Latin name: Sus scrofa
Common names: Swine, Pig, Hog, Boar
Direct or indirect contact with animal allergens frequently causes sensitisation.
Animal allergens are major components of farm, home and animal laboratory dust.
The name Swine is applied mainly to domestic animals, though several wild varieties, native to Eurasia and North Africa and introduced to North America and other regions, belong to the same species. (But 16 species of Pigs and Hogs in 8 genera make up the modern family Suidae.) Swine are valuable for their flesh, prepared as Ham, Bacon, and Pork, and for their fat (lard); they also provide many other products, e.g., leather for gloves, footballs, and other articles, and bristles for brushes.
A great majority of US Swine production has moved from open pens to enclosed, mechanized facilities. The trend is toward huge, factory-like farms where Swine are born and bred inside structures that feed, water, and dispose of wastes while controlling ambient temperature. The giant modern farms produce enormous amounts of waste; this has become of increasing concern as a potential source of water pollution.
No allergens from this animal have yet been characterised.
Inhibition experiments have demonstrated that the spectrum of IgE reactivity to Cat serum albumin completely contains IgE reactivity to Swine serum albumin, suggesting that sensitisation to Cat is the primary event. The frequency of sensitisation to Cat serum albumin lies between 14% and 23%. Sensitisation to Swine albumin was found to be between 3% and 10%. About 1/3 of these individuals may experience allergic symptoms following Pork consumption, the Cat-Pork syndrom. Sensitisation to Cat serum albumin should be considered a useful marker of possible cross-sensitisation not only to Swine serum albumin but also to other mammalian serum albumins (1).
Asthma, occupational asthma, allergic rhinitis (2-3) and Swine Breeder's Lung, a form of exogenous allergic alveolitis (4) may occur in Swine/Pig breeders following exposure to Swine epithelium, Swine serum albumin and Swine urine proteins.
Reports in the literature have not differentiated which of the three is predominantly responsible for adverse symptoms, and as with other mammalian allergens, the assumption is reasonable that all three contribute.
Reports in the literature of the atopic sensitisation risk that Swine pose to farmers and other individuals, and of the prevalence of allergic conditions, are contradictory.
An early study reported that Pig farming was a risk factor for asthma, chronic bronchitis, and wheezing during work (5).
Subsequent studies have concurred that Pig farmers have increased wheezing and significantly lower FEV1 measurements than controls, but that few Pig farmers demonstrate atopy as determined by skin-specific IgE tests, suggesting that occupational exposure in Swine confinement buildings is associated only with mild increases of nonspecific, nonatopic airways responsiveness in Pig farmers (6-7).
Further studies, including cross-sectional surveys among Pig farmers, report an increased prevalence of cough, morning phlegm and chronic bronchitis, but not of asthma, despite many factors promoting the manifestation of asthma. Importantly, compared with controls, Pig farmers reported fewer allergies to common allergens and fewer symptoms of atopy in childhood (8, 9). Health-based selection of non-asthmatics for Pig farming, a selection that tends to mask a work-related hazard for asthma, was offered as an explanation for these results (9).
The results of a questionnaire sent to 6,156 randomly selected animal farmers in Denmark, Germany, Switzerland, and Spain showed that Pig farmers were at highest risk for the development of work-related symptoms. A significant dose-response relationship between symptoms and daily hours worked inside animal houses was established for Pig. Self-reported nasal allergies and nasal irritation during work were said to be associated with the development of chronic phlegm (10). A Swiss study concurred that Pig farming was a risk factor for reporting nasal irritation at work (11).
A study conducted among farmers in eastern Poland examined 68 farmers from 17 randomly selected family farms. None of the farmers complained of any symptoms when working with Cows or Pigs. In 13 farmers either positive skin-specific IgE and/or the presence of serum-specific IgE to Cow dander and/or Pig epithelia was found. Seven farmers were positive on skin-specific IgE tests: 2 to Cow epithelium, 2 to Pig epithelium, and 3 to both allergens (12).
In New Zealand, in a postal questionnaire sent to a random sample of 2,500 farmers throughout the country, 77% of the 2,203 who were eligible replied. Asthma prevalence was higher for Horse breeders/groomers (16.5%), Pig farmers (18.2%), poultry farmers (17.4%), and those working with Oats (17.4%) (13).
Furthermore, farmers have more complaints of work-related symptoms of smell impairment, and more often have nasal polyps and hyperaemia of the nasal mucosa. They also have higher levels of myeloperoxidase in nasal lavage (especially dairy farmers and Pig farmers), and a tendency to more-swollen nasal mucosa and lower olfactory threshold (especially grain farmers) (14).
Although reports of atopic sensitisation to Swine do not necessarily concur, some authors conclude that detection of Cow and Swine antigen-specific IgE may be a useful screening tool, although an exact assessment of sensitivity and specificity of the method in a larger population of exposed farmers will be required (15).
Swine farmers may develop Swine Breeder's Lung, a form of extrinsic allergic alveolitis, although this condition does not appear to be commonly reported as associated with Swine farming. A study reported on 2 Pig breeders who had typical symptoms after working in a pigsty. The diagnosis of Swine Breeder's Lung was confirmed by the finding of precipitating antibodies against Pig epidermal components and Pig serum in the patients' sera (4, 16). An earlier study reported that sensitisation against Swine antigens correlated with exposure but not with the presence of symptoms and that a large antigen panel should be used in testing for sensitisation because of the many immunogenic dusts that are present in the air in Swine barns (17). This early study has been supported by a more recent report that demonstrated an increased prevalence of bronchitis, but showed that Swine building workers had no precipitins to antigens found in their environment and no clinical evidence of extrinsic allergic alveolitis. The number of years on the farm, dual exposure with Dairy Cattle, positive skin prick tests, type of piggery, and type of feeding did not change the respiratory health impact of Swine buildings (18).
In healthy subjects, acute inhalation of Swine dust has been shown to cause an influx of inflammatory cells into the airways and increased bronchial responsiveness. The exposure may also cause fever and generalised symptoms. Proinflammatory cytokines appear to be involved in the response to inhaled Swine dust. A significant correlation between the IL-6 response in BAL fluid and exposure to airborne dust endotoxin activity and 3-OH fatty acids was demonstrated (19).
Some Swine diseases are transmissible to humans. Among them are brucellosis, trichinosis, and cysticercosis.
- Hilger C, Kohnen M, Grigioni F, Lehners C, Hentges F. Allergic cross-reactions between cat and pig serum albumin. Study at the protein and DNA levels. Allergy 1997;52(2):179-87
- Bessot JC, Blaumeiser M, Kopferschmitt MC, Pauli G. Occupational asthma in an agricultural setting. [French] Rev Mal Respir 1996;13(3):205-15
- Fedotova EV, Spirin VF, Smirnov IV. Prevalence of allergic diseases in workers of industrial swine breeding. [Russian] Med Tr Prom Ekol 1995;(8):32-3
- Schlegel V, Liebetrau G, Pohl WD. Swine breeder's lung--a form of exogenous allergic alveolitis. [German] Z Erkr Atmungsorgane 1990;174(2):143-8
- Iversen M, Dahl R, Korsgaard J, Hallas T, Jensen EJ. Respiratory symptoms in Danish farmers: an epidemiological study of risk factors. Thorax 1988;43(11):872-7
- Zhou C, Hurst TS, Cockcroft DW, Dosman JA. Increased airways responsiveness in swine farmers. Chest 1991;99(4):941-4
- Scheefeldt M, Wilfert A, Lehnigk B, Wosnitzka H. Bronchial hyperreactivity of employees in swine and cattle breeding. [German] Z Erkr Atmungsorgane 1990;174(2):131-6
- Choudat D, Goehen M, Korobaeff M, Boulet A, Dewitte JD, Martin MH. Respiratory symptoms and bronchial reactivity among pig and dairy farmers. Scand J Work Environ Health 1994;20(1):48-54
- Vogelzang PF, van der Gulden JW, Tielen MJ, Folgering H, van Schayck CP. Health-based selection for asthma, but not for chronic bronchitis, in pig farmers: an evidence-based hypothesis. Eur Respir J 1999;13(1):187-9
- Radon K, Danuser B, Iversen M, Jorres R, Monso E, Opravil U, Weber C, Donham KJ, Nowak D. Respiratory symptoms in European animal farmers. Eur Respir J 2001;17(4):747-54
- Danuser B, Weber C, Kunzli N, Schindler C, Nowak D. Respiratory symptoms in Swiss farmers: an epidemiological study of risk factors. Am J Ind Med 2001;39(4):410-8
- Spiewak R. Sensitization to cow and pig allergens among farmers in Eastern Poland. [Polish] Med Pr 2001;52(5):351-4
- Kimbell-Dunn M, Bradshaw L, Slater T, Erkinjuntti-Pekkanen R, Fishwick D, Pearce N. Asthma and allergy in New Zealand farmers. Am J Ind Med 1999;35(1):51-7
- Ahman M, Holmstrom M, Kolmodin-Hedman B, Thelin A. Nasal symptoms and pathophysiology in farmers. Int Arch Occup Environ Health 2001;74(4):279-84
- Spiewak R, Dutkiewicz J, Skorska C. Detection of specific IgE as a screening tool for cow and swine breeders' occupational allergic dermatoses. Ann Agric Environ Med 2000;7(2):145-7
- Baur X. Case report published by V. Schlegel, G. Liebetrau, W. D. Pohl, "Swine breeder's lung--a form of exogenous allergic alveolitis". [Letter] [German] Pneumologie 1992;46(9):491
- Katila ML, Mantyjarvi RA, Ojanen TH. Sensitisation against environmental antigens and respiratory symptoms in swine workers. Br J Ind Med 1981;38(4):334-8
- Cormier Y, Boulet LP, Bedard G, Tremblay G. Respiratory health of workers exposed to swine confinement buildings only or to both swine confinement buildings and dairy barns. Scand J Work Environ Health 1991;17(4):269-75
- Wang Z, Larsson K, Palmberg L, Malmberg P, Larsson P, Larsson L. Inhalation of swine dust induces cytokine release in the upper and lower airways. Eur Respir J 1997;10(2):381-7