Monthly Archives: September 2010

Porcine reproductive and respiratory syndrome virus (PRRSV) crosses the placenta during late gestation and productively infects the fetus. Virus replication and cytokine responses were measured in tissues of fetuses recovered at 109-112 days of gestation, just prior to parturition. At the time of recovery, gross anatomical abnormalities were evident in both infected and non-infected fetuses from the infected dams. Virus isolation and immunohistochemistry identified the thymus as the primary site of virus replication. Steady state RT-PCR amplification of inflammatory, Th1 and Th2 cytokines, showed elevated IFN-γ and TNF-α mRNAs in tissues from infected fetuses, which corresponded to elevated cytokine proteins in serum but not amniotic fluid. Further evidence for induction of immunity was found in the hyperplastic response of lymph nodes, which included the development of germinal centers occupied CDw75+ B cells. Collectively, these data support the notion that the immunocompetent fetus is capable of initiating an antiviral response, which is compartmentalized within the infected fetus. Furthermore, fetal pathology may not be a direct result of virus replication in the fetus.

In the first of 2 experiments, we evaluated the effects on anestrous sows of pretreatment with FSH to stimulate the growth of small follicles, followed by eCG to stimulate the growth of medium follicles, estrus, and ovulation. In Exp. 2, we examined the effect of sows receiving 400 IU of eCG plus 200 IU of hCG (PG 600, Intervet/Schering Plough Animal Health, Boxmeer, the Netherlands) at weaning and then different doses and timing of supplemental hCG. In Exp. 1, a total of 87 multiparous Hypor sows deemed anestrus 7 d after weaning were assigned to intramuscular (i.m.) injection of 1) PG 600, 2) eCG (600 IU), 3) pretreatment with 87.5 IU of FSH on d 7 and 8 plus eCG on d 9, or were 4) noninjected controls. Sows had daily boar contact for 15 d after weaning for estrus detection. Blood samples were obtained on d 9 and 19 and assayed for progesterone to determine ovulation status. The weaning-to-estrus interval, number of sows in estrus and ovulating, farrowing rate, and litter size were not different (P > 0.1) in treated groups compared with controls. In Exp. 2, a total of 247 Hypor sows were assigned at weaning by parity (1 and 2 or > or = 3) to receive 1) an i.m. injection of PG 600, 2) PG 600 supplemented with 100 IU of hCG injected either concurrently or after 24 h, 3) 200 IU of hCG after 24 h, or 4) no injection (controls). Sows were exposed to boars daily for 7 d. After treatment of parity 1 and 2 sows, all gonadotropin-treated groups had an increased (P < 0.05) number of sows in estrus compared with the control group; weaning-to-estrus interval, farrowing rates, and litter size were unaffected (P > 0.1). After treatment of parity > or = 3 sows, there was no treatment effect on the estrous response and weaning-to-estrus interval; compared with control and PG 600-treated sows, farrowing rate was decreased (P < 0.05) for sows receiving 200 IU of hCG after 24 h. There was no effect (P > 0.1) of treatment on litter size. We conclude that gonadotropins can be used to increase estrus response in weaned sows, but that hCG treatment subsequent to PG 600 may be detrimental to sow fertility in parity > or = 3 sows.