In 2-4 hours. According to official website's query, Health Network shows that. A small amount of dichlorvos will cause death within 2-4 hours after ingestion. So the cat ate dichlorvos and should be taken to the vet for treatment immediately. Dichlorvos is an organophosphorus pesticide. Cats eating dichlorvos by mistake may be poisoned and die. Symptoms of poisoning include respiratory obstruction, vomiting, diarrhea, cough, dyspnea and decreased energy.