Fungi of the Fusarium species can infect food and feed commodities and produce the mycotoxins zearalenone (ZEA) and deoxynivalenol (DON). Since both toxins have been reported to reduce fertility, the mechanisms of ZEA and DON on inhibition of oocyte maturation were examined. Pig oocytes were matured in the presence of ZEA (a mycotoxin with estrogenlike activity), 17beta-estradiol, and DON (all 3.12 micromol/L). Zearalenone, 17beta-estradiol, and DON inhibited oocyte maturation and caused approximately 34% of the oocytes to form an aberrant spindle. Different ratios of ZEA:DON did not lead to a more severe inhibition of oocyte maturation. Both mycotoxins caused abnormal formation of the meiotic spindle. The developmental competence of oocytes matured in the presence of mycotoxins was further investigated after in vitro fertilization. Presence of ZEA (3.12 micromol/L) during maturation reduced the percentages of oocytes that cleaved and formed a blastocyst to about 12%, compared with 25% of control oocytes. Maturation in the presence of equimolar concentrations of DON was not compatible with development. The ploidy of blastomeres from blastocysts derived from mycotoxin-exposed oocytes was analyzed with fluorescent in situ hybridization. All blastocysts, even those from the control group, contained at least one blastomere with abnormal ploidy, but the variation in the percentages of aneuploid blastomeres was significantly larger in embryos from oocytes exposed to mycotoxins. It is concluded that ZEA and DON can lead to abnormal spindle formation, leading to less fertile oocytes and embryos with abnormal ploidy, and that the effects of ZEA and DON are not synergistic.

Staphylococcus aureus is a major human and animal pathogen and a common cause of mastitis in cattle. S. aureus secretes several leukocidins that target bovine neutrophils, crucial effector cells in the defence against bacterial pathogens. In this study, we investigated the role of staphylococcal leukocidins in the pathogenesis of bovine S. aureus disease. We show that LukAB, in contrast to the γ-hemolysins, LukED, and LukMF′, was unable to kill bovine neutrophils, and identified CXCR2 as a bovine receptor for HlgAB and LukED. Furthermore, we assessed functional leukocidin secretion by bovine mastitis isolates and observed that, although leukocidin production was strain dependent, LukMF′ was most abundantly secreted and the major toxin killing bovine neutrophils. To determine the role of LukMF′ in bovine mastitis, cattle were challenged with high (S1444) or intermediate (S1449, S1463) LukMF′-producing isolates. Only animals infected with S1444 developed severe clinical symptoms. Importantly, LukM was produced in vivo during the course of infection and levels in milk were associated with the severity of mastitis. Altogether, these findings underline the importance of LukMF′ as a virulence factor and support the development of therapeutic approaches targeting LukMF′ to control S. aureus mastitis in cattle.

The spread of an infectious agent in a population can be reduced by interfering in the infectiousness or susceptibility of individuals, and/or in their contact structure. The aim of this study was to quantify the effect of prevention of direct contact between infectious and susceptible pigs on the transmission of Streptococcus suis (S. suis). In three replicate experiments, S. suis-free pigs were housed in boxes either in pairs (25 pairs) or alone (15 pigs). The distance between the boxes was ±1 m. At 7 weeks of age, one pig of each pair was inoculated intranasally with S. suis serotype 9; the other pigs were exposed to S. suis by either direct (pairs) or indirect contact (individually housed pigs). Tonsillar brush and saliva swab samples from all pigs were collected regularly for 4 weeks post inoculation to monitor colonization with S. suis. All inoculated pigs became infected, and their pen mates became colonized within 2 days. Thirteen indirectly exposed pigs became positive within 7–25 days after exposure. The rate of direct transmission βdir was estimated to be 3.58 per pig per day (95% CI: 2.29–5.60). The rate of indirect transmission increased in time, depending on the cumulative number of days pigs tested positive for the presence of S. suis. The estimate β’ind was 0.001 (95% CI: 0.0006–0.0017) new infections per pig per day for each day that an infected pig was tested positive for S. suis. We conclude that prevention of direct contact reduces the rate at which susceptible pigs become colonized. Simulation studies using these parameters showed, however, that such intervention measure would not limit S. suis serotype 9 spread in a commercial pig farm to a relevant extent, implying that spatial separation of groups op pigs within a compartment would not be effective on a farm.

Vaccines against S. aureus bovine mastitis are scarce and show limited protection only. All currently available vaccines are applied via the parenteral (usually intramuscular) route. It is unknown, however, whether this route is the most suitable to specifically increase intramammary immunity to combat S. aureus at the site of infection. Hence, in the present study, immunization via mucosal (intranasal; IN), intramuscular (triangle of the neck; IM), intramammary (IMM) and subcutaneous (suspensory ligament; SC) routes were analyzed for their effects on the quantity of the antibody responses in serum and milk as well as the neutralizing capacity of the antibodies within serum. The experimental vaccine comprised the recombinant S. aureus immune evasion proteins extracellular fibrinogen-binding protein (Efb) and the leukotoxin subunit LukM in an oil-in-water adjuvant combined with a hydrogel and alginate. The highest titer increases for both Efb and LukM specific IgG1 and IgG2 antibody levels in serum and milk were observed following SC/SC immunizations. Furthermore, the harmful effects of Efb and leukotoxin LukMF’ on host-defense were neutralized by serum antibodies in a route-dependent manner. SC/SC immunization resulted in a significant increase in the neutralizing capacity of serum antibodies towards Efb and LukMF’, shown by increased phagocytosis of S. aureus and increased viability of bovine leukocytes. Therefore, a SC immunization route should be considered when aiming to optimize humoral immunity against S. aureus mastitis in cattle.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0243-7) contains supplementary material, which is available to authorized users.

-This study investigated the possible effects of milk production level on the host resistance of dairy cows. High (n = 18) and low (n = 18) producing cows on a research farm, which respectively produced 11 443 and 7 727 kg milk in their previous lactation, were compared. To enhance the possible differences in host resistance between high and low producing cows, the animals in both groups were metabolically stressed by overfeeding during the dry period or were fed according to requirements, resulting in four groups of nine cows. The metabolic status was monitored from two weeks pre-partum until 2.5-4.5 weeks post-partum. Host resistance was assessed by measuring the severity of experimentally induced Escherichia coli mastitis. Pre-partum blood glucose levels tended to be higher in overfed cows than in cows fed according to requirements. The post-partum energy balance was significantly more negative in high producing cows than in low producers, and tended to be more negative in overfed cows compared to cows fed according to the requirements. Post-partum plasma glucose, NEFA, β-OH-butyrate and urea concentrations were similar in the four groups. Plasma glucose concentrations were significantly lower and liver triacylglycerol concentrations were significantly higher in third than in second parity cows. Host resistance was not affected by the production level or feeding regimen. There were no significant correlations between the metabolic status and the severity of experimental E. coli mastitis, except for the relatively more severe mastitis in the cows with β-OH-butyrate concentrations above 1.4 mmol/L. In conclusion, milk production level did not affect host resistance in dairy cows, as measured by the severity of experimental E. coli mastitis. Even in a situation where cows were metabolically stressed by overfeeding, high producers were as able as low producers to cope with the demands of milk production, without consequences for host resistance. dairy cow / milk production / host resistance / metabolism / E. coli mastitis * Corresponding author: j.e.kornalijnslijper@vet.uu.nl 722 E. Kornalijnslijper et al.