Modest genetic differentiation among North American populations of Sarcocystis neurona may reflect expansion in its geographic range

Evidence for a recent population bottleneck in an Apicomplexan parasite of caribou and reindeer, Besnoitia tarandi

“…Microsatellites markers were chosen for this analysis because of their high polymorphism and presumed selective neutrality (Rosenthal, 2001). They have been used in studies of T. gondii, S. neurona, and other Apicomplexan parasites such as Plasmodium falciparum and Plasmodium vivax, two malarial agents (Ajzenberg et al, 2002;Lehmann et al, 2006;Annan et al, 2007;Karunaweera et al, 2008;Sundar et al, 2008;Su et al, 2010).…”

“…Insights into the history and ongoing transmission of parasitic organisms has begun to accrue as genetic markers have been assessed for the extent and geographic distribution of such genetic variation (Rich and Ayala, 2000;Ajzenberg et al, 2004;Imwong et al, 2006;Sundar et al, 2008;Rich et al, 2009;Rosenthal, 2009;Khan et al, 2011a,b). Among parasites in the subclass Coccidia, only Toxoplasma gondii has been subjected to intensive study of the genetic structure of its populations (Ajzenberg et al, 2002(Ajzenberg et al, , 2004Grigg and Suzuki, 2003;Lehmann et al, 2006;Khan et al, 2007Khan et al, , 2011aGrigg and Sundar, 2009;Wendte et al, 2010Wendte et al, , 2011Frazao-Teixeira et al, 2011).…”

“…(Lehmann et al, 2006). Similarly, most North American isolates of S. neurona are demarcated by unique multilocus genotypes when assayed at a dozen microsatellite markers, nearly all of which have been shown to harbor allelic polymorphism (mean alleles/locus = 4) Sundar et al, 2008). Evidently, coccidian parasites are capable of accumulating appreciable genetic variability given adequate population size and age.…”

“…Does B. tarandi more closely resemble S. neurona, a parasite which maintains an ample fund of genetic variability owing to its prevalence in an abundant, wildlife host? (Sundar et al, 2008) Or might the relatively recent establishment of Rangifer in its extant Arctic range (Flagstad and Roed, 2003) have restricted genetic variability in B. tarandi, akin to clonal lineages of T. gondii? Accordingly, we examined the extent of genetic variation among different geographic populations of B. tarandi.…”

An update on Sarcocystis neurona infections in animals and equine protozoal myeloencephalitis (EPM)

“…A restriction fragment length polymorphism (RFLP) at the 33/54 locus was used to distinguish S. neurona from S. falcatula , and nucleotide sequence polymorphisms at the 25/396 locus identified two major alleles that resolved North American from South American S. neurona strains (Rosenthal et al, 2001). To estimate whether the S. neurona population genetic structure was genetically diverse or clonal, Asmundsson and Rosenthal (2006) and Asmundsson et al (2006) developed and applied 12 highly polymorphic microsatellite markers against 34 predominantly North American Sarcocystis samples collected from both definitive and intermediate hosts isolated from diverse geographical origins (Sundar et al, 2008). This important study established that substantial allelic and genotypic diversity exists among circulating S. neurona strains and showed that one genotype is more prevalent than expected for a strictly outbred population, indicating that some degree of clonal expansion has occurred within the species (Asmundsson et al, 2006).…”