TY - JOUR
T1 - Detection of malaria sporozoites by standard ELISA and VecTest™ dipstick assay in field-collected anopheline mosquitoes from a malaria endemic site in Ghana
AU - Appawu, Maxwell A.
AU - Bosompem, Kwabena M.
AU - Dadzie, Samuel
AU - McKakpo, Uri S.
AU - Anim-Baidoo, Isaac
AU - Dykstra, Elizabeth
AU - Szumlas, Daniel E.
AU - Rogers, William O.
AU - Koram, Kwadwo
AU - Fryauff, David J.
PY - 2003/11
Y1 - 2003/11
N2 - We compared the VecTest™ dipstick assay for detection of Plasmodium sporozoites in Anopheles vectors of malaria with standard circumsporozoite (CS) microplate ELISA for detection of Plasmodium falciparum circumsporozoite protein (PfCSP) in Anopheles mosquitoes. Mosquitoes were collected from a malaria endemic site (Kassena Nankana district) in northern Ghana. Of 2620 randomly sampled mosquitoes tested, the standard CS-ELISA gave a sporozoite rate of 10.8% compared with 11.2% by VecTest™, which was not statistically different (P = 0.66). Visual reading of the CS-ELISA results gave a sporozoite rate of 13.4%, which was higher than the other tests (P > 0.05). To allow a more objective evaluation of the sensitivity of the dipstick, an additional 136 known CS-ELISA-positive specimens were analysed. The prevalence of the test (including the additional samples) was 14.6% and 14.7% for CS-ELISA and dipstick, respectively (P > 0.05). The estimated prevalence by visual assessment of the CS-ELISA results was 17.5%. The relative specificity and sensitivity of the VecTest™ dipstick and visually read ELISA were estimated based on the CS-ELISA as a gold standard. The specificities of the dipstick and visual ELISA were high, 98.0% and 96.6%, respectively. However, the sensitivities of the two assays were 88.8% for VecTest and 100% for visual ELISA (P < 0.01). Concordance between VecTest and CS-ELISA was good (κ = 0.86). Similarly, there was a good concordance between the dipstick and the visually read ELISA (κ = 0.88). Extrapolating from PfCSP controls (titrated quantities of P. falciparum sporozoites), mean sporozoite loads of CS-ELISA-positive An. gambiae (286 ± 28.05) and An. funestus (236 ± 19.32) were determined (P = 0.146). The visual dipstick grades showed high correlation with sporozoite load. The more intense the dipstick colour, the higher the mean sporozoite load (+ = 108, ++ = 207, +++ = 290, r = 0.99, r2 = 1). The VecTest dipstick offers practical advantages for field workers needing rapid and accurate means of detection of sporozoites in mosquitoes.
AB - We compared the VecTest™ dipstick assay for detection of Plasmodium sporozoites in Anopheles vectors of malaria with standard circumsporozoite (CS) microplate ELISA for detection of Plasmodium falciparum circumsporozoite protein (PfCSP) in Anopheles mosquitoes. Mosquitoes were collected from a malaria endemic site (Kassena Nankana district) in northern Ghana. Of 2620 randomly sampled mosquitoes tested, the standard CS-ELISA gave a sporozoite rate of 10.8% compared with 11.2% by VecTest™, which was not statistically different (P = 0.66). Visual reading of the CS-ELISA results gave a sporozoite rate of 13.4%, which was higher than the other tests (P > 0.05). To allow a more objective evaluation of the sensitivity of the dipstick, an additional 136 known CS-ELISA-positive specimens were analysed. The prevalence of the test (including the additional samples) was 14.6% and 14.7% for CS-ELISA and dipstick, respectively (P > 0.05). The estimated prevalence by visual assessment of the CS-ELISA results was 17.5%. The relative specificity and sensitivity of the VecTest™ dipstick and visually read ELISA were estimated based on the CS-ELISA as a gold standard. The specificities of the dipstick and visual ELISA were high, 98.0% and 96.6%, respectively. However, the sensitivities of the two assays were 88.8% for VecTest and 100% for visual ELISA (P < 0.01). Concordance between VecTest and CS-ELISA was good (κ = 0.86). Similarly, there was a good concordance between the dipstick and the visually read ELISA (κ = 0.88). Extrapolating from PfCSP controls (titrated quantities of P. falciparum sporozoites), mean sporozoite loads of CS-ELISA-positive An. gambiae (286 ± 28.05) and An. funestus (236 ± 19.32) were determined (P = 0.146). The visual dipstick grades showed high correlation with sporozoite load. The more intense the dipstick colour, the higher the mean sporozoite load (+ = 108, ++ = 207, +++ = 290, r = 0.99, r2 = 1). The VecTest dipstick offers practical advantages for field workers needing rapid and accurate means of detection of sporozoites in mosquitoes.
KW - Anopheles
KW - Circumsporozoite protein
KW - Dipstick assay
KW - Malaria vectors
KW - Plasmodium falciparum
UR - http://www.scopus.com/inward/record.url?scp=0242408550&partnerID=8YFLogxK
U2 - 10.1046/j.1360-2276.2003.00127.x
DO - 10.1046/j.1360-2276.2003.00127.x
M3 - Article
C2 - 14629768
AN - SCOPUS:0242408550
SN - 1360-2276
VL - 8
SP - 1012
EP - 1017
JO - Tropical Medicine and International Health
JF - Tropical Medicine and International Health
IS - 11
ER -