Figure 1.
Inferring the transmission process from patterns of parasite genetic variation among hosts.
Circles represent individual definitive hosts. Colors within circles are different parasite genetic variants. Dashed and solid arrows indicate limited and major paths of recruitment for parasite offspring into definitive hosts, respectively. Four generations (rows) of adult parasites are illustrated. (A) Parasite genetic variation is randomly distributed among hosts with a high amount of mixing among parasite offspring before recruitment into definitive hosts. This pattern indicates that hosts are randomly sampling from a common infectious pool of parasites. (B) Low mixing of parasite offspring (i.e., clumped transmission) predicts high genetic differentiation among individual hosts. This pattern indicates that hosts are sampling distinct infectious pools.
Figure 2.
Distribution of A. lumbricoides genetic clusters in Jiri, Nepal.
Each bar is a house and the height is the number of genotyped worms from that house. Colors within each house show the proportion of worms from the 13 core genetic clusters identified by structure. The latter was generated by summing the Q-values of individual worms within houses. (A) The geographic location of each house is illustrated over the landscape of the village. (B) The same information as in (A) but is linear to show full coloration of each house. (C) Displays the houses that could be tested for changes in parasite genetic composition over the two temporal samples (∼3 years apart). After correction for multiple comparisons, no household showed a significant change in parasite genetic composition. As an example to illustrate the house effect, house #97 had 59 genotyped worms (B), 22 and 37 from the two temporal samples (C). House 97 consisted of 77% of the pink genetic cluster and accounted for over 85% of the pink cluster in all the data. These results were obtained with k set to 15. Figure S4 shows the distribution of genetic clusters for k = 5.
Table 1.
Results of the non-parametric multivariate analysis of variance with different distance matrices used as the dependent variable.
Figure 3.
Spatial autocorrelation analysis showing nearby houses share genetically related parasites.
Distance classes up to 540 m show higher parasite genetic similarity compared to values generated from random allocation of households among geographic locations (95% upper and lower confidence values). This result was also found when a single parasite was sampled from each household (Fig. S5), demonstrating that this result is not driven by a small number of heavily infected households.