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A six-year follow-up of antibody levels against microbes present in the farming environment in a group of dairy farmers in finland.

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American Journal of Industrial Medicine 103W-309 (1986)
A Six-Year Follow-Up of Antibody Levels Against
Microbes Present in the Farming Environment in a
Group of Dairy Farmers in Finland
Marja-Leena Katila, MD, Tarja Ojanen, MSC, and Rauno Mantyjarvi, MD
Key words: hay dust, moulds, sensitization, ELISA titers
A group of 325 dairy farmers and 107 rural, nonfarming controls (N = 432),
which were studied 6 years earlier for respiratory symptoms and antibodies against
known farmer’s lung (FL) antigens [Katila, 19791, were restudied by a symptom
questionnaire and by antibody analysis. Ninety percent of the farmers and 71 % of the
control group were reached for reevaluation. Serum samples of the two surveys were
tested for IgG antibodies against Micropolysporu fueni (Mf), Themactinomyces
vulgaris (Tv) , Aspergillus umbrosus (Au), and Aspergillus fimigutus (Af) using
ELISA technique [Ojanen et al, 19801, which allows quantitation of antibody levels.
Sensitization, when measured by antibody titers, varied greatly in respect to
different microbes (Table I). High antibody titers against Au and Mf were more
common in farming men and women than in the controls (p < 0.001 and < 0.05,
respectively). High antibody titers against Af were equally common in all study
groups, and those against Tv were equally or more common in controls than in the
farming men and women.
The levels of specific IgG against the four microbes were measured from the
two serum samples of each person. The majority of farmers (70%) (Table 11) and
controls (74%) had no significant changes in antibody levels against any of the studied
microbes. Elevations in antibody levels against one or more of the test antigens were
detected in 20% and decreases in 11% of the farmers and in 20% and 14% of the
controls, respectively. In the farmers, Aspergillus antibody levels changed more
(24%) than antibody levels against actinomyces (12%). Some persons had both rises
and falls in antibody titers against different microbes, but this was uncommon.
In the farmers, decreases in antibody titers were found more often in older age
groups and in those persons who had quit farming (p c 0.01) (Table II). In the entire
farming population, decreases were detected in 29% of the farmers retired for
illnesses compared to 8 % of those farming throughout the follow-up period and 10%
of those having stopped because of older age or reasons other than illness. Decreases
Department of Clinical Microbiology, Kuopio University Central Hospital, Kuopio, Finland.
Address reprint requests to Dr. Marja-Leena Katila, Mycobacterium Reference Unit, Public Health
Laboratory Service, University Hospital, Wales, Cardiff CF4 4XW, UK.
Accepted for publication January 16, 1986.
0 1986 Alan R. Liss, Inc.
308
Katila et a1
TABLE I. Prevalence of High Antibody Titers in Farmers and Controls (1975)
High antibody
titer against
Men
Farming
Control
(N = 151) (N = 44)
Au ( 2 2.50)
No.
%
Af ( 2 2.80)
No.
%
Mf ( 2 2.80)
No.
%
Tv ( 2 3.90)
No.
%
Women
Farming
Control
(N = 138) (N = 36)
Total
(N = 369)
Significance:
farmers vs
controls
p < 0.01
54
36
2
5
75
54
3
8
134
36
34
22
10
23
35
25
9
25
88
24
NS
19
13
4
9
29
21
2
6
54
15
p < 0.05
16
11
12
27
30
21
9
25
67
18
p < 0.05
TABLE II. Changes in Antibody Levels by Changes in OccupationalStatus in the Farming
Population (1975-1981)
Occupational status in
the second survey
Farming
No.
%
Increasea
Decreasea
No change
Total
45
22
17
8
149
72
208
6
14
12
29
21
64
42
8
20
4
10
29
71
41
59
20
p = 0.05
33
11
p < 0.01
205
70
29 1
Retired for illness
No.
%
Changed occupation
or on pension
No.
%
Total
No.
%
Significance
aSome persons had both increases and decreases against different microbes.
in Aspergillus antibodies had the closest association with these occupational changes,
especially in women aged 30 to 65 years by the end of the follow-up period (p C
0.001).
In contrast to decreases, increases in antibody levels were more frequent in
younger age groups, being found in 31 % (4/13) of farmers under 31 years, in 25%
(28/114) of those aged 31-50 years, and 14% (19/138) of those aged 51-65 years.
There was an association between onset of respiratory symptoms in previously
asymptomatic farmers and rises in antibody levels. Of the 34 who began to experience
dust-related symptoms, 12 (35%) had rises in antibody levels compared to 27 (18%)
of those 146 who had no symptoms in the second survey.
The ELISA method is very suitable for antibody measurements in environmental
microbial exposure. In view of this 6-year follow-up, the degree of sensitization when
Six-Year Follow-Up of Antibody Levels
309
expressed as titers was surprisingly stable in constantly exposed “healthy” farmers.
Rises in antibody levels were more common in the younger age groups, and levels
seemed to have an association with the onset of respiratory symptoms in previously
asymptomatic farmers. Decreases in antibody titers against all microbes but especially
against Aspergilli were associated with definite cessation of exposure only. In those
continuously exposed, the association between specific IgG antibody titers, level of
exposure, and respiratory symptoms is very complex. According to preliminary
experiences, changes in specific IgG subclasses, as well as in other immunoglobulin
classes, may offer some advantages for diagnostic work in this field.
REFERENCES
Katila M-L (1979): “Respiratory Disease in a Farming Population. A Sero-Epidemiological Survey of
Farmer’s Lung and Chronic Non-Specific Lung Disease Among Dairy Farmers in Eastern
Finland. PhD Thesis, University of Kuopio, 1979.
Ojanen TH, Katila M-L,Mantyjiirvi RA (1980): The use of enzyme-linked immunosorbent assay
(ELISA) in the diagnosis of farmer’s lung. Allergy 35537-542.
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environment, years, level, follow, group, present, farming, finland, antibody, six, farmer, microbes, dairy
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