Digestion 16: 1 9 (1977)
Seabirds —a Possible Environmental Factor in Gastric Cancer in Newfoundland C.J. Pfeiffer and W. Threlfall Laboratory of Investigative Gastroenterology, Faculty of Medicine, and Department of Biology, Faculty of Science, Memorial University of Newfoundland, St, John’s, Nfld.
Key Words. Epidemiology • Fishes - Seabirds • Stomach cancer Abstract. Because of the high incidence of gastric cancer in fishermen, in seabird catchers, and in regions generally associated with a temperate or cool marine environment, the association of seabirds with gastric cancer risk was investigated regionally in New foundland. Cartographic plotting and correlation analyses of 23 individual or combined regions of Newfoundland with respect to M, F or M + F mortality rates showed a close similarity between high risk areas and large seabird aggregations which were in the southeast region of the island. Coastal fish processing plants were also prevalent focal points in this region between fishermen and seabird populations, suggesting that a chemical or viral carci nogen should be sought within this triad of fishermen, seabirds, and fish plants.
The etiologic factors involved in the causation of gastric cancer remain obscure, and therefore epidemiologic studies may provide clues to factors associ ated with this disease. Evidence has accumulated to suggest that environmental factors, such as viral and/or chemical carcinogens or cofactors may be respon sible for cancers of many different sites, and indirect evidence for pathogenic environmental factors in gastric cancer is particularly strong (13). Inasmuch as most countries or national subregions in the world which present the highest risk for gastric cancer mortality occur in the vicinity of the marine environment in cooler zones of the northern or southern hemispheres (Iceland, Japan, New foundland, Finland, Chile), there may be a carcinogenic factor related to this cool, marine environment. Furthermore, fishermen have been shown as an occu1 This study was supported in part by PHS grant No. CA 14704-03, of the National Canadian Institute USDHEW.
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Received: December 10, 1976; accepted: February 8, 1977.
Pfeiffer/Threlfall
2
Fig. J. The 23 regions in Newfoundland which were analyzed with respect to gastric cancer risk and seabird populations. The central clear 24th region (No. 10) was not in cluded. Region numbers correspond to table 1. Several regions were combined into 4 zones for further analysis: east (black), north (crossed), west (dotted), and south (lined).
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pational group to be at greatly enhanced risk to gastric cancer in England and Wales (3) and in Newfoundland. It is possible that exposure to seabirds, their excreta or parasites, might be linked directly or indirectly with the prevalence of gastric cancer; indeed, birds are transmitters of many human and other mammalian diseases in temperate climates (2, 4) and data have been reported which documented a 2.5—5-fold increase in gastric cancer mortality in seabird catchers in Skagafjardarsysla (1), a generally high gastric cancer risk area in Iceland. In Canada the maritime prov inces have the highest mortality rates attributable to stomach cancer, and the relative regional risks within the island of Newfoundland have previously been documented (12). Accordingly, the purpose of tire present study was to determine if a rela tionship existed between variation in gastric cancer mortality and exposure of humans to specific seabird populations.
Seabirds and Gastric Cancer
3
Methods Mortality rates for gastric cancer were calculated for each of 23 regions comprising the entire island of Newfoundland except a small central area of the island for the period 1967-71. Labrador, a political region of Newfoundland which is geographically separate from the island was not included due to the small human population there. These data were obtained from the Department of National Health Annual Reports (Ottawa). Seabird popu lations were regionally determined by (a) reference to published accounts (6). or (b) by field study in which estimates were made by counts undertaken at breeding colonies located onshore or at offshore, insular colonies, or by flight counts undertaken in many locations in Newfoundland by standard ornithological counting procedures (10). The seabird population data were obtained with the aid of two ornithological field research assistants. The statistical correlation between bird populations and gastric cancer mortality rates was made with an SPSS statistical program (11), with the aid of an IBM System 370/155 Computer. The correlation was done between (a) the individual 23 regions and bird popula tions associated with each region, or between (b) four composite regions of Newfoundland, designated in figure 1, as N, E, S or W, and the average seabird population representated for each region within the composite. Data on the location of fish processing plants were obtained from unpublished records of the Newfoundland Government, Department of Fisheries, for the year 1971 72 (7).
Variations in crude death rates attributable to gastric cancer throughout Newfoundland are shown in table I. The rates varied front 3.1 deaths to 53.0 male deaths/100,000. The 5 regions with the highest mortality rates were all adjacent to each other, as shown in figures 2—5, in the black-shaded regions, and were located on the eastern end of the island, encompassing part of the Avalon Peninsula. This general area has been associated with enhanced mortality due to gastric cancer, cancer of all sites, and death due to all causes for many years in Newfoundland (12). Cartographic representations of known seabird colonies around Newfound land are shown in figures 2, 3 and 4 for auk, gull and total seabird populations, respectively. As can be seen, these colonies tend to be near the eastern aspect of Newfoundland, with no known colonies of any significant size near the western coast. Thus, by geographic representation, the area of highest gastric cancer mortality in Newfoundland corresponds to the general regions at which most seabirds are congregated along tire coast. Seabirds tend to fly daily over an area of several miles so their presence is evident over a larger zone than the smaller region of their nesting or breeding site. Quantitative analysis of this cartographic finding indicated that (a) signifi cant correlation coefficients were not derived between the bird populations associated with individual regions of Newfoundland (each of 23) and gastric cancer mortality for males, females or combined sexes, but (b) significant corre-
Downloaded by: King's College London 137.73.144.138 - 3/7/2018 12:22:34 PM
Results
Pfeiffer ¡Threlfatl
4
Table I. Regional variations in crude mortality rates in Newfoundland due to gastric cancer, 1967 71 Male
Female
Combined sexes
zone rate (deaths/100,000)
zone rate (deaths/100,000)
zone rate (deaths/100,000)
12 5 18 16 23
53.0 49.1 46.5 45.0 44.9
18 16 7 24 23
30.5 29.6 17.0 16.9 16.7
18 16 12 23 5
38.5 37.6 33.1 31.1 29.2
Medium risk 22 8 4 20 3 24 21 17 9 14 7 13 25
39.3 38.2 36.8 36.3 35.2 31.5 23.1 20.5 19.2 17.3 16.5 15.6 12.8
2 13 12 9 25 11 21 4 1 6 3 5 14
13.9 13.9 13.2 11.7 11.7 11.2 11.0 10.8 10.8 10.1 9.1 8.9 8.5
24 4 22 20 8 3 25 21 7 9 13 14 11
24.5 24.0 23.7 22.6 22.4 22.3 22.2 16.9 16.8 15.5 14.8 12.9 11.6
Low risk
11.4 11.0 9.2 5.4 3.1
20 22 8 19 17
7.9 7.0 5.5 3.3 0.1
17 6 1 19 2
10.4 9.6 8.1 7.6 2.3
High risk
19 11 6 1 2
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lations were evident when the 23 small geographic regions were combined into larger eastern, northern, western, and southern zones. The boundaries of these zones are illustrated in figure 1. Specifically, significant correlation coefficients (p < 0.01) were obtained between the male mortality rates and population of gulls (herring and greater black-backed gulls, black-legged kittiwakes, etc.), and between female mortality rates and combined populations of gulls, auks (common and thick-billed murres, Atlantic puffins, razorbills, etc.), tube-noses (Northern fulmars, shearwaters, storm-petrels), and pelecaniformes (gannets, etc.) species (table II). A cartographic association of the location of fish plants around Newfound land and the high risk gastric cancer mortality zone (5 adjacent regions) is
5
Fig. 2. Distribution of known auk colonies (dotted areas) greater than 5,500 birds, relative to the 5 highest risk regions (black) for gastric cancer mortality in Newfoundland. Fig. 3. Distribution of known gull colonies relative to the 5 highest risk regions (black) for gastric cancer mortality in Newfoundland. Dotted area = 2,000 5,000 birds; lined area = > 20,000 birds in known colonies.
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Seabirds and Gastric Cancer
Pfeiffer/Threlfall
6
Fig. 4. Distribution of the largest aggregation of seabirds (all species combined) relative to the 5 highest risk regions (black) for gastric cancer mortality in Newfoundland. Dotted area = > 1 million; lined area = 14,000-40,000.
Table II. Positive correlations between regional gastric cancer mortality rates and colonies of seabirds in Newfoundland' Seabird type
Mortality type
Correlation coefficient
Significance
Gulls Gulls, auks, tube noses pelecaniformes combined
male death rates
0.996
pCO.Ol
female death rates
0.978
pCO.Ol
Tube noses Auks Pelecaniformes Combined species Gulls
M, F, T M, F, T M, F, T M.T F .T
No significant correlations observed
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1 The correlation was made between the population of each type of seabird (or combined species) and male, female or total mortality rate, each for the four regions (E, S, W, N) as shown in figure 1.
Seabirds and Gastric Cancer
7
Fig. 5. Distribution of fish processing plants in Newfoundland, 1971 72. Each dot represents 1 plant, except where indicated as 4, 11, 10 or 5 plants. The black areas are the 5 regions of highest risk for gastric cancer mortality.
illustrated in figure 5. There is a general scarcity of plants in tire lower risk regions, while two of the highest risk regions contained 11 and 10 fish plants, the majority of fishermen in Newfoundland are independent ‘inshore fishermen’ who reside in coastal villages all around the island. Larger numbers live in the bays shown in figure 5 where fish plants are most numerous.
The above data present an analysis in geographic pathology, including a quantitative survey, and correlate a specific disease of unknown etiology with biologic parameters. Because of the obscure causation of gastric cancer, a disease which may have multiple causes and which likely relates to environmental factors, it is desirable to investigate factors near the marine environment because the disease is especially but not exclusively present there. The moderate degree of correlation observed between the regional variations in gastric cancer and
Downloaded by: King's College London 137.73.144.138 - 3/7/2018 12:22:34 PM
Discussion
Pfeiffer/Threlfall
8
seabird populations, as well as the possible linking factor, fish processing plants, may be a useful epidemiologic lead, especially in view of the enhanced risk of fishermen in Newfoundland, Iceland, England and Wales to this disease (3). It is important to stress that these data, while showing association, do not prove causality, and indeed may be coincidental. However, this finding, when taken into consideration with other and international data, may indicate a promising line of investigation for further study. Many infectious and viral diseases are already known to be transmitted in temperate climates to humans by birds, including histoplasmosis, central Euro pean encephalitis, Californian encephalitis, ornithosis, brucellosis, leptospirosis, Kyasanur fever, salmonellosis, listeriosis, toxoplasmosis, tularemia, Q fever, etc. (4). Seabirds are usually infested with ticks, which can harbor viruses for extended periods of time. In Newfoundland the presence of an arbovirusinfection of ticks on seabirds of several species has recently been reported (5, 9) and at least one strain of these arboviruses has been shown to be fatal to mice after inoculation (8). Although such an arbovirus link for human cancer may be dubious, even though one has been suggested for Burkitt’s lymphoma in Africa, a more plausible link might be with accidental ingestion of carcinogenic fungal metabolites, present on seabird excreta, to which fishermen or others in the marine environment might be exposed. In this respect, the presence of coastal fish processing plants, which attracts seabirds because of an easy food supply, might be a component of the triad (a) increased risk for gastric cancer: (b) in creased concentrations of seabirds, and (c) presence of fish processing plants which both attract seabirds and congregate fishermen, who are known to have an increased incidence of gastric cancer. Although these data are presented only to provide documentation for a hypothesis, this lead may be useful for further studies on the occupational risks and environmental factors which influence the mortality due to gastric cancer.
References
Downloaded by: King's College London 137.73.144.138 - 3/7/2018 12:22:34 PM
1 Dungal, N.: Stomach cancer in Iceland. Proc. Can. Can. Coni'. 6: 441 -450 (1964). 2 Joint WHO/FAO Expert Committee on Zoonoses: 2nd Report. WHO Tech. Rep. Ser. No. 169. pp. 56-61 (WHO. Geneva 19S9). 3 The Registrar General’s Decennial Supplement, England and Wales, 1961: Occupa tional mortality tables, p. 1 32 (HMSO, London 1961). 4 Report of a WHO scientific group, arboviruses and human disease. WHO Tech. Rep. Ser. No. 369, pp. 27 31 (WHO, Geneva 1967). 5 Eveleigh, b.S. and Threlfall, IV.. Bionomics of Ixodes (Ceratixodes) uriae White, 1852 on auks (Alcidae) from Newfoundland. Can. J. Zool. 55: 82-86 (1975). 6 Gillespie, D.l. and Learning, J. W.: Eider numbers and distribution off Newfoundland; in Boyd Waterfowl studies. Can. Wldl. Surv. Rpt. Ser. 29: 73 78 (1974).
Seabirds and Gastric Cancer
8
9
10 11 12 13
List of registered filleting and freezing plants in Newfoundland, 1971 72: Unpub lished records, Department of Fisheries, Newfoundland Government, St. John’s (1972). Main, A.J.; Downs, W.G.: Shope, R.E., and Wallis, R.C.: Great Island and Bauline. Two new Kemerovo group orbiviruses from Ixodes uriae in eastern Canada. J. med. Ent. 10: 229-235 (1973). Main, A.J.; Downs, W.G.: Shope, R.E., and Wallis, R.C.: Avian arboviruses of the Witless Bay seabird sanctuary, Newfoundland, Canada. J. wldl. Dis. 12: 182-194 (1976). Nettleship, D.N.: Census techniques for seabirds of arctic and eastern Canada. Can. Wldl. Serv. Occ. Paper 25: 1-33 (1976). Nie, N.H.: Bent, D.H., and Hull, C.H.: Statistical package for the social sciences, pp. 174-195 (McGraw-Hill, New York 1970). Pfeiffer, C.J.; Fodor, J.G., and Canning, E.: An epidemiologic analysis of mortality and gastric cancer in Newfoundland. Can. med. Ass. J. 108: 1374 1380 (1973). Pfeiffer, C.J.: Epidemiologie des Magenkarzinoms. Leber Magen Darm. 6: 59-71 (1976).
Prof. Carl J. Pfeiffer, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Nfld. AIC3V6 (Canada)
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9
Seabirds —a Possible Environmental Factor in Gastric Cancer in Newfoundland C.J. Pfeiffer and W. Threlfall Laboratory of Investigative Gastroenterology, Faculty of Medicine, and Department of Biology, Faculty of Science, Memorial University of Newfoundland, St, John’s, Nfld.
Key Words. Epidemiology • Fishes - Seabirds • Stomach cancer Abstract. Because of the high incidence of gastric cancer in fishermen, in seabird catchers, and in regions generally associated with a temperate or cool marine environment, the association of seabirds with gastric cancer risk was investigated regionally in New foundland. Cartographic plotting and correlation analyses of 23 individual or combined regions of Newfoundland with respect to M, F or M + F mortality rates showed a close similarity between high risk areas and large seabird aggregations which were in the southeast region of the island. Coastal fish processing plants were also prevalent focal points in this region between fishermen and seabird populations, suggesting that a chemical or viral carci nogen should be sought within this triad of fishermen, seabirds, and fish plants.
The etiologic factors involved in the causation of gastric cancer remain obscure, and therefore epidemiologic studies may provide clues to factors associ ated with this disease. Evidence has accumulated to suggest that environmental factors, such as viral and/or chemical carcinogens or cofactors may be respon sible for cancers of many different sites, and indirect evidence for pathogenic environmental factors in gastric cancer is particularly strong (13). Inasmuch as most countries or national subregions in the world which present the highest risk for gastric cancer mortality occur in the vicinity of the marine environment in cooler zones of the northern or southern hemispheres (Iceland, Japan, New foundland, Finland, Chile), there may be a carcinogenic factor related to this cool, marine environment. Furthermore, fishermen have been shown as an occu1 This study was supported in part by PHS grant No. CA 14704-03, of the National Canadian Institute USDHEW.
Downloaded by: King's College London 137.73.144.138 - 3/7/2018 12:22:34 PM
Received: December 10, 1976; accepted: February 8, 1977.
Pfeiffer/Threlfall
2
Fig. J. The 23 regions in Newfoundland which were analyzed with respect to gastric cancer risk and seabird populations. The central clear 24th region (No. 10) was not in cluded. Region numbers correspond to table 1. Several regions were combined into 4 zones for further analysis: east (black), north (crossed), west (dotted), and south (lined).
Downloaded by: King's College London 137.73.144.138 - 3/7/2018 12:22:34 PM
pational group to be at greatly enhanced risk to gastric cancer in England and Wales (3) and in Newfoundland. It is possible that exposure to seabirds, their excreta or parasites, might be linked directly or indirectly with the prevalence of gastric cancer; indeed, birds are transmitters of many human and other mammalian diseases in temperate climates (2, 4) and data have been reported which documented a 2.5—5-fold increase in gastric cancer mortality in seabird catchers in Skagafjardarsysla (1), a generally high gastric cancer risk area in Iceland. In Canada the maritime prov inces have the highest mortality rates attributable to stomach cancer, and the relative regional risks within the island of Newfoundland have previously been documented (12). Accordingly, the purpose of tire present study was to determine if a rela tionship existed between variation in gastric cancer mortality and exposure of humans to specific seabird populations.
Seabirds and Gastric Cancer
3
Methods Mortality rates for gastric cancer were calculated for each of 23 regions comprising the entire island of Newfoundland except a small central area of the island for the period 1967-71. Labrador, a political region of Newfoundland which is geographically separate from the island was not included due to the small human population there. These data were obtained from the Department of National Health Annual Reports (Ottawa). Seabird popu lations were regionally determined by (a) reference to published accounts (6). or (b) by field study in which estimates were made by counts undertaken at breeding colonies located onshore or at offshore, insular colonies, or by flight counts undertaken in many locations in Newfoundland by standard ornithological counting procedures (10). The seabird population data were obtained with the aid of two ornithological field research assistants. The statistical correlation between bird populations and gastric cancer mortality rates was made with an SPSS statistical program (11), with the aid of an IBM System 370/155 Computer. The correlation was done between (a) the individual 23 regions and bird popula tions associated with each region, or between (b) four composite regions of Newfoundland, designated in figure 1, as N, E, S or W, and the average seabird population representated for each region within the composite. Data on the location of fish processing plants were obtained from unpublished records of the Newfoundland Government, Department of Fisheries, for the year 1971 72 (7).
Variations in crude death rates attributable to gastric cancer throughout Newfoundland are shown in table I. The rates varied front 3.1 deaths to 53.0 male deaths/100,000. The 5 regions with the highest mortality rates were all adjacent to each other, as shown in figures 2—5, in the black-shaded regions, and were located on the eastern end of the island, encompassing part of the Avalon Peninsula. This general area has been associated with enhanced mortality due to gastric cancer, cancer of all sites, and death due to all causes for many years in Newfoundland (12). Cartographic representations of known seabird colonies around Newfound land are shown in figures 2, 3 and 4 for auk, gull and total seabird populations, respectively. As can be seen, these colonies tend to be near the eastern aspect of Newfoundland, with no known colonies of any significant size near the western coast. Thus, by geographic representation, the area of highest gastric cancer mortality in Newfoundland corresponds to the general regions at which most seabirds are congregated along tire coast. Seabirds tend to fly daily over an area of several miles so their presence is evident over a larger zone than the smaller region of their nesting or breeding site. Quantitative analysis of this cartographic finding indicated that (a) signifi cant correlation coefficients were not derived between the bird populations associated with individual regions of Newfoundland (each of 23) and gastric cancer mortality for males, females or combined sexes, but (b) significant corre-
Downloaded by: King's College London 137.73.144.138 - 3/7/2018 12:22:34 PM
Results
Pfeiffer ¡Threlfatl
4
Table I. Regional variations in crude mortality rates in Newfoundland due to gastric cancer, 1967 71 Male
Female
Combined sexes
zone rate (deaths/100,000)
zone rate (deaths/100,000)
zone rate (deaths/100,000)
12 5 18 16 23
53.0 49.1 46.5 45.0 44.9
18 16 7 24 23
30.5 29.6 17.0 16.9 16.7
18 16 12 23 5
38.5 37.6 33.1 31.1 29.2
Medium risk 22 8 4 20 3 24 21 17 9 14 7 13 25
39.3 38.2 36.8 36.3 35.2 31.5 23.1 20.5 19.2 17.3 16.5 15.6 12.8
2 13 12 9 25 11 21 4 1 6 3 5 14
13.9 13.9 13.2 11.7 11.7 11.2 11.0 10.8 10.8 10.1 9.1 8.9 8.5
24 4 22 20 8 3 25 21 7 9 13 14 11
24.5 24.0 23.7 22.6 22.4 22.3 22.2 16.9 16.8 15.5 14.8 12.9 11.6
Low risk
11.4 11.0 9.2 5.4 3.1
20 22 8 19 17
7.9 7.0 5.5 3.3 0.1
17 6 1 19 2
10.4 9.6 8.1 7.6 2.3
High risk
19 11 6 1 2
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lations were evident when the 23 small geographic regions were combined into larger eastern, northern, western, and southern zones. The boundaries of these zones are illustrated in figure 1. Specifically, significant correlation coefficients (p < 0.01) were obtained between the male mortality rates and population of gulls (herring and greater black-backed gulls, black-legged kittiwakes, etc.), and between female mortality rates and combined populations of gulls, auks (common and thick-billed murres, Atlantic puffins, razorbills, etc.), tube-noses (Northern fulmars, shearwaters, storm-petrels), and pelecaniformes (gannets, etc.) species (table II). A cartographic association of the location of fish plants around Newfound land and the high risk gastric cancer mortality zone (5 adjacent regions) is
5
Fig. 2. Distribution of known auk colonies (dotted areas) greater than 5,500 birds, relative to the 5 highest risk regions (black) for gastric cancer mortality in Newfoundland. Fig. 3. Distribution of known gull colonies relative to the 5 highest risk regions (black) for gastric cancer mortality in Newfoundland. Dotted area = 2,000 5,000 birds; lined area = > 20,000 birds in known colonies.
Downloaded by: King's College London 137.73.144.138 - 3/7/2018 12:22:34 PM
Seabirds and Gastric Cancer
Pfeiffer/Threlfall
6
Fig. 4. Distribution of the largest aggregation of seabirds (all species combined) relative to the 5 highest risk regions (black) for gastric cancer mortality in Newfoundland. Dotted area = > 1 million; lined area = 14,000-40,000.
Table II. Positive correlations between regional gastric cancer mortality rates and colonies of seabirds in Newfoundland' Seabird type
Mortality type
Correlation coefficient
Significance
Gulls Gulls, auks, tube noses pelecaniformes combined
male death rates
0.996
pCO.Ol
female death rates
0.978
pCO.Ol
Tube noses Auks Pelecaniformes Combined species Gulls
M, F, T M, F, T M, F, T M.T F .T
No significant correlations observed
Downloaded by: King's College London 137.73.144.138 - 3/7/2018 12:22:34 PM
1 The correlation was made between the population of each type of seabird (or combined species) and male, female or total mortality rate, each for the four regions (E, S, W, N) as shown in figure 1.
Seabirds and Gastric Cancer
7
Fig. 5. Distribution of fish processing plants in Newfoundland, 1971 72. Each dot represents 1 plant, except where indicated as 4, 11, 10 or 5 plants. The black areas are the 5 regions of highest risk for gastric cancer mortality.
illustrated in figure 5. There is a general scarcity of plants in tire lower risk regions, while two of the highest risk regions contained 11 and 10 fish plants, the majority of fishermen in Newfoundland are independent ‘inshore fishermen’ who reside in coastal villages all around the island. Larger numbers live in the bays shown in figure 5 where fish plants are most numerous.
The above data present an analysis in geographic pathology, including a quantitative survey, and correlate a specific disease of unknown etiology with biologic parameters. Because of the obscure causation of gastric cancer, a disease which may have multiple causes and which likely relates to environmental factors, it is desirable to investigate factors near the marine environment because the disease is especially but not exclusively present there. The moderate degree of correlation observed between the regional variations in gastric cancer and
Downloaded by: King's College London 137.73.144.138 - 3/7/2018 12:22:34 PM
Discussion
Pfeiffer/Threlfall
8
seabird populations, as well as the possible linking factor, fish processing plants, may be a useful epidemiologic lead, especially in view of the enhanced risk of fishermen in Newfoundland, Iceland, England and Wales to this disease (3). It is important to stress that these data, while showing association, do not prove causality, and indeed may be coincidental. However, this finding, when taken into consideration with other and international data, may indicate a promising line of investigation for further study. Many infectious and viral diseases are already known to be transmitted in temperate climates to humans by birds, including histoplasmosis, central Euro pean encephalitis, Californian encephalitis, ornithosis, brucellosis, leptospirosis, Kyasanur fever, salmonellosis, listeriosis, toxoplasmosis, tularemia, Q fever, etc. (4). Seabirds are usually infested with ticks, which can harbor viruses for extended periods of time. In Newfoundland the presence of an arbovirusinfection of ticks on seabirds of several species has recently been reported (5, 9) and at least one strain of these arboviruses has been shown to be fatal to mice after inoculation (8). Although such an arbovirus link for human cancer may be dubious, even though one has been suggested for Burkitt’s lymphoma in Africa, a more plausible link might be with accidental ingestion of carcinogenic fungal metabolites, present on seabird excreta, to which fishermen or others in the marine environment might be exposed. In this respect, the presence of coastal fish processing plants, which attracts seabirds because of an easy food supply, might be a component of the triad (a) increased risk for gastric cancer: (b) in creased concentrations of seabirds, and (c) presence of fish processing plants which both attract seabirds and congregate fishermen, who are known to have an increased incidence of gastric cancer. Although these data are presented only to provide documentation for a hypothesis, this lead may be useful for further studies on the occupational risks and environmental factors which influence the mortality due to gastric cancer.
References
Downloaded by: King's College London 137.73.144.138 - 3/7/2018 12:22:34 PM
1 Dungal, N.: Stomach cancer in Iceland. Proc. Can. Can. Coni'. 6: 441 -450 (1964). 2 Joint WHO/FAO Expert Committee on Zoonoses: 2nd Report. WHO Tech. Rep. Ser. No. 169. pp. 56-61 (WHO. Geneva 19S9). 3 The Registrar General’s Decennial Supplement, England and Wales, 1961: Occupa tional mortality tables, p. 1 32 (HMSO, London 1961). 4 Report of a WHO scientific group, arboviruses and human disease. WHO Tech. Rep. Ser. No. 369, pp. 27 31 (WHO, Geneva 1967). 5 Eveleigh, b.S. and Threlfall, IV.. Bionomics of Ixodes (Ceratixodes) uriae White, 1852 on auks (Alcidae) from Newfoundland. Can. J. Zool. 55: 82-86 (1975). 6 Gillespie, D.l. and Learning, J. W.: Eider numbers and distribution off Newfoundland; in Boyd Waterfowl studies. Can. Wldl. Surv. Rpt. Ser. 29: 73 78 (1974).
Seabirds and Gastric Cancer
8
9
10 11 12 13
List of registered filleting and freezing plants in Newfoundland, 1971 72: Unpub lished records, Department of Fisheries, Newfoundland Government, St. John’s (1972). Main, A.J.; Downs, W.G.: Shope, R.E., and Wallis, R.C.: Great Island and Bauline. Two new Kemerovo group orbiviruses from Ixodes uriae in eastern Canada. J. med. Ent. 10: 229-235 (1973). Main, A.J.; Downs, W.G.: Shope, R.E., and Wallis, R.C.: Avian arboviruses of the Witless Bay seabird sanctuary, Newfoundland, Canada. J. wldl. Dis. 12: 182-194 (1976). Nettleship, D.N.: Census techniques for seabirds of arctic and eastern Canada. Can. Wldl. Serv. Occ. Paper 25: 1-33 (1976). Nie, N.H.: Bent, D.H., and Hull, C.H.: Statistical package for the social sciences, pp. 174-195 (McGraw-Hill, New York 1970). Pfeiffer, C.J.; Fodor, J.G., and Canning, E.: An epidemiologic analysis of mortality and gastric cancer in Newfoundland. Can. med. Ass. J. 108: 1374 1380 (1973). Pfeiffer, C.J.: Epidemiologie des Magenkarzinoms. Leber Magen Darm. 6: 59-71 (1976).
Prof. Carl J. Pfeiffer, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Nfld. AIC3V6 (Canada)
Downloaded by: King's College London 137.73.144.138 - 3/7/2018 12:22:34 PM
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9
