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Molecular evidence of Sarcocystis nesbitti in water samples of Tioman Island, Malaysia

View Article: PubMed Central - PubMed

ABSTRACT

Background: Sarcocystis are intracellular protozoan parasites that are characterised by their ability to invade muscle tissue and form intramuscular sarcocysts. A muscular sarcocystosis outbreak was reported by travellers returning from Tioman Island in 2011 and 2012 where Sarcocystis nesbitti was identified as the main cause. The source of the S. nesbitti that was involved has remained elusive, although water is hypothesised to be the main cause of transmission. A surveillance study was therefore undertaken in the northern regions of Tioman Island to identify the source of S. nesbitti by screening rivers, water tanks, wells and seawater.

Methods: Water samples were collected from rivers, water tanks, wells and seawater on Tioman Island over the course of April to October 2015. Water samples were indirectly screened for Sarcocystis species by obtaining sediment from respective water sources. PCR amplification of the 18S rRNA gene region was conducted to identify positive samples. Microscopy was used in an attempt to reappraise PCR results, but no sporocysts were detected in any of the samples.

Results: A total of 157 water samples were obtained and 19 were positive for various Sarcocystis species. Through BLASTn and phylogenetic analysis, these species were found to be S. singaporensis, S. nesbitti, Sarcocystis sp. YLL-2013 and one unidentified Sarcocystis species.

Conclusions: This is the first positive finding of S. nesbitti in water samples on Tioman Island, which was found in a water tank and in river water samples. This finding supports the hypothesis that water was a potential medium for the transmission of S. nesbitti during the outbreak. This will potentially identify areas in which preventive measures can be taken to prevent future outbreaks.

No MeSH data available.


Neighbour-Joining tree constructed with MEGA6 using 18S rRNA gene sequences of Sarcocystis spp. Values represent percentage of replicate trees in which the associated sequences cluster together in the bootstrap test (1000 replicates)
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Fig1: Neighbour-Joining tree constructed with MEGA6 using 18S rRNA gene sequences of Sarcocystis spp. Values represent percentage of replicate trees in which the associated sequences cluster together in the bootstrap test (1000 replicates)

Mentions: Following species identification, the results were reappraised by comparing the 21 cloned sequences with another 31 sequences of the 18S rRNA gene from various other Sarcocystis species obtained from GenBank. This resulted in the construction of a Neighbour-Joining phylogenetic tree (Fig. 1) that was divided in to 2 clades (A and B). Clade A had two subclades, Subclade I and Subclade II, with Subclade I consisting of Sarcocystis species that infect snakes as definitive hosts, and Subclade II consisting of Sarcocystis species that infect snakes as definitive hosts and ruminants as intermediate hosts. Clade B consisted of Sarcocystis species that infect various hosts such as lizards and felines. All samples in this study, S. singaporensis, S. nesbitti, Sarcocystis sp. YLL-2013 and an unidentified Sarcocystis species, reside in Clade A.Fig. 1


Molecular evidence of Sarcocystis nesbitti in water samples of Tioman Island, Malaysia
Neighbour-Joining tree constructed with MEGA6 using 18S rRNA gene sequences of Sarcocystis spp. Values represent percentage of replicate trees in which the associated sequences cluster together in the bootstrap test (1000 replicates)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5120450&req=5

Fig1: Neighbour-Joining tree constructed with MEGA6 using 18S rRNA gene sequences of Sarcocystis spp. Values represent percentage of replicate trees in which the associated sequences cluster together in the bootstrap test (1000 replicates)
Mentions: Following species identification, the results were reappraised by comparing the 21 cloned sequences with another 31 sequences of the 18S rRNA gene from various other Sarcocystis species obtained from GenBank. This resulted in the construction of a Neighbour-Joining phylogenetic tree (Fig. 1) that was divided in to 2 clades (A and B). Clade A had two subclades, Subclade I and Subclade II, with Subclade I consisting of Sarcocystis species that infect snakes as definitive hosts, and Subclade II consisting of Sarcocystis species that infect snakes as definitive hosts and ruminants as intermediate hosts. Clade B consisted of Sarcocystis species that infect various hosts such as lizards and felines. All samples in this study, S. singaporensis, S. nesbitti, Sarcocystis sp. YLL-2013 and an unidentified Sarcocystis species, reside in Clade A.Fig. 1

View Article: PubMed Central - PubMed

ABSTRACT

Background: Sarcocystis are intracellular protozoan parasites that are characterised by their ability to invade muscle tissue and form intramuscular sarcocysts. A muscular sarcocystosis outbreak was reported by travellers returning from Tioman Island in 2011 and 2012 where Sarcocystis nesbitti was identified as the main cause. The source of the S. nesbitti that was involved has remained elusive, although water is hypothesised to be the main cause of transmission. A surveillance study was therefore undertaken in the northern regions of Tioman Island to identify the source of S. nesbitti by screening rivers, water tanks, wells and seawater.

Methods: Water samples were collected from rivers, water tanks, wells and seawater on Tioman Island over the course of April to October 2015. Water samples were indirectly screened for Sarcocystis species by obtaining sediment from respective water sources. PCR amplification of the 18S rRNA gene region was conducted to identify positive samples. Microscopy was used in an attempt to reappraise PCR results, but no sporocysts were detected in any of the samples.

Results: A total of 157 water samples were obtained and 19 were positive for various Sarcocystis species. Through BLASTn and phylogenetic analysis, these species were found to be S. singaporensis, S. nesbitti, Sarcocystis sp. YLL-2013 and one unidentified Sarcocystis species.

Conclusions: This is the first positive finding of S. nesbitti in water samples on Tioman Island, which was found in a water tank and in river water samples. This finding supports the hypothesis that water was a potential medium for the transmission of S. nesbitti during the outbreak. This will potentially identify areas in which preventive measures can be taken to prevent future outbreaks.

No MeSH data available.