Angiostrongylasis cantonensis is the main cause of eosinophilic meningitis or meningoencephalitis in humans.
The pathogen is Angiostrogylus cantonensis. Angiostrongylus cantonensis parasitizes the pulmonary artery of rats, where it lays eggs and hatches the eggs into the first-stage larvae. The first-stage larvae penetrate the pulmonary capillaries and enter the alveoli, migrate up to the pharynx along the respiratory tract, and are swallowed into the digestive tract. The larvae are discharged through the feces. The first-stage larvae can survive for 3 weeks in a humid environment in vitro. When the larvae are swallowed in or actively invade the intermediate host such as snails, the larvae can develop into second-stage and third-stage larvae in the internal organs or muscles of the host, forming infective larvae. Humans are mostly infected by ingestion of freshwater snail meat containing infective larvae, and can also be infected by ingestion of intermediate hosts such as the infected fishes, shrimps, and frogs. In addition, the disease can also be caused by ingestion of water and food contaminated by the infective larvae.
Signs and Symptoms
The most prominent symptom is severe acute headache, mostly in the occipital and temporal regions. Headaches aggravate during activities and are intermittent initially. Subsequently, the attacks are more frequent or protracted, and persistent headaches occurs. There are generalized pain or migratory pain, tender skin, and symptoms of meninges such as neck stiffness, pain, nausea, and vomiting. Neurological abnormalities include hypoesthesia or anesthesia, cranial nerve damage, paralysis of the lateral rectus muscle, facial paralysis, visual impairment, and ocular abnormalities. Severe patients may develop dementia or even die.
The stage is 3 - 36 days, averagely 15 days.
The symptoms in the prodromal stage are not obvious. Patients may present with fever, headache, dizziness, fatigue, abdominal pain, and diarrhea, but the symptoms are not severe, and few mild patients may spontaneously heal in this phase.
There are aggravated fever and headache, neck stiffness, nausea, vomiting, cutaneous paresthesia such as numbness, pain, acanthesthesia, and burning sensation, facial palsy, acroparalysis, photophobia, and diplopia. The stage lasts for about 1 week in mild patients, and lasts for 1 week to 2 months or even longer in moderate and severe patients.
The clinical symptoms are relieved gradually. The stage can last for several weeks. Mild paresthesia may persist for a long time.
If there are a history of ingestion of undercooked snails, fishes, shrimps, or frogs, clinical manifestations, and adults or eggs of Angiostrongylasis cantonensis found in the cerebrospinal fluid or eyes, the disease can be diagnosed.
The disease is self-limiting, and the treatment regimen is albendazole 20mg/(kg.d), maximally 1.2g/day, orally in 3 divided doses for 7 - 10 days.