Prevalence of Antibodies to Toxoplasma gondii in South Korean Wild Boar (Sus scrofa coreanus) Author(s): Wooseog Jeong, Hachung Yoon, Yong Kwan Kim, Oun-kyong Moon, Do-Soon Kim, and Dong-Jun An Source: Journal of Wildlife Diseases, 50(4):902-905. Published By: Wildlife Disease Association DOI: http://dx.doi.org/10.7589/2013-03-077 URL: http://www.bioone.org/doi/full/10.7589/2013-03-077
BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/ terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder.
BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.
DOI: 10.7589/2013-03-077
Journal of Wildlife Diseases, 50(4), 2014, pp. 902–905 # Wildlife Disease Association 2014
Prevalence of Antibodies to Toxoplasma gondii in South Korean Wild Boar (Sus scrofa coreanus) Wooseog Jeong,1 Hachung Yoon,1 Yong Kwan Kim,1 Oun-kyong Moon,1 Do-Soon Kim,1 and DongJun An1,2 1Animal and Plant Quarantine Agency, 175 Anyang-ro, Manan-gu, Anyang-si, Gyeonggi-do 430-824, Republic of Korea; 2Corresponding author (email: [email protected])
et al. 1997; Sohn et al. 2000). We surveyed the prevalence of T. gondii antibodies in wild boar in South Korea. We analyzed 426 blood samples from wild boar killed by hunters in the eight mainland provinces of South Korea (Fig. 1) during the hunting season (November to February) in 2008–12. Most samples were obtained from adult boar, but information about age and sex was not available. Hunters sent the blood samples to the Animal and Plant Quarantine Agency for a serologic survey of classical swine fever. The blood samples were centrifuged, and the sera were stored at 220 C, until they were tested for antibodies against T. gondii, which were measured using the ID ScreenH toxoplasmosis indirect enzyme-linked immunosorbent assay (ELISA; ID VET, Grabels, France), according to the manufacturer’s instructions. Briefly, wash and conjugate solutions were prepared by diluting concentrated stock solutions 1:20 with deionized distilled water and 1:10 with dilution buffer 3, respectively. We added 75 and 90 ml of dilution buffer 2 to the wells of control and sample plates, respectively, followed by 25 ml of the negative or positive controls, or 10 ml of the serum samples. The plates were kept at room temperature for 4564 min before washing three times with wash solution. We added 100 ml of conjugate to each well, and the plates were incubated at room temperature for 3063 min. After washing three times, 100 ml of substrate solution was added to each well, and the plates were incubated at room temperature for 1562 min in the dark. The reactions were stopped by adding 0.5 M H2SO4, and the optical density (OD) of each sample was
Toxoplasma gondii is an obligate intracellular protozoan parasite and a commonly encountered pathogen in humans and animals. The wild boar (Sus scrofa coreanus) is considered a good indicator when monitoring environmental contamination by T. gondii. We surveyed the prevalence of antibodies against T. gondii in wild boars from South Korea. Blood samples were collected from 426 wild boars captured in eight provinces of South Korea during the hunting seasons in 2008–12. Antibodies against T. gondii were detected using an indirect enzyme-linked immunosorbent assay in samples from 152 of boars, indicating an overall antibody prevalence of 36% (95% confidence interval531– 40%). Key words: ELISA, seroepidemiologic study, Toxoplasma gondii, wild boar.
ABSTRACT:
Toxoplasma gondii is a protozoan parasite that infects most warm-blooded animals, including humans. This pathogen, which has a worldwide distribution, can be transmitted by congenital infection or ingestion of infected tissues or oocysts. The number of humans infected by ingestion of T. gondii-infected meat or with food or water contaminated with T. gondii oocysts is unknown. Most evidence is based on epidemiologic investigations of human cases and prevalence studies in animals (Dubey and Jones 2008). The omnivorous wild boar (Sus scrofa coreanus) is regarded as a good indicator for monitoring environmental contamination with T. gondii. In South Korea, approximately four sounders (groups) of wild boar are observed per each 100 ha, although this number varies among regions. Given that human infections with T. gondii and Trichinella spiralis share similar modes of transmission and that they both can originate from wild boar, it would be beneficial to conduct surveillance studies of T. gondii in wild boar (Choi 902
SHORT COMMUNICATIONS
903
FIGURE 1. Maps of South Korea showing the (A) location of South Korea within East Asia; (B) prevalence of antibodies against Toxoplasma gondii for each province; (C) population density of wild boar (number of boars per 100 ha); and (D) forest area (percentage of province area covered by forest). The increasingly darker shading is in proportion to increasing antibody prevalence, population density, and forest area by province.
read at 450 nm using an ELISA reader (Tecan, Mannedorf, Switzerland). Results were expressed as the ratio of the OD of the sample (S) and the OD of the positive control (P). As advised by the manufacturer, sera were considered positive when the S/P ratio was .50%, doubtful when S/P .40% and ,50%, or negative when S/P ,40%. The 95% confidence interval (CI) of the prevalence was estimated using a binomial method. The antibody prevalence among provinces was compared using a chi-square test. To find a predicting parameter for prevalence of Toxoplasma antibodies, the association of antibody prevalence with wild boar population density (number of boars per 100 ha) or with forest area was
measured. The values of these three variables were divided into two classes based on their median. Two logistic regression models were established, where the response (dependent) variable was antibody prevalence, and the explanatory (independent) variables of each model were boar density and forest area. Forest areas and densities were based on annual data supplied by the National Geographic Information Institute and the National Institute of Biological Resources (Han 2011). Statistical analyses were performed using IBM Statistical Package for the Social Sciences Statistics 21 (IBM, Seoul, Korea). The overall T. gondii antibody prevalence was 36% (95% CI531.1–40%;
904
JOURNAL OF WILDLIFE DISEASES, VOL. 50, NO. 4, OCTOBER 2014
TABLE 1. Numbers of samples of wild boar (Sus scrofa coreanus) tested by enzyme-linked immunosorbent assay for antibodies to Toxoplasma gondii and the test results for each province in South Korea.a Province
Gyeonggi Chungnam Chungbuk Gyeongnam Gyeongbuk Jeonnam Jeonbuk Gangwon Nationwide a
Positive (%) (50%#S/P)
34 12 17 17 16 21 9 26 152
(65) (27) (39) (27) (33) (37) (41) (27) (36)
Negative (%) (S/P#40%)
18 31 27 44 30 35 13 68 266
Doubtful (%) (40%,S/P,50%)
(35) (70) (61) (70) (61) (62) (59) (71) (62)
0 1 0 2 3 0 0 2 8
(0) (2) (0) (3) (6) (0) (0) (2) (2)
Total
52 44 44 63 49 56 22 96 426
S/P 5 ratio of optical density of the sample (S) to that of positive control (P).
Table 1). Only the prevalence in Gyeonggi was significantly different from the other seven provinces (P,1023 chi-square test). The prevalence of antibodies against T. gondii, population density of wild boars, and forest cover are presented in Figure 1. We found no association between prevalence and either population density of wild boars or forest cover, with odds ratios (95% CI) of 1.00 (0.06–15.99) for boar density and 0.11 (0.01–2.73) for forest cover. The widespread prevalence of Toxoplasma as a pathogen is attributable to its ease of transmission between intermediate hosts. Meat from wild boar or other game animals may harbor T. gondii tissue cysts, whose transmission would result in human toxoplasmosis. Any part of the infected pork may be a source of infection, because T. gondii has been found in most edible tissues or cuts of meat in experimentally and naturally infected pigs (Dubey et al. 1986). Usually, humans become infected with T. gondii either via the ingestion of oocysts in soil or water that has been contaminated by cat feces or by the ingestion of cysts in undercooked meat. In South Korea, at least six cases of T. spiralis infections of humans were reported to have originated from wild boar (Shin et al. 2008). This suggests that direct transmission from wild boar via consumption of raw or undercooked meat was the main route of infection. The antibody prevalence in wild boars in South Korea (36%) was high compared
with other countries except Spain. Antibodies against T. gondii were found in 6% (11 of 175) of wild boar from Japan (Matsumoto et al. 2011), 26% (148 of 565) from the Czech Republic (Bartova et al. 2006), 19% (52 of 269) from Austria (Edelhofer et al. 1996), 33% (18 of 54) from Germany (Rommel et al. 1967), and 36% (33 of 91) from Spain (Ruiz-Fons et al. 2006). Although no predicting factor for toxoplasmosis could be identified, the impact of zoonotic infections should not be taken lightly in any situation. This is especially relevant for the province of Gyeonggi, where one quarter of the South Korean population lives and the highest antibody prevalence in boars was found. Appropriate measures should be implemented to address possible public health concerns. LITERATURE CITED Bartova E, Sedlak K, Literak I. 2006. Prevalence of Toxoplasma gondii and Neospora caninum antibodies in wild boars in the Czech Republic. Vet Parasitol 142:150–153. Choi WY, Nam HW, Kwak NH, Hun W, Kim YR, Kang MW, Cho SY, Dubey JP. 1997. Foodborne outbreaks of human toxoplasmosis. J Infect Dis 175:1280–1282. Dubey JP, Jones JL. 2008. Toxoplasma gondii infection in humans and animals in the United States. Int J Parasitol 38:1257–1278. Dubey JP, Murrell KD, Fayer R, Schad GA. 1986. Distribution of Toxoplasma gondii tissue cysts in commercial cuts of pork. J Am Vet Med Assoc 188:1035–1037.
SHORT COMMUNICATIONS
Edelhofer R, Prosl H, Kutzer E. 1996. Zur Trichinellose und Toxoplasmose der Wildschweine in Osto¨sterreich. Wien Tiera¨rztl Monatsschr 83:225–229. Han SH. 2011. Survey and resource management of wildlife. National Institute of Biological Resources, Seoul, South Korea, 25 pp. Matsumoto J, Kako Y, Morita Y, Kabeya H, Sakano C, Nagai A, Maruyama S, Nogami S. 2011. Seroprevalence of Toxoplasma gondii in wild boars (Sus scrofa leucomystax) and wild sika deer (Cervus nippon) in Gunma Prefecture, Japan. Parasitol Int 60:331–332. Rommel M, Sommer R, Janitschke K. 1967. Toxoplasma-infektionen beim Schwarzwild. Z Jagdwiss 13:35–36.
905
Ruiz-Fons F, Vicente J, Vidal D, Hofle U, Villanua D, Gauss C, Segales J, Almeria S, Montoro V, Gortazar C. 2006. Seroprevalence of six reproductive pathogens in European wild boar (Sus scrofa) from Spain: The effect on wild boar female reproductive performance. Theriogenology 65:731–743. Shin EH, Guk SM, Kim HJ, Lee SH, Chai JY. 2008. Trends in parasitic diseases in the Republic of Korea. Trends Parasitol 24:143–150. Sohn WM, Kim HM, Chung DI, Yee ST. 2000. The first human case of Trichinella spiralis infection in Korea. Korean J Parasitol 38:111–115. Submitted for publication 29 March 2013. Accepted 31 March 2014.
BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/ terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder.
BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.
DOI: 10.7589/2013-03-077
Journal of Wildlife Diseases, 50(4), 2014, pp. 902–905 # Wildlife Disease Association 2014
Prevalence of Antibodies to Toxoplasma gondii in South Korean Wild Boar (Sus scrofa coreanus) Wooseog Jeong,1 Hachung Yoon,1 Yong Kwan Kim,1 Oun-kyong Moon,1 Do-Soon Kim,1 and DongJun An1,2 1Animal and Plant Quarantine Agency, 175 Anyang-ro, Manan-gu, Anyang-si, Gyeonggi-do 430-824, Republic of Korea; 2Corresponding author (email: [email protected])
et al. 1997; Sohn et al. 2000). We surveyed the prevalence of T. gondii antibodies in wild boar in South Korea. We analyzed 426 blood samples from wild boar killed by hunters in the eight mainland provinces of South Korea (Fig. 1) during the hunting season (November to February) in 2008–12. Most samples were obtained from adult boar, but information about age and sex was not available. Hunters sent the blood samples to the Animal and Plant Quarantine Agency for a serologic survey of classical swine fever. The blood samples were centrifuged, and the sera were stored at 220 C, until they were tested for antibodies against T. gondii, which were measured using the ID ScreenH toxoplasmosis indirect enzyme-linked immunosorbent assay (ELISA; ID VET, Grabels, France), according to the manufacturer’s instructions. Briefly, wash and conjugate solutions were prepared by diluting concentrated stock solutions 1:20 with deionized distilled water and 1:10 with dilution buffer 3, respectively. We added 75 and 90 ml of dilution buffer 2 to the wells of control and sample plates, respectively, followed by 25 ml of the negative or positive controls, or 10 ml of the serum samples. The plates were kept at room temperature for 4564 min before washing three times with wash solution. We added 100 ml of conjugate to each well, and the plates were incubated at room temperature for 3063 min. After washing three times, 100 ml of substrate solution was added to each well, and the plates were incubated at room temperature for 1562 min in the dark. The reactions were stopped by adding 0.5 M H2SO4, and the optical density (OD) of each sample was
Toxoplasma gondii is an obligate intracellular protozoan parasite and a commonly encountered pathogen in humans and animals. The wild boar (Sus scrofa coreanus) is considered a good indicator when monitoring environmental contamination by T. gondii. We surveyed the prevalence of antibodies against T. gondii in wild boars from South Korea. Blood samples were collected from 426 wild boars captured in eight provinces of South Korea during the hunting seasons in 2008–12. Antibodies against T. gondii were detected using an indirect enzyme-linked immunosorbent assay in samples from 152 of boars, indicating an overall antibody prevalence of 36% (95% confidence interval531– 40%). Key words: ELISA, seroepidemiologic study, Toxoplasma gondii, wild boar.
ABSTRACT:
Toxoplasma gondii is a protozoan parasite that infects most warm-blooded animals, including humans. This pathogen, which has a worldwide distribution, can be transmitted by congenital infection or ingestion of infected tissues or oocysts. The number of humans infected by ingestion of T. gondii-infected meat or with food or water contaminated with T. gondii oocysts is unknown. Most evidence is based on epidemiologic investigations of human cases and prevalence studies in animals (Dubey and Jones 2008). The omnivorous wild boar (Sus scrofa coreanus) is regarded as a good indicator for monitoring environmental contamination with T. gondii. In South Korea, approximately four sounders (groups) of wild boar are observed per each 100 ha, although this number varies among regions. Given that human infections with T. gondii and Trichinella spiralis share similar modes of transmission and that they both can originate from wild boar, it would be beneficial to conduct surveillance studies of T. gondii in wild boar (Choi 902
SHORT COMMUNICATIONS
903
FIGURE 1. Maps of South Korea showing the (A) location of South Korea within East Asia; (B) prevalence of antibodies against Toxoplasma gondii for each province; (C) population density of wild boar (number of boars per 100 ha); and (D) forest area (percentage of province area covered by forest). The increasingly darker shading is in proportion to increasing antibody prevalence, population density, and forest area by province.
read at 450 nm using an ELISA reader (Tecan, Mannedorf, Switzerland). Results were expressed as the ratio of the OD of the sample (S) and the OD of the positive control (P). As advised by the manufacturer, sera were considered positive when the S/P ratio was .50%, doubtful when S/P .40% and ,50%, or negative when S/P ,40%. The 95% confidence interval (CI) of the prevalence was estimated using a binomial method. The antibody prevalence among provinces was compared using a chi-square test. To find a predicting parameter for prevalence of Toxoplasma antibodies, the association of antibody prevalence with wild boar population density (number of boars per 100 ha) or with forest area was
measured. The values of these three variables were divided into two classes based on their median. Two logistic regression models were established, where the response (dependent) variable was antibody prevalence, and the explanatory (independent) variables of each model were boar density and forest area. Forest areas and densities were based on annual data supplied by the National Geographic Information Institute and the National Institute of Biological Resources (Han 2011). Statistical analyses were performed using IBM Statistical Package for the Social Sciences Statistics 21 (IBM, Seoul, Korea). The overall T. gondii antibody prevalence was 36% (95% CI531.1–40%;
904
JOURNAL OF WILDLIFE DISEASES, VOL. 50, NO. 4, OCTOBER 2014
TABLE 1. Numbers of samples of wild boar (Sus scrofa coreanus) tested by enzyme-linked immunosorbent assay for antibodies to Toxoplasma gondii and the test results for each province in South Korea.a Province
Gyeonggi Chungnam Chungbuk Gyeongnam Gyeongbuk Jeonnam Jeonbuk Gangwon Nationwide a
Positive (%) (50%#S/P)
34 12 17 17 16 21 9 26 152
(65) (27) (39) (27) (33) (37) (41) (27) (36)
Negative (%) (S/P#40%)
18 31 27 44 30 35 13 68 266
Doubtful (%) (40%,S/P,50%)
(35) (70) (61) (70) (61) (62) (59) (71) (62)
0 1 0 2 3 0 0 2 8
(0) (2) (0) (3) (6) (0) (0) (2) (2)
Total
52 44 44 63 49 56 22 96 426
S/P 5 ratio of optical density of the sample (S) to that of positive control (P).
Table 1). Only the prevalence in Gyeonggi was significantly different from the other seven provinces (P,1023 chi-square test). The prevalence of antibodies against T. gondii, population density of wild boars, and forest cover are presented in Figure 1. We found no association between prevalence and either population density of wild boars or forest cover, with odds ratios (95% CI) of 1.00 (0.06–15.99) for boar density and 0.11 (0.01–2.73) for forest cover. The widespread prevalence of Toxoplasma as a pathogen is attributable to its ease of transmission between intermediate hosts. Meat from wild boar or other game animals may harbor T. gondii tissue cysts, whose transmission would result in human toxoplasmosis. Any part of the infected pork may be a source of infection, because T. gondii has been found in most edible tissues or cuts of meat in experimentally and naturally infected pigs (Dubey et al. 1986). Usually, humans become infected with T. gondii either via the ingestion of oocysts in soil or water that has been contaminated by cat feces or by the ingestion of cysts in undercooked meat. In South Korea, at least six cases of T. spiralis infections of humans were reported to have originated from wild boar (Shin et al. 2008). This suggests that direct transmission from wild boar via consumption of raw or undercooked meat was the main route of infection. The antibody prevalence in wild boars in South Korea (36%) was high compared
with other countries except Spain. Antibodies against T. gondii were found in 6% (11 of 175) of wild boar from Japan (Matsumoto et al. 2011), 26% (148 of 565) from the Czech Republic (Bartova et al. 2006), 19% (52 of 269) from Austria (Edelhofer et al. 1996), 33% (18 of 54) from Germany (Rommel et al. 1967), and 36% (33 of 91) from Spain (Ruiz-Fons et al. 2006). Although no predicting factor for toxoplasmosis could be identified, the impact of zoonotic infections should not be taken lightly in any situation. This is especially relevant for the province of Gyeonggi, where one quarter of the South Korean population lives and the highest antibody prevalence in boars was found. Appropriate measures should be implemented to address possible public health concerns. LITERATURE CITED Bartova E, Sedlak K, Literak I. 2006. Prevalence of Toxoplasma gondii and Neospora caninum antibodies in wild boars in the Czech Republic. Vet Parasitol 142:150–153. Choi WY, Nam HW, Kwak NH, Hun W, Kim YR, Kang MW, Cho SY, Dubey JP. 1997. Foodborne outbreaks of human toxoplasmosis. J Infect Dis 175:1280–1282. Dubey JP, Jones JL. 2008. Toxoplasma gondii infection in humans and animals in the United States. Int J Parasitol 38:1257–1278. Dubey JP, Murrell KD, Fayer R, Schad GA. 1986. Distribution of Toxoplasma gondii tissue cysts in commercial cuts of pork. J Am Vet Med Assoc 188:1035–1037.
SHORT COMMUNICATIONS
Edelhofer R, Prosl H, Kutzer E. 1996. Zur Trichinellose und Toxoplasmose der Wildschweine in Osto¨sterreich. Wien Tiera¨rztl Monatsschr 83:225–229. Han SH. 2011. Survey and resource management of wildlife. National Institute of Biological Resources, Seoul, South Korea, 25 pp. Matsumoto J, Kako Y, Morita Y, Kabeya H, Sakano C, Nagai A, Maruyama S, Nogami S. 2011. Seroprevalence of Toxoplasma gondii in wild boars (Sus scrofa leucomystax) and wild sika deer (Cervus nippon) in Gunma Prefecture, Japan. Parasitol Int 60:331–332. Rommel M, Sommer R, Janitschke K. 1967. Toxoplasma-infektionen beim Schwarzwild. Z Jagdwiss 13:35–36.
905
Ruiz-Fons F, Vicente J, Vidal D, Hofle U, Villanua D, Gauss C, Segales J, Almeria S, Montoro V, Gortazar C. 2006. Seroprevalence of six reproductive pathogens in European wild boar (Sus scrofa) from Spain: The effect on wild boar female reproductive performance. Theriogenology 65:731–743. Shin EH, Guk SM, Kim HJ, Lee SH, Chai JY. 2008. Trends in parasitic diseases in the Republic of Korea. Trends Parasitol 24:143–150. Sohn WM, Kim HM, Chung DI, Yee ST. 2000. The first human case of Trichinella spiralis infection in Korea. Korean J Parasitol 38:111–115. Submitted for publication 29 March 2013. Accepted 31 March 2014.
