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Chapter

35

Disease Transmission at the Interface between

Wild and Domestic Suiform Species in the Old

and New Worlds

Ferran Jori, Ariane Payne, Richard Kock, Alessandra Nava, Karl Ståhl, and Sophie Rossi

This chapter provides a review of the most important infectious

and parasitic diseases (and their associated pathogens) reported

in pig-like species worldwide. Many of these pathogens can

have an impact on pig production, human health (in the case of

zoonotic diseases), and the conservation of pig populations. In

addition, the chapter also gives an overview of some reported

case studies of pathogen transmission between sympatric pig-

like species and reviews the main methods currently used to

assess interactions between them, such as telemetry, camera

traps, collection of traditional knowledge, or the use of bio-

markers. The amount of knowledge gaps on the ecology and

epidemiology of infectious pathogens affecting these species is

very significant. Improving this state of knowledge should be a

challenge for future research that can have benefits for disease

control but also benefit the conservation of the many endan-

gered pig species which are becoming increasingly vulnerable.

Introduction

Wild and domestic animal interactions have received increas-

ing attention in the last decade, especially due to the emergence

of infectious diseases linked with wildlife which could have a

massive impact on human health such as avian influenza or

Ebola. Many of these interactions are facilitated by interactions

between phylogenetically closely related species such as wild

birds and poultry, or wild and domestic ruminants (Wiethoelter

et al. 2015). From that perspective and considering the phylo-

genetic proximity between domestic pig (DP) and many wild

pig species, it could be expected that a wide range of pathogens

could be shared between suiform species sharing the same envi-

ronment. Currently, there is abundant information published

on shared diseases between different varieties of Sus scrofa (wild

boars, feral pigs) and some studies have recently analysed the

ways in which these species interact and are likely to affect DP

or human health (in the case of zoonotic diseases). However, for

most tropical species of Suiforms, ecological and epidemiologi-

cal information on the pathogens they carry is very scarce and

potential contacts with DP are seldom investigated or reported

in the literature. In addition, a large proportion of tropical sui-

forms are endangered species living in fragile habitats and,

therefore, more susceptible to potentially introduced pathogens

that can impact their populations. The present chapter intends

to compile the available information on diseases reported in

pig-like species (and their related pathogens) in the Old and

New Worlds, with emphasis on those diseases that are known to

have a major impact on livestock production, public health, or

the conservation of endangered populations.

Wild boars, feral pigs and DP have a wide distribution in the

world (Massei et al. 2011). In areas where they are sympatric,

interactions are reported, particularly if DP are reared outdoors

or in free-ranging conditions, but also if pigsties are left unat-

tended with limited human presence. In developing countries,

commercial pig food often becomes expensive for small-scale

farmers and DP are left roaming free to find their own food.

Similarly, keeping pigs under free-ranging conditions is a tra-

ditional practice in several Mediterranean locations (Mur et al.

2014; Trabucco et  al. 2014; Carrasco-Garcia et  al. 2015) and

some Baltic (Martinez-Lopez et al. 2014) and Caucasian coun-

tries (Vergne et  al. 2017). Equally, outdoor farming is on the

increase in developed countries where there is a higher demand

for pork produced under better welfare conditions (Wu et  al.

2012). If wild boars are present in those areas, they can become

sexually attracted by receptive domestic sows and direct sexual

contact is often reported. Those can result in fertile mating and

the birth of hybrid litters, but also in fights between wild and

domestic boars in competition for females (Jori et  al. 2015).

These sexual and agonistic interactions have been reported in

diverse countries and ecosystems (Wyckoff et al. 2009; Wu et al.

2012; Jori et al. 2017). However, in some habitats, despite both

species being sympatric, they have been reported to avoid each

other (Carrasco-Garcia et al. 2015) and the drivers of attraction

or avoidance in shared environments are not clear and deserve

further investigation.

The impact of the abundance of feral wild boar × DP hybrids

resulting from sexual contact in the wild is another field that

deserves further investigation. Those hybrids are different from

pure wild boar in many aspects such as behaviour, susceptibility

to pathogens or reproductive turnover, which are likely to influ-

ence the ecological dynamics of diseases in areas where they are

abundant. They are suspected to interact more frequently with

DP than pure wild boars and, therefore, abundant populations

of hybrids could have an impact on the dissemination or main-

tenance of pathogens in the environment (Jori et al. 2016).

Indirect interactions without physical contact can also

occur when wild species are attracted to DP production units at

present human settlements attracted by the availability of water

or different food resources (Kukielka et  al. 2013; Carrasco-

Garcia et al. 2015). This is a particular issue in rural and peri-

urban areas in Africa where domestic or agricultural waste is

left in proximity to human settlements and largely available to

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