Mycoplasma species in vaginas of dairy cows before and after exposure to bulls and their association with conception.

Mycoplasma species can colonize the urogenital tract of dairy cattle. However, interrelationships between Mycoplasma spp. and reproductive performance in dairy herds are unclear. In this study, we measured apparent prevalences of Mycoplasma spp. in the vaginas of dairy cows (n = 629) pre- and post-bull exposure in dairy herds with and without Mycoplasma bovis clinical disease (n = 5 herds), and assessed associations between variables describing reproductive performance and consequent Mycoplasma spp. isolation. Mycoplasma spp. were infrequently isolated from the vagina pre- (1.9%; 12/629) and post-bull (3.2%; 20/629) exposure. Of the mycoplasmas isolated, Mycoplasma bovigenitalium was isolated most frequently (87.5%; 28/32), followed by Mycoplasma californicum (9.3%; 3/32). Mycoplasma bovis was only isolated from one cow. We were unable to provide any evidence of venereal transmission of M. bovis in cows in M. bovis-infected herds that use natural service bulls. There was an insufficient number of cows with Mycoplasma spp. in the vagina pre-bull exposure to assess effects on subsequent reproductive performance. Cows that had not conceived before post-bull exposure sampling had much greater odds (odds ratio 14.8; 95% confidence interval 4.2 to 52.3) of having a Mycoplasma sp. isolated from the vagina at this time compared with those that had conceived. Also, within those that had conceived, delayed conception increased the odds of having a Mycoplasma spp. isolated from the vagina at the post-bull exposure sampling by a factor of 1.62 for every additional week not pregnant. The likely cause of these findings is that cows that remain not pregnant for longer are more likely to be served by a bull (likely repeatedly) and subsequently become colonized with a Mycoplasma sp. (mostly M. bovigenitalium) through venereal transmission. In dairy herds that use bulls, there is a greater chance of isolating a Mycoplasma sp. (mostly M. bovigenitalium) after a period of bull breedings from the vaginas of cows that have remained nonpregnant for longer during the bull breeding period.

Mycoplasma bovis and other Mollicutes in replacement dairy heifers from Mycoplasma bovis-infected and uninfected herds: A 2-year longitudinal study.

Replacement dairy heifers exposed to Mycoplasma bovis as calves may be at risk of future clinical disease and pathogen transmission, both within and between herds; however, little information is available about these risks. We conducted a 2-yr longitudinal (panel) study starting with 450 heifer calves reared to weaning in 8 herds (7 M. bovis infected with clinical disease, 1 uninfected) under the same ownership. After weaning, heifers were commingled and managed with non-study heifers at a single heifer rearing facility. Nose, conjunctival, and vaginal swabs were collected along with a blood sample at weaning, prebreeding, precalving, and approximately 1 mo postcalving. Additionally, a colostrum sample was collected upon calving and a composite milk sample was collected 1 mo postcalving. The swabs, colostrum, and milk samples were cultured for Mycoplasma spp., and serum from the blood was evaluated for serological evidence of exposure to M. bovis using an ELISA. Despite a high M. bovis ELISA seroprevalence at weaning in the heifers from the 7 M. bovis-infected herds with clinical disease [72% (289/400); range by herd: 28-98%], M. bovis was isolated from only 4% (16/400) of the same heifers at the same time. In heifers from the uninfected herd at weaning, M. bovis seroprevalence was 2% (1/50) and M. bovis was not detected by culture. Mycoplasma bovis was isolated from 0.5% (2/414) of heifers at prebreeding, 0% (0/374) of heifers at precalving, and 0.3% (1/356) of heifers 1 mo postcalving. The nose was the predominant anatomical site of M. bovis colonization (74%; 14/19 culture positives). A single heifer (from an M. bovis-infected herd with clinical disease) was repeatedly detected with M. bovis in its nose at weaning, prebreeding, and postcalving samplings. This demonstrates the possibility, albeit rare, of a long-term M. bovis carrier state in replacement heifers exposed to M. bovis as calves, up to at least 1 mo after entry into the milking herd. No M. bovis clinical disease was detected in any heifer from weaning through to the end of the study (approximately 1 mo after calving). Acholeplasma spp. were commonly isolated throughout the study. Mycoplasma bovigenitalium, Mycoplasma bovoculi, and Mycoplasma bovirhinis were isolated infrequently. Mycoplasma bovis seroprevalences at prebreeding, precalving, and postcalving samplings were 27% (112/414), 12% (46/374), and 18% (65/356), respectively. Overall, the results show that replacement heifers from groups exposed to M. bovis preweaning can become colonized with M. bovis and that colonization can, uncommonly, be present after their first calving. For groups of 50 or more heifers exposed to M. bovis preweaning, there is at least a nontrivial probability that the group will contain at least 1 shedding heifer postcalving.

Isolation of Mycoplasma spp. and serological responses in bulls prior to and following their introduction into Mycoplasma bovis-infected dairy herds.

With the common use of bulls for breeding following a period of artificial insemination in seasonally bred dairy herds, it is important to consider the potential role of the bull in transmission of Mycoplasma spp. within and between herds. This study aimed to assess the prevalence of Mycoplasma spp. in a population of bulls before and after use in Mycoplasma bovis-infected herds. The frequency of subclinical infection was also measured serologically postbreeding, and the association of Mycoplasma spp. on semen quality was evaluated. Mycoplasma bovis was isolated from 4 of 118 bulls after use in 4 herds infected with M. bovis. In the bulls, M. bovis seroprevalence increased from 9% prebreeding to 46% postbreeding with a total seroconversion rate of 44% across the 4 herds, with no evidence of clinical disease. There was no association of Mycoplasma spp. in the bulls' semen and abnormal palpation characteristics (enlarged or nodular) of seminal vesicular glands or poor semen quality attributes such as semen mass activity, sperm motility, and morphology. These results demonstrate a high degree of subclinical exposure of the bulls to M. bovis in infected herds and highlight the potential for bulls to be mycoplasma carriers within and between herds. Herd biosecurity protocols and control programs should take into account the potential role of bulls in the introduction and spread of Mycoplasma spp.

Short communication: Shedding of Mycoplasma bovis and antibody responses in cows recently diagnosed with clinical infection.

Mycoplasma bovis can have significant consequences when introduced into immunologically naïve dairy herds. Subclinically infected carrier animals are the most common way that M. bovis is introduced into herds. Although M. bovis udder infections can be detected by milk sampling lactating animals before their introduction, currently, no definitive way of identifying M. bovis carrier animals that are nonlactating (i.e., calves, heifers, dry cows, or bulls) is available. Understanding the prevalence of M. bovis shedding from various body sites in clinically infected animals could inform strategies for the detection of subclinical infection in nonlactating stock. The mucosal surfaces of the nose, eye, and vagina of 16 cows with recent clinical mastitis caused by M. bovis were examined for the presence of M. bovis shedding. Blood was collected for serological evaluation by a commercially available ELISA. Mycoplasma bovis was isolated from the vagina of only 3 (18.8%) of the cows and was not detected from the noses or eyes of any of the cows. Fifteen of the 16 (93.8%) cows were seropositive to the ELISA. With such low prevalence of detection of M. bovis from the vagina and no detections from the noses or eyes of recently clinically infected animals, it is very likely that sampling these sites would be ineffective for detecting subclinical infection in cattle. Serology using the ELISA may have some use when screening animals for biosecurity risk assessment. However, more information regarding time to seroconversion, antibody longevity, and test diagnostic sensitivity and specificity are required to define the appropriate use of this ELISA for biosecurity purposes.