Sensitization to cow and pig allergens among farmers in eastern Poland

Radoslaw Spiewak

Institute of Agricultural Medicine, Lublin, Poland

Introduction

Occupational dermatitis caused by allergy to cow dander was first described in 1948 (1). Reports followed from other authors on similar problems among farmers (2-5) and veterinary surgeons (6, 7). In Finland, cow dander and epithelium cause 28% of all occupational dermatoses among farmers; they are also the most frequent cause of occupational urticaria (8, 9). The frequency of allergy to farm animals among Polish farmers was unknown until the present study was undertaken. In an own questionnaire-based study, only 2 of 145 surveyed farmers (1.4%) complained of skin symptoms caused by contact with cows or pigs; in contrast, 35 farmers (24.1%) indicated plant substances as the reason for their work-related skin problems (10). The aim of this study was to investigate the frequency of allergy to cow and pig allergens among Polish self-employed farmers.

Study population

In the Lublin Voivodship (an large administrative province in eastern Poland), there are 245,000 family farms. The number of active farmers is estimated as nearly 0.5 million. The study was carried out in 17 randomly selected farms located in the province. These were farms of a traditional type with mixed crop production and a handful of animals. The area of the included farms ranged from 6.5 to 18 (median 9.5) hectares. The criteria of inclusion into the study were: 1) age from 18 years old, 2) regularly tending cows and pigs, and 3) the consent to participate in the study, including undergoing skin tests and laboratory tests. The number of adults living on the included farms was 75. Of these, 2 persons worked outside farming and did not participate in tending the animals, 2 persons refused to take part in the study, 2 persons were absent on the study day, and 1 person was excluded from testing because of pregnancy. Finally, 68 farmers were included, 30 women and 38 men aged 18-84 (median 47) years. Their employment in agriculture lasted from 2 to 73 (median 32) years. The period of a regular contact with cows ranged from 3 to 80 (median 30) years, and with pigs - from 1 to 80 (median 30) years. The number of animals tended was 1-7 (median 4) cows and 1-40 (median 7) pigs.

Methods

The farmers underwent a detailed, physician-administered questionnaire examination. It was focused on skin and respiratory symptoms that would appear during or within a few hours after contact with cows or pigs (feeding and cleaning the animals, milking cows). Subsequently, all farmers underwent skin prick tests with allergens of cow epithelium (Allergopharma, Cat. No. 317) and pig epithelium (Allergopharma, Cat. No. 319). Skin tests were carried out on the ventral surface of the left forearm using prick lancets from Allergopharma. A reaction was considered positive if the wheal diameter was equal to or greater than half the diameter for histamine control. Blood samples were drawn from each tested farmer in order to detect serum IgE antibodies specific to cow dander and pig epithelium allergens. The detection was carried out using UniCAP 100 (Pharmacia & Upjohn Diagnostics AB) with cow dander allergen (e4) and pig epithelium allergen (e83). The antibody concentration was expressed in CAP classes that may range from 0 to 6.

Results

Of 68 farmers tested, none complained of skin or respiratory symptoms that would be provoked by contact with cows or pigs. Specific immune reactivity - either positive skin prick tests and/or specific IgE was found in 13 farmers (19.1%) - 6 women and 7 men. In 6 cases (8.8%) this was positive skin test, in another 6 (8.8%) - detectable specific IgE. In 1 farmer (1.5%) both prick test and specific IgE were positive. The age of farmers with specific immune reactivity ranged from 24 to 72 (median 42) years and did not differ significantly from the remaining farmers (18-84, median 48.5 years). Table I compares the results in farmers who reacted to cow allergens and those non-reactive. Table II presents the results for farmers reactive to pig allergens.

Positive skin prick tests were recorded in 7 farmers (10.3%): 2 persons reacted to cow epithelium, another 2 - to pig epithelium, and the remaining 3 - to both allergens. The 5 farmers (7.4%) with positive skin prick tests to cow epithelium were 2 women and 3 men aged 31-72 (median 35) years. Their contact with cows lasted from 14-51 (median 35) years; the number of cows tended by them was 3-5 (median 4). Positive prick tests with pig epithelium were recorded in 5 farmers (7.4%): in 1 woman and 4 men aged 31-72 (median 61) years. The duration of their contact with pigs was 21 - 58 (median 41) years; the number of pigs looked after by them was 4-20 (median 12). IgE antibodies specific to cow dander or pig epithelium were detected in sera of 7 farmers (10.3%). In 4 persons these were IgE against cow dander, in 1 - against pig epithelium, and in the remaining 2 - against both allergens. The sIgE levels were relatively low and did not exceed CAP class 2. Cow dander-specific IgE was found in 6 farmers (8.8%): 3 women and 3 men aged 30-60 (median 38) years. The duration of their contact with cows ranged from 7-48 (median 27) years. The maximal number of cows tended in this period was 3-5 (median 4). Pig epithelium-specific IgE was detected in 3 farmers (4.4%): 1 woman and 2 men aged 24-60 (median 34) years. Contact of these persons with pigs lasted from 12-46 (median 20) years; the maximal number of pigs tended was 4-6 (median 5). There was no association between skin test results and sIgE. A co-existence of positive skin prick test and sIgE in serum against cow allergens was observed in only 1 farmer. With respect to pig allergens, such a co-existence was not observed.

Discussion

Systematic studies on allergy to farm animals was carried out in Finland, where among 93 healthy cattle breeders 14.0% had positive response to skin tests with cow dander, and 2.2% with pig epithelium (11). Among 620 cases of occupational urticaria and protein contact dermatitis registered in Finland in 1990-1993, cow dander was the most frequent cause and accounted for 276 cases (8). In another Finnish study of farmers with hand eczema, cow dander was responsible for most of positive skin test reactions recorded - 41 of 104 surveyed farmers reacted to it (12). The high frequency of cow allergy in Finland may be due to the fact that cows in that country, due to the cold climate, are kept indoors through most of the year. This leads to the accumulation of allergens and higher exposure of the farmers (8). Less frequent is allergy to farm animals in Denmark, where IgE specific to cow dander was found in 1 of 60 cow breeders, and IgE specific to pig epithelium in 1 of 127 pig breeders (13).

The results of the present study are close to the Danish observations. They also confirm results of a previous questionnaire survey of Polish farmers (10), as well as a study for the presence of IgE specific to cow and pig allergens among Polish breeders (14). In the former study, only 2 (1.4%) of 145 surveyed farmers complained of skin symptoms provoked by contact with cows and pigs (10). In the present study, none of the 68 farmers noticed any skin or respiratory problems in such circumstances. In the second study, cow-specific IgE was detected in 1 of 29 cattle breeders. At that time, the IgE-positive farmer had only mild conjunctivitis when working in cowsheds. However, a year later he developed hand dermatitis provoked by contact with cows (14). It seems that cow allergy in Poland is not as frequent as in Finland. However, such a possibility must be considered in the case of occupational dermatitis or urticaria in cattle breeders.

Allergy to pig epithelium seems to be much less frequent which also becomes apparent from the very scarce reports in the literature. In the only published case report known to the author, symptoms of pig allergy appeared after the 60th year of life (15). In the previously mentioned own study, 22 pig breeders were tested for IgE antibodies specific to pig epithelium, serum albumin and urine proteins. IgE to pig epithelium was detected in 1 farmer - a 63 year-old man who did not experience any health problems related to work with pigs (14). Altogether, these data suggest that pig epithelium is a weak allergen.

In this study, the positive skin test response to farm animal allergens was observed in 7 of 68 farmers (10.3%). In the previous study on the sensitisation to farm allergens of plant origin (16), positive skin tests were recorded in 19.2%, which is almost twice as high. Also, 19.2% farmers complained of work-related skin symptoms, mostly due to hops (11.0%), grain (5.6%), hay (5.5%) and straw (4.1%). In the present study none of the farmers complained of any symptoms while working with animals. In collating the observations, health problems among Polish farmers are more frequently caused by allergens of cultivated plants than by allergens of farm animals.

Conclusions

1. Sensitization (positive skin prick test and/or presence of specific IgE) to cow and pig allergens was found in 19.1% farmers.
2. In no single case did this sensitivity cause any clinical symptoms upon contact with the animals.
3. In Poland, animal allergens pose a lesser threat to farmers' health than plant allergens.

This study was carried out as a part of the statutory research of the Institute of Agricultural Medicine in Lublin, Poland, No. 1.8/01 "Detailed analysis of the causes of occupational skin diseases in farmers". Project co-ordinator: R. Spiewak, MD.

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© Radoslaw Spiewak