The first report of Cryptosporidium andersoni in horses with diarrhea and multilocus subtype analysis

BACKGROUND: Horses interact with humans in a wide variety of sport competitions and non-competitive recreational pursuits as well as in working activities. Cryptosporidium spp are one of the most important zoonotic pathogens causing diarrhea of humans and animals. The reports of Cryptosporidium in horses and the findings of zoonotic Cryptosporidium species/genotypes show a necessity to carry out molecular identification of Cryptosporidium in horses, especially in diarrheic ones. The aim of the present study was to understand Cryptosporidium infection and species/genotypes in diarrheic horses, and to trace the source of infection of horse-derived Cryptosporidium isolates at a subtype level. FINDINGS: Fecal specimens of 29 diarrheic adult horses were collected in Taikang County in northeastern China’s Heilongjiang Province. Cryptosporidium oocysts were concentrated by Sheather’s sugar flotation technique, and then examined by a bright-field microscope. Meanwhile, all the specimens were subjected to PCR amplification of the small subunit (SSU) rRNA gene of Cryptosporidium. C. andersoni isolates were further subtyped by multilocus sequence typing (MLST) at the four microsatellite/minisatellite loci (MS1, MS2, MS3 and MS16). One and two Cryptosporidium-positive isolates were obtained in horses by microscopy and by PCR, respectively. The two C. andersoni isolates were identified by sequencing of the SSU rRNA gene of Cryptosporidium. Both of them were identical to each other at the MS1, MS2, MS3 and MS16 loci, and MLST subtype A4,A4,A4,A1 was found here. CONCLUSIONS: This is the first report of C. andersoni in horses. The fact that the MLST subtype A4,A4,A4,A1 was reported in cattle suggests a large possibility of transmission of C. andersoni between cattle and horses.