Table 1.

Spillover barriers and associated conventional and ecological interventions that target each barrier layer.

location	spillover barrier	conventional intervention	ecological intervention	examples of ecological interventions	status	intervention no. (figure)
zoonotic reservoir	reservoir density or distribution	fences, culling	habitat modification	altered food distribution on elk feeding grounds to reduce brucellosis [3].	demonstrated, with correlational/observational support	1
			natural enemies	maintenance of leopard populations to limit rabid feral dog populations [4]. See also [5].	hypothesized	2
	pathogen prevalence (in reservoir)	chemotherapy, vaccination of reservoir, test and remove	dilution hosts	increased diversity of host community for Ixodes ticks (e.g. by increasing size of forest fragments) may increase abundance of incompetent hosts for Borrelia burgdorferi, reducing Lyme disease spillover [6].	demonstrated, but generality of dilution effect of increased biodiversity is debated [7–9]	3
			genetic management	reducing population size and stay-time of poultry in markets minimizes prevalence and genome reassortment of influenza viruses [10].	demonstrated	4
	infection intensity or pathogen shedding		reservoir nutrition and susceptibility	supplementing key flowering tree food resources for flying foxes (via habitat conservation/restoration) to boost nutrition and immunity in bats and decrease viral shedding rates of Hendra by bats [11], or similarly preserving native prey communities for vampire bats (rabies) via habitat conservation/restoration, which also encourages bats to feed on wildlife rather than humans or livestock. See also [12].	hypothesized	5
environment	pathogen survival and spread	insecticides, disinfection	habitat modification	Anopheles (malaria) [13] and Culex (West Nile virus, Japanese encephalitis, St Louis encephalitis, also filariasis) mosquito reductions by fish additions to rice fields, while simultaneously increasing rice yields [14].	hypothesized	6
			gene management	gene drive in Anopheles gambiae to control spread of Plasmodium spp. causing malaria [15].	demonstrated	7
			natural enemies	maintaining the scavenger community (e.g. eagles and coyotes in the USA, vultures in India [16]) as an important consumer of carcasses that harbour Brucella, anthrax, and other pathogens. See also [17].	demonstrated, with correlational/observational support	8
spillover host	spillover host exposure	chemical repellents, biosecurity	human behaviour modification	bamboo skirts over date palm sap collection pots to reduce bat contamination of sap with Nipah virus in Bangladesh [18,19]. See also [20].	demonstrated	9
	spillover host susceptibility and infection	chemotherapy, vaccination	managing coinfections or microbiome, genetic management	the use of faecal transplant procedures to treat Clostridium difficile with microbial competitors [21].	demonstrated	no corresponding number in figure