At least eight veterinary workers have been poisoned by exposure to potentially lethal phosphine gas when dogs being treated for ingesting pest-killing chemicals have thrown up in their offices, and health officials suspect there may be other unreported cases as well. All of the human victims recovered with no lasting effects, but the Centers for Disease Control and Prevention warned that more serious incidents could occur and cautioned veterinarians to be alert.

Zinc phosphide is a widely used rodent killer. When it is ingested, contact with stomach acid and water produces phosphine gas, which is highly toxic. If the animals are induced to regurgitate the poison -- standard procedure -- phosphine gas can be released into the office, exposing workers.

In one such incident reported in the CDC’s Morbidity and Mortality Weekly Report on Thursday, a 70-pound dog that had eaten rodenticide was brought into a veterinary hospital in Michigan. When vomiting was induced with hydrogen peroxide, two workers were poisoned by exposure to the resulting gas. One technician reported shortness of breath, difficulty breathing, headache and nausea. An office manager reported similar symptoms, as well as lightheadedness. Four other workers reported only one symptom, such as chest tightness, chest pain or headache, and were not considered poisoned. All six recovered without hospitalization.

New recommendations by the American Veterinary Medical Assn. call for inducing vomiting in such dogs outdoors when possible and remaining upwind from the animals. If vomiting occurs indoors, the room should be evacuated as soon as possible. And, the CDC said, the risk to dogs and workers can be reduced by using alternative methods of gopher and mole control, such as snap traps.



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