162
ABSTRACTS
Viability of parasitic protozoa after the death of the host. HEGNER, R. (Am.
J. Hyg. 24, p. 309-31 , 1936).
EXACT data on the period of viability of each type of protozoan organism in a dead
host are not available in literature, but they are required for assisting in the diagnosis
of specific infections, in the understanding of immunity reactions and also in the elabora-
tion of effective public health measures. The author has, therefore, carried out experi-
ments to determine the extent to which the customary belief that with the death of
the host the harboured parasites die out, is justified. The usual difficulties in arriving
at diagnosis due to partial or complete disintegration of parasites during the interim
between death and autopsy, as for instance in fatal cases of human dysentery where it
may not be possible to decide whether the original incitant of lesions happened to be
Entamoeba histolytica or Balantidium coli, and also the possibility of the histological study
of the host-parasite relationship being vitiated due to the migratory and penetrative
action of parasites in dead tissues, as may happen in amoebiasis, have been mentioned.
The mode of infection with human sarcocysts and with blood-inhabiting protozoa and
the infectivity of parasites lodged in the host's tissues or when voided outside the animal
body have been discussed. The contradictory results obtained in autopsical survey
of intestinal protozoa of man carried out by previous workers have been mentioned.
Hegner's studies were restricted to protozoa in laboratory animals, including intes-
tinal protozoa of rats, guinea pigs and frogs, malaria parasites in birds, and trypanosomes
in rats. However, as the author points out, the experimental methods adopted by him
are equally applicable in experiments with larger animals.
Faecal smears from small animals having been found to be positive for trichomonad
flagellates, the animals were killed by cervical shock. The caecum was withdrawn through
an abdominal slit, and portions of the caecal contents extracted at varying times. A
faecal pellet culture method was adopted, and its result controlled by direct cover-slip
preparations from the caecal contents. Each time a portion of the material was planted
into 1 to 3 culture tubes, and the tubes were tested at the end of three days, and the
caecal material was examined first every 3 hours and later at 24 hours' interval. A
counting method was used in the case of Balantidial cysts. Trichomonad flagellates
remained alive and multiplied on transference to suitable media, after being in the caecum
of a dead rat at 37°C. for 24 hours, at room temperature for 4 days, and at 5°C. for 13
days. Balantidial trophozoites were viable in the caecum of dead guinea pigs at room
temperature or refrigerator for at least 4 days. Pig Balantidia when kept in Ringer's
solution were viable at room temperature for 6 days. Intestinal protozoa of frogs,
Nyctotherus, Opalina, Trichomonas and Hexamita were found to live up to 20 days in dead
frogs. The ciliates were apparently less resistant than flagellates. Plasmodium cathe¬
merium in canaries is capable of infecting after the bird has been dead for 2 days, and
Trypanosoma lewisi remained alive in the body of dead rats at room temperature for
3 days, and at 5°C. for 10 days. The parasites in a dead rat kept at 5°C. were capable
of infecting clean rats after 9 days. Further the author attempted to demonstrate
the failure of the trypanocidal antibody to appear at the peak of infection in dead rats.
[S. C. A. D.].