# Monitoring the trends of Angiostrongylus cantonensis infection in humans and Pomacea spp. Snails in Dali, Yunnan, China, 2007–2021

## TL;DR

This study tracks the spread of a parasitic infection in humans and snails in Dali, China, from 2007 to 2021, highlighting public health responses.

## Contribution

The study provides a detailed epidemiological analysis of angiostrongyliasis in Dali and its correlation with snail infection trends.

## Key findings

- 125 cases of angiostrongyliasis were reported in Dali from 2007 to 2021, with common symptoms including headache and muscle pain.
- 0.75% of 49,970 Pomacea spp. snails tested positive for Angiostrongylus cantonensis infection.
- The highest incidence of cases and snail infections occurred during spring months (February to May).

## Abstract

We summarize historical events related to angiostrongyliasis and analyze surveys of clinically diagnosed and suspected cases of angiostrongyliasis in Dali from 2007 to 2021. We also randomly tested market sold Pomacea spp. snails to detect whether Angiostrongylus cantonensis was present in Dali market stalls from 2008 to 2021. There were a total of 125 cases of angiostrongyliasis (92 clinically diagnosed and 33 suspected) reported in the Dali Prefecture from 2007-2021. Of the 125 cases, 72 patients from 2010 to 2021 were investigated, with the main clinical manifestations being headache (100%), muscle pain (61%), neck stiffness (58.3%), paresthesia (58.3%), fever (55.5%), nausea (48.6%), coughing (26.3%), vomiting (44.4%), photophobia (18%), diplopia (25%), and visual impairment (5.5%). Laboratory testing showed cerebrospinal fluid qualitative protein levels and blood eosinophil levels were abnormal in 100% and 87.5% of patients tested, respectively. Moreover, of the 49,970 Pomacea spp. checked for A. cantonensis infection, 373 (0.75%) were found infected. Our study highlights the importance of enhancing public education, stricter food safety measures, and improved diagnostic methods to help mitigate future outbreaks of angiostrongyliasis.

Human angiostrongyliasis is an emerging parasitic disease endemic in developing countries. It is commonly caused by the rat lungworm, Angiostrongylus cantonensis, which is currently a public health concern in Dali, Yunnan Province, People’s Republic of China, as well as other places in Asia and the Pacific. Our study examines the epidemiology and control measures from 2007 to 2021, during which 125 cases (92 diagnosed, 33 suspected) of human angiostrongyliasis were reported in Dali. Patients experienced many clinical symptoms, with the most common ones being headache, muscle pain, neck stiffness, paresthesia, fever, and nausea. Standardized laboratory tests revealed abnormal cerebrospinal fluid protein levels in all patients tested (n = 72), with the majority of patients showing elevated blood eosinophil levels. In addition to humans, Pomacea spp. snails sold in a local Dali market, were screened for A. cantonensis infection, with 373 of the 49,970 snails testing positive for infection. Analysis of the monthly averages of angiostrongyliasis cases and Pomacea spp. infection prevalence revealed a similar trend, with the highest incidence occurring during the spring months (February to May). Human angiostrongyliasis outbreaks in Dali has prompted the implementation of public health interventions, leading to enhanced monitoring and control efforts.