Abstract
The current serological test for human onchocerciasis relies on IgG4 reactivity against the parasite Ov-16 antigen, with reported sensitivities of only 60–80%. As control programs move from control to elimination, it is imperative to identify novel molecules that could improve the serodiagnosis reliability of this disease. In this study we compared the sensitivity of total IgG against OvMANE1—a chimeric antigen previously identified as a potential biomarker of human onchocerciasis—with that of an Ov-16 antibody test to detect an Onchocerca volvulus infection in persons presenting with microfilaria in skin snips. One hundred and ninety serum samples were obtained from persons with epilepsy in an onchocerciasis-endemic area at Ituri in the Democratic Republic of Congo where ivermectin has never been distributed. Fifty-nine (31.1%) samples were from individuals with a positive skin snip test; 41 (69.5%) of these 59 samples were positive with the OvMANE1 test and 41 (69.5%) with the Ov-16 test; 30 (50.8%) samples were positive for both tests and in 52 (88.1%) at least one of the tests was positive. Testing the 131 sera from persons with a negative skin snip result revealed that 63 (48.1%) were positive exclusively with the OvMANE1 test, 13 (9.9%) exclusively with the Ov-16 test and 25 (19.1%) with both tests. Nine European samples from individuals without past travel history in onchocerciasis endemic zones and 15 samples from Rwanda, a hypoendemic country for onchocerciasis were all negative for the OvMANE1 and Ov-16 tests. However, the specificity of both tests was difficult to determine due to the lack of a gold standard for antibody tests. In conclusion, the tandem use of OvMANE1 and Ov-16 tests improves the sensitivity of detecting Onchocerca volvulus seropositive individuals but, the OvMANE1 test needs to be further evaluated on samples from a population infected with other helminths to cautiously address its specificity.
Highlights
Among the 20 Neglected Tropical Diseases recognized by the World Health Organization (WHO, Geneva, Switzerland) as diseases of global public health importance is onchocerciasis—a vector-borne parasitic disease caused by infection with the filarial nematode Onchocerca volvulus (Ov; O. volvulus) [1,2]
Serum samples from 190 participants were randomly selected from 387 serum samples obtained during O. volvulus infection screening of persons with epilepsy in Ituri province, Democratic Republic of Congo [19]
Entomological of the positive presencesamples of O. volvulus blackwere flies positive for onchocerciasis using the skin snip test
Summary
Among the 20 Neglected Tropical Diseases recognized by the World Health Organization (WHO, Geneva, Switzerland) as diseases of global public health importance is onchocerciasis—a vector-borne parasitic disease caused by infection with the filarial nematode Onchocerca volvulus (Ov; O. volvulus) [1,2]. About 21 million people are reported to be infected with O. volvulus among which 1.15 and 14.6 million have vision loss and skin disease respectively [3]. Close to 217.2 million people living in 30 countries mostly in sub-Saharan. Africa are in need of preventive chemotherapy for the disease [7]. The standard method for the diagnosis of active O. volvulus infection is the skin snip test. This test demonstrates the presence of O. volvulus microfilariae in skin snips by microscopy, a practice that is widely frowned upon because it is invasive and unable to detect mild infection, besides the challenges to make the difference between
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