Diagnostics of loiasis
Diagnosis of loiasis is complex due to the different developmental stages and varying clinical penetrance of the disease. Direct diagnostic assays provide proof of infection while indirect diagnostic assays rely on antibody detection or unspecific clinical and laboratory signs of the disease.
Direct diagnostic assays include:
Visualization or removal of the adult worm while migrating
- through conjunctiva of the eye
- under the skin
Detection of microfilariae in blood
- Standard microscopy for detection of microfilariae in fresh blood smears or stained blood smears. Concentration techniques may be used to improve sensitivity in individuals with low levels of microfilaraemia
- PCR or LAMP detection of microfilariae in peripheral blood
Fresh blood is examined under the microscope. The red dots are the red blood cells of the patient. The rapidly moving “snake-like objects” are the microfilariae of Loa loa that swim in the patient’s blood.
Indirect diagnostic assays:
- Other clinical signs including Calabar swelling are sensitive but lack high specificity in the diagnosis of loiasis
- Serological detection of antibodies provides helpful diagnostic information in patients from non-endemic regions but lack diagnostic specificity in populations residing in endemic regions
- Indirect laboratory markers (eosinophilia, IgE elevation, etc.) may be helpful in patients from non-endemic regions but lack diagnostic specificity in populations residing in endemic regions
References:
Ramharter M, Butler J, Mombo-Ngoma G, Nordmann T, Davi SD, Zoleko Manego R. Lancet Infect Dis. 2024 Mar;24(3):e165-e178. doi: 10.1016/S1473-3099(23)00438-3.
Ekoka Mbassi FA, Mombo-Ngoma G, Ndoumba WN, Yovo EK, Eberhardt KA, Ekoka Mbassi D, Adegnika AA, Agnandji ST, Bouyou-Akotet MK, Ramharter M, Zoleko-Manego R. Am J Trop Med Hyg. 2022 Jul 5;107(2):383-387. doi: 10.4269/ajtmh.22-0061.
Mischlinger J, Manego RZ, Mombo-Ngoma G, Ekoka Mbassi D, Hackbarth N, Ekoka Mbassi FA, Davi SD, Kreuzmair R, Veletzky L, Hergeth J, Ndoumba WN, Pitzinger P, Groger M, Matsiegui PB, Adegnika AA, Agnandji ST, Lell B, Ramharter M. PLoS Negl Trop Dis. 2021 Aug 16;15(8):e0009623. doi: 10.1371/journal.pntd.0009623.
