Figure 8
Analysis of density of trypanosomes in salivary glands. Histograms comparing the proportion of the salivary gland occupied by trypanosomes in infections with single or both red and green strains. A total of 63 glands from 41 individual flies were analysed, comprising 27 glands with only green trypanosomes, 11 glands with only red trypanosomes and 25 glands with a mixed infection. Bars show geometric means and geometric standard errors. (A) Proportion of the gland occupied by trypanosomes in single infections compared to mixed infections. There were significantly more trypanosomes present in glands containing the green strain compared to the red strain, and significantly more trypanosomes present in glands with mixed compared to single infections. (B) Comparison of salivary glands dissected at different timepoints shows that trypanosomes became more dense in glands with a mixed infection compared to a single strain infection after 3 weeks duration of infection. (C) Proportion of the gland occupied by the same trypanosome strain in a single compared to a mixed infection. There were significantly more trypanosomes of the red strain present in glands containing the green trypanosome strain as well; the converse was not true for the green strain. (D) Comparison of salivary glands dissected at different timepoints shows that this effect became pronounced for the red strain from 2 weeks duration of infection.