Leishmania tropica, Wright, 1903.
Syn.: Helcosoma tropicum, Wright, 1903; L. wrighti, Nicolle, 1908; Ovoplasma orientale, Marzinowsky and Bogrow.
It is believed by some that the parasite was first described by Cunningham in 1885, and studied by Firth in 1891, being called by him Sporozoon furunculosum. If these earlier studies were of the parasite, then its correct name is L. furunculosa, Firth, 1891.
The benign disease produced by this parasite has received many names, among the best known being Oriental sore, Tropical sore, Delhi boil and Aleppo button. These names, however, are not happy ones, as cutaneous leishmaniasis (e.g., on the ear) is now known to occur in the New World, for example in Mexico, Venezuela, Brazil and neighbouring States. However, it may be necessary to subdivide cutaneous leishmaniases later.
In the Old World the disease occurs in India, Persia, Arabia and Transcaucasia. It is also known in Algeria, Northern Nigeria, Egypt, Sudan, Crete, Calabria, Sicily and Greece.
The boils often occur on the face, and before ulceration the parasites may be found in the cells at the margin and floor of the “button.” In searching for parasites the scab should be removed and scrapings made from the floor and edges. Where lesions occur atrophy of the epidermis takes place, and infiltration of mononuclear cells (e.g., plasma cells, lymphoid and endothelial cells) follows. The parasites are intracellular, being found inside mononuclear cells. In non-ulcerating sores, Cardamitis found some free parasites. Non-ulcerating forms are said to occur in the Sudan. In the Old World the sores are often limited to exposed surfaces of the body. Infection of mucous membranes (such as the lip, palate, buccal and nasal membranes) may occur, especially in South America, and are often known there as “Espundia.” Christopherson (1914) has recorded a case in Khartoum.
Leishmania tropica is equally well cultivated on Novy-MacNeal-Nicolle medium or on citrated blood. The usual temperature for cultivation is 22° to 28° C., though Marzinowski claims to have cultivated the parasite at 37° C. L. tropica can be inoculated into monkeys and dogs, with the production of local lesions. Material from a human sore or flagellates from a culture may be thus successfully inoculated. Also infected material may be rubbed directly into a scarified surface. The incubation period is long, extending over several months. The duration of the disease may be from twelve to eighteen months. Recovery from one attack of tropical sore confers immunity, and the Jews in Bagdad inoculate their children with the disease on a part of the body which will be covered, and so secure immunity in adult life.
The mode of transmission of L. tropica is unknown. Wenyon (1911)127 has found that the parasite develops into the flagellate stage in the digestive tract of Stegomyia fasciata in Bagdad. Patton (1912)128 has found similar development in the bed-bug in Cambay. The house-fly, Phlebotomus and Simulium have been suspected as transmitters in different parts of the world.
An interesting announcement has been made recently (May, 1913), that Neligan has found that L. tropica occurs in dogs in Teheran, Persia, producing ulcers on the dogs’ faces (cf. natural occurrence of L. infantum in dogs—see p. 110). Yakimoff and Schokhor (1914),129 have found the disease in dogs in Tashkent.
Gonder130 (1913) has performed some interesting experiments showing the relation of infantile kala-azar to Oriental sore. Gonder infected mice with L. infantum and with L. tropica. He used culture material and injected intraperitoneally or intravenously. In each a general infection resulted, with enlargement of the liver and spleen. Later, however, mice injected with Oriental sore (North African variety) developed peripheral lesions on the feet, tail and head, and the lesions contained Leishmania. No such peripheral lesions developed in the case of the mice infected with the kala-azar virus. Gonder suggested that Oriental sore, like kala-azar, is really a general infection overlooked in its earlier stages, and that it is in the later stages that peripheral lesions on the skin are developed. Row (1914)131 also obtained a general infection in a mouse by the injection of cultures of L. tropica from Oriental sore of Cambay.
Leishmania infantum, Nicolle, 1908.132
Infantile splenic anæmia has been long known in Italy. It also occurs in Algeria, Tunis, Tripoli, Syria, Greece, Turkey, Crete, Sicily, Malta,133 Spain and Portugal. This leishmaniasis is, then, distributed along the Mediterranean littoral; also in Russia. Cathoire (1904) in Tunis and Pianese (1905) in Italy were among the first to see the parasite. Nicolle then found the parasite in patients in Tunis, and further found spontaneous infection in dogs. The patients are usually children between the ages of 2 and 5 years. There are a few cases known in which the infantile type of leishmaniasis occurred in youths and adults of the ages of 17 to 19, while one patient in Calabria was 38 years old. The symptoms are like those of Indian kala-azar. Several Italian investigators and others consider that L. infantum is the same as L. donovani, and that the latter name should be used for the parasite of Mediterranean leishmaniasis. This view, as to the identity of L. donovani and L. infantum, seems coming into general favour.
There are, however, differences between the Indian and infantile kala-azars, in addition to the ages of the patients affected, thus: (a) As regards cultures, it is found that L. infantum is readily grown on the Novy-MacNeal-Nicolle (“N.N.N.”) medium (saline blood-agar), and that sub-cultures are easily obtained; in citrated blood L. infantum grows with difficulty. The reverse is the case with regard to culture media for L. donovani, which grows with difficulty on the N.N.N. medium, but relatively easily in citrated splenic blood. (b) Considering inoculability into experimental animals, it is found that L. donovani is inoculated generally with some difficulty into white rats, white mice and monkeys, and with greater difficulty into dogs, while L. infantum can be inoculated into several experimental animals, especially into dogs and monkeys, with ease. (c) At present L. donovani is not known to occur spontaneously in animals, but L. infantum is found naturally in dogs in the Mediterranean region, and the disease in dogs is often referred to as canine kala-azar. Kittens have occasionally been found infected. However, these differences must not be emphasized too much.
The material for cultivation is obtained from punctures of spleen, liver or bone-marrow of cases infected with L. infantum. It is not always easy, however, to infect from cultures, as the cultural flagellates inoculated into the body are often phagocytosed.
Similarly, the material for animal inoculation is obtained from emulsions of infected spleen, liver or bone-marrow. Dogs and monkeys are easily inoculated with such material; Nicolle inoculates into the liver or the peritoneal cavity. Mice, white rats, guinea-pigs and rabbits only show slight infections after such inoculations.
Dogs infected experimentally with infantile leishmaniasis may show either acute or chronic symptoms. The acute course occurs more often in young dogs, and is usually fatal in three to five months. The chronic course is found more commonly in older dogs, and may last seventeen to eighteen months. In acute forms there is irregular fever, progressive wasting, diarrhœa occasionally, motor disturbances involving the hind quarters, and the animal dies in a comatose condition. In the chronic form the animal may appear well, except for loss of weight. The parasites may be found in the internal organs of these experimental dogs, but are not numerous in the peripheral blood except at times of high fever. Experimental monkeys live about three months.
It may be interesting to record the number of dogs found to be infected naturally with leishmaniasis in various countries. In Tunis, Nicolle