Materials and Methods

An online survey of miniature swine owners was undertaken to obtain information about the number of pigs owned; food waste feeding; veterinary care; movements on and off the premises; and contacts with humans, other miniature swine, and livestock species. An Internet search revealed associations, individuals, and veterinarians linked to miniature swine. Individuals were contacted and invited to help distribute the survey to owners of miniature swine. Four hundred individuals received an e-mail^a explaining the purpose and nature of the survey and giving the Web address of and a link to the online survey. Recipients of these e-mails were asked to complete the survey and to encourage other miniature swine owners to do so. In addition, 21 veterinarians working at practices in California that provide services to owners of miniature swine were identified. The veterinarians were contacted and asked to invite clients with miniature swine to participate in the survey. A reminder e-mail was sent to organization members a few weeks after the initial survey announcement was e-mailed.

From June 8, 2005, to August 8, 2005, after a 10-day period of pilot testing, the survey format was made available online through a Web-based survey service.^b Questions asked had closed-ended, partially open-ended, and open-ended formats. Owners’ ZIP codes and nearest cross street were collected to identify the state and city of premises location. Each respondent was limited to 1 survey submission. No information that would enable identification of an owner was collected or made available to the investigator. Prior to survey distribution, authorization for the study of human subjects was obtained from the university institutional review board (Protocol 200513389-1).

Respondents’ general locations were recorded in a geographic information system software program.^c If the nearest intersection to the respondent’s premises was provided, the latitude and longitude of the location were identified by use of the software program’s georeferencing tool or through a combination of Web-based mapping services.^d-f When only a city or ZIP code was provided, the latitude and longitude of centroid of the city or of the ZIP code region were recorded. To evaluate swine movement distances, respondents were asked to identify the city of origin for movements to their premises or destination city for movements from their premises. The latitude and longitude of the centroid of the identified origin or destination city were used. The distance between the movement origin or destination and the respondent’s premises location was calculated. All distances were measured with straight lines between origin and destination locations as opposed to measuring the length of the actual routes of travel.

Results

Demographics—After initially contacting 400 miniature swine owners, 106 (26.5%) survey responses were collected. Three hundred seventeen miniature swine were accounted for by these owners. Of the 106 respondents, 81 (76%) resided in California. Eighty of those 81 respondents reported owning a total of 257 miniature swine. The remaining respondent from California owned pigs but did not report how many. Respondents were also from New York (n = 2 [2%]), Hawaii (1 [1%]), Florida (5 [5%]), Utah (2 [2%]), Washington (1 [1%]), Virginia (1 [1%]), West Virginia (3 [3%]), Oregon (1 [1%]), Alaska (1 [1%]), Nevada (1 [1%]), and Pennsylvania (2 [2%]). Locations of 5 respondents who did not provide a complete or accurate ZIP code could not be identified; data from those records were included only in values reported for the total of all responses. Because the survey responses were predominantly, but not exclusively, from California, we reported the data by Californian, non-Californian, and overall responses.

Owners generally kept only 1 or 2 miniature swine (Table 1). A maximum of 39 miniature swine were kept at 1 California premises, which reported rescue or fostering as their primary activity. Approximately one third of respondents also owned other livestock. Although ≥ 85% of owners reported keeping miniature swine as family pets, ≥ 33% of miniature pigs were considered to have been rescued or fostered.

Veterinary care and carcass disposal—More than 40% of the veterinarians consulted by miniature swine owners were in mixed-animal practice (Table 2). More than 20% of practitioners treating miniature swine were in small animal practice, and fewer were in large-animal practice. The mean number of veterinary visits per year was approximately 1. In California, > 50% of veterinary examinations of miniature swine occurred at a veterinary clinic; outside of California, examinations occurring at a clinic were reported by 20% of owners. The remainder of veterinary examinations occurred on the owner’s property or at either location. A small percentage of miniature swine did not receive any veterinary care.

Thirty-five percent to 70% of owners reported they were unlikely to request postmortem examination if a miniature pig died (Table 1). More than 40% of owners reported that, in the event of a miniature pig’s death, they would bury the carcass on their property (Table 3). Fewer than 12% of owners reported they would have the carcass rendered.

Contacts with humans and other animals—Approximately 50% of all owners indicated that ≥ 3 humans came into contact with their animals (Table 1). Regular contact with cloven-hoofed animals on other premises was reported by 12% (10/18) of owners in California and 15% (3/20) of owners in other states.

For a typical year, ≤ 25% of respondents reported visits to their premises by hay trucks (8/81 [10%] of respondents in California; median, 6.3 visits/y; 4/20 [25%] non-California respondents; median, 2 visits/y), feed trucks (2/81 [2%] respondents in California; median, 7.5 visits/y; 1/20 [5%] non-Californian respondents; median, 52 visits/y), animal haulers (5/81 [6%] respondents in California; median, 2 visits/y; 1/20 [5%] non-Californian respondents; median, 6 visits/y), other supply trucks (12/81 [15%] respondents in California; median, 3.5 visits/y; 3/20 [15%] non-Californian respondents; median, 6 visits/y), or sales representatives (5/81 [6%] respondents in California; median, 2 visits/y; 1/20 [5%] non-California respondents; median, 3 visits/y). Other miniature swine owners visited respondents’ premises both in California (28/81 [35%]; median, 3.5 visits/y) and outside California (6/20 [30%]; median, 5.5 visits/y). Visits to premises by door-to-door delivery service personnel were reported by approximately two thirds (54/81 [67%] respondents in California; median, 12 visits/y; 12/20 [60%] non-Californian respondents; median, 4.5 visits/y) of miniature swine owners. Visitation of the premises by school children or 4-H or Future Farmers of America groups was reported by 44% (36/81; median, 19.5 visits/y) of respondents in California and 35% (7/20; median, 12 visits/y) of non-Californian respondents.

During the past year, ≤ 15% of miniature swine owners had visited other cloven-hoofed livestock operations, such as dairies (2/81 [3%] respondents in California; median, 26.5 visits/y; 0/20 non-Californian respondents), beef ranches (2/81 [3%] respondents in California; median, 26.5 visits/y; 0/20 non-Californian respondents), other (nonminiature) swine operations (3/81 [4%] respondents in California; median, 6 visits/y; 3/20 [15%] non-Californian respondents; median, 10 visits/y), small ruminant premises (5/81 [6%] respondents in California; median, 4 visits/y; 3/20 [15%] non-Californian respondents; median, 12 visits/y), or sales or auction yards (3/81 [4%] respondents in California; median, 2 visits/y; 1/20 [5%] non-Californian residents; median, 2 visits/y). Approximately 30% of owners reported visiting other premises where miniature swine were kept (23/81 [28%] respondents in California; median, 3 visits/y; 6/20 [30%] non-Californian respondents; median, 8 visits/y). In the previous year, approximately one third of owners attended shows or fairs (32/81 [40%] respondents in California; median, 1 visit/y; 6/20 [30%] non-Californian respondents; median, 1.5 visits/y) or miniature swine club or association events where miniature pigs were present (31/81 [38%] respondents in California; median, 2 visits/y; 7/20 [35%] non-Californian respondents; median, 2 visits/y). In California, > 25% of owners attended a miniature swine club or association event where miniature pigs were not present (23/81 [28%]; median, 2 visits/y). Fewer than 10% of owners outside California attended a similar event (1/20 [5%]; median, 1 visit/y).

Wild deer were observed within 500 feet (152.4 m) of miniature swine on 20% (16/81 respondents; median, 30 observations/y) of premises in California and 25% (5/20 respondents; median, 75 observations/y) of premises outside California. One owner reported seeing elk near miniature swine once yearly. Feral pigs were observed daily at 1 premises in Florida.

Food waste feeding practices—Twenty percent (non-California) to 50% (California) of owners reported feeding food waste from any source to their miniature swine. The most frequently reported source of food waste was the owner’s household (36%). A single owner fed food waste from an industrial source such as a prison or school but did not report feeding meat or dairy waste from this source. Food waste containing meat, dairy products, or both was fed at up to 16% of miniature swine premises. Of those owners who fed any food waste, feeding of dairy waste was reported by 33% to 60% of owners and feeding of meat waste was reported by 10% to 20% of California and non-California owners, respectively.

Animal movement—Of the 3 most recent movements of miniature swine from an owner’s premises, > 66% were to visit a veterinarian. At least 60% of movements from the premises involved only 1 pig and had taken place in the previous 6 months. Most animal movements from owners’ premises in California involved distances < 50 km (1 way). More than 30% of movements for owners outside California involved distances ≥ 100 km.

One-way movements of miniature swine to owners’ premises were most often from the veterinarian, a rescue or fostering facility, or another private individual. Of the 3 most recent movements of miniature swine to owners’ premises, most involved only 1 or 2 pigs, had taken place in the previous 6 months, or were estimated to have involved distances < 100 km. No movements were reported involving pet or livestock dealers, sales yards, or auctions.

Discussion

Miniature swine owners reported feeding dairy products, meat products, or both to pigs, which could lead to the introduction of FMD or another foreign animal disease. Feeding of food waste to swine has been associated with several outbreaks of FMD, classical swine fever, and African swine fever.^7,14–16 Miniature swine fed contaminated food waste that has not been adequately cooked prior to feeding could initiate an outbreak of 1 or more of these diseases. It is reported that the risk of transmitting FMD through milk and dairy products is low.²² However, imported meat and meat products have been implicated in the introduction of foreign animal disease outbreaks, including FMD, through food waste feeding of swine.^{16,17, 23}

Delays in FMD diagnosis in miniature swine could lead to disease establishment and transmission to other livestock populations. The present study revealed that miniature swine may receive veterinary care 1 time/y and that some pigs receive none. In general, veterinary practitioner preparedness for foreign animal diseases has been viewed as critically deficient.^24,25 Many owners of miniature swine indicated that their pigs received veterinary care from small animal practitioners, who may not be as alert to or educated about signs of foreign animal diseases as practitioners who regularly deal with livestock species. In the event of a miniature pig’s death, most owners reported that they would be unlikely to request a necropsy and many would bury the carcass on their property. Under these circumstances, a veterinarian would have little opportunity to detect a foreign animal disease that caused a pig’s death.

Disease transmission interfaces between miniature swine and other susceptible livestock populations through indirect contacts appeared to be more limited than those that could occur through direct contacts. Most miniature swine owners either did not visit other livestock premises or did so infrequently, indicating a restricted opportunity for disease transmission through human contact. Vehicles and humans who also visit other livestock premises, such as hay and feed trucks, were uncommon visitors to miniature swine premises, suggesting limited indirect contact between miniature swine and other livestock, such as on dairy, beef, and commercial swine operations. Visits by public groups and delivery services were most commonly reported; the risk of disease transmission to other miniature swine or livestock premises by these types of indirect contacts is unknown but likely to be low. Most owners reported that their veterinarian was a mixed animal practitioner, indicating a potential for direct and indirect contact with other susceptible livestock species either at the veterinary clinic or through contact with the clinician.

Direct contact of miniature swine with other miniature swine, livestock, and wildlife could allow for transmission of a foreign animal disease. The results of this study reveal that miniature swine in the surveyed population have opportunities for contact with other miniature swine, wild deer, and other cloven-hoofed livestock that are susceptible to FMD. Movement of miniature swine to or from shows, association events, and rescue facilities could result in disease spread. In California, miniature swine are subject to the same interstate importation regulations as are other swine; however, no intrastate movement regulations apply to these animals.^26,g No movements of miniature swine were reported for high–animal-contact livestock environments such as sales yards, auctions, and animal dealers. This finding suggests a limited opportunity for disease transmission to occur from miniature swine to a larger or commercial livestock population through such environments. Rather, transmission may be more likely to occur from miniature swine to other miniature swine and smaller or hobby animal operations via shows, fostering environments, and pig-related events.

Because most survey respondents were likely to be affiliated with 1 or more miniature swine associations, they may attend events or shows more frequently than owners who are not affiliated with similar associations. In addition, respondents were contacted via e-mail and completed the survey online. The results of this survey may not be fully representative of miniature swine owners who do not have Internet access or who are not affiliated with miniature swine associations.

Recognizing and describing risk factors for development of foreign animal disease in miniature swine can aid in assessing the potential for disease introduction, establishment, and transmission both before and during a foreign animal disease outbreak. In addition to FMD, miniature swine are also susceptible to infection with viruses that cause classical swine fever,²⁷ African swine fever,^28,29 and H5N1 avian influenza.³⁰ Risk factors for FMD in miniature swine are likely to apply also to other foreign animal disease pathogens. Education of miniature swine owners and small animal veterinarians about proper food waste feeding and biosecurity practices may help mitigate disease risk in this population of susceptible pet pigs.