Avicenna J Med Biotech arij002 Avicenna Journal of Medical Biotechnology 2008-2835 2008-4625 Avicenna Research Institute ajmb40448 An Evaluation of Transmission Dynamics of Cryptosporidium Using Molecular Methods Mahdavi PoorBehrozRashediJalilAsgharzadehMohammadFallahEsmaeel 13 1 51 52 15 6 2020 30 9 2020

<p style="text-align:justify"><span style="font-size:11pt"><strong><span style="font-size:10.0pt">Dear Editor-in-Chief, </span></strong></span></p> <p style="text-align:justify"><span style="font-size:11pt"><span style="font-size:10.0pt">The members of genus <em>Cryptosporidium</em> are intracellular parasites that infect mammals, poultry, reptiles and amphibians. From the total of 30 valid species mentioned currently, 14 have been determined to infect the human being. Two species,<span style="background-color:#dddddd"><em> </em></span><em><span style="background-color:white">Cryptosporidium hominis</span></em> (<em>C. hominis)</em> (Anthroponotic species) and<em> <em><span style="background-color:white">Cryptosporidium parvum</span></em> (C. parvum)</em> bovine genotype (Zoonotic species), are considered of major public health importance </span><sup><span style="font-size:10.0pt">1</span></sup><span style="font-size:10.0pt">. </span></span></p> <p style="text-align:justify"><span style="font-size:11pt"><span style="font-size:10.0pt">Commonly, the ubiquitous oocysts of <em>Cryptosporidium</em> are transmitted <em>via</em> direct contact with infected hosts or indirectly <em>via</em> contaminated food and water </span><sup><span style="font-size:10.0pt">2</span></sup><span style="font-size:10.0pt">. The low infectious dose and its resistance against common water disinfectants make it a challenge for the drinking water plants </span><sup><span style="font-size:10.0pt">3</span></sup><span style="font-size:10.0pt">. Common laboratory techniques which are being used for diagnosis of <em>Cryptosporidium</em> cannot discriminate it at species and genotype level. However, the genetic tools allow species determination of the parasite as well as tracing its transmission routes </span><sup><span style="font-size:10.0pt">2</span></sup><span style="font-size:10.0pt">.</span></span></p> <p style="text-align:justify"><span style="font-size:11pt"><span style="font-size:10.0pt">In this study, a total of 55 drinking water samples were collected from 11 different areas of Tabriz, the largest city in North West of Iran.</span><span style="font-size:10.0pt"> Each sample contained 30 <em>L</em> of water. To collect the suspended particles, samples were filtered through a membrane filter with 1.2 <em>&mu;m</em> pore size (Sartorius, Germany). The pellets trapped on the filter were collected </span><sup><span style="font-size:10.0pt">4</span></sup><span style="font-size:10.0pt">. All water pellets were subjected to DNA extraction by a method described previously </span><sup><span style="font-size:10.0pt">5</span></sup><span style="font-size:10.0pt">. Then, the amplification of small ribosomal subunit RNA (SSU-rRNA; 18S rRNA) gene was done using a two step nested PCR method </span><sup><span style="font-size:10.0pt">6</span></sup><span style="font-size:10.0pt">. A sample of <em>C. parvum </em>DNA that was extracted by the extraction method was included in each round of PCR as a positive control. The multi copy nature of 18S rRNA gene and nested format of the PCR make it a very sensitive method for detection of <em>Cryptosporidium</em> oocysts in water samples <sup>7</sup>. However, the expected amplicon (826-864-<em>bp</em>) was not detected in any of the water samples.</span></span></p> <p style="text-align:justify"><span style="font-size:11pt"><span style="font-size:10.0pt">Various</span><span style="font-size:10.0pt"> reports from many areas of the world provide strong evidence that contaminated water is an important risk factor for cryptosporidiosis <sup>8</sup>. </span><span style="font-size:10.0pt">Several factors, including</span><span style="font-size:10.0pt"> water source, location of sampling, number and volumes of samples, type of ecosystem, climate and detecting procedures are effective for detection of <em>Cryptosporidium</em> oocysts in the water samples <sup>9</sup>. </span><span style="font-size:10.0pt">The drinking water supplied from surface water sources is more susceptible to contamination. </span><span style="font-size:10.0pt">Thus, underground</span><span style="font-size:10.0pt"> water is a more protected source</span><span style="font-size:10.0pt"> <sup>10</sup>. In our study area, the main </span><span style="font-size:10.0pt">part of the drinking water supplies comes from rivers.</span> </span></p> <p style="text-align:justify"><span style="font-size:11pt"><span style="font-size:10.0pt">The role of rainfall as a determining risk factor for the waterborne transmission of <em>Cryptosporidium</em> can be&nbsp;</span></span><span style="font-size:11pt"><span style="font-size:10.0pt">significant</span><span style="font-size:10.0pt">. The rela</span><span style="font-size:10.0pt">tionship between increased rainfall and an increase in the concentration of <em>Cryptosporidium</em> oocysts in nearby river waters has been reported <sup>10</sup>. The North West part of Iran is an area with lower than average rainfall, </span><span style="font-size:10.0pt">which could be the most important reason for the lack of parasites in the water.</span></span></p> <p style="text-align:justify"><span style="font-size:11pt"><span style="font-size:10.0pt">There are not many reports about the prevalence of <em>Cryptosporidium</em> in water samples in Iran. Meanwhile, the prevalence of</span><span style="font-size:10.0pt"> <em>Cryptosporidium</em> on the surface and recreational water was 36 and 20%, respectively </span><sup><span style="font-size:10.0pt">4,9</span></sup><span style="font-size:10.0pt">. The two researches conducted in </span><span style="font-size:10.0pt">Ardabil and </span><span style="font-size:10.0pt">Chaharmahal va Bakhtiyari provinces as well as our study are limited studies with small sample size. Thus, more comprehensive studies with large samples from different sources and in different seasons are required to assess the real risk of waterborne cryptosporidiosis in Iran.&nbsp; </span></span></p> <p style="text-align:justify"><span style="font-size:11pt"><span style="font-size:10.0pt">Previous studies in Tabriz showed that 1.76% of diarrheic children and 3.8% of cattle have been infected with <em>C. parvum</em> <sup>2,6</sup> (Table 1). The presence of <em>C. parvumm</em> in children, as a sensitive group and in cattle, as a major source for zoonotic disease may be associated with zoonotic transmission of the parasite in the study area. Lack of parasite in drinking water may indicate that this cannot be an important route for transmission; instead, it can be a reason for the low prevalence of the infection in children. Lack of <em>C. hominis</em> (</span><span style="font-size:10.0pt">Anthroponotic species</span><span style="font-size:10.0pt">) in children and the prevalence of <em>C. parvum</em>, potentially zoonotic species, in cattle and its presence in </span><span style="font-size:10.0pt">diarrheic rural children</span><span style="font-size:10.0pt"> would raise the possibility that zoonotic transmission originally occurs through direct contact with farm animals</span> <span style="font-size:10.0pt">in this region.</span></span></p> <p style="text-align:justify"><span style="font-size:11pt"><span style="font-size:10.0pt">Therefore, cattle and other domestic animals should be considered as important sources of infection in the North-western part of Iran.</span></span></p>