Foodborne parasitic diseases in China: A scoping review on current situation, epidemiological trends, prevention and control

Objective: Foodborne parasitic diseases, although with a declining overall incidence rate, are still endangering local public safety. This review aims to describe the current situation and epidemiological trends of foodborne parasitic diseases in China in order to explore possible reasons contributors to its high prevalence in some areas, and propose strategies for prevention and control accordingly. Methods: A scoping review was conducted by searching PubMed, CNKI, Wanfang, CQVIP, Embase, and the Cochrane Library using search formula “foodborne parasitic diseases (or foodborne parasites)” AND “China”. Studies on foodborne parasitic diseases in China were considered, but only articles in English or Chinese published between January 1980 and June 2020 were retrieved. Included studies were screened according to the eligibility criteria: 1) diseases consistent with the WHO definition of foodborne parasitic diseases; 2) the food carriers were included in the WHO food classification; 3) data related to epidemiology, pathogenicity, and prevention and control; 4) Foodborne parasitic diseases cases or outbreaks in China. Results: A total of 111 out of 665 records were included and summarized. The prevalence of clonorchiasis, angiostrongyliasis, echinococcosis, trichinellosis and cysticercosis was still increasing although the infection rate of soil-transmitted nematodes has substantially decreased in recent years. Diverse eating habits, close contact with animals, and urbanization were contributing factors to the increase. Conclusions: Foodborne parasitic diseases remain an important public health issue in China with the progress of economic globalization and food diversification. We should manage to raise public awareness about the prevention and control of foodborne parasitic diseases, improve health and safety inspections, as well as public health practice.

Comprehensive Review of Ocular Angiostrongyliasis with Special Reference to Optic Neuritis

Angiostrongyliasis, caused by Angiostrongylus cantonensis infection, is a food-borne parasitic disease. Its larvae evoke eosinophilic inflammation in the central nervous system, but can also cause pathological changes in the eyes. Among ocular angiostrongyliasis cases, the incidence of optic neuritis is low and only few sporadic reports exist. Some patients with optic neuritis developed obvious hypopsia or even vision loss, which would seriously influence the quality of life of patients. Prompt treatment of optic neuritis caused by A. cantonensis is the key factor for minimizing the incidence of serious complications of this disease. In this review, we first provide a comprehensive overview of ocular angiostrongyliasis, and then focus on the clinical features of optic neuritis caused by A. cantonensis.

Angiostrongylus cantonensis: Scanning Electron Microscopic Observations on the Cuticle of Moulting Larvae

Angiostrongylus cantonensis is a parasitic nematode that needs to develop in different hosts in different larval stages. Freshwater snails, such as Pomacea canaliculata, are the intermediate host, and rats are the definitive host. Periodic shedding of the cuticle (moulting) is an important biological process for the survival and development of the parasite in the intermediate and definitive hosts. However, there are few studies on the cuticle alterations between different stages of this parasite. In this study, we observed the ultrastructural appearance and changes of the cuticle of the 2nd/3rd stage larvae (L2/L3) and the 3rd/4th stage larvae (L3/L4) using a scanning electron microscope. We also first divided L2/L3 into late L2 and early L3. The late L2 lacked alae, but possessed a pull-chain-like fissure. Irregular alignment of spherical particles on the cuticle were noted compared to the L3. Alae appeared in the early L3. The old cuticle turned into a thin film-like structure which adhered to the new cuticle, and spherical particles were seen regularly arranged on the surface of this structure. Regular rectangular cavities were found on the surface of L3/L4. The caudal structure of L3/L4 was much larger than that of L3, but caudal inflation, such as seen in L4, was not observed. These results are the first to reveal the ultrastructural changes of the cuticle of A. cantonensis before and after moulting of L2/L3 and L3/L4.

Experimental Establishment of Life Cycle of Clonorchis sinensis / 中国寄生虫学与寄生虫病杂志

Objective To establish and maintain the life cycle of Clonorchis sinensis in laboratory.Methods Adult worms and eggs of Clonorchis sinensis were collected from naturally infected cats.Eggs were ingested by freshwater snails in aquarium.When the cercariae were released from infected snails, they invaded into freshwater fishes.From the 30th day on after the release of cercariae, the infection rate and metacercariae density in freshwater fishes were determined.Results After 95 days the infected snails began shedding cercariae in a temperature range of 24.3-37.2 ℃, and no cercariae were found under 20 ℃.The infection rate in the snails Parafossarulus striatulus and Alocinma longicornis was 12.5% and 18.0%, respectively.Metacercariae were found in fish at 30 days after cercariae infection, and matured metacercariae were detected in 45 days.The number of metacercariae per gram of fish meat in Pseudorasbora parva, Ctenopharyngodon idellus, Rhodeus sinensis, Hypophthalmichthys nobilis, Cirrhinus molitorella, Carassius auratus, Cyprinus carpio and Oreochromis niloticus was 1 792, 16, 8, 6, 5, 4, 4, and 2, respectively.Rats and cats were fed with metacercariae from fish to receive adult worms.Conclusion Life cycle of Clonorchis sinensis has been established and maintained in the laboratory.