Case History

In late July a family physician consulted with the Agromedicine Program regarding a 31-year-old farmer who developed shortness of breath and wheezing after exposure to amitraz. The farmer had been spraying the chemical when he stopped his enclosed-cab tractor to inspect a spray nozzle. He reported that he stopped downwind of the application and some spray drifted over him while he was dismounted.

The farmer’s wheezing and coughing grew progressively worse over the next three days. On the third day, he was examined by his family physician. The patient was afebrile, pulse was 98, and blood pressure was normal. Wheezing and coughing were present. Oral and nasal membranes were normal and showed no irritation. A chest x-ray was negative for pneumonia. No neurological deficits were observed.

The physician’s differential diagnosis included early chemical pneumonitis, amitraz toxicity, and allergic reaction. The patient was prescribed steroids and a bronchodilator for 12 days.

Amitraz is a triazapentadiene insecticide and acaricide approved for use on fruit, cotton, tobacco, and ornamentals to control a variety of pests. It is also approved for use on cattle and swine to control mites, ticks, and lice. Its oral LD50 is 650 mg/kg and dermal LD50 is >1600 mg/kg. Eleven cases of human poisoning have been reported in the medical literature. Symptoms include drowsiness, bradycardia, miosis and/or hyperglycemia, hypotension, and vomiting.

Amitraz poisoning was ruled out based on the symptomatology discussed above. An allergic reaction was thought unlikely because the patient had no conjunctivitis at the onset of his symptoms and because the patient’s symptoms became more severe without further exposure.

There are two likely causes for the patient’s illness:

1) respiratory irritation from the exposure leading to bronchospasms, or

2) an upper respiratory tract virus. Seven days after his initial visit, the patient was much improved. He was to continue his medication for the full 12 days.

DEPARTMENT OF FAMILY MEDICINE – DIVISION OF PUBLIC HEALTH AND PUBLIC SERVICE

MEDICAL UNIVERSITY OF SOUTH CAROLINA, 171 ASHLEY AVENUE, CHARLESTON, SC 29425-2217