Pharmacokinetics and Efficacy of a Long-lasting, Highly Concentrated Buprenorphine Solution in Rats.

Buprenorphine (Bup) is an opioid analgesic that is commonly used in laboratory rodents to provide postoperative analgesia. However, dosing every 4 to 6 h is necessary to maintain an analgesic plasma concentration of the drug. A long lasting, highly concentrated veterinary formulation of Bup (LHC-Bup) has been used to provide prolonged analgesia in cats and nonhuman primates. In the current study, we evaluated the duration of efficacy of LHC-Bup to determine if this formulation would provide a similarly prolonged analgesia in rats. Drug concentrations were measured after subcutaneous injection of 0.5 mg/kg LHC-Bup in both male and female rats. Plasma levels were measured at 0.25, 0.5, 1, 2, 4, 8, 12, 24, 36, 48, and 72 h. Male and female rats had peak plasma levels of LHC-Bup at 90 ng/mL and 34 ng/mL, respectively, at 15 min after administration, with a steady decrease by 24 h to 0.7 ng/mL in males and 1.3 ng/mL in females. Mechanical pain tolerance was evaluated after LHC-Bup administration using a Randall-Selitto analgesiometer to assess paw withdrawal. Male rats had a significantly longer paw withdrawal time for up to 12 h after administration, and females had longer paw withdrawal times for up to 24 h. An experimental laparotomy model was then used to assess the clinical efficacy of LHC-Bup at 0.5 mg/kg. LHC-Bup treatment was associated with a greater total distance traveled, reduced time to retrieve a food treat, and reduced grooming from 3 to 12 h after surgery as compared with saline controls. Groups receiving LHC-Bup showed coprophagy whereas other rats did not. These results suggest that administering LHC-Bup at 0.5 mg/kg provides therapeutic plasma concentrations for 12 to 24 h after administration and analgesic efficacy for at least 12 h after dosing. As such, LHC-Bup is a suitable alternative to Bup-HCl.

Pharmacokinetics and Efficacy of a Long-lasting, Highly Concentrated Buprenorphine Solution in Mice.

Buprenorphine is a commonly used opioid for mitigating pain in laboratory mice after surgical procedures; however, the dosing interval necessary for standard buprenorphine may require treatment every 4 to 6 h to maintain an adequate plane of analgesia. An alternative formulation that provides prolonged plasma concentration with long-lasting effects would be beneficial in achieving steady-state analgesia. We evaluated a long-lasting and highly concentrated formulation of buprenorphine (Bup-LHC) in mice. Pharmacokinetic analysis was performed to assess plasma concentrations in male C57BL/6J (B6) and female CD1 mice after subcutaneous injection of 0.9 mg/kg. The Bup-LHC formulation provided plasma drug levels that exceeded the therapeutic level for at least 12 h in male B6 mice and was below therapeutic levels by 8 h in female CD1 mice. An experimental laparotomy model was used to assess analgesic efficacy. Female CD1 mice were treated with either Bup-LHC (0.9 mg/kg) or saline at 1 h before undergoing an ovariectomy via a ventral laparotomy. At 3, 6, 12, 24, and 48 h after surgery, pain was assessed based on the following behaviors: orbital tightness, grooming, wound licking, rearing, arched posture, ataxia, piloerection, nest building, and general activity. At 3 and 6 h after surgery, Bup-LHC-treated mice had significantly less wound licking and orbital tightness and considerably higher activity levels than did saline-treated mice. At 12 h, wound licking, orbital tightness and activity in Bup-LHC-treated mice were no longer significantly different from those of saline-treated mice. The results of this study suggest that Bup-LHC at 0.9 mg/kg provides sufficient plasma concentrations for analgesia in mice for 6 to 12 h after administration, as demonstrated behaviorally for at least 6 h after surgery.

Comprehensive review on immunopathogenesis, diagnostic and epidemiology of Senecavirus A.

Senecavirus A (SVA), formerly known as Seneca Valley virus, is a single-strand, positive-sense RNA virus in the family Picornaviridae. This virus has been associated with recent outbreaks of vesicular disease (SVA-VD) and epidemic transient neonatal losses (ETNL) in several swine-producing countries. The clinical manifestation of and lesion caused by SVA are indistinguishable from other vesicular diseases. Pathogenicity studies indicate that SVA could regulate the host innate immune response to facilitate virus replication and the spread of the virus to bystander cells. SVA infection can induce specific humoral and cellular responses that can be detected within the first week of infection. However, SVA seems to produce persistent infection, and the virus can be shed in oral fluids for a month and detected in tissues for approximately two months after experimental infection. SVA transmission could be horizontal or vertical in infected herds of swine, while positive animals can also remain subclinical. In addition, mice seem to act as reservoirs, and the virus can persist in feed and feed ingredients, increasing the risk of introduction into naïve farms. Besides the pathological effects in swine, SVA possesses cytolytic activity, especially in neoplastic cells. Thus, SVA has been evaluated in phase II clinical trials as a virotherapy for neuroendocrine tumors. The goal of this review is summarize the current SVA-related research in pathogenesis, immunity, epidemiology and advances in diagnosis as well as discuses current challenges with subclinical/persistent presentation.

Detecting and Monitoring Porcine Hemagglutinating Encephalomyelitis Virus, an Underresearched Betacoronavirus.

Members of family Coronaviridae cause a variety of diseases in birds and mammals. Porcine hemagglutinating encephalomyelitis virus (PHEV), a lesser-researched coronavirus, can infect naive pigs of any age, but clinical disease is observed in pigs ≤4 weeks of age. No commercial PHEV vaccines are available, and neonatal protection from PHEV-associated disease is presumably dependent on lactogenic immunity. Although subclinical PHEV infections are thought to be common, PHEV ecology in commercial swine herds is unknown. To begin to address this gap in knowledge, a serum IgG antibody enzyme-linked immunosorbent assay (ELISA) based on the S1 protein was developed and evaluated on known-status samples and then used to estimate PHEV seroprevalence in U.S. sow herds. Assessment of the diagnostic performance of the PHEV S1 ELISA using serum samples (n = 924) collected from 7-week-old pigs (n = 84; 12 pigs per group) inoculated with PHEV, porcine epidemic diarrhea virus, transmissible gastroenteritis virus, porcine respiratory coronavirus, or porcine deltacoronavirus showed that a sample-to-positive cutoff value of ≥0.6 was both sensitive and specific, i.e., all PHEV-inoculated pigs were seropositive from days postinoculation 10 to 42, and no cross-reactivity was observed in samples from other groups. The PHEV S1 ELISA was then used to estimate PHEV seroprevalence in U.S. sow herds (19 states) using 2,756 serum samples from breeding females (>28 weeks old) on commercial farms (n = 104) with no history of PHEV-associated disease. The overall seroprevalence was 53.35% (confidence interval [CI], ±1.86%) and herd seroprevalence was 96.15% (CI, ±3.70%).IMPORTANCE There is a paucity of information concerning the ecology of porcine hemagglutinating encephalomyelitis virus (PHEV) in commercial swine herds. This study provided evidence that PHEV infection is endemic and highly prevalent in U.S. swine herds. These results raised questions for future studies regarding the impact of endemic PHEV on swine health and the mechanisms by which this virus circulates in endemically infected populations. Regardless, the availability of the validated PHEV S1 enzyme-linked immunosorbent assay (ELISA) provides the means for swine producers to detect and monitor PHEV infections, confirm prior exposure to the virus, and to evaluate the immune status of breeding herds.

Porcine Hemagglutinating Encephalomyelitis Virus: A Review.

The porcine hemagglutinating encephalomyelitis virus (PHEV) is classified as a member of genus Betacoronavirus, family Coronaviridae, sub-family Cornavirinae, and order Nidovirales. PHEV shares the same genomic organization, replication strategy, and expression of viral proteins as other nidoviruses. PHEV produces vomiting and wasting disease (VWD) and/or encephalomyelitis, being the only known neurotropic coronavirus affecting pigs. First clinical outbreak was reported in 1957 in Ontario, Canada. Although pigs are the only species susceptible to natural PHEV infections, the virus displays neurotropism in mice and Wistar rats. Clinical disease, morbidity, and mortality is age-dependent and generally reported only in piglets under 4 weeks old. The primary site of replication of PHEV in pigs is the respiratory tract, and it can be further spread to the central nervous system through the peripheral nervous system via different pathways. The diagnosis of PHEV can be made using a combination of direct and indirect detection methods. The virus can be isolated from different tissues within the acute phase of the clinical signs using primary and secondary pig-derived cell lines. PHEV agglutinates the erythrocytes of mice, rats, chickens, and several other animals. PCR-based methods are useful to identify and subsequently isolate animals that are actively shedding the virus. The ability to detect antibodies allows producers to know the status of first-litter gilts and evaluate their risk of tier offspring to infection. PHEV is highly prevalent and circulates subclinically in most swine herds worldwide. PHEV-related disease is not clinically relevant in most of the swine-producing countries, most likely because of dams are immune to PHEV which may confer passive immunity to their offspring. However, PHEV should be considered a major source of economic loss because of the high mortality on farms with high gilt replacement rates, specific pathogen-free animals, and gnotobiotic swine herds. Thus, in the absence of current PHEV vaccines, promoting virus circulation on farms with early exposure to gilts and young sows could induce maternal immunity and prevent disease in piglets.

Seroprevalence of Senecavirus A in sows and grower-finisher pigs in major swine producing-states in the United States.

Senecavirus A (SVA) is a single-stranded RNA virus in the family Picornaviridae. Recently, SVA has been associated with idiopathic vesicular disease and increased neonate mortality outbreaks in the United States, Brazil, China, Colombia, and Thailand, with increasing incidence since 2014. Indirect detection by antibody detection methods, including indirect immunofluorescence assay (IFA), virus neutralization assay, and competitive or indirect enzyme-linked immunosorbent assays (ELISAs), have been reported in clinical and experimental trials. The objective of this study was to determine the seroprevalence of SVA in nonclinical affected herds in the United States. Individual samples were collected from 3654 and 2433 clinically healthy grower-finisher pigs and sows, respectively, from 219 unique commercial swine production sites. SVA seroprevalence was evaluated by SVA rVP1 ELISA and SVA IFA. The estimated seroprevalence for grower-finisher pigs and sows was 12.2% and 34.0%, respectively. The herd prevalence was 42.7% for grower-finisher farms and 75.8% for sow farms. The SVA rVP1 ELISA and SVA IFA exhibited a fair (sows) and moderate (grower-finisher) agreement at the herd level, while a fair agreement was observed at the individual level for both pig categories evaluated. The McNemar's test was significant at the individual and herd level (p < 0.05). In this study, we demonstrated the presence of SVA IgG antibodies in pigs from clinically healthy grower-finisher and sow herds. These results suggest that SVA is circulating subclinically in sow farms and grower-finisher pig farms in major swine producing-states in the United States.