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0Percentage/antibody titreMean oocyst intensitySex ratioSex ratio1234 56
Day of infection1234 56
Day of infection(a)(b)Fig. 10.3. (a) Parasite, haematological and immunological parameters during the course of
a single infection ofPlasmodium gallinaceumin its chicken host. Gametocyte sex ratio (open
bars), % of red blood cells which are reticulocytes, indicating erythropoiesis (n), agglutinating
antibody titre (s), parasitaemia (percentage of red blood cells infected) (+). (Data adapted
from Carteret al., 1979, and Paulet al., 2000). (b). Comparison of observed (solid bars) and
expected (open bars) parasite oocyst loads in mosquitoes under observed (line) and fixed
female-biased (4 : 1) sex ratios during the course of aPlasmodium gallinaceuminfection in
its chicken host. Observed infection loads are based on the oocyst density from 30 mosqui-
toes gorged on the infected chicken each day. Expected values are estimated as follows. By
inputting the observed mean oocyst loads into the fertilization model (details in Paulet al.,
1999a), the number of effective male gametes produced per male gametocyte (i.e. resulting
from the negative effect of the agglutinating antibody on male efficacy) can be calculated for
the observed gametocytaemias and sex ratio. Then, changing only the gametocyte sex ratio
to a constant 4 : 1, the model will produce the new expected mean oocyst loads.