Automatic Cryptosporidium and Giardia viability detection in treated water

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RESEARCH

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Automatic Cryptosporidium and Giardia viability detection in treated water Shahriar Badsha1, Norrima Mokhtar1*, Hamzah Arof1, Yvonne Ai Lian Lim2, Marizan Mubin1 and Zuwairie Ibrahim3

Abstract In the automatic detection of Cryptosporidium and Giardia (oo)cysts in water samples, low contrast and noise in the microscopic images can adversely affect the accuracy of the segmentation results. An improved partial differential equation (PDE) filtering that achieves a better trade-off between noise removal and edge preservation is introduced where the compass operator is utilized to attenuate noise while retaining edge information at the cytoplasm wall and around the nuclei of the (oo)cysts. Then the anatomically important information is separated from the unwanted background noise using the Otsu method to improve the detection accuracy. Once the (oo)cysts are located, a simple technique to classify the two types of protozoans using area, roundness metric and eccentricity is implemented. Finally, the number of nuclei in the cytoplasm of each (oo)cyst is counted to check the viability of individual parasite. The proposed system is tested on 40 microscopic images obtained from treated water samples, and it gives excellent detection and viability rates of 97% and 98%, respectively. Keywords: Parasite calculation; Parasite differentiation; Nucleus calculation; Automatic viability confirmation

1. Introduction Cryptosporidium parvum and Giardia lamblia are two common waterborne parasites infecting humans worldwide [1]. In infected humans, the organisms normally attack the small intestine after being ingested [2,3]. They are found mostly in surface waters, where their concentration is related to the level of faecal pollution or human use of the water [4-6]. Cryptosporidium and Giardia parasites can also be found in infected sheep, cattle and many other animal species such as cat, beaver, deer and flies. Besides diarrhoea, other symptoms of giardiasis and cryptosporidiosis are slight fever, fatigue and myalgia. In rare cases, these parasites may infect the lungs and trachea, resulting in cough, dehydration and extreme weight loss [7-9]. The impact of epidemic Cryptosporidium and Giardia outbreaks has motivated many researchers to find measures to prevent them from recurring worldwide. As a result, studies related to the transmission, detection and life cycle of the parasites have proliferated. The process * Correspondence: [email protected] 1 Applied Control and Robotics Laboratory, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia Full list of author information is available at the end of the article

of detecting the presence of Cryptosporidium and Giardia (oo)cysts in water and wastewater samples involves filtration, isolation, staining and microscopy. In microscopy, direct visual inspection under a microscope is performed by an expert to detect the presence of Cryptosporidium and Giardia (oo)cysts. This manual inspection is tedious and time-consuming. Attempts have been