3.1 Angiostrongylus cantonensisoutbreaks in Taiwan
Instances of human infection by Angiostrongylus cantonensis have
been reported in Taiwan and details of those cases including clinical
manifestation, diagnosis and treatments are provided in Table- 1,
including whether direct or indirect involvement of gastropod species
was reported. The first outbreak in this review occurred during
1968-1969 (Table 1) among whom many patients displayed severe
manifestations. Three patients suffered from permanent sequelae from the
infection including blindness, and there were four deaths (Yii, 1976).
Sequelae were noted in only two other reports; one toddler among the 37
cases presented in Tseng et al. (2011) with weakness in lower limbs, and
a 15-year old with pica disorder who presented with urine retention
(Hsueh et al., 2013). In addition, a case study of a 66-year old
homeless man who presented with neuroangiostrongyliasis in 2022
mentioned transfer of the patient to long term care post-treatment,
however the reason for transfer was not clear (Luo et al., 2023).
Children appeared to be more vulnerable to severe manifestations, as
well as had greater chances of parasite recovery from the CSF, as seen
in the 87 cases of children reviewed by Hwang et al. (1994). They were
found to be more likely to get infected, and quicker to manifest
symptoms than adults. This implies the large populations of invasive
gastropod vectors, including Achatina fulica and Pomaceaspp. pose a high infection risk to children.
Mode of infection appeared to be highly variable among cases (Table 1),
where direct consumption of raw Pomacea sp. alone or with wine
(Tsai et al., 2001; Wang et al., 2011) as well as boiled Pomaceasp. (http://www.mohw.gov.tw/), and even raw vegetable juice
without any apparent involvement of a host (Tsai et al., 2004) have
resulted in cases of neuroangiostrongyliasis. Involvement of paratenic
hosts in causing infection, such as the Eastern Golden Frog Rana
plancyi , which was consumed as Chinese medicine by a 70-year old man,
have also been reported (Lai et al., 2007). Interestingly, in a case
reported by Wan and Weng (2004), a 10-year old boy displayed
intermittent headache, low grade fever, and blurred vision after raisingPomacea spp. as pets, suggesting an indirect infection route.
Since the first reported case in 1945, there has been a number of
neuroangiostrongyliasis cases in Taiwan, including four outbreaks. While
recently within the past three decades, there have been relatively fewer
cases reported, there is still a high risk of infection from consuming
raw or undercooked snails, or even through close contact with infected
gastropod hosts (Tsai et al., 2013). As seen in Table- 1, a considerable
number of cases have resulted from infection through handling or
consuming gastropods such as Pomacea canaliculata andAchatina fulica , which may be attributed to the prevalence of
these snails in Taiwanese cuisine, or to the large population sizes of
these invasive snails. This implies a high prevalence of A.
cantonensis among the gastropod species in Taiwan (Banerjee et al.,
unpublished data).