Emergence of Distinct Genotypes of Cryptosporidium parvum in Structured Host Populations

Abstract

Cryptosporidium parvum is an apicomplexan parasite that infects humans and ruminants. C. parvum isolated from cattle in northeastern Turkey and in Israel was genotyped using multiple polymorphic genetic markers, and the two populations were compared to assess the effect of cattle husbandry on the parasite's population structure. Dairy herds in Israel are permanently confined with essentially no opportunity for direct herd-toherd transmission, whereas in Turkey there are more opportunities for transmission as animals range over wider areas and are frequently traded. A total of 76 C. parvum isolates from 16 locations in Israel and seven farms in the Kars region in northeastern Turkey were genotyped using 16 mini-and microsatellite markers. Significantly, in both countries distinct multilocus genotypes confined to individual farms were detected. The number of genotypes per farm was higher and mixed isolates were more frequent in Turkey than in Israel. As expected from the presence of distinct multilocus genotypes in individual herds, linkage disequilibrium among loci was detected in Israel. Together, these observations show that genetically distinct populations of C. parvum can emerge within a group of hosts in a relatively short time. This may explain the frequent detection of host-specific genotypes with unknown taxonomic status in surface water and the existence of geographically restricted C. hominis genotypes in humans.

Inferences about the Global Population Structures of Cryptosporidium parvum and Cryptosporidium hominis

“…The United Kingdom isolates had been previously identified at the COWP locus by PCR-restriction fragment length polymorphism and were additionally tested by using the LIB13 marker. Nine mini-and microsatellite markers were used to subtype C. parvum and C. hominis as previously described (35,36). Markers are located on chromosome I (MSA, MSB), chromosome II (MSC), chromosome III (MSK), chromosome IV (MSE), chromosome V (MS9), chromosome VI (MSG), chromosome VII (1887), and chromosome VIII (TP14).…”

“…A total of 62 DNA samples from C. parvum-positive fecal specimens collected between March 2004 and April 2005 from 7-to 13-day-old calves on 14 farms (n ϭ 60), from a horse (n ϭ 1), and from a goat kid (n ϭ 1) were used. The collection sites, oocysts purification, and DNA extraction method were previously described (35).…”

“…Cryptosporidium parvum oocysts were isolated between September 2001 and May 2005 from 15 fecal specimens from calves on 14 farms in the Kars region in northeastern Turkey. Oocyst purification and DNA extraction methods were previously described (35).…”

“…Purified oocysts were suspended in 100 l Tris-EDTA buffer and subjected to three cycles of freezethawing. DNA was extracted from the oocyst lysate by using a commercial column DNA purification kit (HiPure template preparation kit; Roche Diagnostics, Indianapolis, IN) as previously described (35) and the DNA eluted in 50 l of distilled water.…”

“…Cryptosporidium parasite populations have been studied using PCR-based amplification of single or multiple genetic markers in Italy (3,4), Denmark (9), Scotland (16,23,24), India (12), Israel and Turkey (35), England and Wales (20), France and Haiti (27), India, Kenya, the United States, and Peru (13), and Belgium (14). Some studies have used a gene encoding the sporozoite surface glycoprotein GP45/15 (also dubbed GP60) (5,32).…”