Micro-CT visualisation of the parasite-host interface in small biting flies

Micro-computed tomography, µCT, is a technique that takes about 3,000 X-ray images from the full 360° around a specimen and uses them to reconstruct a virtual 3D model of the external and internal anatomy of that specimen, which can then be examined and dissected in any orientation. We are a group of researchers from UK, Ghana and Bangladesh with a shared interest in what µCT can bring to the science of neglected tropical diseases (NTD) and vector biology, especially the parasite-host interface. We will build on the potential that we have seen for this technique in work that some of us have already done to study the metamorphosis of blow flies and the parasitisation of ants with lancet liver fluke.

Although the techniques could be applied to any vector system, our proposal will focus on addressing two specific hypotheses: 1) that specialised morphological forms of Leishmania concentrate around the stomodeal valve of infected sandflies, with the sandfly midgut being deformed by a gel secreted by the parasites; 2) that a thinner peritrophic matrix in Forest blackflies of the Simulium damnosum complex allows them to develop more Onchocerca L3 larvae than Savanna species. The µCT technique enables both qualitative and quantitative (e.g. volume) analyses. In addition to tackling research questions of fundamental and applied importance, we anticipate that using our Zeiss Versa system will generate striking images of parasitized sandflies and blackflies that can also be used for public education and engagement.

Project data

2-D and 3-D images of sandflies and blackflies were generated during the project, showing differences between unfed and blood-fed flies and between sandflies with different levels of parasite infection. Here, Dr Martin Hall explains the findings from his Gnatwork Transformative Science project.

False-coloured 3-D video of a gravid adult female of Lutzomia longipalpis, with the cuticle made transparent to reveal nearly mature eggs.

False-coloured 3-D video of an adult female of Lutzomia longipalpis, nine days after ingesting a first blood-meal infected with amastigotes of Leishmania mexicana and five days after a second, non-infected blood meal. The cuticle is rendered transparent to enable visualisation of the distended midgut (green) filled with promastigote secretory gel (PSG, blue) secreted by the Leishmania parasites. The clearly opened stomodeal valve is visible at the anterior end of the midgut.

False-coloured 3-D video of an adult female of a savannah strain of Simulium black fly revealing a single L1 stage larva in an intramuscular space within the thoracic flight muscle blocks. The larva is approximately 218 µm long by 23 µm in diameter.

False-coloured 3-D video of an adult female of a savannah strain of Simulium black fly. As the cuticle and internal tissues are stripped away, a single L1 stage larva is revealed within an intramuscular space in the thoracic flight muscle blocks. The larva is approximately 218 µm long by 23 µm in diameter.