Food Environ Virol DOI 10.1007/s12560-016-9231-y
BRIEF COMMUNICATION
Prevalence of Hepatitis E Virus (HEV) Antibodies in Mexican Pigs Teresa Merino-Ramos1 • Miguel A. Martı´n-Acebes1 • Jordi Casal2,3 Juan-Carlos Saiz1 • Elizabeth Loza-Rubio4
•
Received: 15 December 2015 / Accepted: 8 February 2016 Springer Science+Business Media New York 2016
Abstract The hepatitis E virus (HEV) is the causative agent of Hepatitis E, an enterically transmitted disease. HEV infections in pigs and humans have been reported worldwide, but data from Mexico are scarce. In the present study, the prevalence of anti-HEV IgG antibodies was investigated in a quite large number of swine from Mexico by means of an ELISA based on a recombinant open reading frame 2 protein of HEV genotype 3. Serum samples from 683 healthy pigs (1–48 months old), collected during 2010–2013 in 109 herds from 48 municipalities located in 9 states in the centre of the country were assayed. A 30.75 % (210/683) of the sera tested were positive, and they were distributed along all the states included in the study. The prevalence of anti-HEV antibodies varied widely between municipalities and herds, and it was higher in pigs 4–6 months of age. No relationships were detected between seroprevalences and farm characteristics. Forty individual faecal samples were analysed by RT-PCR and all resulted negative. These data indicate that HEV infection is widespread in Mexican pigs; thus, representing a potential zoonotic risk for humans.
& Juan-Carlos Saiz [email protected] 1
Departamento de Biotecnologı´a, Instituto Nacional de Investigacio´n y Tecnologı´a Agraria y Alimentaria (INIA), Madrid, Spain
2
Departament de Sanitat i Anatomia Animals, Universitat Auto`noma de Barcelona (UAB), Barcelona, Spain
3
Institut de Recerca i Tecnologia Agroalimenta`ries (IRTA), Bellaterra, Barcelona, Spain
4
Instituto Nacional de Investigaciones Agrı´colas, Forestales y Pecuarias (CENID-Microbiologı´a), Carretera Me´xico-Toluca Km. 15.5, Colonia Palo Alto, 05110 Me´xico, DF, Mexico
Keywords HEV Mexico Pigs Seroprevalence ELISA RNA
Introduction Hepatitis E is an enterically transmitted disease caused by the hepatitis E virus (HEV) that is endemic in regions where sanitary conditions and water supplies are inadequate (Kamar et al. 2014). In contrast to the usually waterborne HEV infections reported in endemic developing countries, in non-endemic countries sporadic hepatitis E is mainly a zoonotic and food-borne disease (Yugo and Meng 2013). Although only a single serotype is recognized, considerable genetic diversity occurs among HEV isolates, so that they are grouped into four genotypes (gt). Viruses responsible for epidemics and sporadic cases in endemic regions are mainly classified into gt 1 and 2, which only infect humans. Those viruses detected in sporadic cases of acute hepatitis E elsewhere in the world are clustered into gt 3 and 4, and are considered as zoonotic strains (Okamoto 2007). After the first isolation of a HEV swine strain was reported in 1997 (Meng et al. 1997), several evidences have pointed to pigs as a natural reservoir of HEV with a potential zoonotic risk (Pavio et al. 2015). Infected pigs shed virus through faeces, but infection is sub-clinical and asymptomatic and viremia is short, which makes difficult viral detection. However, RT-PCR amplification of HEVRNA has shown that HEV is present in pig farms around the world (Pavio et al. 2010), and that it can be amplified from pork meat sold in local markets (Renou et al. 2014; Riveiro-Barciela et al. 2014), including Mexican’s ones (Cantu´-Martı´nez et al. 2013). These facts stress the possible risk of a zoonotic transmission, as it has been
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previously confirmed in people that ate dear, pork, or wild boar uncooked meat and liver (Pavio et al. 2010). Likewise, a quite high prevalence of anti-HEV IgG in swine populations around the world has also been reported (Pavio et al. 2010); being usually higher in animals older than 4 months of age (Meng et al. 1997; De Deus et al. 2008; Pavio et al. 2010). However, little is known about HEV activity in Mexico. Human outbreaks were reported in Mexico in 1986–1987, and the further described prevalence (ranging from 1 to 10 %) is similar to that of other regions in Central and South America (Echevarrı´a et al. 2013). Information about HEV circulation in Mexican swine populations is even scarcer, although porcine production in Mexico is second to Brazil in Central and South America, with over 1300 million tons of meat/year (http:// www.financierarural.gob.mx/). An early report (Cooper et al. 2005) described that up to 81 % of the 125 pigs tested were IgG positive, and detected HEV-RNA in 6.4 % (8/125) and 30.4 % (28/92) of sera and faecal samples, respectively, from 2- to 4-month-old pigs. All swine-amplified genomes corresponded to gt 3 strains, as were those very recently amplified from HEV-RNA positive pigs liver sold for human consumption in local markets form Nuevo Leo´n, Mexico (Cantu´-Martı´nez et al. 2013). In the present study, the prevalence of anti-HEV IgG in the serum of a large number (n = 683) of Mexican pigs collected in 109 herds from 48 municipalities located in 9 states in the centre of the country has been determined.
Methods Swine serum samples (n = 683) were collected along 2010–2013 as part of a non-probabilistic convenience cross-sectional survey conducted in 9 states in the centre of the country (Fig. 1). Sample size was estimated by the proportion formula (Levy and Lemeshow 1980) with a 50 % estimated prevalence (as no previous data were available in the country), a 4 % desired precision, and 95 % of confidence level. Samples were from pigs ([1 to 48 months of age) grown in backyard and commercial farms (average 6 samples/farm) from 48 municipalities. Written permission was obtained from the farm’s owners for sampling collection and the study was conducted following all applicable guidelines related to animal welfare. The study was approved by the Institutional Animal Care and Use Committee (IACUC) of the Centro Nacional de Investigacio´n Disciplinaria en Microbiologı´a Animal (No. approval: 001-2012). A questionnaire was filled up by most of the farm’s managers, which includes information about type of farming and production, kind and way of feeding,
123
water sources, sanitary status (vaccination, recent diseases sings,…), etc. Serum samples were tested by means of a validated ELISA based on the use of recombinant HEV gt 3 ORF-2 expressed in Trichoplusia ni larvae as antigen (Jime´nez de Oya et al. 2009a, b). As controls, previously characterized positive and negative swine sera pools were used (Lupulovic et al. 2010; Jime´nez de Oya et al. 2011). The cut-off of the assay was established as 2.5 times the A495 value of the negative sera pool that was included in each plate (0.15, range 0.08–0.14). Test samples with optical density equal to or greater than cut-off value were considered positive. In addition, presence of HEV-RNA was analysed, by means of a nested RT-PCR (Jime´nez de Oya et al. 2011), in 40 individual faecal samples (20 from male and 20 from female pigs) from farms located in three of the states (Queretaro, Guanajuato and Estado de Me´xico). A Chisquared test was used to determine possible relationships between positive results and the different variables analysed.
Results A total of 210 of the 683 (30.75 %) serum samples tested were ELISA positive (Table 1). The proportion of antiHEV IgG positive animals was statistically significantly higher among animals 4–6 months of age (43 %) than among younger (17.6 %, p \ 0.0001) or older pigs (31.5 %. p \ 0.01). The prevalence of anti-HEV antibodies varied widely between and within states and municipalities, but there were seropositive pigs in all states covered by the study with prevalence ranging from 3 % in Puebla to 46 % and 58 % in Queretaro and Jalisco, being these figures significantly different (p \ 0.005) when compared with the remaining states included in the study (Table 1). However, no appreciable geographical or climatic differences were found regarding the seroprevalence rates. For instance, farms from the same state showed uneven seroprevalences, and similar patterns were also observed in farms located within a single municipality. As shown in Table 1, at least one pig was positive for anti-HEV IgG 63.3 % of the tested herds (69/109). However, the prevalence was again quite variable between farms and locations. Likewise, the proportion of tested pigs with anti-HEV IgG among positive farms was also quite variable (66.7 %, range 8–100 %), and no differences were observed regarding the information provided by farmers on the variables included in the questionnaire (type of management, feeding, water supplies or sanitary status). No HEV-RNA was amplified in any of the 40 faecal samples from pigs of different ages tested, corresponding
Food Environ Virol
Fig. 1 Map showing the percentage of HEV-IgG positive pigs in the states included in the study
Table 1 Number and percentages of HEV positive municipalities, farms and pigs in the Mexican states included in the study State San Luis Potosı´ Estado de Me´xico Quere´taro
HEV positive municipalities/total municipalities (%) 7/8 (87.5) 7/10 (70)
14/25 (56) 13/23 (56.5)
HEV positive pigs/total pigs (%) 28/100 (28) 26/99 (26.2)
12/14 (85.7)
46/100 (46)
5/10 (50)
6/12 (50)
16/100 (16)
Puebla
1/5 (20)
1/5 (20)
1/34 (2.9)
Veracruz
1/1 (100)
1/1 (100)
1/6 (16)
Morelos
2/4 (50)
2/4 (50)
12/45 (26.6) 23/101 (22.8)
Guanajuato
6/7 (85.7)
HEV positive farms/total farms (%)
Michoaca´n
2/2 (100)
10/14 (71.4)
Jalisco
1/1 (100)
10/11 (90.9 %)
Total
32/48 (66.6)
32.5 % of them to animals that resulted anti-HEV IgG positive.
Discussion The high prevalence (30.8 %) of anti-HEV antibodies in pigs analysed in this report across Mexico is similar to that described in other regions of the world (Yugo and Meng 2013; Pavio et al. 2014), and shows that HEV is widespread among
69/109 (63.3)
57/98 (58.1) 210/683 (30.7)
the country’s swine population. The proportion of anti-HEV IgG positive pigs was statistically significantly higher among animals 4–6 months of age, in line with what has been reported previously (Casas et al. 2009, 2011; Jime´nez de Oya et al. 2011). This fact is consistent with the natural infection of pigs aged around 10–12 weeks, as maternal antibodies to HEV might persist up to 9 weeks and confer resistance to viral infection in young pigs (Pavio et al. 2010). Differences between the proportions of positive animals were found in the states included in the study, but no
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climatic or geographical differences were found regarding the seroprevalence rates. Even though there were positive animals in over 60 % of the farms, unequal figures were found in farms from the same state or the same municipality, as reported before in other countries (Pavio et al. 2010). No relationship was found between the seroprevalence data and farming structure of pig production, routine management or hygiene practices applied on the studied farms. HEV-RNA was not detected in any of the 40 faecal samples However, a larger number of faecal samples should be tested to clearly determine the risk of HEV shedding by infected animals. These data indicate that HEV infection either already is, or is likely to become, endemic in the country’s swine population. The relatively high proportion of seropositive pigs found here, together with previous reports detecting HEV-RNA in raw pig livers and meat sold around the world (Pavio et al. 2010), including Mexico (Cantu´-Martı´nez et al. 2013), as well as the reported infection of slaughterhouse workers (Pe´rez-Gracia et al. 2007), suggests that infected pigs can enter the food chain; thus representing a potential zoonotic risk for humans. Acknowledgments This work was supported in part by grants E-RTA2013-0013 from Instituto Nacional de Investigacio´n y Tecnologı´a Agraria y Alimentaria (INIA) and S2013/ABI-2906, (PLATESA) from Comunidad Auto´noma de Madrid.
References Cantu´-Martı´nez, M. A., Roig-Sague´s, A. X., Cedillo-Rosales, S., ´ vila, D. E., & Avalos-Ramı´rez, R. (2013). Molecular Zamora-A detection of hepatitis E virus in pig livers destined for human consumption in the state of Nuevo Leon, Mexico. Salud Pu´blica Mexicana, 55(2), 193–195. Casas, M., Corte´s, R., Pina, S., Peralta, B., Allepuz, A., Cortey, M., et al. (2011). Longitudinal study of hepatitis E virus infection in Spanish farrow-to-finish swine herds. Veterinary Microbiology, 148(1), 27–34. Casas, M., Pujols, J., Rosell, R., de Deus, N., Peralta, B., Pina, S., et al. (2009). Retrospective serological study on hepatitis E infection in pigs from 1985 to 1997 in Spain. Veterinary Microbiology, 135(3–4), 248–252. Cooper, K., Huang, F. F., Batista, L., Rayo, C. D., Bezanilla, J. C., Toth, T. E., & Meng, X. J. (2005). Identification of genotype 3 hepatitis E virus (HEV) in serum and fecal samples from pigs in Thailand and Mexico, where genotype 1 and 2 HEV strains are prevalent in the respective human populations. Journal of Clinical Microbiology, 43(4), 1684–1688. De Deus, N., Casas, M., Peralta, B., Peralta, B., Nofrarı´as, M., Pina, S., et al. (2008). Hepatitis E virus infection dynamics and organic distribution in naturally infected pigs in a farrow-tofinish farm. Veterinary Microbiology, 132, 19–28.
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Echevarrı´a, J. M., Gonza´lez, J. E., Lewis-Ximenez, L. L., Dos Santos, D. R., Munne´, M. S., Pinto, M. A., et al. (2013). Hepatitis E virus infection in Latin America: A review. Journal of Medical Virology, 85(6), 1037–1045. Jime´nez de Oya, N., de Blas, I., Bla´zquez, A. B., Martı´n-Acebes, M. A., Halaihel, N., Girone´s, O., et al. (2011). Widespread distribution of hepatitis E virus in Spanish herds. BMC Research Notes, 4, 412. Jime´nez de Oya, N., Galindo, I., Escribano-Romero, E., Bla´zquez, A. B., Alonso-Padilla, J., Halaihel, N., et al. (2009a). Expression and immunoreactivities of Hepatitis E virus (HEV) genotype 3 open reading frame-2 (ORF-2) recombinant proteins expressed in insect cells. Food and Environmental Virology, 1(2), 77–84. Jime´nez de Oya, N., Galindo, I., Girone´s, O., Duizer, E., Escribano, J. M., & Saiz, J. C. (2009b). Serological immunoassay for detection of hepatitis E virus on the basis of genotype 3 open reading frame 2 recombinant proteins produced in Trichoplusia ni larvae. Journal of Clinical Microbiology, 47(10), 3276–3282. Kamar, N., Dalton, H. R., Abravanel, F., & Izopet, J. (2014). Hepatitis E virus infection. Clinical Microbiology Reviews, 27(1), 116–138. Levy, S. P., & Lemeshow, S. (1980). Sampling for health professionals. Lifetime learning publications. Ann Arbor: Universidad de Michigan. Lupulovic, D., Lazic, S., Prodanov-Radulovic, J., Jime´nez de Oya, N., Escribano-Romero, E., Saiz, J. C., & Petrovic, T. (2010). First serological study of hepatitis E virus infection in backyard pigs from Serbia. Food and Environmental Virology, 2, 110–113. Meng, X. J., Purcell, R. H., Halbur, P. G., Lehman, J. R., Webb, D. M., Tsareva, T. S., et al. (1997). A novel virus in swine is closely related to the human hepatitis E virus. Proceedings of the National Academy of Sciences of the United States of America, 94(18), 9860–9865. Okamoto, H. (2007). Genetic variability and evolution of hepatitis E virus. Virus Research, 127, 216–228. Pavio, N., Meng, X. J., & Doceul, V. (2015). Zoonotic origin of hepatitis E. Current Opinion in Virology, 10, 34–41. Pavio, N., Meng, X. J., & Renou, C. (2010). Zoonotic hepatitis E: Animal reservoirs and emerging risks. Veterinary Research, 41, 46. Pavio, N., Merbah, T., & The`bault, A. (2014). Foodborne hepatitis: frequent detection of HEV in raw pork liver foods. Emerging Infectious Diseases, 20(11), 1925–1927. Pe´rez-Gracia, M. T., Mateos, M. L., Galiana, C., Ferna´ndez-Barredo, S., Garcı´a, A., Go´mez, M. T., & Moreira, V. (2007). Autochthonous hepatitis E infection in a slaughterhouse worker. American Journal of Tropical Medicine and Hygiene, 77(5), 893–896. Renou, C., Roque-Afonso, A. M., & Pavio, N. (2014). Foodborne transmission of hepatitis E virus from raw pork liver sausage. France. Emerging Infectious Diseases 20(11):1945–1947. doi: 10.3201/eid2011.140791. Erratum in: Emerging Infectious Diseases (2015). 21(2):384. Riveiro-Barciela, M., Minguez, B., Girone´s, R., Rodrı´guez-Frı´as, F., Quer, J., & Buti, M. (2014). Phylogenetic demonstration of hepatitis E infection transmitted by pork meat ingestion. Journal of Clinical Investigation, 49, 165–168. FND. http://www.financierarural.gob.mx/. Yugo, D. M., & Meng, X. J. (2013). Hepatitis E virus: Foodborne, waterborne and zoonotic transmission. International Journal of Environmental Research and Public Health, 10(10), 4507–4533.
BRIEF COMMUNICATION
Prevalence of Hepatitis E Virus (HEV) Antibodies in Mexican Pigs Teresa Merino-Ramos1 • Miguel A. Martı´n-Acebes1 • Jordi Casal2,3 Juan-Carlos Saiz1 • Elizabeth Loza-Rubio4
•
Received: 15 December 2015 / Accepted: 8 February 2016 Springer Science+Business Media New York 2016
Abstract The hepatitis E virus (HEV) is the causative agent of Hepatitis E, an enterically transmitted disease. HEV infections in pigs and humans have been reported worldwide, but data from Mexico are scarce. In the present study, the prevalence of anti-HEV IgG antibodies was investigated in a quite large number of swine from Mexico by means of an ELISA based on a recombinant open reading frame 2 protein of HEV genotype 3. Serum samples from 683 healthy pigs (1–48 months old), collected during 2010–2013 in 109 herds from 48 municipalities located in 9 states in the centre of the country were assayed. A 30.75 % (210/683) of the sera tested were positive, and they were distributed along all the states included in the study. The prevalence of anti-HEV antibodies varied widely between municipalities and herds, and it was higher in pigs 4–6 months of age. No relationships were detected between seroprevalences and farm characteristics. Forty individual faecal samples were analysed by RT-PCR and all resulted negative. These data indicate that HEV infection is widespread in Mexican pigs; thus, representing a potential zoonotic risk for humans.
& Juan-Carlos Saiz [email protected] 1
Departamento de Biotecnologı´a, Instituto Nacional de Investigacio´n y Tecnologı´a Agraria y Alimentaria (INIA), Madrid, Spain
2
Departament de Sanitat i Anatomia Animals, Universitat Auto`noma de Barcelona (UAB), Barcelona, Spain
3
Institut de Recerca i Tecnologia Agroalimenta`ries (IRTA), Bellaterra, Barcelona, Spain
4
Instituto Nacional de Investigaciones Agrı´colas, Forestales y Pecuarias (CENID-Microbiologı´a), Carretera Me´xico-Toluca Km. 15.5, Colonia Palo Alto, 05110 Me´xico, DF, Mexico
Keywords HEV Mexico Pigs Seroprevalence ELISA RNA
Introduction Hepatitis E is an enterically transmitted disease caused by the hepatitis E virus (HEV) that is endemic in regions where sanitary conditions and water supplies are inadequate (Kamar et al. 2014). In contrast to the usually waterborne HEV infections reported in endemic developing countries, in non-endemic countries sporadic hepatitis E is mainly a zoonotic and food-borne disease (Yugo and Meng 2013). Although only a single serotype is recognized, considerable genetic diversity occurs among HEV isolates, so that they are grouped into four genotypes (gt). Viruses responsible for epidemics and sporadic cases in endemic regions are mainly classified into gt 1 and 2, which only infect humans. Those viruses detected in sporadic cases of acute hepatitis E elsewhere in the world are clustered into gt 3 and 4, and are considered as zoonotic strains (Okamoto 2007). After the first isolation of a HEV swine strain was reported in 1997 (Meng et al. 1997), several evidences have pointed to pigs as a natural reservoir of HEV with a potential zoonotic risk (Pavio et al. 2015). Infected pigs shed virus through faeces, but infection is sub-clinical and asymptomatic and viremia is short, which makes difficult viral detection. However, RT-PCR amplification of HEVRNA has shown that HEV is present in pig farms around the world (Pavio et al. 2010), and that it can be amplified from pork meat sold in local markets (Renou et al. 2014; Riveiro-Barciela et al. 2014), including Mexican’s ones (Cantu´-Martı´nez et al. 2013). These facts stress the possible risk of a zoonotic transmission, as it has been
123
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previously confirmed in people that ate dear, pork, or wild boar uncooked meat and liver (Pavio et al. 2010). Likewise, a quite high prevalence of anti-HEV IgG in swine populations around the world has also been reported (Pavio et al. 2010); being usually higher in animals older than 4 months of age (Meng et al. 1997; De Deus et al. 2008; Pavio et al. 2010). However, little is known about HEV activity in Mexico. Human outbreaks were reported in Mexico in 1986–1987, and the further described prevalence (ranging from 1 to 10 %) is similar to that of other regions in Central and South America (Echevarrı´a et al. 2013). Information about HEV circulation in Mexican swine populations is even scarcer, although porcine production in Mexico is second to Brazil in Central and South America, with over 1300 million tons of meat/year (http:// www.financierarural.gob.mx/). An early report (Cooper et al. 2005) described that up to 81 % of the 125 pigs tested were IgG positive, and detected HEV-RNA in 6.4 % (8/125) and 30.4 % (28/92) of sera and faecal samples, respectively, from 2- to 4-month-old pigs. All swine-amplified genomes corresponded to gt 3 strains, as were those very recently amplified from HEV-RNA positive pigs liver sold for human consumption in local markets form Nuevo Leo´n, Mexico (Cantu´-Martı´nez et al. 2013). In the present study, the prevalence of anti-HEV IgG in the serum of a large number (n = 683) of Mexican pigs collected in 109 herds from 48 municipalities located in 9 states in the centre of the country has been determined.
Methods Swine serum samples (n = 683) were collected along 2010–2013 as part of a non-probabilistic convenience cross-sectional survey conducted in 9 states in the centre of the country (Fig. 1). Sample size was estimated by the proportion formula (Levy and Lemeshow 1980) with a 50 % estimated prevalence (as no previous data were available in the country), a 4 % desired precision, and 95 % of confidence level. Samples were from pigs ([1 to 48 months of age) grown in backyard and commercial farms (average 6 samples/farm) from 48 municipalities. Written permission was obtained from the farm’s owners for sampling collection and the study was conducted following all applicable guidelines related to animal welfare. The study was approved by the Institutional Animal Care and Use Committee (IACUC) of the Centro Nacional de Investigacio´n Disciplinaria en Microbiologı´a Animal (No. approval: 001-2012). A questionnaire was filled up by most of the farm’s managers, which includes information about type of farming and production, kind and way of feeding,
123
water sources, sanitary status (vaccination, recent diseases sings,…), etc. Serum samples were tested by means of a validated ELISA based on the use of recombinant HEV gt 3 ORF-2 expressed in Trichoplusia ni larvae as antigen (Jime´nez de Oya et al. 2009a, b). As controls, previously characterized positive and negative swine sera pools were used (Lupulovic et al. 2010; Jime´nez de Oya et al. 2011). The cut-off of the assay was established as 2.5 times the A495 value of the negative sera pool that was included in each plate (0.15, range 0.08–0.14). Test samples with optical density equal to or greater than cut-off value were considered positive. In addition, presence of HEV-RNA was analysed, by means of a nested RT-PCR (Jime´nez de Oya et al. 2011), in 40 individual faecal samples (20 from male and 20 from female pigs) from farms located in three of the states (Queretaro, Guanajuato and Estado de Me´xico). A Chisquared test was used to determine possible relationships between positive results and the different variables analysed.
Results A total of 210 of the 683 (30.75 %) serum samples tested were ELISA positive (Table 1). The proportion of antiHEV IgG positive animals was statistically significantly higher among animals 4–6 months of age (43 %) than among younger (17.6 %, p \ 0.0001) or older pigs (31.5 %. p \ 0.01). The prevalence of anti-HEV antibodies varied widely between and within states and municipalities, but there were seropositive pigs in all states covered by the study with prevalence ranging from 3 % in Puebla to 46 % and 58 % in Queretaro and Jalisco, being these figures significantly different (p \ 0.005) when compared with the remaining states included in the study (Table 1). However, no appreciable geographical or climatic differences were found regarding the seroprevalence rates. For instance, farms from the same state showed uneven seroprevalences, and similar patterns were also observed in farms located within a single municipality. As shown in Table 1, at least one pig was positive for anti-HEV IgG 63.3 % of the tested herds (69/109). However, the prevalence was again quite variable between farms and locations. Likewise, the proportion of tested pigs with anti-HEV IgG among positive farms was also quite variable (66.7 %, range 8–100 %), and no differences were observed regarding the information provided by farmers on the variables included in the questionnaire (type of management, feeding, water supplies or sanitary status). No HEV-RNA was amplified in any of the 40 faecal samples from pigs of different ages tested, corresponding
Food Environ Virol
Fig. 1 Map showing the percentage of HEV-IgG positive pigs in the states included in the study
Table 1 Number and percentages of HEV positive municipalities, farms and pigs in the Mexican states included in the study State San Luis Potosı´ Estado de Me´xico Quere´taro
HEV positive municipalities/total municipalities (%) 7/8 (87.5) 7/10 (70)
14/25 (56) 13/23 (56.5)
HEV positive pigs/total pigs (%) 28/100 (28) 26/99 (26.2)
12/14 (85.7)
46/100 (46)
5/10 (50)
6/12 (50)
16/100 (16)
Puebla
1/5 (20)
1/5 (20)
1/34 (2.9)
Veracruz
1/1 (100)
1/1 (100)
1/6 (16)
Morelos
2/4 (50)
2/4 (50)
12/45 (26.6) 23/101 (22.8)
Guanajuato
6/7 (85.7)
HEV positive farms/total farms (%)
Michoaca´n
2/2 (100)
10/14 (71.4)
Jalisco
1/1 (100)
10/11 (90.9 %)
Total
32/48 (66.6)
32.5 % of them to animals that resulted anti-HEV IgG positive.
Discussion The high prevalence (30.8 %) of anti-HEV antibodies in pigs analysed in this report across Mexico is similar to that described in other regions of the world (Yugo and Meng 2013; Pavio et al. 2014), and shows that HEV is widespread among
69/109 (63.3)
57/98 (58.1) 210/683 (30.7)
the country’s swine population. The proportion of anti-HEV IgG positive pigs was statistically significantly higher among animals 4–6 months of age, in line with what has been reported previously (Casas et al. 2009, 2011; Jime´nez de Oya et al. 2011). This fact is consistent with the natural infection of pigs aged around 10–12 weeks, as maternal antibodies to HEV might persist up to 9 weeks and confer resistance to viral infection in young pigs (Pavio et al. 2010). Differences between the proportions of positive animals were found in the states included in the study, but no
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Food Environ Virol
climatic or geographical differences were found regarding the seroprevalence rates. Even though there were positive animals in over 60 % of the farms, unequal figures were found in farms from the same state or the same municipality, as reported before in other countries (Pavio et al. 2010). No relationship was found between the seroprevalence data and farming structure of pig production, routine management or hygiene practices applied on the studied farms. HEV-RNA was not detected in any of the 40 faecal samples However, a larger number of faecal samples should be tested to clearly determine the risk of HEV shedding by infected animals. These data indicate that HEV infection either already is, or is likely to become, endemic in the country’s swine population. The relatively high proportion of seropositive pigs found here, together with previous reports detecting HEV-RNA in raw pig livers and meat sold around the world (Pavio et al. 2010), including Mexico (Cantu´-Martı´nez et al. 2013), as well as the reported infection of slaughterhouse workers (Pe´rez-Gracia et al. 2007), suggests that infected pigs can enter the food chain; thus representing a potential zoonotic risk for humans. Acknowledgments This work was supported in part by grants E-RTA2013-0013 from Instituto Nacional de Investigacio´n y Tecnologı´a Agraria y Alimentaria (INIA) and S2013/ABI-2906, (PLATESA) from Comunidad Auto´noma de Madrid.
References Cantu´-Martı´nez, M. A., Roig-Sague´s, A. X., Cedillo-Rosales, S., ´ vila, D. E., & Avalos-Ramı´rez, R. (2013). Molecular Zamora-A detection of hepatitis E virus in pig livers destined for human consumption in the state of Nuevo Leon, Mexico. Salud Pu´blica Mexicana, 55(2), 193–195. Casas, M., Corte´s, R., Pina, S., Peralta, B., Allepuz, A., Cortey, M., et al. (2011). Longitudinal study of hepatitis E virus infection in Spanish farrow-to-finish swine herds. Veterinary Microbiology, 148(1), 27–34. Casas, M., Pujols, J., Rosell, R., de Deus, N., Peralta, B., Pina, S., et al. (2009). Retrospective serological study on hepatitis E infection in pigs from 1985 to 1997 in Spain. Veterinary Microbiology, 135(3–4), 248–252. Cooper, K., Huang, F. F., Batista, L., Rayo, C. D., Bezanilla, J. C., Toth, T. E., & Meng, X. J. (2005). Identification of genotype 3 hepatitis E virus (HEV) in serum and fecal samples from pigs in Thailand and Mexico, where genotype 1 and 2 HEV strains are prevalent in the respective human populations. Journal of Clinical Microbiology, 43(4), 1684–1688. De Deus, N., Casas, M., Peralta, B., Peralta, B., Nofrarı´as, M., Pina, S., et al. (2008). Hepatitis E virus infection dynamics and organic distribution in naturally infected pigs in a farrow-tofinish farm. Veterinary Microbiology, 132, 19–28.
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