In people who have been bitten by the flies that carry Loa loa in areas where Loa loa is known to exist, the diagnosis can be made in the following ways:
- Identification of the adult worm by a microbiologist or pathologist after its removal from under the skin or eye
- Identification of an adult worm in the eye by a health care provider
- Identification of the microfilariae on a blood smear made from blood taken from the patient between 10AM and 2PM
- Identification of antibodies against L. loa on specialized blood test
Diagnosis of loiasis can be difficult, especially in light infections where there are very few microfilariae in the blood. The specialized blood test is not widely available in the United States. A positive antibody blood test in someone with no symptoms means only that the person was infected sometime in his/her life. It does not mean that the person still has living parasites in his/her body.