Infection with Cryptosporidium parvum Affects Secondary Sexual Characteristics of Male Mice by Altering the Pheromone Content in Preputial Gland

SIMPLE SUMMARY: During the breeding process of mice, the females can evaluate the health status of males and choose the suitable mates through the smell of urine. Under the natural conditions, parasitic infections in small mammals are very common, and parasitic infections can affect the health status of hosts. However, the impact of parasitic infection on mammalian reproductive capacity has not been fully studied. In this study, we used the ICR/CD-1 mouse model to explore the relationship between parasitic infection and pheromone content; Cryptosporidium parvum was used as the infectious agent. This study revealed that the urine attractiveness of the ICR/CD-1 male mice was decreased after parasitic infection when compared with the uninfected group. Both the gene expression level and protein concentration of MUP in liver and urine were down-regulated after parasitic infection. The results of GC-MS analysis indicated that the contents of different pheromones were significantly reduced after parasitic infection. In summary, this study revealed that infection with C. parvum affects the secondary sexual characteristics of male ICR/CD-1 mice and alters the pheromone contents in the foreskin gland. ABSTRACT: The olfactory acuity of female mice allows them to discriminate the urinary odors of males. Parasitic infection can reduce the odor attractiveness of male mice to females and result in female aversion or avoidance responses in odor selection. However, the chemical signaling changes in the pheromone contents produced by the foreskin gland were not fully revealed after parasitic infection. Cryptosporidium parvum (C. parvum) is a common zoonotic intestinal parasite and has a wide range of hosts, including human, domestic animals, and wild animals. In this study, we immunosuppressed ICR/CD-1 male mice by dexamethasone sodium phosphate treatment. After C. parvum infection, physiological indexes such as body weight and organ weight were significantly decreased. Furthermore, the gene expression level of MUP (major urinary protein) in liver and urine were significantly down-regulated, which could be the reason for the decrease in urine attractiveness to females. GC-MS was performed to analyze the changes in the pheromone produced by the preputial gland before and after parasitic infection, and the results indicated that the levels of different pheromones were significantly reduced after parasitic infection. In summary, this study reveals that C. parvum infection damages the secondary sexual characteristics of male ICR/CD-1 male mice and decreases the pheromone content produced by the foreskin gland.