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Parasitaemia in mice inoculated with T. cruzi at different ages
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TRYPANOSOMIASIS SEMINAR
To enable further study of these phenomena, isolations of trypanosomes obtained from the cow at different times of the year, together with clone populations grown on blood agar, have been stored at --79°C. Comparisons of these populations are being made by quantitative and qualitative studies both on blood agar slopes at 28°C. and leucocyte monolayers at 37°C. and also by electron microscopy. The
attachment
of
Trypanosoma lewisi i n the r e c t u m Nosopsyllus fasciatus D. H. MOLYNEUX
of
its
vector
flea
Liverpool School of Tropical Medicine In the continually active gut of the flea, trypanosomes must remain in position if they are to survive. The epimastigote trypanosomes of T. lewisi in the rectum act as a source of infective metatrypanosomes. Two types of epimastigote forms are classically recognized, the sessile haptomonad forms, and the nectomonad epimastigotes capable of movement. The short flagellum of the haptomonad epimastigote has an increased intraflagellar area. The flagellar membrane of these epimastigotes forms a junctional complex of the zonula adherens type with the cuticle of the rectal wall. The flagellum of the haptomonad epimastigotes and the parasites themselves may become wedged between the highly folded wall of the rectum. The flagellum of the nectomonad epimastigote is long and does not have an increased intraflagellar area. The flagella of these forms penetrate deeply between the folds of the rectal wall. The parasites remain associated with each other by their flagella. Groups of flagella aggregate together. The axonemes produced during division are retained within the parent flagellar membrane; the delayed division of the flagellar membrane results in up to 4 axonemes being found within a single flagellar membrane. The parasites accumulate together in masses in the lumen of the rectum and their surfaces interdigitate, with the result that the masses of parasites are retained together. P a r a s i t a e m i a i n m i c e i n o c u l a t e d w i t h T. c r u z / a t d i f f e r e n t ages
B. FISTEIN Department of Biology, University of Salford During the course of experimental studies on the host-parasite relation in infections with Trypanosoma cruzi the effects of age at the time of initial infection on the intensity and course of parasitaemia were measured. Albino mice were inoculated at different ages wkh a single dose of a culture of the relatively non-virulent PG41 Trinidad strain, and absolute counts were made serially of parasites.in peripheral blood. In mice inoculated when 2 days old, parasites appeared in appreciable numbers in the peripheral blood 7 days after infection and quickly rose to a peak at about the 17th day, when the animals were moribund with more than 104 parasites per c.mm. In mice older at the time of inoculation the parasitaemia appeared later, and was less intense, and more animals survived; approximately half of the animals inoculated when 9 days old survived. Adult mice infected with this strain of T. cruzi remained apparently healthy, and showed a barely detectable and irregular parasitaemia. The parasitaemia in the younger mice which survived the infection tended to show an irregular periodicity of about 10 days. These results can be used to make a model for infection. If a group of animals born at the same time are exposed to infection, but happen to be infected at different times, then' the community will have a high parasitaemia at the age of 20 days.
TRYPANOSOMIASIS SEMINAR
To enable further study of these phenomena, isolations of trypanosomes obtained from the cow at different times of the year, together with clone populations grown on blood agar, have been stored at --79°C. Comparisons of these populations are being made by quantitative and qualitative studies both on blood agar slopes at 28°C. and leucocyte monolayers at 37°C. and also by electron microscopy. The
attachment
of
Trypanosoma lewisi i n the r e c t u m Nosopsyllus fasciatus D. H. MOLYNEUX
of
its
vector
flea
Liverpool School of Tropical Medicine In the continually active gut of the flea, trypanosomes must remain in position if they are to survive. The epimastigote trypanosomes of T. lewisi in the rectum act as a source of infective metatrypanosomes. Two types of epimastigote forms are classically recognized, the sessile haptomonad forms, and the nectomonad epimastigotes capable of movement. The short flagellum of the haptomonad epimastigote has an increased intraflagellar area. The flagellar membrane of these epimastigotes forms a junctional complex of the zonula adherens type with the cuticle of the rectal wall. The flagellum of the haptomonad epimastigotes and the parasites themselves may become wedged between the highly folded wall of the rectum. The flagellum of the nectomonad epimastigote is long and does not have an increased intraflagellar area. The flagella of these forms penetrate deeply between the folds of the rectal wall. The parasites remain associated with each other by their flagella. Groups of flagella aggregate together. The axonemes produced during division are retained within the parent flagellar membrane; the delayed division of the flagellar membrane results in up to 4 axonemes being found within a single flagellar membrane. The parasites accumulate together in masses in the lumen of the rectum and their surfaces interdigitate, with the result that the masses of parasites are retained together. P a r a s i t a e m i a i n m i c e i n o c u l a t e d w i t h T. c r u z / a t d i f f e r e n t ages
B. FISTEIN Department of Biology, University of Salford During the course of experimental studies on the host-parasite relation in infections with Trypanosoma cruzi the effects of age at the time of initial infection on the intensity and course of parasitaemia were measured. Albino mice were inoculated at different ages wkh a single dose of a culture of the relatively non-virulent PG41 Trinidad strain, and absolute counts were made serially of parasites.in peripheral blood. In mice inoculated when 2 days old, parasites appeared in appreciable numbers in the peripheral blood 7 days after infection and quickly rose to a peak at about the 17th day, when the animals were moribund with more than 104 parasites per c.mm. In mice older at the time of inoculation the parasitaemia appeared later, and was less intense, and more animals survived; approximately half of the animals inoculated when 9 days old survived. Adult mice infected with this strain of T. cruzi remained apparently healthy, and showed a barely detectable and irregular parasitaemia. The parasitaemia in the younger mice which survived the infection tended to show an irregular periodicity of about 10 days. These results can be used to make a model for infection. If a group of animals born at the same time are exposed to infection, but happen to be infected at different times, then' the community will have a high parasitaemia at the age of 20 days.