An outbreak of food-borne illness due to methomyl contamination

On December 26, 2002, 124 dinners took ill while eating lunch at a seafood restaurant in the town of Chiching in Kaohsiung municipality of Taiwan. Sixty-nine people were sent to the emergency departments of the Municipal Chiching Hospital and Yuan's General Hospital.

We analyzed the clinical symptoms, detailed food history, and ingested amount of each food from 59 hospitalized adult patients and identified the source of the outbreak.

The median latency period from beginning eating to first symptoms was 5 min. Twenty-six symptoms and signs were recorded. The most commonly reported clinical effects were general weakness (84%), ataxia (82%), dizziness (82%), vomiting (80%), sweating (75%), floating sensation (71%), headache (69%), dyspnea (69%), and blurred vision (67%). Thirty-one patients had residual symptoms 7 days after ingestion. Of the six residual symptoms reported, the most frequent ones were dizziness (40%), poor appetite and dry mouth (11%), and gastrointestinal disturbance (11%). The presence of residual symptoms correlated with the severity of the initial complaints (p < 0.01). Almost all patients ate cooked rice (93%) and leaf vegetable stir-fried with crab claw (93%). The amount of each food eaten by the patients was not associated with the severity of symptoms (p > 0.05). High levels of methomyl in leaf vegetables of "leaf vegetables stir-fried with crab claws" (380 ppm) and fried mussels (1113 ppm) were found by the Food Inspection Center at the Department of Health. The food history and chemical analysis of the poison indicated methomyl was the cause of this outbreak. Twenty-four patients recovered completely within 7 days.

Food-related methomyl intoxication produced a rapid onset of significant clinical toxicity in 124 individuals. Based on the analysis of 55 adult patients, the most common effects were gait ataxia, dizziness, generalized weakness, and vomiting.