Application of enzyme-linked immunosorbent assay (ELISA) to identification of Anopheles mosquito bloodmeals

Abstract

The microplate method of the ELISA described by Voller et al. (1974) was manipulated for identification of Anopheles bloodmeals. Blood samples collected from man and from laboratory animals were put in small amounts (1 to 2 μl) on filter paper. Also bloodmeals from A. stephensi fed on human volunteers and guinea-pig were smeared on filter paper one, six 12, 24 and 48 hours after ingestion. The samples were tested by a modified microplate ELISA, using alkaline phosphatase anti-human IgG conjugate. Results showed that ELISA is a quite specific and sensitive technique for the detection of a small amount of human blood, even 24 hours after ingestion by anopheline mosquitoes. The ELISA seems to be a more practical and reproducible method than the precipitin test for identification of arthropod blood-meals, and could also be used for identification of blood spots in forensic laboratories. The anthropophilic index of anopheline mosquitoes is an important factor in the role of different Anopheles mosquitoes in malaria transmission. The technique which has been most commonly used for determination of the source of Anopheles bloodmeals is the precipitin test which was first employed by Uhlenhuth et al. (1908) as a medicolegal procedure for the identification of human blood stains. Later it was used and modified for determining the sources of bloodmeals in mosquitoes and other insects ( King & Bull, 1923 ; Rice & Barber, 1935 ). Although the precipitin test is quite a specific and reliable test, the microplate indirect method of enzyme-linked immunosorbent assay (ELISA) developed by Voller et al. (1974) may be more practical for the identification of human blood in engorged anopheline mosquitoes. The ELISA test has, therefore, been modified for mosquito bloodmeal identification in this study.