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Blood (Intracellular) and Other Tissue Protozoa 81

a medication successfully used to prevent malarial In the New World, either cutaneous or mucocutane-
infections. In 1862, the disease had spread in a mere ous leishmaniasis is responsible for causing disfiguring
38 years to Burdwan, with infection rates reaching epi- conditions. Evidence of these medical conditions are
demic levels. The disease was thought to be caused by found in sculptures since the fifth century, and in related
a virulent form of malaria by a number of clinicians, writings of Spanish missionaries in the Americas during the
including Ronald Ross. But the cause of the disease re- sixteenth century. It was originally thought that New World
mained unknown until the early 1900s, when Leishman leishmaniasis and Old World leishmaniasis were the same.
and Donovan discovered the parasite, L. donovani, lend- However, in 1911 Gaspar Vianna found that the parasites
ing their names to the infective organism (Cox, 2002). in South America differed from those in Africa and India
During the late 1800s, literature in Asia, Europe, and created a new species, Leishmania braziliensis, ostensi-
and Africa described a number of structures that may or bly due to the discovery of the diseases in the area of South
may not have been a species related to Leishmania. Some America. Since then, a number of other species unique to
victims had epithelial sores that were labeled as oriental the New World have been described. Following the discov-
sores by medical practitioners at that time, which could ery in 1921 of the sand fly transmission of Old World leish-
have resulted from any number of organisms that may not maniasis, it was assumed that the vectors of Leishmania in
have even been a result of intraerythrocytic parasites. Bac- the New World would also belong to the genus Phlebotomus
terial, viral, and fungal infections may have been the caus- but was later identified as the genus Lutzomyia. Over the
ative agents in at least some of these medical conditions. last two decades, the complex pattern of the life cycle and
Credit for the discovery of Leishmania is often given to an the transmission of the organism based on the species of
American, James Homer Wright (Cox, 2002), although both the parasite and the vector, the reservoir host, and
there is little doubt that parasites responsible for leishma- the disease has been extensively verified and described by
niasis were actually seen by David Cunningham in 1885. Ralph Lainsonand his colleagues (Cox, 2002).
Cunningham may not have realized what these organisms
were. In 1898 a Russian military surgeon, P. F. Borovsky, Morphology
also discovered similar structural organisms. The dis-
covery of the parasite that causes visceral leishmaniasis, The Leishmania tropica complex includes three different
L. donovani, is less controversial than those just discussed. species that are similar in many ways but are genetically
It is almost universally accepted that a Scottish army and therefore serologically different that occupy differ-
doctor, William Leishman, for whom the organism is ent geographical regions of the world. The three species
named, first definitively identified L. donovani. Also, are: Leishmania tropica, Leishmania aethiopica, and
and somewhat concurrently, a professor of physiology Leishmania major. The morphologic forms for these or-
at Madras University, Charles Donovan (Cox, 2002), in- ganisms are the amastigote, promastigote, epimastigote,
dependently discovered the parasite in the spleens of opisthomastigote, and the trypomastigote and they differ
patients with kala-azar. Apparently the discovery by the significantly in size (Table 4-1).
Russian military surgeon, Borovsky, was unknown to
Homer Wright and to Leishman and Donovan, although Symptoms
their discoveries were made during a short period of time.
It was not discovered until 1921 that Leishmania Tissue destruction occurs as amastigotes are released
was transmitted by a vector. The search leading to the im- and invade new macrophage cells. Cutaneous leishma-
plication of a specific vector was sought for a number of niasis occurs when a red papular structure develops
years, before the Sergent brothers, Edouard and Etienne, as a primary lesion that may be 2 centimeters or more
demonstrated through experimental proof the transmis- in size and is often extremely itchy. Bacterial infections
sion to humans from sand flies of the genus Phlebotomus. often occur in the primary site due to the breakdown of
However, the actual mode of infection, through the bite the skin. “Dry” lesions occur with infections by L. tropica
of the sand fly, was not finally demonstrated until 1941 and L. aethiopica but moist, weeping lesions occur with
(Cox, 2002). The history of Old World leishmaniasis is L. major. Lesions heal quickly unless a secondary bacte-
also extensively described by Garnham, Manson-Bahr, rial infection complicates the condition, but considerable
and Wenyon (Cox, 2002). scarring to areas of the body may follow healing of the