Heartworm therapy in dogs has been reported as a source of exposure to which toxin?

• A. Lead
• B. Arsenic
• C. Mercury
• D. Cadmium

Answer: (B)

Some heartworm therapies for dogs use arsenic-containing compounds to kill adult worms. The drug most commonly involved is an organoarsenical (melarsomine dihydrochloride), which delivers arsenic to the dog to interrupt the parasites’ metabolism. Because this medication contains arsenic, exposure can occur to people handling the drug or to the environment through spills or improper disposal, making arsenic the toxin of concern in this scenario. This is different from lead, mercury, or cadmium, which are not used therapeutically for heartworm treatment. Proper handling, dosing, and protective equipment are important to minimize exposure during administration.