The Animal Parasites of Man. Max Braun

Чтение книги онлайн.

СКАЧАТЬ On the other hand, the illustrations of E. tetragena show that the authors have been dealing with the small generation or reduced forms (“E. minuta”), which are the direct descendants of the large trophozoites. If kittens are inoculated rectally with dysenteric material containing large trophozoites, the strain may be carried in successive kittens for four to six transfers. If, on the other hand, kittens are inoculated rectally with small trophozoites of the pre-cyst generation, the transmission cannot be carried through more than one or two kittens. Wenyon has succeeded in maintaining E. tetragena in kittens for several generations.

      In some of the preparations from the last remove, pathological forms of the trophozoites may be seen. These show abnormal forms of budding, especially peripherally, such as have been described by Schaudinn and by Craig as characteristic of E. histolytica. Schaudinn’s small peripheral, exogenous buds and cysts are thus explained. Craig has latterly changed his views.

      Further, Darling states that tetragena cysts fed by the mouth to kittens produce bowel lesions in which trophozoites having the characters of E. tetragena, E. histolytica and E. nipponica (Koidzumi) occur.

      In view of the work of recent observers, the peculiar exogenous encystment which Schaudinn made characteristic of Entamœba histolytica has been shown to be due to degenerative changes in senile races of the amœba. E. histolytica and E. tetragena are one and the same species, and its trophozoite is subject to variation. According to some observers the histolytica type of nucleus—described by Schaudinn as being poor in chromatin and not easily seen in the fresh state—occurs frequently in patients with severe symptoms of dysentery; on the other hand, the tetragena type of nucleus—round and easily seen in the fresh state—may occur in cases presenting slight dysenteric symptoms. Intermediate types of nuclei are seen. The name of this species, the principal pathogenic amœba of man, must then be E. histolytica by priority. The cystic stages of E. histolytica are those first recorded by Viereck and formerly described as E. tetragena. The geographical distribution of E. histolytica is wide.

      Noc’s Entamœba (1909).

      A species of Entamœba was cultivated by Noc26 in 1909 from cysts derived from liver abscesses, from dysenteric stools and from the water supply of Saigon, Cochin China. He cultivated it in association with bacteria. It is pathogenic. It has been considered allied to E. histolytica, and shows internal segmentation or schizogony. It exhibits polymorphism. This amœba has been found by Greig and Wells (1911) in cases of dysentery in India. It is an important organism and requires further investigation.

      Certain other Entamœbæ27 have been described at various times from the intestinal tract of man. Probably most, if not all, of these are not good species and in some cases much more information is needed.

      Entamœba tropicalis (Lesage, 1908). This parasite is said to be non-pathogenic, and to occur in the intestine of man in the tropics. It has a general resemblance to E. coli, but forms small cysts (6 µ to 10 µ in diameter). The nucleus of the cyst is said to break up into a variable number of daughter nuclei, from three to thirteen having been noted. Lesage states that it is culturable in symbiosis with bacteria. It is probably a variety of E. coli, if not a cultural amœba.

      Entamœba hominis (Walker, 1908) has a diameter of 6 µ to 15 µ. A contractile vacuole is present. Encystment is total, and small cysts are formed. It is culturable. The original strain, now lost, was obtained from an autopsy in Boston Hospital. This organism is probably a cultural amœba.

      Entamœba phagocytoides (Gauducheau, 1908). This parasite was discovered in a case of dysentery at Hanoi, Indo-China. The amœba is small, 2 µ to 15 µ in diameter. It is active. It ingests bacteria and red blood corpuscles, while peculiar spirilla-like bodies are found in its cytoplasm. It multiplies by binary and multiple fission. It can be cultivated. More recently (1912) the author appears to consider the amœba to be a stage of a Trichomonas, but abandons the view later (1914). Further researches on this organism are needed.

      Entamœba minuta (Elmassian, 1909)28 was found, in association with E. coli, in a case of chronic dysentery in Paraguay. It resembles E. tetragena but is smaller, rarely exceeding 14 µ in diameter. Schizogony occurs, four merozoites being produced. The encystment is total and endogenous, giving rise to cysts containing four nuclei. This amœba is considered by Darling and others to be the pre-cyst trophozoite stage of E. histolytica (tetragena).

      Entamœba nipponica (Koidzumi, 1909) was found in the motions of Japanese suffering from dysentery or from diarrhœa, in the former case in company with Entamœba histolytica. Its diameter is 15 µ to 30 µ. The endoplasm is phagocytic for red blood corpuscles. The nucleus is well defined, resembling that of E. coli and of E. tetragena. Multiplication occurs by binary fission and by schizogony. Encystment is total, but has not been completely followed. Darling and others consider that this is an abnormal form of E. histolytica, while Akashi (1913) doubts if it is an amœba at all, but rather is to be regarded as shed epithelial cells.

      General Remark.—It is now considered by some workers that true Entamœbæ cannot be cultivated on artificial media. Quite recently Williams and Calkins (1913)29 have somewhat doubted this opinion, and state that certain cultural amœbæ, originally obtained from Musgrave in Manila, exhibit the various morphological variations associated with true entamœbæ of the human digestive tract.

      Entamœba buccalis, Prowazek, 1904.

      The size varies from 6 µ to 32 µ. Ectoplasm is always present; the endoplasm contains numerous food-vacuoles. The nucleus is vesicular, with a greenish tinted membrane which is poor in chromatin. The size of the nucleus is from 1·5 µ to 4·5 µ. A contractile vacuole is not visible. The pseudopodium is broad. It was discovered in the mouths of persons with dental caries at Rovigno and also at Trieste, being most easily found in dense masses of leucocytes, also among leptothrix and spirochæte clusters. It can be easily distinguished from leucocytes by more intense staining with neutral red. Multiplication proceeds by fission. Transmission may take place through the small spherical cysts. This species (fig. 10) has since been observed in Berlin, and is also occasionally found in carcinoma of various regions of the oral cavity. (Leyden and Löwenthal, 1905).

      Fig. 10.—Entamœba buccalis, Prow. a-d, the same specimen observed during five minutes. × 1,000. e, amœba fixed and stained with iron-hæmatoxylin. × 1,500. (After Leyden and Löwenthal.)

      Entamœba buccalis, Prow., is said to be allied to a protozoön which A. Tietze has found either encysted or free in the lumen of the orifice of the parotid gland of an infant aged 4 months. The gland had undergone pathological change, and had therefore been extirpated. The organisms, which were roundish and three to four times the size of the normal epithelial cells of the gland, were without a membrane and possessed a nucleus in which the chromatic substance appeared to be contained in a karyosome. Bass and John’s30 (Feb. 1915) and Smith, Middleton and Barrett (1914) state that E. buccalis is the cause of pyorrhœa alveolaris.

      Entamœba undulans, Aldo Castellani, 1905.

Under this name a protozoön is described which A. Castellani found in addition to Entamœba histolytica and Trichomonas intestinalis in the fæces of an European planter living in Ceylon, who had suffered from amœbic enteritis and liver abscess. The shape of the body was roundish or oval, 25 µ to 30 µ in the greatest diameter. It was without a flagellum, but with an undulating membrane, and capable of protruding a long pseudopodium from different parts of its body at short intervals. The nucleus could not always СКАЧАТЬ