Although the symptoms of malaria were known since ancient times, the discovery of the cause of the disease had to wait until the end of the nineteenth century. A French military doctor - Alphonse Laveran - was the first person to recognise a parasite as the causative agent of malaria. Medicine in Europe had been revolutionised by Robert Koch and Louis Pasteur’s work in the 1860s and ‘70s that showed that most infectious diseases are caused by microbial agents (the “germ theory” of disease). With the wide-spread acceptance of this idea, researchers (the first modern malariologists) were soon looking for the microbial agent that caused malaria, and many studies were conducted on various algae, protozoa, fungi and bacteria that were associated with malarious areas.
It appeared that the problem was solved when, in 1879, Corrado Tommasi-Crudeli and Edwin Klebs (already famous for his isolation of the diphtheria bacillus) identified a bacterium in the soil of the swamps of the Roman Campagna, which, they claimed, could induce a malaria-like disease when injected into rabbits. It was duly named “Bacillus malariae”, and despite some unsuccessful attempts to reproduce the rabbit-infection experiment, such was Klebs’ reputation at the time that this bacterium was widely accepted as the causative agent of malaria.
In fact, this theory actually ignored evidence to the contrary that had been known for over 150 years before the discovery of Bacillus malariae. It had long been observed that the spleen and brain of malaria victims contained a dark pigmented material which had first been described by Giovanni Maria Lancisi in 1717 (Lancisi was a remarkable character in the history of malaria research who not only appears to be the first person to have described evidence of malaria parasites, but who also suggested a link between the disease and the mosquitoes associated with malarious areas). Laveran’s breakthrough was to realise that this dark pigmented material was associated with the cause, and not the result, of malaria.
In 1878 he began working with malarious French soldiers in Constantine, Algeria, and his autopsies of the victims of the disease constantly revealed the same pigmented bodies in the spleen and brain that had first been described by Lancisi. He was unable, however, to collate any evidence from tissue samples that these pigmented bodies were anything other than a pathological symptom of the disease, and he switched his investigations to the study of fresh blood from malaria patients. This was to prove to be the decisive step in the discovery of the malaria parasite, when on November 6th 1880, Lavern observed the vigorous movement of one of the pigmented bodies in fresh blood. He instantly realised that the pigmented malarious bodies that he and other researchers had long observed in the tissue and blood of malaria patients were living parasites, and were the causal agents of the disease. Laveran communicated his discovery to the Academy of Medicine in Paris, and named the parasite “Oscillaria malariae” (Lehrer, 1979; National Center for Infectious Diseases, 2004; Schmidt and Roberts, 2004).
There followed a period of some years in which the scientific community were slow to accept Laveran’s discovery, such was the enthusiasm for Bacillus malariae, but by the early 1890s, it was generally accepted that Laveran’s parasites were, indeed, responsible for malaria. This acceptance was bolstered by the new blood staining techniques developed by Romanovsky in Russia that allowed the parasites to be visualised in great detail in blood smears. In 1884, Ettore Marchiafava (a long time advocate of Bacillus malariae) and Angello Celli verified Laveran’s claims, and named the parasite they’d observed “Plasmodium malariae”. Camillo Golgi was the first to realise that there were different species of the parasite, each with a characteristic morphology and pathology, and by 1897 three distinct human parasite species had been described; Plasmodium vivax, Plasmodium malariae and Plasmodium falciparum. A fourth, Plasmodium ovale, was described in 1922. |
