In order to determine the prevalence and risk factors for shedding of Cryptosporidium spp. in dairy calves, a cross-sectional study was carried out in the northeastern region of Buenos Aires Province, Argentina. Fecal samples from a total of 552 calves from 27 dairy herds were collected, along with a questionnaire about management factors. Cryptosporidium spp. oocysts were detected by light microscopy using Kinyoun staining. Putative risk factors were tested for association using generalized linear mixed models (GLMMs). Oocyst shedding calves were found in 67% (CI95% = 49-84) of herds (corresponding to a true herd prevalence of 98%) and 16% (CI95% = 13-19) of calves (corresponding to a true calve prevalence of 8%). Within-herd prevalence ranged from 0 to 60%, with a median of 8%. Cryptosporidium spp. excretion was not associated with the type of liquid diet, gender, time the calf stayed with the dam after birth, use of antibiotics, blood presence in feces, and calving season. However, important highly significant risk factors of oocyst shedding of calves was an age of less or equal than 20 days (OR = 7.4; 95% CI95% = 3-16; P < 0.0001) and occurrence of diarrhea (OR = 5.5; 95% CI95% = 2-11; P < 0.0001). The observed association with young age strongly suggests an early exposure of neonatal calves to Cryptosporidium spp. oocysts in maternity pens and/or an age-related susceptibility. Association with diarrhea suggests that Cryptosporidium spp. is an important enteropathogen primarily responsible for the cause of the observed diarrheal syndrome. Results demonstrate that Cryptosporidium spp. infection is widespread in the study region. Monitoring and control of this parasitic protozoan infection in dairy herds is recommended.

Background/Objectives: Vaccines may improve the control and eradication of bovine tuberculosis. However, the evaluation of experimental candidates requires the assessment of the protection, excretion, transmission and biosafety. A natural transmission trial among likely infected animals was conducted. Methods: Seventy-four male heifers were randomly distributed (five groups) and vaccinated subcutaneously with attenuated strains (M. bovis Δmce2 or M. bovis Δmce2-phoP), a recombinant M. bovis BCG Pasteur (BCGr) or M. bovis BCG Pasteur. Then, they cohoused with a naturally infected bTB cohort under field conditions exposed to the infection. Results: A 23% of transmission of wild-type strains was confirmed (non-vaccinated group). Strikingly, first vaccination did not induce immune response (caudal fold test and IFN-gamma release assay). However, after 74 days of exposure to bTB, animals were re-vaccinated. Although their sensitization increased throughout the trial, the vaccines did not confer significant protection, when compared to the non-vaccinated group, as demonstrated by pathology progression of lesions and confirmatory tools. Besides, the likelihood of acquiring the infection was similar in all groups compared to the non-vaccinated group (p > 0.076). Respiratory and digestive excretion of viable vaccine candidates was undetectable. To note, the group vaccinated with M. bovis Δmce2-phoP exhibited the highest proportion of animals without macroscopic lesions, compared to the one vaccinated with BCG, although this was not statistically supported. Conclusions: This highlights that further evaluation of these vaccines would not guarantee better protection. The limitations detected during the trial are discussed regarding the transmission rate of M. bovis wild-type, the imperfect test for studying sensitization, the need for a DIVA diagnosis and management conditions of the trials performed under routine husbandry conditions. Re-vaccination of likely infected bovines did not highlight a conclusive result, even suggesting a detrimental effect on those vaccinated with M. bovis BCG.

Background/Objectives: Cryptosporidium parvum is a zoonotic enteroparasite causing severe diarrhea in newborn calves, leading to significant economic losses in dairy and beef farming. This study aimed to evaluate whether C. parvum p23-specific IgY antibodies could control neonatal calf diarrhea caused by C. parvum. Methods: A recombinant immunogen comprising the p23 protein fused to the antigen-presenting cell homing (APCH) molecule was expressed using the baculovirus system. Hens were immunized with the APCH-p23 immunogen, and the resulting IgY was spray-dried for treatment use. Eight newborn calves were included in the study and received commercial colostrum within the first 12 h of life. Four calves were treated with 20 g of powdered egg containing IgY (p23-specific IgY titer of 256 in milk) twice daily for 7 days. The remaining four calves received regular non-supplemented milk. All calves were orally infected with 6 million oocysts and monitored for 21 days. Results: Calves treated with p23-specific IgY exhibited significantly reduced diarrhea duration (3.5 vs. 7.5 days; p = 0.0397) and oocyst shedding duration (6.50 vs. 12 days; p = 0.0089). In addition, the total number of excreted oocysts, as measured by the change of the area under the curve (AUC), was significantly reduced in the treated group (14.25 vs. 33.45; p = 0.0117). Although the onset of diarrhea was delayed (3.5 to 6.5 days post-infection; p = 0.1840), and diarrhea severity was reduced (24.25 to 17 AUC; p = 0.1236), both parameters were not statistically significant. Conclusions: P23-specific IgY antibodies effectively reduced the C. parvum-induced duration of diarrhea in experimentally infected calves. These findings highlight the potential of this passive treatment as a promising strategy for controlling neonatal calf diarrhea.