Research Article: Invasive Snails and an Emerging Infectious Disease: Results from the First National Survey on Angiostrongylus cantonensis in China

Date Published: February 10, 2009

Publisher: Public Library of Science

Author(s): Shan Lv, Yi Zhang, He-Xiang Liu, Ling Hu, Kun Yang, Peter Steinmann, Zhao Chen, Li-Ying Wang, Jürg Utzinger, Xiao-Nong Zhou, Matty Knight

Abstract: BackgroundEosinophilic meningitis (angiostrongyliasis) caused by Angiostrongylus cantonensis is emerging in mainland China. However, the distribution of A. cantonensis and its intermediate host snails, and the role of two invasive snail species in the emergence of angiostrongyliasis, are not well understood.Methodology/Principal FindingsA national survey pertaining to A. cantonensis was carried out using a grid sampling approach (spatial resolution: 40×40 km). One village per grid cell was randomly selected from a 5% random sample of grid cells located in areas where the presence of the intermediate host snail Pomacea canaliculata had been predicted based on a degree-day model. Potential intermediate hosts of A. cantonensis were collected in the field, restaurants, markets and snail farms, and examined for infection. The infection prevalence among intermediate host snails was estimated, and the prevalence of A. cantonensis within P. canaliculata was displayed on a map, and predicted for non-sampled locations. It was confirmed that P. canaliculata and Achatina fulica were the predominant intermediate hosts of A. cantonensis in China, and these snails were found to be well established in 11 and six provinces, respectively. Infected snails of either species were found in seven provinces, closely matching the endemic area of A. cantonensis. Infected snails were also found in markets and restaurants. Two clusters of A. cantonensis–infected P. canaliculata were predicted in Fujian and Guangxi provinces.Conclusions/SignificanceThe first national survey in China revealed a wide distribution of A. cantonensis and two invasive snail species, indicating that a considerable number of people are at risk of angiostrongyliasis. Health education, rigorous food inspection and surveillance are all needed to prevent recurrent angiostrongyliasis outbreaks.

Partial Text: Eosinophilic meningitis, a potentially fatal disease caused by Angiostrongylus cantonensis, is considered an emerging infectious disease in mainland China [1],[2]. The first human case of angiostrongyliasis in mainland China was reported in 1978, and a few more cases were diagnosed until the mid-1990s. Subsequently, several outbreaks have been recorded [1]. The first major angiostrongyliasis outbreak, involving 65 patients, was documented from Wenzhou in Zhejiang province in 1997 [3]. The biggest outbreak in China thus far could be attributed to a freshwater snail, i.e., Pomacea canaliculata, and took place in the capital Beijing in 2006 [4]. Of the 160 infected individuals involved in this outbreak, 100 were hospitalized [5]. This outbreak also demonstrated that angiostrongyliasis had moved beyond its traditional endemic areas located in the southeastern coastal regions of China.

Eosinophilic meningitis caused by A. cantonensis is endemic in Southeast Asia, Australia, the Pacific Islands and the Caribbean. To date, more than 2,800 human cases have been reported [23]. It had been suggested that the parasite was dispersed from East Asia to other regions in two important hosts, i.e., rats (definitive host) and A. fulica (intermediate host) especially during World War II [24]. Today, the parasite is still expanding its range and the associated disease is emerging in some regions, particularly China [1], [25]–[28].

Source:

http://doi.org/10.1371/journal.pntd.0000368

 

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