Outbreak of eosinophilic meningitis in Kuchinarai district, Kalasin province, Thailand, February 2019

Abstract

Background: On 22 February 2019, the Epidemiology Unit of Kalasin Provincial Health Office was notified of 5 suspected eosinophilic meningitis cases treated at Crown Prince Kuchinarai Hospital. The surveillance and rapid response team from Kalasin Provincial Health Office investigated this outbreak during 22 February 2019–28 March 2019. The objectives of investigation were to confirm diagnosis and outbreak, determine epidemiologic characteristics by person, time and place, identify source and mode of disease transmission, and recommend preventive and control measures.
Methods: We conducted a descriptive epidemiologic study including medical record reviews of the suspected patients, patient interview, active case finding and environmental investigation in the affected area, and laboratory diagnosis from blood and cerebrospinal fluid specimens of the patients and from samples of freshwater snails in suspected water source. A case-control study was conducted to determine possible risk factors.
Results: A total of 10 eosinophilic meningitis cases living in the same community were found. The male to female ratio was 1.5: 1. All the cases were workers and the mean age of them was 35.9 years old, with a range of 26–48 years. All the cases had severe headache and some had confusion/unconsciousness or fever. The epidemic curve showed a common source outbreak pattern. A case-control study found a significant association between eating uncooked freshwater snails (Pila spp.) and the disease. The specimens of blood and cerebrospinal fluid from the cases were tested for antigen detection of Angiostrongylus cantonensis by immunoblotting and all were positive. The larvae of this parasitic nematode were also identified in samples of snails of Pila spp. collected from the suspected water source. All the cases recovered uneventfully. The outbreak rapidly subsided, with no additional cases during the following 2-month surveillance
Conclusion: This outbreak of eosinophilic meningitis might be caused by Angiostrongylus cantonensis through eating uncooked freshwater snails of Pila spp. Health care provided should be aware of this disease in differential diagnosis in a patient having severe headache and prior history of eating uncooked freshwater snails.