Analysis of the community composition and interactions of invertebrate predators within schistosome-infected temporary and permanent waterbodies in Tanzania Restricted; Files Only

Abstract

Community context is an important factor in understanding the ecology of infectious diseases. Hosts and parasites do not exist in isolation, and their interactions can be influenced by the other species in the communities where they reside. 

Biocontrol of human parasites, such as schistosomes, has been attempted using predators/competitors of either wildlife reservoir hosts or disease vectors with variable success. Frequently, these attempts have introduced new species into disease transmission sites, rather than using species normally found at these locations. Current thinking in ecology is that disrupting an environment by introducing non-native species can have unintended, and potentially seriously negative, consequences. Therefore, we sought to evaluate potential predators that naturally co-occur with the snails that are schistosome hosts and if snail size/infection status affected their predation. We conducted a field survey around Mwanza, Tanzania, focusing on the parasite Schistosoma haematobium, its freshwater snail host Bulinus nasutus, and the broader macroinvertebrate communities in waterbodies identified by rural communities as potential transmission sites. We found that two distinct macroinvertebrate communities varied over space and time, one dominated by dragonflies, damselflies, water bugs, and diving beetles, and the other dominated by crabs and backswimmers. Whether the waterbodies dried in the previous year explained a significant amount of variation in abundance for several taxa. We then found that snails were significantly larger and more likely to be infected in communities dominated by the invertebrate backswimmer insect Notonectidae and water boatman insect Corixidae; two unconfirmed predators of snails. These patterns suggest natural macroinvertebrate predators could influence schistosome transmission, and a deeper understanding of the factors that influence their abundance and their resulting effects on transmission potential could improve predictions and interventions for schistosomiasis in this region.

Table of Contents

Table of Contents

Introduction………………………………………………….………………..1

Methods………………………………………………….…………...……….5

Field Study……………………………………………………….….......……5

Laboratory processing and trials……………………………...…….……...6

Digital data collection……………………………………………….………..6

Multivariate analysis of community composition……………….……….…7

Correlating community composition with snail size and infections…...…9

Results……………………………………………………..…………..……..11

Predation trials……………………………………………………..….……..11

Dynamics of raw counts of invertebrates……………………...…………..11

Community composition…………………………………………………......11

Correlating community composition with snail size and infections…..….12

Discussion……………………………………………………………….…….13

Tables…………………………………………………………………..………16

Table 1……………………………………………………………………..…..16

Table 2a………………………………………………………………..………18

Table 2b……………………………………………………………..…………18

Table 2c……………………………………………………………..…………18

Table 2d……………………………………………………………..…………19

Table 2e……………………………………………………………..…………19

Figures………………………………………………………………………….20

Figure 1…………………………………………………………………………20

Figure 2…………………………………………………………………………21

Figure 3…………………………………………………………………………22

Figure 4a………………………………………………………………………..23

Figure 4b………………………………………………………………………..24

Figure 5……………………………………………………………….….……..25

Figure 6……………………………………………………………….….……..26

Figure 7…………………………………………………………….….………..27

References……………………………………………………………..……….28

About this Honors Thesis

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School	Emory College
Department	Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Biology, Parasitology Biology, Ecology
Keyword	Predators Disease dynamics Schistosomiasis Invertebrate communities
Committee Chair / Thesis Advisor	Civitello, David, Emory University
Committee Members	Vazquez-Prokopec, Gonzalo, Emory University L'Hernault, Steven, Emory University

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