The distribution of the parasites in the body of the human patient is much the same as in the case of Indian kala-azar. Critien records the finding of parasites in the mucous flakes of the stools of a three-year-old Maltese child.135 Intestinal lesions rarely occur in infantile leishmaniasis.
Ætiology.—Infantile leishmaniasis is stated to be transmitted by fleas, especially dog fleas, Ctenocephalus canis (= Pulex serraticeps), and by Pulex irritans. Children living in contact with infected dogs may be bitten by infected dog fleas, and so contract the disease. Basile (1910–11) and Sangiorgi (1910) state that they found L. infantum parasites in the digestive tract of the dog flea. After searching they found infected dog fleas on the beds, mattresses, and pillows used by children suffering from the disease. Franchini (1912) thinks that Anopheles maculipennis may be concerned in the transmission.
Basile136 tried a number of experiments to show that infantile leishmaniasis is transmitted by fleas, thus:—
(1) Fleas were taken from a healthy dog. They were placed in vessels containing infected spleen-pulp and allowed to feed thereon. The fleas were then killed and dissected, and portions of the gut-contents examined for parasites. The remainder of the gut was emulsified and injected into a young puppy, whose bone-marrow had been shown previously to be uninfected. Basile states that the puppy became infected. The parasites are said to increase in number in the flea’s gut.
(2) Two healthy pups, each a month old, and born in the laboratory, were placed in a disinfected, flea-proof cage. A few days after, an infected dog was placed in the cage, so that fleas from the infected dog could pass on to the puppies. A month later the two pups became infected, parasites being found in them after liver puncture. A number of control puppies from the same litter remained uninfected and in good health.
(3) Basile next used other laboratory-born puppies, a month old. Four of the litter were placed in a disinfected, flea-proof gauze cage in Rome. The cage was isolated from other dogs. Fleas obtained from an infected area in Sicily were placed in the cage. The puppies were examined by hepatic puncture, but were found to be negative for two months. Then two of the puppies showed infection, and six days later the remaining two puppies were found to be infected, and all four died. They showed irregular temperatures, and were getting thin. Control puppies remained healthy.
From these experiments Basile concludes that fleas transmit leishmaniasis. However, Basile did not exclude the possible occurrence of natural herpetomonads in the gut of the fleas.137 Herpetomonas ctenocephali is known to occur in the gut of Ctenocephalus canis. A natural Herpetomonas is also known in the gut of Pulex irritans, as well as a Crithidia (C. pulicis, Porter). These natural flagellates of the fleas pass through non-flagellate stages, like the Leishman-Donovan body. In consequence Wenyon and Patton, among others, have criticized Basile’s results. Further, other investigators, such as Wenyon and Da Silva (1913), have repeated Basile’s flea experiments and been unable to confirm them.
In feeding and inoculation experiments the incubation period of the parasite may be long, and so it is necessary to wait a long time to see whether the parasite will develop.
Immunity.—Nicolle has tried some experiments with L. infantum and L. tropica. He finds that in animals recovery from an attack of the former confers immunity against infection by the latter and vice-versâ.
Laveran138 records that a monkey having an immunity against L. infantum was also immune to L. donovani.
As mentioned on p. 103, Laveran and Franchini (1913), working in Paris, have succeeded in inoculating Herpetomonas ctenocephali, a natural flagellate in the gut of the flea, Ctenocephalus canis, into white mice. Leishmaniform stages of the flea flagellate were recovered from the peritoneal exudate, blood and organs of the mice some weeks after inoculation. The parasites may also be conveyed by way of the digestive tract of the vertebrate. Similar experiments have succeeded with H. pattoni. These experiments go to show, together with those of Fantham and Porter with H. jaculum (see p. 104), that, in the words of the latter authors, “it may be expected that the various leishmaniases, occurring in different parts of the world, will prove to be insect-borne herpetomoniases.”
Genus. Histoplasma, Darling, 1906.
Under the name Histoplasma capsulatum,139 Darling described small round or oval parasites, enclosed in a refractile capsule, and each containing a single nucleus. The bodies were found in cases of splenomegaly in Panama. They occurred in the endothelial cells of the small blood-vessels of the liver, spleen, lungs, intestine and lymphatic glands, and also within the leucocytes. A few flagellates were stated to occur in the lungs. The parasite has usually been placed near Leishmania, but recently Rocha-Lima has stated that Histoplasma is a yeast.
Genus. Toxoplasma, Nicolle and Manceaux, 1908.
The genus was created for crescentic, oval or reniform parasites, 2·5 µ to 6 µ by 2 µ to 3 µ, possessing a single nucleus and multiplying by binary fission. They occur in mononuclear and polymorphonuclear cells in the blood, spleen, liver, peritoneum etc. (fig. 51). The parasites have been found in the gondi, dog, rabbit, mole, mouse, pigeon and other birds. Although various species names have been given to the parasites in these hosts, it seems probable, from cross infection experiments, that there is but one species with several physiological races. Splendore140 (1913) has described a flagellate stage.
Fig. 51.—Toxoplasma gondii, endocellular or free in the peritoneal exudate of infected mice. 1, 2, mononuclear leucocytes containing toxoplasms. 3, polynuclear, containing parasites. 4, 5, 6, endothelial cells containing toxoplasms, agglomerated in 6. 7, agglomeration forms. 8–11, free forms. 12–13, division stages. × 1,600. (After Laveran and Marullaz.)
Fig. 52.—Toxoplasma pyrogenes. 1, body found in blood. 2–7, bodies found
in spleen. [1 is about the size of a red blood corpuscle, as drawn in the figures]. Magnification not stated. (After Castellani.)]
Castellani (1913–14)141 has described similar parasites from a case of splenomegaly, with fever of long standing, in a Sinhalese boy. The bodies were found in the spleen and more rarely in the blood (fig. 52). Castellani has named them Toxoplasma pyrogenes. Further researches are needed.
THE SPIROCHÆTES.
The Spirochætes are long, narrow, wavy, thread-like organisms, with a firm yet flexible outer covering or periplast. There is a diffuse nucleus internally in the form of bars or rodlets of chromatin distributed along the body. In some forms there is a membrane or crista present (fig. 53), which in the past was compared with the undulating membrane of a trypanosome, but the membrane of a spirochæte does not undulate. Progression is very rapid, corkscrew-like and undulatory movements occurring simultaneously.
The genus Spirochæta was founded by Ehrenberg in 1833 for an organism which he discovered in stagnant water in Berlin. Ehrenberg named the organism Spirochæta plicatilis. According to Zuelzer (1912) S. plicatilis does not possess a membrane or crista, but an axial filament. S. gigantea has been described by Warming from sea-water.