Genetic diversity of Cryptosporidium in fish at the 18S and actin loci and high levels of mixed infections

Abstract

a b s t r a c tCryptosporidium is an enteric parasite that infects humans and a wide range of animals. Relatively little is known about the epidemiology and taxonomy of Cryptosporidium in fish. In the present study, a total of 775 fish, belonging to 46 species and comprising ornamental fish, marine fish and freshwater fish were screened for the prevalence of Cryptosporidium by PCR. The overall prevalence of Cryptosporidium in fish was 5.3% (41/775), with prevalences ranging from 1.5 to 100% within individual host species. Phylogenetic analysis of these Cryptosporidium isolates as well as 14 isolates from previous studies indicated extensive genetic diversity as well as evidence for mixed infections. At the 18S locus the following species were identified; Cryptosporidium molnari-like genotype (n = 14), Cryptosporidium huwi (n = 8), piscine genotype 2 (n = 4), piscine genotype 3-like (n = 1), piscine genotype 4 (n = 2), piscine genotype 5 (n = 13), piscine genotype 5-like (n = 1) and five novel genotypes (n = 5). At the actin locus, species identification agreed with the 18S locus for only 52.3% of isolates sequenced, indicating high levels of mixed infections. Future studies will need to employ both morphological characterization and deep sequencing amplicon-based technologies to better understand the epidemiological and phylogenetic relationships of piscine-derived Cryptosporidium species and genotypes, particularly when mixed infections are detected.

Molecular characterisation of a disseminated Cryptosporidium infection in a Koi carp (Cyprinus carpio)

“…The prevalence of Cryptosporidium in fish is highly variable with prevalences ranging 0.8% to 100% mostly among juvenile fish (Landsberg and Paperna, 1986;Sitjà-Bobadilla et al, 2005;Alvarez-Pellitero et al, 2004, Murphy et al, 2009Reid et al, 2010;Zanguee et al, 2010;Morine et al, 2012;Koinari et al, 2013;Certad et al, 2015;Yang et al, 2015). Molecular characterization has identified additional piscine genotypes (piscine genotypes 2-8, C. molnari-like and 5 un-named novel genotypes) as well as C. parvum, C. xiaoi, C. scrofarum, C. hominis and rat genotype III in adult and juvenile fish (Murphy et al, 2009;Reid et al, 2010;Zanguee et al, 2010;Barugahare et al, 2011;Morine et al, 2012;Koinari et al, 2013;Ryan and Xiao, 2014;Certad et al, 2015;Yang et al, 2015).…”

“…Molecular characterization has identified additional piscine genotypes (piscine genotypes 2-8, C. molnari-like and 5 un-named novel genotypes) as well as C. parvum, C. xiaoi, C. scrofarum, C. hominis and rat genotype III in adult and juvenile fish (Murphy et al, 2009;Reid et al, 2010;Zanguee et al, 2010;Barugahare et al, 2011;Morine et al, 2012;Koinari et al, 2013;Ryan and Xiao, 2014;Certad et al, 2015;Yang et al, 2015). In the present study, we present evidence of a disseminated case of cryptosporidiosis in the gills, all parenchymous organs and intestines of a Koi carp (Cyprinus carpio) and molecular identification as a novel isolate, that was most closely related to C. molnari.…”

“…Relatively little is known about Cryptosporidium species infecting piscine hosts but cryptosporidiosis in fish can cause high morbidity and a variety of clinical signs (AlvarezPellitero and Sitja-Bobadilla, 2002;Alvarez-Pellitero et al, 2004;Ryan et al, 2004;Murphy et al, 2009;Zanguee et al, 2010;Ryan and Xiao, 2014;Ryan et al, 2015;Yang et al, 2015). Currently three species are recognized in fish hosts; Cryptosporidium molnari which was originally described in gilthead sea bream (Sparus aurata) and European sea bass (Dicentrarchus labarx) (AlvarezPellitero and Sitja-Bobadilla, 2002) and was characterised genetically in 2010 (Palenzuela et al, 2010), (2) Cryptosporidium scophthalmi was described in turbot in 2004 (Psetta maxima.…”

Prevalence, Molecular Identification, and Risk Factors for Cryptosporidium Infection in Edible Marine Fish: A Survey Across Sea Areas Surrounding France

“…Additionally, other Cryptosporidium species identified in other groups of vertebrates such as C. parvum, C. hominis, C. scrofarum and C. xiaoi , have also been detected in fish. Furthermore, fifteen Cryptosporidium fish genotypes, and one Cryptosporidium rat III-like genotype, have been reported (Ryan et al, 2014; Yang et al, 2015, 2016; Couso-Pérez et al, 2018).…”

First molecular characterization of Cryptosporidium from three different points of two main rivers in Kuantan, Malaysia using 18S rRNA gene nested PCR

“…In fact, phylogenetic tree construction was used to root novel Cryptosporidium sequences with known species or genotypes based on the genotypic variations of sequence diversity, thereby resulting in non-homologous copies of this gene due to different factors like host adaptation and geographical distribution [30]. In this study, for all five positive samples with C. parvum, the samples might contain sequence polymorphisms at the 18S rRNA gene location as reported in many cases of 18S rRNA partial sequences [31][32][33]. Moreover, it is troublesome to verify either variation of sequences corresponding to species diversity or reflecting non-homologous copies of ribosomal RNA [28,34].…”