In the United States, it is available only from the Centers for Disease Control and Prevention (CDC) after laboratory confirmation of loiasis; clinicians should seek expert advice before they initiate treatment, and they should do the following before initiating treatment with DEC: Measure the number of microfilariae in the blood, because using DEC to treat heavy infections (≥ 8000 microfilariae / mL blood) can result in potentially fatal encephalopathy Exclude coinfection with onchocerciasis because DEC can cause a severe hypersensitivity reaction (Mazzotti reaction) and worsen eye and skin disease in patients with onchocerciasis Clinicians should seek expert assistance when measuring the number of microfilariae and thus determining the severity of the infection.