The Animal Parasites of Man. Max Braun
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Название: The Animal Parasites of Man
Автор: Max Braun
Издательство: Bookwire
Жанр: Медицина
isbn: 4057664648037
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(3) T. lewisi from the blood of a rat when transferred to a snake seems largely to disappear, as very few flagellates are seen. When blood from the snake is inoculated into a clean rat, then trypanosomes reappear in the rat, but they are not all like those originally inoculated. It seems certain that, in such a case, changes in form and virulence of the trypanosome have occurred. Similar experiments were made with T. brucei from rats to adders and other animals and back to rats. Changes in the form and virulence of T. brucei occurred.
These interesting experiments were performed by Wendelstadt and Fellmer.114
Genus. Herpetomonas, Saville Kent, 1881.
Herpetomonas is a generic name for certain flagellates possessing a vermiform or snake-like body, a nucleus placed approximately centrally, and a blepharoplast (kinetic nucleus) near the flagellar end. There is no undulating membrane (fig. 49, a). The organisms included in this genus certainly possess one flagellum, while according to Prowazek (1904) Herpetomonas muscæ-domesticæ, the type species, possesses two flagella united by a membrane. Patton,115 Porter116 and others affirm, however, that the biflagellate character of H. muscæ-domesticæ (from the gut of the house-fly) is merely due to precocious division. The matter is further complicated by the generic name Leptomonas, given by Kent in 1881, to an uniflagellate organism found by Bütschli in the intestine of the Nematode worm, Trilobus gracilis. This parasite, Leptomonas bütschlii, has not yet been completely studied. Until these controversial points relating to the identity or separation of Herpetomonas and Leptomonas have been satisfactorily settled, we may retain the better known name Herpetomonas for such uniflagellate, vermiform organisms. However, the name Leptomonas, having been used by Kent two pages earlier in his book (“Manual of the Infusoria”) than Herpetomonas, would have priority if the two generic names were ultimately shown to be synonymous.
A full discussion of these interesting and important flagellates hardly comes within the purview of the present work; brief mention can only be given here to certain species.
The Herpetomonads occur principally in the digestive tracts of insects, such as Diptera and Hemiptera. They are also known in the guts of fleas and lice, but are not confined to blood-sucking insects. One example, H. ctenocephali (Fantham, 1912)117 occurs in the digestive tracts of dog fleas, Ctenocephalus canis, in England, France, Germany, Italy, India, Tunis, etc. It is a natural flagellate of the flea, and might easily be confused with stages of blood parasites in the gut of the dog flea. Dog fleas are stated by Basile to transmit canine kala-azar, which is believed to be the same as human infantile kala-azar. Confusion is further likely to arise since herpetomonads pass through pre-flagellate, flagellate and post-flagellate or encysted stages; pre- and post-flagellate stages being oval or rounded and Leishmania-like. The post-flagellate stages are shed in the fæces, and are the cross-infective stages by means of which new hosts are infected by the mouth. The possible presence of such natural flagellates must always be considered when experimenting with fleas, lice, mosquitoes, etc., as possible vectors of pathogenic flagellates like Leishmania and Trypanosoma. H. pediculi (Fantham, 1912) occurs in human body lice.118 See further remarks on pp. 107, 112.
Fig. 49.—a, Herpetomonas; b, Crithidia; c, Trypanosoma. (After Porter.)
Laveran and Franchini (1913–14)119 have recently succeeded in inoculating Herpetomonas ctenocephali, from the gut of the dog flea, intraperitoneally into white mice, and producing an experimental leishmaniasis in the mice. A dog was also infected. They have also succeeded in infecting mice with H. pattoni—a natural flagellate of the rat flea—by mixing infected rat fleas with the food of the mice, and by causing them to ingest infected fæces of rat fleas. Further, they have shown that infection with the herpetomonas occurs naturally by this method, that is, by the rodents eating the fleas and not by the insects inoculating the flagellates into the vertebrates when sucking blood. These experiments shed an interesting light on the probable origin of Leishmania and its cultural herpetomonad stage, which were very probably once parasitic flagellates in the gut of an insect.
Fantham and Porter120 (1914–15) have shown that young mice may be inoculated or fed with Herpetomonas jaculum, from the gut of the Hemipteran, Nepa cinerea (the so-called “water-scorpion”), with fatal results. The pathogenic effects are like those of kala-azar. They also showed that the post-flagellate stages of the herpetomonads seemed most capable of developing in the vertebrate.
A herpetomonad, H. davidi, has been found in the latex of species of the plant-genus Euphorbia in Mauritius, India, Portugal, etc. It is apparently transmitted to the plants by Hemiptera. The plants sometimes suffer from “flagellosis.”
Franchini (1913)121 has described a new parasite, Hæmocystozoon brasiliense, from the blood of a man who had lived in Brazil for many years. It possesses flagellate and rounded stages, and is closely allied to the herpetomonads.
Genus. Crithidia, Léger, 1902, emend. Patton, 1908.
Crithidia is the generic name of vermiform flagellates with a central nucleus, a blepharoplast or kinetic nucleus in the neighbourhood of the principal nucleus, and a rudimentary undulating membrane bordered by a flagellum arising from a basal granule, which is the centrosome of the kinetic nucleus (fig. 49b). The anterior or flagellar end of the body is attenuated and fades off as the undulating membrane.
Crithidia fasciculata, the type species, was found by Léger in the alimentary canal of Anopheles maculipennis. Crithidia occur in bugs, flies, fleas,122 and ticks. Some of them are found in the body-fluid of the invertebrate host as well as in the gut. Others may be restricted to the body cavity or intestine respectively. C. melophagia from the sheep-ked, Melophagus ovinus, and C. hyalommæ from the hæmocœlic fluid of the tick, Hyalomma ægyptium, pass into the ovaries and eggs of their hosts, and the young keds or ticks are born infected.
C. fasciculata has been shown by Laveran and Franchini to be inoculable into white mice, producing a sort of experimental leishmaniasis therein. In one case cutaneous lesions were produced like those of Oriental sore.
Crithidia are natural flagellates of Arthropoda, with their own pre-flagellate, flagellate and post-flagellate stages, and must not be confused with transitory crithidial stages of trypanosomes.
Genus. Leishmania, Ross, 1903.
With an oval body containing nucleus and blepharoplast (kinetic nucleus) but no flagellum. An intracellular parasite in the vertebrate host.
Included in the genus Leishmania are three species, namely:—
(1) Leishmania donovani, Laveran and Mesnil, 1903, the parasite of Indian kala-azar, a generalized systemic disease, usually fatal, occurring in subjects of all ages.
(2) Leishmania tropica, Wright, 1903, the parasite of Delhi boil, Oriental СКАЧАТЬ