Potential for dissemination of Phytophthora cinnamomi by feral pigs via ingestion of infected plant material

Abstract

IntroductionCollectively, invasive animals, plants and microbes are a major threat to ecosystems worldwide, yet the compounding impact of invasive species is not widely recognised (van der Putten et al., 2007). Feral pigs (Sus scrofa) present an undefined threat to native ecosystems worldwide through their potential to spread secondary invasive species such as pathogens and weeds. While many animals are capable of acting as vectors for a number of disease agents including microbial pathogens, the nonfastidious diet, foraging habits and home range of feral pigs brings them in direct contact with invasive plant pathogens such as Phytophthora cinnamomi in many of the temperate regions of the world thus increasing the potential cumulative impact of both pigs and pathogens on native and horticultural plant communities (Feio et al., 1999;Martin and Dale, 2001).Feral pigs are a widespread pest species that are present throughout many regions and habitat types of the world (Tierney and Cushman, 2006), and they have been implicated in the decline of 257 and 8 plant and bird species, respectively, in the United States (Gurevitch and Padilla, 2004). They also impact on agricultural production and in Australia alone damage due to feral pigs is estimated to cost in excess of $107 million per annum (McLeod, 2004). The highly invasive plant pathogen P. cinnamomi infects over 3000 plant species worldwide including many agricultural, ornamental and forest species (Erwin and Ribeiro, 1996;Hardham, 2005). Shearer et al. (2004) estimated that 2284 (40%) of the 5710 plant species in the South-West Botanical Province of Western Australia are susceptible to P. cinnamomi infection. The pathogen has been estimated to cost the Australian economy $1.6 billion over the course of a decade (Carter, 2004). Despite the introduction of both feral pigs and P. cinnamomi in many temperate habitats worldwide, very little is understood of the compounding potential of these two highly destructive and invasive species. Anecdotally, feral pigs have long been implicated in the spread of P. cinnamomi although relatively little data exists to support these claims.The non-fastidious diet of feral pigs typically incorporates a significant proportion of plant material including woody root material and underground structures (Masters, 1979;Choquenot et al., 1996;Giménez-Anaya et al., 2008), which are the primary sites for infection with P. cinnamomi in susceptible plants (Hardham, 2005;Hardy et al., 2007). Such foraging behaviour presents a means of pathogen dispersal in addition to the transport of contaminated soil. This study investigated the potential for pigs to disseminate viable P. cinnamomi in their faeces following the ingestion of infected plant material. As such we demonstrate the ability of P. cinnamomi to survive passage through the pig digestive tract and the potential for long distance dispersal of the pathogen by feral pigs in native forest ecosystems. Methods Determining pig gastrointestinal passage rate; experimental and pig maintenancePig f...

Endemic and Emerging Pathogens Threatening Cork Oak Trees: Management Options for Conserving a Unique Forest Ecosystem

“…Since grazing animals may be important vectors of Phytophthora species, grazing should be prohibited wherever these oomycetes are known or suspected to occur, especially at times when the soil is wet (Li et al 2014). The eradication of root pathogens such as Phytophthora and Pythium species once they are established in a new environment is difficult, if not impossible, to achieve (Brasier 2008).…”

Spatio-temporal analysis at landscape scale of the Iberian oak decline epidemic caused by Phytophthora cinnamomi

“…However, it turns out that big wild ungulates use thick forest stands as shelters and corridors; therefore, the presence of these animals is usually greater than in open woodlands (Bosch et al, 2014). As a matter of fact, wild boars and feral pigs have been reported as Phytophthora cinnamomi vectors by several authors (Kliejunas and Ko, 1976; Krull et al 2013; Li et al, 2014). As such animals feed on roots and bulbs digging in soil and frequently wallow in mud, they may carry infected material both internally and externally and subsequently transport this material over considerable distances.…”

Migratory passerine birds in Britain carry Phytophthora ramorum inoculum on their feathers and “feet” at low frequency

“…Previous studies have found that non‐avian taxa could be associated with new outbreaks of Phytophthora spp. ; these included goats ( Capra aegagrus hircus ) (Cardillo, Acedo, & Abad, ), feral pigs ( Sus scrofa ) (Li, Williams, Fenwick, Hardy, & Adams, ) and slugs (Parke et al, ; Telfer et al, ), the latter two showing viable spores excreted after ingestion of infected material. The role of animals in the spread of P. ramorum is still unclear and under‐studied.…”