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Taenia asiatica and pig cysticercosis
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Veterinary Parasitology 157 (2008) 160–161 www.elsevier.com/locate/vetpar
Letter to the Editor Taenia asiatica and pig cysticercosis§ In a recently published article by Krecek et al. [Veterinary Parasitology 154 (2008) 38–47], the authors report the results of a survey on the prevalence of Taenia solium pig cysticercosis in an area of South Africa. The diagnostic methods used by the authors are tongue palpation and immunological techniques (ELISAs and EITB), although they recognise that the ‘‘gold standard’’ for diagnosis of T. solium cysticercosis is the complete dissection and recovery of the cysticerci. They point out that this method was not carried out due to cost constraints and local socio-economic infrastructural conditions. In those pigs which were positive in the ELISA tests the authors only consider a possible cross-reaction with T. hydatigena, a parasite already found in pigs in South Africa. In addition to T. solium and T. hydatigena, pigs are appropriate intermediate host for a third Taenia species, T. asiatica. T. asiatica’s definitive hosts are humans, just as in the case of T. solium, and it is still not clear whether T. asiatica is able to cause human cysticercosis, as T. solium does (Gala´n-Puchades and Fuentes, 2004). This is an important uncertainty concerning this species because humans are likely to be at risk to acquire T. asiatica cysticercosis. From an immunological point of view, T. asiatica cross-reacts with T. solium in the EITB in pigs (Pilcher et al., 1991), therefore this species might also be responsible of cysticercosis in the animals studied by Krecek et al. T. asiatica and T. solium have been found in the same human definitive hosts (Anantaphruti et al., 2007), so the same might occur at intermediate host level. We assume that Krececk et al. did not consider T. asiatica in their diagnosis due to its, until now, known geographical distribution, i.e., the majority of Asian countries. Taking into account that T. asiatica has
DOI of original article: 10.1016/j.vetpar.2008.03.005. 0304-4017/$ – see front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2008.07.008
cosmopolitan hosts (humans and pigs), there do not seem to be clear reasons why this species has to be confined to Asia. T. asiatica cysticerci show a liver tropism in pigs, therefore raw or poorly cooked pork liver has to be eaten and that might perfectly well happen not only in Asian countries. Furthermore, in areas of Vietnam where pork meat is more often ingested than pork viscera, a high human T. asiatica prevalence has been detected (Sommers et al., 2006), suggesting alternative parasitation sites. Simply, if only immunological methods are employed in the diagnosis of porcine cysticercosis, it is impossible to assess whether T. asiatica is present or not in South African pigs or in whatever country in the world. In addition, cysticerci in porcine livers were described as very similar to those of T. asiatica in Africa (Fan et al., 1990). As the authors acknowledge, a specific diagnosis can only be carried out by means of the recovery of the cysticerci. The cysticercus of T. asiatica is smaller than that of T. solium, and with vestigial hooklets or without. Alas, to avoid confusion with young T. solium cysticerci, molecular methods should be employed in the diagnostic procedures. As liver seems to be a preferential parasitation site, liver ultrasonography might be a useful tool in live animals to select those pigs from which cysticerci might be recovered (Herrera Garcı´a et al., 2007). This is the only way to discover T. asiatica in pigs out of Asia. References Anantaphruti, M.T., Yamasaki, H., Nakao, M., Waikagul, J., Watthanakulpanich, D., Nuamtanong, S., Maipanich, W., Pubampen, S., Sanguankiat, S., Muennoo, C., Nakaya, K., Sato, M.O., Sako, Y., Okamoto, M., Ito, A., 2007. Sympatric occurrence of Taenia solium, T. saginata, and T. asiatica, Thailand. Emerg. Infect. Dis. 13, 1413–1416. Fan, P.C., Chung, W.C., Lo, C.T., Lin, C.Y., 1990. The pig as an experimental host of Taenia saginata (Ethiopia and Madagascar strains). Ann. Trop. Med. Parasitol. 84, 93–95.
Letter to the Editor / Veterinary Parasitology 157 (2008) 160–161 Gala´n-Puchades, M.T., Fuentes, M.V., 2004. Taenia asiatica intermediate hosts. Lancet 363, 660. Herrera Garcı´a, S., de Aluja, A.S., Mendez Aguilar, R.E., 2007. Use of ultrasound to diagnose porcine cysticercosis. Vet Me´x 38, 125– 133. Pilcher, J.B., Tsang, V.C., Gilman, R.H., Rhodes, M.L., Pawlowski, Z.S., 1991. Further evidence of 100% specificity in a recently developed Taenia solium (cysticercosis) immunoblot assay. Am. J. Trop. Med. Hyg. 45 (Suppl. 3), 131. Sommers, R., Dorny, P., Geysen, D., Nguyen, L.A., Thach, D.C., Vercruysse, J., Nguyen, V.K., 2006. Human tapeworms in north Vietnam. Trans. Roy. Soc. Trop. Med. Hyg. 101, 275–277.
161
M.T. Gala´n-Puchades* M.V. Fuentes University of Valencia, 46100 Burjassot, Valencia, Spain *Corresponding author E-mail address: [email protected] (M.T. Gala´n-Puchades) 24 June 2008
Veterinary Parasitology 157 (2008) 160–161 www.elsevier.com/locate/vetpar
Letter to the Editor Taenia asiatica and pig cysticercosis§ In a recently published article by Krecek et al. [Veterinary Parasitology 154 (2008) 38–47], the authors report the results of a survey on the prevalence of Taenia solium pig cysticercosis in an area of South Africa. The diagnostic methods used by the authors are tongue palpation and immunological techniques (ELISAs and EITB), although they recognise that the ‘‘gold standard’’ for diagnosis of T. solium cysticercosis is the complete dissection and recovery of the cysticerci. They point out that this method was not carried out due to cost constraints and local socio-economic infrastructural conditions. In those pigs which were positive in the ELISA tests the authors only consider a possible cross-reaction with T. hydatigena, a parasite already found in pigs in South Africa. In addition to T. solium and T. hydatigena, pigs are appropriate intermediate host for a third Taenia species, T. asiatica. T. asiatica’s definitive hosts are humans, just as in the case of T. solium, and it is still not clear whether T. asiatica is able to cause human cysticercosis, as T. solium does (Gala´n-Puchades and Fuentes, 2004). This is an important uncertainty concerning this species because humans are likely to be at risk to acquire T. asiatica cysticercosis. From an immunological point of view, T. asiatica cross-reacts with T. solium in the EITB in pigs (Pilcher et al., 1991), therefore this species might also be responsible of cysticercosis in the animals studied by Krecek et al. T. asiatica and T. solium have been found in the same human definitive hosts (Anantaphruti et al., 2007), so the same might occur at intermediate host level. We assume that Krececk et al. did not consider T. asiatica in their diagnosis due to its, until now, known geographical distribution, i.e., the majority of Asian countries. Taking into account that T. asiatica has
DOI of original article: 10.1016/j.vetpar.2008.03.005. 0304-4017/$ – see front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2008.07.008
cosmopolitan hosts (humans and pigs), there do not seem to be clear reasons why this species has to be confined to Asia. T. asiatica cysticerci show a liver tropism in pigs, therefore raw or poorly cooked pork liver has to be eaten and that might perfectly well happen not only in Asian countries. Furthermore, in areas of Vietnam where pork meat is more often ingested than pork viscera, a high human T. asiatica prevalence has been detected (Sommers et al., 2006), suggesting alternative parasitation sites. Simply, if only immunological methods are employed in the diagnosis of porcine cysticercosis, it is impossible to assess whether T. asiatica is present or not in South African pigs or in whatever country in the world. In addition, cysticerci in porcine livers were described as very similar to those of T. asiatica in Africa (Fan et al., 1990). As the authors acknowledge, a specific diagnosis can only be carried out by means of the recovery of the cysticerci. The cysticercus of T. asiatica is smaller than that of T. solium, and with vestigial hooklets or without. Alas, to avoid confusion with young T. solium cysticerci, molecular methods should be employed in the diagnostic procedures. As liver seems to be a preferential parasitation site, liver ultrasonography might be a useful tool in live animals to select those pigs from which cysticerci might be recovered (Herrera Garcı´a et al., 2007). This is the only way to discover T. asiatica in pigs out of Asia. References Anantaphruti, M.T., Yamasaki, H., Nakao, M., Waikagul, J., Watthanakulpanich, D., Nuamtanong, S., Maipanich, W., Pubampen, S., Sanguankiat, S., Muennoo, C., Nakaya, K., Sato, M.O., Sako, Y., Okamoto, M., Ito, A., 2007. Sympatric occurrence of Taenia solium, T. saginata, and T. asiatica, Thailand. Emerg. Infect. Dis. 13, 1413–1416. Fan, P.C., Chung, W.C., Lo, C.T., Lin, C.Y., 1990. The pig as an experimental host of Taenia saginata (Ethiopia and Madagascar strains). Ann. Trop. Med. Parasitol. 84, 93–95.
Letter to the Editor / Veterinary Parasitology 157 (2008) 160–161 Gala´n-Puchades, M.T., Fuentes, M.V., 2004. Taenia asiatica intermediate hosts. Lancet 363, 660. Herrera Garcı´a, S., de Aluja, A.S., Mendez Aguilar, R.E., 2007. Use of ultrasound to diagnose porcine cysticercosis. Vet Me´x 38, 125– 133. Pilcher, J.B., Tsang, V.C., Gilman, R.H., Rhodes, M.L., Pawlowski, Z.S., 1991. Further evidence of 100% specificity in a recently developed Taenia solium (cysticercosis) immunoblot assay. Am. J. Trop. Med. Hyg. 45 (Suppl. 3), 131. Sommers, R., Dorny, P., Geysen, D., Nguyen, L.A., Thach, D.C., Vercruysse, J., Nguyen, V.K., 2006. Human tapeworms in north Vietnam. Trans. Roy. Soc. Trop. Med. Hyg. 101, 275–277.
161
M.T. Gala´n-Puchades* M.V. Fuentes University of Valencia, 46100 Burjassot, Valencia, Spain *Corresponding author E-mail address: [email protected] (M.T. Gala´n-Puchades) 24 June 2008