Developing a wide field-of-view digital microscope system for low-resource settings with applications in schistosomiasis diagnosis

Schistosomiasis is a neglected tropical disease that affects hundreds of millions of people, especially in developing countries with poor sanitation and lack of potable water. While the infection can be treated with the drug praziquantel, appropriate targeting and drug distribution is crucial in ensuring a cost-effective disease control program. Hence, methods facilitating rapid screening and diagnosis of schistosomiasis are necessary to aid in population assessment and geographical mapping of the disease. Nevertheless, schistosomiasis-endemic regions tend to be resource-constrained, and thus lack specialized facilities and equipment. We are hence interested in developing a tool to aid in rapid schistosomiasis diagnosis for low-resource settings.
Light microscopy for schistosomiasis diagnosis is simple yet effective, although the procedure tends to be time-consuming and laborious. This is largely due to the microscope’s limited field of view when the sample is magnified, resulting in the need for manual panning the sample. Thus, our goal was to develop a portable digital microscope system that has good resolution and wide field of view, thereby minimizing or even eliminating the need for panning the sample. Such a system would help in making schistosomiasis diagnosis more efficient.
We proposed the development of two digital microscope systems, one using a smartphone camera and another using an interchangeable lens camera. Both systems have reasonable resolution that would enable us to capture sufficient details of schistosome eggs on a microscope slide. The second system, in particular, is capable of a wide field of view, measuring about 17 x 13 mm2, i.e., capable of imaging an entire 13-mm filter membrane in a single field of view. Since the 13-mm filter membrane is used in a common sample preparation protocol to filter the eggs from human urine sample for schistosomiasis diagnosis, the ability to image the membrane in a single field of view meant that we can image, and subsequently quantify, the eggs from a single image without the need for panning the sample under the system. The results of our preliminary tests using schistosome eggs on such filter membranes are reported in this thesis, demonstrating the system’s potential in schistosomiasis diagnosis.
We also achieved a range of imaging modes, such as bright-field, dark-field, Rheinberg and reflective light illumination for our microscope system, demonstrating its versatility. Specifically, dark-field and Rheinberg illuminations are ways that can enhance contrast when imaging the samples, as demonstrated in this thesis. These illumination schemes may potentially help in making identification of schistosome eggs easier.
All in all, the camera-based digital microscope system that we developed is able to image a wide field of view with reasonable resolution, making it compatible for use with 13-mm filter membranes for urinary schistosomiasis diagnosis. By eliminating the need for panning, the imaging step of microscopy examination would hence be more efficient. Future works, such as computer vision algorithms, could be incorporated to help create a rapid yet reliable automated workflow for diagnosis of the infection and determination of the egg count. In addition, both systems presented in this thesis are portable and use components that can be easily obtained off- the-shelf, making them suitable for field work in low-resource settings. Nevertheless, field testing would be necessary to test the system to investigate its practicality and reliability for schistosomiasis diagnosis in low-resource settings.

Keywords: Microscope
Single Field of View
Schistosomiasis
Camera
Thesis
Advisor: Bowden Audrey K.
Andrews Jason R.