Transmission of pathogens between domestic and wild life animals plays an important role in epidemiology. Feral pig populations are increasing and expanding in the USA, and may constitute a risk to non-biosecure domestic pig facilities by serving as reservoirs for pathogens. We surveyed, for Sarcocystis infection, the myocardium of 1006 feral pigs (Sus scrofa) trapped or hunted in 29 states during the Comprehensive Feral Swine Disease Surveillance Program of the USDA's Animal and Plant Health Inspection Service, Wildlife Services unit during 2012–2014. Sarcocysts were detected in histological sections of 25% (251/1006) of myocardium with an average parasitic load/intensity of infection of 3·03 sarcocysts/section (1·5×0·7 cm), and higher prevalence of myocarditis in severe infections. Microscopic examination of pepsin digests of 147 hearts revealed a higher prevalence of Sarcocystis bradyzoites (49%, 72/147) than when diagnosed by histology. A fragment of Sarcocystis 18S rRNA was amplified and digested with a restriction endonuclease, revealing a pattern consistent with Sarcocystis miescheriana in all 44 selected samples. Sequencing 31 of these 44 isolates confirmed their correspondence to S. miescheriana. Thus, S. miescheriana infection, but not the zoonotic parasite Sarcocystis suihominis, appears to be prevalent and widespread in feral pigs in the USA.

Carpal glands (CG) of 105 feral pigs Sus domesticus, caught in the tropical lowland rainforest in north-east Queensland, Australia, between 1999 and 2004, were investigated to examine their function in chemical communication between animals, and their histology. Female feral pigs show significantly larger CG on the right leg than on the left leg while there were no side-specific differences in males. CG on both legs were significantly larger in reproductive than in non-reproductive females, but they did not differ between pregnant and lactating females. The results suggest that CG are involved in the defensive behaviour of reproductive females but not in the identification of the mother by piglets. The area of the left CG was significantly bigger in males compared to females, but no significant difference could be shown for the CG on the right legs. CG of same-aged boars did not change significantly in size throughout the year while females showed smaller CG on the left leg in January and February suggesting that CG may be involved in intra-matriarchal group communication. Same sized and aged boars did not show any correlations between the size of the CG and the weight of their testes and the serum levels of testosterone. These results suggest that CG are not involved in advertising dominance in boars. The histological investigation of CG showed that they are active in feral pigs in the lowland rainforest, consist mainly of apocrine tissue and that their hairs may play a role in distributing secretion.

The introduction of swine (Sus scrofa) has adversely affected the environment of many natural habitats throughout the world. Basin marshes are dwindling ecosystems in Florida that are especially vulnerable to damage by feral swine. In January 2003, the estimated amount of swine damage to the exposed portion of the last remnant of a basin marsh system in Savannas Preserve State Park (SPSP) was 19% (an area of 5 ha). Economic valuations for the swine damage were based on the monetary amounts that wetland regulators have allowed permit applicants to spend in mitigation attempts to replace lost wetland resources. In 2003, the area of natural habitat damaged by swine had a total value of US$ 1 238 760–4 036 290. The SPSP implemented a contract for swine control throughout 2003 in all areas of the Park. The damage to the basin marsh was re-estimated in January 2004, after swine removal. The damage sampling transects remained the same as the 2003 survey, but damage was significantly reduced, with 31% of sampling transects showing damage in January 2004 versus 92% in January 2003. Similarly, the total area of swine damage had decreased to 0.95 ha, and the value of the lost habitat had been reduced to US$ 235 355–766 865, an economic benefit of US$ 1 003 355–3 269 265. The benefit-cost ratio (BCR) relating the economic value of the damage reduction against the swine control costs (not all swine control in the park was carried out in the vicinity of the basin marsh) was conservatively estimated at 134–436. When estimating costs for swine control in the vicinity of the marsh based on the proportional number of swine removed there as compared to the Park as a whole, the BCR increased to 480–1562. Benefits of swine removal are very high relative to the costs of control.

Feral swine (Sus scrofa) adversely affect the environment in many of the places where they have been introduced. Such is the case in Florida, but quantification and economic evaluation of the damage can provide objective bases for developing strategies to protect habitats. Swine damage to native wet pine-flatwoods at three state parks in Florida was monitored from winter 2002 to winter 2003. Economic valuations of damage were based on the US dollar amounts that wetland regulators have allowed permit applicants to spend in attempts to replace lost resources. The parks had different swine management histories and the damage patterns differed among them over time. Swine were intensively removed in 2000 from the first park, and it initially had the lowest habitat damage at 1.3%, but as a result of natural and artificial population growth this damage rose to 5.4% by the conclusion of the study, and was valued at US$ 19 193–36 498 ha−1. The second park had no history of swine harvest and, over the monitoring period, damage escalated from 2.6%–6.4%, with an associated value of US$ 22 747–43 257 ha−1. Swine were managed as game animals in the third park prior to its inclusion into the state parks system in 2000. Within this park, the proportion of area damaged decreased from 4.3%–1.5%, valued at US$ 5 331–10 138 ha−1. This decrease may be a result of human activities associated with development of the park's infrastructure causing dispersal of animals conditioned to avoid humans by hunting. Damage was highly scattered in each park, as evidenced by a much higher proportion of sampling sites showing damage than the actual proportion of land area damaged. The dispersed nature of small amounts of damage would increase the effort required to recover habitat and thus damage value estimates are probably conservative. It was also impossible to incorporate values for such contingencies as swine impact to state and federally listed endangered plants in the parks, some of which are found nowhere else in the world.

Swine (Sus scrofa) have been introduced in many places throughout the world, and in many places they adversely affect the environment, economically impact agriculture, and/or harbour diseases transmittable to domestic livestock or humans. An easily applied method to assess their abundance is an important need for their management. To monitor efficacy of a swine control programme in Florida, data from passive tracking plots provide an index of feral swine abundance. The same track data coupled with plot locations to numerically describe the spatial pattern of swine activity gave an index of pervasiveness, and a simple rate of interception of damage sites to index damage was used. The assessments were conducted in January, May, and August 2000 in Jonathan Dickinson State Park, Florida, USA. Between the first two assessments a swine control programme removed 25 feral swine from the 8.3 km2 study area, after which the value of the passive tracking index was reduced by 81% and the fresh damage index by 89%, while the index of spatial pattern (pervasiveness index) showed only a small localized concentration after control. In the three months following the second assessment, Park personnel removed three additional swine from the study area, and a follow-up assessment indicated slightly less swine activity than immediately after the post-control assessment, however the index of pervasiveness showed a similar spatial pattern of activity as the initial assessment, possibly indicating re-invasive pressure. The passive tracking plots proved to be an uncomplicated, easily applied means to gather data for assessing and comparing swine abundance and distribution.