† Shared piglet production rings typical of the Swiss pig production
chain. AFP stands for the German “Arbeitsteilige
Ferkelproduktion ”.
‡ Close production cycle farms are those performing all steps of pig
production: gilt raising, breeding, weaning and fattening.
Live pig transport
The majority of farmers considered live pig trade as the most important
mechanism of infectious disease introduction into, or spread from, their
farm – except those owning closed production cycle farms, as they are
rarely involved in pig trade. Recognizing the direct exposure to disease
via introduction of new pigs, or indirect exposure via lorry
contamination during transport tours performed by traders, they adopt
different strategies to minimize this risk if possible. Mitigation
strategies include trading as much as possible with the same farm or
requesting to the trader that their farm should be the first one visited
on a transport tour.
Awareness of the risks associated with pig transports via trading
companies was not uniform among the interviewees. Four distinct clusters
were identified with regards to farmers’ attitudes towards lorry drivers
helping with the loading or unloading of pigs. Some farmers stated that
drivers are aware of the most important biosecurity rules, and they
never enter the stables. Other farmers expressed that lorry drivers do
not access the stables, but that they need to be reminded (Table 2,
quote from interview 4). The remaining interviewees revealed that
drivers do enter their stables, either as an exception for difficult
cases or as a regular and completely acceptable practice.
Not all farmers resorted to traders for pig transport. Self-performed
transports are not as much exposed to contamination issues as trader
transport tours, but they present alternative potential exposure
mechanisms, due to the sometimes less professional practices compared to
trader companies (Table 2, quote from interview 1). In our sample, three
distinct situations were observed: farmers in the industrialized pig
production areas of the country only do self-transports on rare
occasions; farmers belonging to an AFP ring sometimes are not associated
to a trader and perform transports personally; farmers with small
holdings outside the main pig production areas perform all transports
independently.
Although nowadays most Swiss breeding holdings practice artificial
insemination, farms with traditional reproduction or farms outside the
main production area still resort to natural insemination with a boar
kept on the premises. Sharing boars with neighboring breeding farms as a
courtesy between colleagues are susceptible to underreporting in the
official national animal transport database, and they are always
performed by farmers themselves with the aforementioned associated
risks. During the interviews, three farmers confirmed that this practice
still exists today (Table 2, quote from interview 5).
Farmer encounters
Many occasions for professional or social encounters between farmers
were reported during the interviews, both on and out of the pig
holdings. Farmers frequently mentioned that they are active in local,
regional, or national farming associations and working groups.
Regardless of the context, most interviewees strongly believed that
meetings happening outside of their farming premises represent a very
low risk for disease spread, as in those occasions they do not meet in
work clothing (Table 2, quote from interview 1). Still, one interviewee
revealed he would meet his colleagues in work clothing.
On-farm contacts with colleagues were also mentioned. For instance, a
pig fattener said he occasionally goes to his neighbor’s pig stall to
help him put down a sick pig (Table 2, quote from interview 12).
The sharing of pig and other farming equipment was also reported (Table
2, quotes from interviews 6 and 10). Most interviewees did not share pig
farming equipment, either because they did not need to, or because they
were afraid it would not be properly handled by other farmers. The most
frequently shared pig farming items were narcosis tools for piglet
castration and ultrasound machines for gestating sows. Other farming
equipment, such as seeders, fertilizer spreaders and manure tanks, was
shared more often.
Visitation to carcass collection points was reported by most farmers as
a frequent task. Some of them said it is common to meet other farmers
there, or even to help other farmers in the carcass disposal process
(Table 2, quote from interview 17). During the interviews we identified
three factors affecting the occurrence of this pathway: i)
accessibility: limited opening hours may result in increased likelihood
of farmer encounters while waiting for their turn to dispose of the
carcass. Additional risky practices, such as asking other farmers to
help in disposing carcasses, were encouraged by limited accessibility
and farmers’ other engagements. ii) monitoring: according to the
interviewees’ reports, some collection points are attended by personnel,
some have a camera monitoring system, and some are not monitored at all.
Some farmers expressed their concerns about the lack of monitoring as
they believed it encouraged risky practices among their colleagues. iii)
farmer’s risk perception: we encountered very different perceptions,
ranging from feeling very relaxed during the disposal process, to
considering visits to collection points as the most dangerous task for
the health of their herd.
External collaborators
If the carcasses to be disposed of are heavier than a certain threshold
weight (usually 200 kilograms), carcass disposal companies pick them up
on the premises. To avoid incurring in the risk of contamination due to
the collection trucks visiting several holdings on the same day, some
farmers refrained from using this service and would rather manage the
disposal on their own (Table 2, quote from interview 20).
According to the interviewees, pig feed advisors and veterinarians are
external collaborators frequently visiting pig holdings. Both
professionals are often granted access to the pig stables by farmers,
and both may visit multiple stables within the same day. Depending on
the level of observance of biosecurity protocols by themselves and the
farmers, they may act as pathogen vectors. In our sample, not all
farmers were visited by feed advisors. In the case in which they were,
the stated frequency of visits varied from “once in a while” to
“every one or two months”. As for veterinarian visits, most farmers
received visits for official controls or from farm veterinarians. The
frequencies of these visits ranged between “rarely” and “often”, the
latter mostly due to piglet castration. While several farmers revealed
their fear of disease introduction in the farm via veterinarians (Table
2, quote from interview 14), only one farmer shared his worries about
his feed advisor possibly bringing pathogens into the stables.
The management of manure produced on the farm is also a task requiring
the support of external collaborators. Liquid manure was reported to be
transported by specialized companies (Table 2, quote from interview 21).
The fact that these companies handle biological material from pigs and
visit several farms on the same day, make them another possible carrier
of pathogenic agents. Feed delivery trucks represent a similar risk due
to multiple farm visits and the potential spread of pathogens by, for
example, picking up dirt from a farm with truck wheels and subsequently
depositing it in other locations. Some farmers recognized this risk and
adopted preventive strategies such as ordering large amounts of feed to
reduce the number of feed delivery trucks or placing feed silos far from
the main premises in order to avoid truck contamination.
Environment and other
contacts
Presence of wild boars in areas with high density of pig holdings may
facilitate farm-to-farm spread of pathogens affecting domestic pigs.
Most farmers reported that wild boars were spotted in the vicinity of
their holding by themselves or their neighbors. The sightings occurred
in all regions where the interviews took place. Farmers with pigs having
outdoor access shared their concerns about not being prepared to prevent
contact with wild boar because, for instance, of the lack of double
fencing around their farm. Some of them justified their unpreparedness
by the absence of wild boar in their region up to recent times (Table 2,
quote from interview 16).
Other wild animals (e.g., rodents, birds) and pets (mainly cats) were
frequently reported by farmers as being able to access the stables and
potentially move from farm to farm in a short time frame. Only one
farmer named such contacts in the context of potential infectious
disease transmission. This interviewee believed his holding is well
protected from infectious disease exposure but mentioned wild animal
contact as the most probable mechanism of disease introduction.
Visits by non-professional external persons were often mentioned, for
instance in the context of the direct sale of farm products on the
premises, or because of the farmers’ will to show their farm to people
expressing an interest in it (Table 2, quote from interview 5).
Table 2 Exemplary quotes from
farmer interviews. A quote is given for each potential disease pathway
that was identified or discussed with farmers during interviews.
Sentences were translated to English from the original languages of the
interviews.