Cryptosporidium parvum Co-Infection on the Magnitude of Escherichia coli O157:H7 Shedding in Experimentally Inoculated Pigs
Published on: 2019-03-30
Escherichia coli O157:H7 [E. coli O157:H7] and Cryptosporidium parvum [C. parvum] are zoonotic pathogens that have potential for economic impact worldwide. Neonatal animals are especially vulnerable to these types of pathogens. The significance of single vs. concurrent [multiple] infections are unclear. Our objective was to determine differences in the magnitude of daily shedding and colonization by E. coli O157:H7 between pigs co-infected with C. parvum and pigs inoculated only with E. coli O157:H7. Fifteen out of 27 weaned 2-month-old pigs were inoculated with a C. parvum isolate from naturally-infected calves. On the fourth day of infection, 23 pigs were inoculated with approximately 102, 103, 104, 105, or 107 colony forming units or CFU of an E. coli O157:H7 strain. On days 3 and 4 post-inoculation [PI] with E. coli O157:H7, one pig co-infected with C. parvum and 107 CFU E. coli was euthanized and necropsied to determine the enumeration and distribution of colonized E. coli O157:H7. On days 7 and 14 PI, one co-infected and non co-infected pig from each inoculum group was also euthanized for enumeration and distribution of colonized E. coli O157:H7. The total environmental shedding load of E. coli O157:H7 suggested that the amount of time PI and the dose of E. coli O157:H7 are important factors in relation to the magnitude of E. coli O157:H7 shedding. Trends between co-infected and non co-infected groups were seen, but the relationship was non-significant in this model. The infectious dose for 50% [ID50] of the pigs inoculated using the outbreak E. coli O157:H7 strain was determined to be in the range of 103-104 CFU.