THE EFFECT OF INFECTION WITH SCHISTOSOMA-MARGREBOWIEI ON THE GROWTH OF BULINUS-NATALENSIS

Three age groups of Bulinus natalensis, immature, mature but not yet e gg-laying and mature egg-laying, were infected with miracidia of Schis tosoma margrebowiei. The growth of infected, exposed but showing no si gns of infection, and uninfected control groups, were examined at week ly intervals for ten weeks post exposure. Snails exposed to infection when immature, even in the group where no patent development ensued, s howed a statistically significant reduction in growth and this was evi dent as early as 2-5 weeks post exposure. When infection occurred at t he stage prior to egg-laying a significant reduction in growth was see n but only in the group which developed a patent infection. This was a lso the case for the egg-laying group although the reduction in growth was only significant in the final three weeks of the experiment, Thus in all three age groups, growth rate was reduced and the infected sna ils were significantly smaller at the end of ten weeks compared with t he controls. The reasons for these effects are discussed.