Marchiafava first developed his first research interest in pathology from
Robert Koch, whom he met in Berlin during his doctoral course. He studied malaria intensively for eleven years, from 1880 to 1891. With
Angelo Celli, in 1880, he confirmed a new
protozoan (then called
Oscillaria malariae) discovered by
Alphonse Laveran, finding it in the blood of the many patients with malaria fever. They were the first to use proper staining (with
methylene blue) to identify malarial parasite as distinct blue-coloured pigments in the blood cells. They showed that the parasites lived inside blood cell, and that they divide by simple splitting (
fission). They were the first to recognize several the
stages of development of the malarial parasite in human blood. They called the new microorganism
Plasmodium in 1885. Their works helped to differentiate different types of malaria as a result of infection with different species of
Plasmodium. With
Amico Bignami he published a classic monograph
On Summer-Autumnal Fevers in 1892, which was translated into English in 1894. This was a major foundation in modern malariology. They reported the direct evidence of mosquito theory that mosquitoes transmit malaria. Marchiafava was the author of
Sulle febbri malariche estivo-autunnali (1892) and
La infezione malarica (1902). In 1884, with Angel Celli, he first observed
Gram-negative diplococci in the cerebrospinal fluid of a fatal case of
meningitis in 1884. This was the then-unnamed
Neisseria meningitidis (meningococcus), the agent of bacterial meningitis, although this was not proven until 1887 when
Anton Weichselbaum isolated the bacterium from six cases of meningitis and established the isolates as a distinct species. Marchiafava described for the first time the histopathology of syphilitic cerebral arteritis. In 1897, he observed a callused body in the brain of an alcoholic patient, and, in 1903, with Amico Bignami, published a complete description of the insanity of alcoholics, one form of which is today known as
Marchiafava–Bignami disease. (The disease is now known in nonalcoholic but diabetic patients.) He was the first one to prove the importance of sclerosis of the coronary arteries in the pathogenesis of
myocardial infarction. He also worked on
nephropathy and described
streptococcal glomerulonephritis. In 1931, he described
Paroxysmal nocturnal hemoglobinuria in depth, and also a rare form of this disease Strübing-Marchiafava-Micheli Syndrome. In 1925, Marchiafava organised the first international conference on malaria. ==Awards and honours==