Persistence of PRRSV in Nursery Pigs

Porcine Reproductive and Respiratory Syndrome virus (PRRS)V is known to cause persistent infections in swine populations. We inoculated three week-old feeder pigs with PRRSV (ATCC VR-2332) then collected and analyzed biological samples to determine the pigs’ infection status over time post-inoculation (PI). Infectious virus was detected in 100% of animals at 63 days post inoculation and 90% of animals were still carrying infectious virus at 105 days PI

Assessment of age-related changes in pediatric gastrointestinal solubility

PurposeCompound solubility serves as a surrogate indicator of oral biopharmaceutical performance. Between infancy and adulthood, marked compositional changes in gastrointestinal (GI) fluids occur. This study serves to assess how developmental changes in GI fluid composition affects compound solubility.MethodsSolubility assessments were conducted in vitro using biorelevant media reflective of age-specific pediatric cohorts (i.e., neonates and infants). Previously published adult media (i.e., FaSSGF, FeSSGF, FaSSIF.v2, and FeSSIF.v2) were employed as references for pediatric media development. Investigations assessing age-specific changes in GI fluid parameters (i.e., pepsin, bile acids, pH, osmolality, etc.) were collected from the literature and served to define the composition of neonatal and infant media. Solubility assessments at 37°C were conducted for seven BCS Class II compounds within the developed pediatric and reference adult media.ResultsFor six of the seven compounds investigated, solubility fell outside an 80–125% range from adult values in at least one of the developed pediatric media. This result indicates a potential for age-related alterations in oral drug performance, especially for compounds whose absorption is delimited by solubility (i.e., BCS Class II).ConclusionDevelopmental changes in GI fluid composition can result in relevant discrepancies in luminal compound solubility between children and adults.<br/

Control of Porcine Reproductive and Respiratory Syndrome: the challenge of identifying carrier animals

Infection with PRRSV produces clinically normal, but chronically infected, carrier animals. This is old information, but it remains the most difficult problem to solve in the prevention and control of PRRSV. What percentage of pigs are carrier animals over time post infection? At present we have partial information in this area. Our laboratory has demonstrated the presence of infectious PRRSV 60 days post inoculation (PI) in 18 of 18 individually housed pigs. Among gang-housed pigs, virus was detected in 11 of 12 animals on day 77 PI. Previously, Wills et al. (1997) reported isolation of virus from 3 of 4 experimentally infected pigs on day 84 PI, with one pig remaining virus isolation positive up to day 157. Collectively, these data suggest that 100% of pigs are infected for at least 60 days PI. Some time after 60 days PI, animals begin to clear the infection. Identification of carriers is pivotal for the successful implementation of prevention and control procedures in commercial swine herds. Do we have the diagnostic technology to effectively identify carrier animals? At a minimum, developing a process to identify carriers involves: (1) determining which ante mortem diagnostic sample is most likely to contain virus and (2) evaluating the performance characteristics of diagnostic assays for the preferred ante mortem sample. Without good data on diagnostic parameters, it is not possible to confidently interpret results in the diagnostic setting. For PRRSV, tonsil and lymph nodes appear to be the tissues in which virus persists longest. Lymph nodes are not practical to collect ante mortem, but it has been shown to be relatively easy to isolate virus from tonsil scrapings collected from live animals (Wills et al., Vet. Microbiol., 1997). Presumably, more sensitive procedures (i.e., PCR) would be even more efficient in detecting virus. However, it is not certain that current PCR procedures are sufficient to achieve the level of diagnostic sensitivity required to identify carriers. For example, Wagstrom et al. (J. Vet. Diagn. Invest., 1999) assessed the diagnostic performance of a commercial RT-nPCR assay for PRRSV. The study used 297 samples of known PRRSV infection status, including serum samples from 195 individual uninfected swine to estimate diagnostic specificity and day 7 post inoculation serum samples from 102 experimentally infected animals to estimate diagnostic sensitivity. Results showed the diagnostic sensitivity of the assay to be 68.8% and diagnostic specificity to be 99.4%. Because PCR is generally perceived to be extremely sensitive, the diagnostic sensitivity of the assay was unexpectedly low. A search of the literature, however, found no evidence to suggest the results were unrepresentative of PCR performance. Overall, the data suggest that, at the present stage of development, we are not able to identify carrier animals in an accurate and cost effective manner. Future work needs to focus on further characterizing the carrier state, including the factors involved in clearing virus, and on optimizing diagnostic procedures for detecting carriers

Persistence of PRRSV in Nursery Pigs

Porcine Reproductive and Respiratory Syndrome virus (PRRS)V is known to cause persistent infections in swine populations. We inoculated three week-old feeder pigs with PRRSV (ATCC VR-2332) then collected and analyzed biological samples to determine the pigs’ infection status over time post-inoculation (PI). Infectious virus was detected in 100% of animals at 63 days post inoculation and 90% of animals were still carrying infectious virus at 105 days PI.</p