Distribution Of Cryptosporidium And Giardia Duodenalis In Xinghua Dairy Calves In Jiangsu,China

Cryptosporidium and Giardia duodenalis are two common intestinal parasites with a wide range of hosts.Cryptosporidium and Giardia duodenalis can cause hosts diarrhea,indigestion,slow growth,and even result in death.There was a diarrhea outbreak from a dairy cattle farm in Xinghua,Jiangsu in 2016.We collected specimen and conducted a survey about the distribution of Cryptosporidium and Giardia duodenalis from 2016 to 2017 to determine the cause of the diarrhea outbreak in the farm and supplement the epidemiological data in Jiangsu.1390 fresh fecal samples were collected from the dairy farm,including 18 fecal specimens during the outbreak and 1,372 specimens after the outbreak.The pathogenic factors of ill calves were preliminarily judged by Enzyme-Linked ImmunoSorbent Assay(ELISA).The species or genotypes of Cryptosporidium and Giardia duodenalis were indentified by nested PCR and PCR-restriction fragment length polymorphism to find out the reasons for the diarrhea outbreak.The total positive rate of Cryptosporidium in dairy calves was 14.2%,with the highest positive rate of22.7%inpre-weaned calves,8.4%inpost-weaned calves and the lowest positive rate of 1.0%in adults.Four Cryptosporidium species were identified,including C.parvum(n=79),C.ryanae(n=48),C.bovis(n=31),C.andersoni(n=3)and the mixed infection.C.parvum was the dominant species in pre-weaned calves,especially less than the ages of three weeks,which was consistent with the age in dairy calves during the outbreak.C.ryanae and C.bovis were the dominant species in the post-weaned calves.The infection rate of C.parvum in dairy calves during the diarrhea outbreak was significantly higher than that after the outbreak(P<0.05)Based on the χ2 analysis,C.parvum was significantly associated with watery diarrhea in dairy calves(P=0.004),C.ryanae(P=0.000)and C.bovis(P=0.001)were significantly associated with moderate diarrhea.The subtype IIdA19G1 of C.parvum was the main reason for the diarrhea outbreak in the dairy calves,C.ryanae and C.bovis were the potential reasons for the moderate diarrhea in dairy calves through analysis.The positive rate of Giardia duodenalis was 20.6%in dairy calves,with the infection rate of Giardia duodenalis in 2017 significantly lower than that in 2016.The highest infection rate occurred in pre-weaned calves,which was 38.9%.,The infection rates of Giardia duodenalis at the age of 1-5 weeks was relatively lower(2.4-15.2%)in the pre-weaned calves,which was inconsistent with the age of dairy calves during the outbreak.Therefore,Giardia duodenalis was not the main reason for the outbreak.Two genotypes of Giardia duodenalis were determined in this study,including assemblage E(n=278),assemblage A(n=2)and the mixed infections of A+E(n=1).Among the assemblage E,13,7 and 10 subtypes of assemblage E were identified at the bg,gdh and tpi loci,including 5,2,and 3 new subtypes,respectively,forming 65 multilocus genotypes of E.Genetic recombination was responsible for the high polymorphism of assemblage E based on eBURST network analysis.The above results determined the IIdA19G1 subtype of C.parvum as the reason for the diarrhea outbreak,and supplemented the epidemiological data of Cryptosporidium and Giardia duodenalis in dairy calves in Jiangsu dairy calves,providing reference for the prevention and control of parasitic diseases.