Chapter 35: Disease transmission at the interface between wild and domestic Suiform species389
wildlife. In addition in rural areas worldwide, carcasses or offal
from hunted or slaughtered pig species are often left unattended
in nature. Considering the natural scavenging behaviour of pig
species, susceptible individuals can become infected by con-
suming parts of infected carcasses of other domestic, feral or
wild individuals. Therefore, both direct and indirect interac-
tions can easily occur, favouring pathogen transmission and
representing a risk for maintenance and spillover of infectious
diseases between wild and DP species in locations where they
are sympatric.
Wild Boar and Feral Pig Diseases
Eurasian wild boars (Sus scrofa) are host to a great variety
of pathogens that can be shared with domestic species and
humans. A list of commonly reported diseases in Sus scrofa is
provided in Table 35.1. The transmission to other hosts is driven
by factors related to the pathogen, the host and environment. As
discussed in Chapter 31, Sus scrofa populations are reported to
be increasing in many regions of the world and this abundance
results in a higher circulation of infectious diseases in their envi-
ronment (Massei et al. 2011). Changes in population dynamics
sometimes induced by farming or hunting management prac-
tices can have an impact on the disease reservoir and its spillover
to livestock, or vice versa. For instance, this is the case in south
central Spain, where wild boars are acting as a natural reservoir
of bovine tuberculosis (Carrasco-Garcia et al. 2015). Similarly,
dispersal or translocation of wild pig populations by hunters
can allow the long-distance spread of pathogens into new areas
that were originally disease-free.
Pathogens Shared between Wild Boar and
Domestic Pigs
Classical swine fever (CSF) and African swine fever (ASF) are
viral diseases severely impacting pig health and trade world-
wide. CSF is reported to persist for several years in large wild
boar populations living within large forested areas, despite sus-
tained efforts for its control and eradication (Artois et al. 2002;
Rossi et al. 2015). ASF is currently impacting the pig industry
and wild boar populations in Eastern Europe, although there is
not yet evidence that natural populations of wild boar can act
as a reservoir host of the virus (Mur et al. 2014; Vergne et al.
2017). Aujeszky’s disease (also known as pseudorabies) is a
viral disease affecting DP that can also be maintained in wild
boar populations (Müller et al. 2011). This disease is particu-
larly acute and fatal in carnivores and represents a potential
threat for hunting dogs and some endangered carnivore spe-
cies (Ruiz-Fons et al. 2007). Porcine brucellosis caused by dif-
ferent strains of Brucella suis has the potential to affect wild
boar, DP, and humans (Godfroid et al. 2013). All of these dis-
eases become enzootic in many wild and feral pig populations
worldwide, potentially representing a serious challenge for
the pig farming industry. In addition, many other contagious
pathogens are potentially shared between wild and DP over the
world including porcine circovirus, porcine parvovirus, myco-
plasmas, porcine reproductive and respiratory syndrome virus
(Meng et al. 2009).
Pathogens Shared with Livestock
Bovine tuberculosis caused by Mycobacterium bovis infects
many vertebrate species. It is of significant concern in the inten-
sive dairy industry and can become zoonotic, if associated with
HIV infection, or lack of pasteurization or sanitary slaughter.
In the majority of cases, wild boars behave as a spillover host,
vector or sentinel species, rather than as a true reservoir of the
disease (Nugent et al. 2015; Payne et al. 2016). However, in some
circumstances favouring high population densities, spatial
aggregation and resources shared with infected livestock and
other wildlife species, wild boars can act as maintenance hosts
for bovine tuberculosis, as observed in central and southern
Spain (Carrasco-Garcia et al. 2015).
Wild boar and DP have been found infected with foot-and-
mouth disease (FMD) and pig meat can become a cause of intro-
duction of the disease out of the enzootic areas (Weaver et al.
2013). However, it seems unlikely that wild pig populations are
able to spread and/or maintain the virus in natural environ-
ments (Alexandrov et al. 2013).Pathogens Shared with Humans
Wild boar populations can also host some zoonotic pathogens
(Ruiz-Fons 2017). They can become infested with Trichinella
spp., without any apparent symptoms or lesions, being able to
infect humans through consumption of raw or poorly cooked
meat and contributing to the sylvatic cycle of the parasite. Their
scavenger habits enhance their risk of getting infested with
these parasites. However, the occurrence of Trichinella spp. also
depends on the abundance of other hosts (Pozio et al. 2009).
While trichinella prevalence is high in the Iberian peninsula,
these parasites are more rarely detected in northern and western
Europe (Table 35.1), where industrialized indoor pig farming
prevails (Pozio et al. 2009; Payne et al. 2011).
Viral hepatitis E is another emerging human health threat
reported (Meng et al. 2009). Domestic and wild swine can carry
this virus without clinical signs and may infect people through
the consumption of undercooked pork products (Jori et al.
2016; Pavio et al. 2016; Thiry et al. 2017;) or contact with faecal
material from infected animals.
Other potentially zoonotic pathogens that circulate among
wild boar populations include Leptospira spp., Toxoplasma gon-
dii, swine influenza virus, and Coxiella burnetti. However, the
role of Sus scrofa in the maintenance or transmission of these
pathogens to humans is poorly understood (Meng et al. 2009).Infectious Diseases Reported in Tayassuidae
Tayassuidae and Suidae diverged approximately one million
years ago from a common ancestor. The former encompasses the
three species of known peccaries: Pecari tajacu, the collared pec-
cary; Tayassu pecari, the white-lipped peccary; and Catagonus
wagneri, the rare Chacoan peccary. Diseases described in pec-
cary species are limited to a few infectious pathogens. The pres-
ence or exposure to some bacterial and viral pathogens has been
identified in collared and white-lipped peccaries during dif-
ferent disease surveys and are listed in Table 35.3. Brucella suis
biovar 1 has been isolated from humans, DP, collared peccaries,.03712:55:54