Declines in large wildlife increase landscape-level prevalence of rodent-borne disease in Africa.
Populations of large wildlife are declining on local and global scales. The impacts of this pulse of size-selective defaunation include cascading changes to smaller animals, particularly rodents, and alteration of many ecosystem processes and services, potentially involving changes to prevalence and transmission of zoonotic disease. Understanding linkages between biodiversity loss and zoonotic disease is important for both public health and nature conservation programs, and has been a source of much recent scientific debate. In the case of rodent-borne zoonoses, there is strong conceptual support, but limited empirical evidence, for the hypothesis that defaunation, the loss of large wildlife, increases zoonotic disease risk by directly or indirectly releasing controls on rodent density. We tested this hypothesis by experimentally excluding large wildlife from a savanna ecosystem in East Africa, and examining changes in prevalence and abundance of Bartonella spp. infection in rodents and their flea vectors. We found no effect of wildlife removal on per capita prevalence of Bartonella infection in either rodents or fleas. However, because rodent and, consequently, flea abundance doubled following experimental defaunation, the density of infected hosts and infected fleas was roughly twofold higher in sites where large wildlife was absent. Thus, defaunation represents an elevated risk in Bartonella transmission to humans (bartonellosis). Our results (i) provide experimental evidence of large wildlife defaunation increasing landscape-level disease prevalence, (ii) highlight the importance of susceptible host regulation pathways and host/vector density responses in biodiversity-disease relationships, and (iii) suggest that rodent-borne disease responses to large wildlife loss may represent an important context where this relationship is largely negative.
Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106;Department of Biology andDivision of Mammals, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013;
Hillary S
HS
Young
Department of Biology and rdirzo@stanford.edu.
Rodolfo
R
Dirzo
Division of Mammals, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013;
Kristofer M
KM
Helgen
Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106;Department of Biology and.
Douglas J
DJ
McCauley
Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521; rdirzo@stanford.edu.
Sarah A
SA
Billeter
Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521;
Michael Y
MY
Kosoy
Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521;
Lynn M
LM
Osikowicz
Department of Biology, Colorado Sate University, Fort Collins, CO 80523;Woods Institute for the Environment, Stanford University, Stanford, CA 94305;
Daniel J
DJ
Salkeld
Department of Plant Sciences, University of California, Davis, CA 95616; and.
Truman P
TP
Young
Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, NY 14260.
Katharina
K
Dittmar
D000351:Africa, Eastern / Q000453:epidemiology; D000818:Animals; D000835:Animals, Wild / Q000382:microbiology / Q000469:parasitology*; D001474:Bartonella Infections / Q000453:epidemiology* / Q000635:transmission; D044822:Biodiversity; D017753:Ecosystem; D058267:Flea Infestations / Q000453:epidemiology* / Q000635:transmission; D006801:Humans; D007630:Kenya / Q000453:epidemiology; D010373:Lice Infestations / Q000453:epidemiology* / Q000635:transmission; D015995:Prevalence; D012307:Risk Factors; D012376:Rodent Diseases / Q000453:epidemiology*; D012377:Rodentia / Q000382:microbiology / Q000469:parasitology*; D058260:Xenopsylla; D015047:Zoonoses / Q000453:epidemiology
Kenya; dilution effect