The influence of social structure, habitat, and host traits on the transmission of Escherichia coli in wild elephants.
Social structure is proposed to influence the transmission of both directly and environmentally transmitted infectious agents. However in natural populations, many other factors also influence transmission, including variation in individual susceptibility and aspects of the environment that promote or inhibit exposure to infection. We used a population genetic approach to investigate the effects of social structure, environment, and host traits on the transmission of Escherichia coli infecting two populations of wild elephants: one in Amboseli National Park and another in Samburu National Reserve, Kenya. If E. coli transmission is strongly influenced by elephant social structure, E. coli infecting elephants from the same social group should be genetically more similar than E. coli sampled from members of different social groups. However, we found no support for this prediction. Instead, E. coli was panmictic across social groups, and transmission patterns were largely dominated by habitat and host traits. For instance, habitat overlap between elephant social groups predicted E. coli genetic similarity, but only in the relatively drier habitat of Samburu, and not in Amboseli, where the habitat contains large, permanent swamps. In terms of host traits, adult males were infected with more diverse haplotypes, and males were slightly more likely to harbor strains with higher pathogenic potential, as compared to adult females. In addition, elephants from similar birth cohorts were infected with genetically more similar E. coli than elephants more disparate in age. This age-structured transmission may be driven by temporal shifts in genetic structure of E. coli in the environment and the effects of age on bacterial colonization. Together, our results support the idea that, in elephants, social structure often will not exhibit strong effects on the transmission of generalist, fecal-oral transmitted bacteria. We discuss our results in the context of social, environmental, and host-related factors that influence transmission patterns.
Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America.
Patrick I
PI
Chiyo
Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America.
Laura E
LE
Grieneisen
Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, Colorado, United States of America; Save the Elephants, Nairobi, Kenya.
George
G
Wittemyer
Amboseli Trust for Elephants, Langata, Nairobi, Kenya.
Cynthia J
CJ
Moss
Amboseli Trust for Elephants, Langata, Nairobi, Kenya; Behaviour and Evolution Research Group, Department of Psychology, University of Stirling, Scotland, United Kingdom.
Phyllis C
PC
Lee
Save the Elephants, Nairobi, Kenya.
Iain
I
Douglas-Hamilton
Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America.
Elizabeth A
EA
Archie
D000818:Animals; D000835:Animals, Wild; D004269:DNA, Bacterial / Q000032:analysis / Q000302:isolation & purification; D017753:Ecosystem; D004606:Elephants / Q000382:microbiology* / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics; D004927:Escherichia coli Infections / Q000382:microbiology / Q000635:transmission* / Q000662:veterinary; D005260:Female; D051456:Gene Flow; D014644:Genetic Variation; D006239:Haplotypes; D006608:Hierarchy, Social; D058507:Host Specificity; D007630:Kenya; D008297:Male
D004269:DNA, Bacterial