itch cases and febriculae when one has had every right to expect something fairly good.’

  The absence of malaria did, however, inspire Ross to take a leaf out of MacCullum’s book and try to discover how the malaria parasites developed within birds. Manson, meanwhile, had been appointed an adviser to the Colonial Office, and was about to publish his great work, Tropical Diseases. If Ross already felt sorry for himself, then Manson’s hearty letters, while invigorating, made him deeply envious. Less than a month later, Ross was pouring his heart out again: ‘Work such as mine in Bangalore would in any other branch of public service have pushed me on. In the medical service it is of no use, because the medical services have become stagnant ponds full of torpid old carp … The heads of service don’t and won’t recognise anything but seniority and red-tape rules.’

  Ross complained constantly to others as well as to Manson, and was beginning to acquire a reputation as a whiner. But for once his complaining was about to pay off. On 1 February 1898 he wrote to Manson to tell him of a surprising telegram from the Surgeon-General, ordering him to take an appointment on special duty, the study of malaria.

  Finally ensconced in Calcutta in a working laboratory, a luxury he had never really had before, Ross quickly advanced, despite the ‘awful heat’. Using sparrows infected with the malaria parasite, he dissected mosquito after mosquito. He hoped to be able to deliver the final results of his experiments at the meeting of the British Medical. Association in Edinburgh in July, perhaps even in person. Towards the end of June, he wrote to Manson: ‘I think I am on the verge of another great advance.’ Time after time, he observed what he called ‘rods’ in the body cavity of the insects he dissected. He thought they were spermatozoa, or ‘naked spores’, but their behaviour did not fit anything he had imagined within the life cycle of the parasite. He pushed on, and on 6 July he wrote to Manson again.

  As in his earlier letters, Ross’s quick-running handwriting weaves around drawings of cells and ducts and mosquito heads in full array. ‘I hope this letter will reach you in Edinburgh,’ he begins after brief congratulations to Manson on a new job. He moves briskly on to his own preoccupations, and his excitement at sensing that he is closer than ever to his holy grail is plain on every page even now, more than a hundred years on:

  I feel almost justified in saying that I have completed the life cycle, or rather perhaps one life cycle, of proteosoma [a malaria parasite now called Plasmodium relictum that is found in birds], and therefore in all probability of the malaria parasite. I say almost, because though I think I have seized the final position, I have not yet occupied it with my full forces.

  My last letter left me face to face with the astonishing fact that the germinal rods were to be found in the thorax as well as in the abdomen. Instead of the hard resisting spores we expected to arrive at – spores easily seen and followed – here were a multitude of delicate little threads, scarcely more visible than dead flagella and poured out amongst the million objects, which, under an oil-immersion lens, go to make up a mosquito. I dare say you imagined my consternation. I could not conceive what was to happen to the rods.

  Well, I was in for a battle. It was, I think, the last stand – on the very breathless heights of science. I am nearly blind and dead with exhaustion!! – but triumphant. Expect one of the most wonderful things.

  The rods were evidently in the insect’s blood. By merely pricking the back of the thorax and letting the milky juice flow into a minute drop of salt solution thousands of proteosoma-coccidium-rods could easily be obtained. The question was what next?

  Here Ross breaks off, only to start writing again a short while later.

  I now divided my insects before dissection between the thorax and abdomen and examined each part separately. It was found that the rods were often more numerous in the thorax than in the abdomen; there were even cases where scarcely one could be found in the abdomen (the coccidian evidently burst some days previously as shown by their empty capsules), while numbers (4 or 5 in a field) could be detected on teasing up the thorax and head.

  Here however I was brought up standing. Sometimes the rods were more common in the head, sometimes in the thorax. I went at mosquito after mosquito spending hours over each, until I was blind and half silly with fatigue. The object was to find if possible a place or structure where the rods accumulate; or to discover some further development in them. Nothing.

  On the 4th however, after pulling out the head by its roots (oesophagus etc) from the thorax, some delicate structure dropped out of the cervical aperture of the latter. This proved to be a long branching gland of some sort, looking like a coil of large intestine, and consisting of a long duct with closely packed, refractive cells attached to it. I noticed at once that the rods were swarming here and were even pouring out from somewhere in streams. Suddenly to my amazement it was seen that many of the cells of this gland contained the germinal rods of proteosoma-coccidia within them. Looking further the cells of one whole lobe of the gland were simply packed with them, and on bursting the cells the rods poured out of them just a
s they pour out of the original coccidia.

  Here Ross’s nib breaks, and he splashes ink across the page. After re-equipping himself, he sets off once more.

  The rods were quite unmistakeable, having the tapering, flattened and vacuolated structure peculiar to them. They are identified at once and no structures like them exist in the normal mosquito. Here they were in the cells of the gland. [The cells] have a very thin outline and contain a perfectly clear fluid, without granulations or oil-drops such as coccidian possess. The rods lay within them quite regularly and motionless except for Brownian movement. In one lobe almost every cell contained numbers of rods; in other lobes only one or two cells contained them. By the attachment of the cells to the central duct, it seemed quite easy for the rods to pass on occasion from the former into the latter.

  Now what was this gland? Will you believe it, I examined two whole mosquitoes without finding it again? What with the scales, the debris of muscle etc, I could not come upon it. A third mosquito gave the same result, until I opened the head itself. There was the gland attached by its duct which led straight into the structures somewhere between the eyes. The cells were again packed with germinal rods.

  I have found the gland now altogether in seven mosquitoes. In six of them the cells were packed (especially in some lobes) more or less with the germinal rods. In the seventh I could find only a small piece of gland, which was free from rods.

  I still experience, however, the greatest difficulty in dissecting out the gland itself. It appears to lie in front of the thorax close to the head, but breaks so easily in the dissection that I cannot locate it properly. In the second mosquito however there was no doubt, as shown by evident attachment that the duct led straight into the headpiece, probably into the mouth.

  In other words it is a thousand to one, it is a salivary gland.

  I think that this, after further elaboration, will close at least one cycle of proteosoma, and I feel that I am almost entitled to lay down the law by direct observation and tracking the parasite step by step.

  Malaria is conveyed from a diseased person or bird to a healthy one by the proper species of mosquito, and it is inoculated by its bite.

  Remember however that there is virtue in the ‘almost’. I don’t announce the law yet. Even when the microscope has done its utmost, healthy birds must be infected with all due precautions.

  I say one cycle. I think it is likely there is another. I continually observe that only a portion of the coccidian contain germinal rods. The rest, I now think, give rise to the blank sausage-shaped bodies … which I believe may be the true spores of the parasite meant either for free life or to infect grubs. Oddly enough, in old mosquitoes these bodies also get carried away into the tissues – unless they are some disease of the insect. I will attack this next.

  7th. I dissected two healthy mosquitoes this morning and began by dividing up the head and the anterior third of the thorax from the middle third by means of a razor, and then carefully breaking up the anterior third. In both cases the glands were found and their ducts were traced straight into the head.

  In all probability it is these glands which secrete the stinging fluid which the mosquito injects into the bite. The germinal rods, lying, as they do, in the secreting cells begin to perform their function, and are thus poured out in vast numbers under the skin of the man or bird. Arrived there, numbers of them are probably instantly swept away by the circulation of the blood, in which they immediately begin to develop into malaria parasites, thus completing the cycle. No time to write more …

  Manson was the first to recognise the full significance of what Ross had achieved. Despite a bad attack of gout that had left him weak and in pain, he set about making preparations to address the British Medical Association meeting in Edinburgh.

  Ever unselfish, Manson wanted to be the first to tell the world about Ross’s work and why it was so important. This remarkable Plasmodium, with all its sexual complexities, the fecundity of its cells that implanted themselves in the walls of the mosquito’s stomach, the way in which each one grew into a mature individual, navigating unerringly within the mosquito’s innards towards its head and into the salivary glands, where it would steady itself at the top of the insect’s tubular mouth ready to be injected into the next animal host – all of this had been observed by just one man.

  Manson was a warm and generous speaker, and the image he conjured up that July afternoon in Edinburgh was not so much of a new world being unveiled, as of one man who had swum through an uncharted ocean, sighted land and eventually, as a result of his efforts, gained a toehold on a continent that had never been visited before. The meeting ended with a unanimous resolution of congratulations to both Manson and Ross.

  Manson wrote afterwards to Ross: ‘The fat is thoroughly in the fire and you may expect soon to hear more of yourself than your modesty may care for … I was determined if at all feasible to come to this meeting & properly present your work, the importance of which it is difficult to overestimate.’

  Lord Lister, he went on, was there and ‘is taking a very great interest in the progress of the investigation’. Present too was William Osler, then Professor of Medicine at Johns Hopkins University in Baltimore, who had been most sceptical about Laveran’s early findings, but now a convert. ‘I gave him one of your reports,’ Manson wrote. Set on the eastern shore of Maryland, Baltimore was one of the malarial cities in the United States, and Osler had long been an enthusiastic proponent of the use of quinine at the city’s main hospital, where he was the chief physician.

  Manson’s letter delighted Ross, but even so he could not help feeling more than a little envy. It had been their work, their moment. But only Manson had been there. As a later account of the discovery put it: ‘[Manson] had been scrupulous in giving Ross the credit; but still it had been Manson’s announcement, in Manson’s voice; and Manson received the applause. Years later Ross went out of his way to collect memories of those who had been in Edinburgh that July, as though straining still to hear the clapping of hands.’

  His jealousy would flare up again when, just five months later, the Italian professor Giovanni Battista Grassi announced that he had gone one further. Grassi had set about trapping and identifying mosquitoes in different parts of central and southern Italy in an effort to discover once and for all which it was that transmitted malaria in human beings. Not only had he found that the culprit was Anopheles, he had also proved for the Plasmodium that caused human malaria what Ross had discovered about malaria in birds.

  Although Grassi had been inspired directly by Ross’s findings, and in writing up his own experiments showed that he had followed all of Ross’s procedures step by step, he made only a brief and ambiguous reference, late in his paper, to Ross’s work. This constituted the height of scientific rudeness. Perhaps Grassi, as the head of a prestigious university department and with a reputation as the premier zoologist of Italy, if not of the world, thought he could disregard the little-known Major Ross, who worked in India with neither laboratory nor assistants. Whatever the reason, Grassi’s discourtesy broke all the rules of scientific good manners, and it enraged Ross. For the rest of his life he would never let pass an opportunity to insult the Italians and denigrate their achievement. Even being made the sole recipient of the second Nobel Prize for Medicine in 1902 would not be enough to compensate Ross for the slight.

  Grassi’s scientific reputation also suffered badly as a result of his behaviour. The truth was that after four years of research, Ross had discovered the development of one species of Plasmodium in one species of mosquito. The parasite on which he worked, Plasmodium relictum, is one of twenty-five species that infect birds alone. Others infect mice and rats, lemurs, monkeys, porcupines, squirrels, bats, lizards and snakes. There are only four malaria parasites that infect man: Plasmodium vivax, the most common and the most benign form; Plasmodium ovale, a rare species native to the west coast of Africa; Plasmodium malariae, which causes an extraordinarily tenacious fever; and
the deadly Plasmodium falciparum, that still kills nearly three million people every year, most of them children.

  Ross’s observations of the life cycle of the parasite started with the fertilised eggs on the wall of the mosquito’s stomach, and ended when the ‘rods’, the threadlike sporozoites, had made their way into the mosquito’s salivary glands. He knew that healthy birds were infected with parasites after being bitten by mosquitoes that had previously fed on infected blood; he did not know whether the cycle was the same in human beings, nor did he know anything about how the parasite developed once in the bloodstream, either in man or in birds. Grassi would paint in one corner of that map; how the parasite developed in man, and just how quinine acted upon it, would be the work of others.

  As the twentieth century dawned, the age of ignorance appeared to be drawing to a close. Yet malaria was more of a problem than it had ever been. And, despite the celebration in 1930 of the three hundredth anniversary of the discovery of quinine, a large proportion of mankind was about to be deprived of its most famous cure.

  10

  The Last Forest – Congo

  ‘The bark is distinctly better than the bite.’

  DR C.E. CASPARI, St Louis College of Pharmacy,

  speaking at the ‘Celebration of the Three Hundredth

  Anniversary of the First Recognized Use of Cinchona’,

  St Louis, Missouri, 31 October-1 November 1930

  Until the middle of the twentieth century, the legend about the Countess of Chinchón who was cured of a fever after swallowing an infusion of the bark of a tree that grew near Loxa was still regarded as a true story. Sir Clements Markham had been greatly taken by it, and for a long time after his visit to Peru no one had reason to doubt it. Which was why a large number of botanists, chemists, pharmacists and historians gathered together in the early autumn of 1930 at the botanical garden in St Louis, Missouri.