We have read with interest the paper by Khaing et al. [1], in which first data on Taenia solium cysticercosis in pigs from Myanmar are published. The authors found a porcine cysticercosis prevalence of 23.67% in slaughtered pigs, which, as they mention, indicates the presence of human taeniasis and also the risk of acquiring human cysticercosis and, therefore, neurocysticercosis. The high porcine cysticercosis prevalence detected by the authors means, obviously, that there has to be a high prevalence of human T. solium taeniasis among the inhabitants of Myanmar leading to a high presence of infective eggs in the environment. However, as far as we know, the presence of T. solium taeniasis, as well as neurocysticercosis, has only been diagnosed in refugees or immigrants from that country but not in people living in Myanmar [2–6]. There is no doubt that T. solium is present in Myanmar; however, our query is whether other human Taenia species might also be present in that country and, in particular, whether T. asiatica could be present in Myanmar as suggested more than 20 years ago by Fan et al. [7] and recently by Anantaphruti [2]. T. asiatica was described as a new species in 1993 [8]. This third human Taenia species has practically the same gravid proglottid morphology as Taenia saginata, but its life cycle is just the same as that of T. solium; that is, its intermediate hosts are pigs instead of cattle, the intermediate hosts for T. saginata. The clear liver tropism the cysticerci of T. asiatica presents in pigs is worth mentioning. Regarding its geographical distribution, the species has been found in Taiwan, South Korea, Philippines, Indonesia, Thailand, China, Vietnam, Japan, and Nepal [9]. Although T. asiatica was initially considered as an exclusively Southeastern Asian parasite, its finding in Nepal (far from Southeast Asia) and the phenomenon of globalization (it is a parasite with cosmopolitan hosts) have recently led to the notion that the species probably has a wider distribution [10, 11]. The presence of T. asiatica in three more Asian countries, Myanmar, Laos, and Malaysia, is highly suspected [9]. Concerning Myanmar, no cases have been confirmed so far, but a case identified as T. asiatica was detected in a Karen immigrant who moved from Myanmar to Kanchanaburi province, Thailand, in 2005. However, she had already started to expel proglottids in faeces in 1997, when she was still living in Myanmar [2]. Therefore, the presence of T. asiatica in Myanmar is very likely. T. asiatica may be found in the definitive (humans) as well as in the intermediatehost (pigs). The detection of T. asiatica taeniasis is by no means an easy task. Taking into account that neither the characteristics of the eggs nor the morphology of the gravid proglottids are specific enough to distinguish T. asiatica from T. saginata, these two species can only be differentiated by means of molecular techniques (e.g., multiplex PCR (polymerase chain reaction)) [12]. Unfortunately, these expensive molecular methods are not normally employed in routine diagnosis. A specific meat inspection should be carried out to detect T. asiatica cysticerci in pigs. Routine meat inspections conducted in pigs in Myanmar include the study of T. solium predilection sites such as the tongue, masseter, brain, shoulder, diaphragm, heart, and skeletal, fore limb as well as hind limb muscles [1]. Considering that the small cysticerci of T. asiatica are almost exclusively located in the liver, such local inspections would not be sensitive enough to detect infected livers [13]. In addition, T. asiatica cross-reacts even in the most specific immunological method to detect T. solium cysticercosis, the enzyme-linked immunoelectrotransfer blot (EITB) [14]. Therefore, serological tests would currently not be specific enough to detect T. asiatica cysticercosis. For the aforementioned reasons, we urge Khaing and colleagues to take advantage of their research in pigs in Myanmar and carry out a detailed study of the surface as well as the parenchyma of pig livers. T. asiatica cysticerci can easily be differentiated from those of T. solium due to their smaller size as well as the lack of hooklets or the presence of vestigial ones [8]. Molecular techniques, however, would be the key to ascertain whether T. asiatica is definitely present in Myanmar or not.
Read full abstract
Jan 1, 2021
Mwemezi L Kabululu + 1
Open Access
