Determining the impact of vaccination on SARS-CoV-2 RT-PCR cycle threshold values and infectious viral titres.

Background: As the COVID-19 pandemic continues, efforts to better understand severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral shedding and transmission in both unvaccinated and vaccinated populations remain critical to informing public health policies and vaccine development. The utility of using real time RT-PCR cycle threshold values (CT values) as a proxy for infectious viral litres from individuals infected with SARS-CoV-2 is yet to be fully understood. This retrospective observational cohort study compares quantitative infectious viral litres derived from a focus-forming viral titre assay with SARS-CoV-2 RT-PCR CT values in both unvaccinated and vaccinated individuals infected with the Delta strain. Methods: Nasopharyngeal swabs positive for SARS-CoV-2 by RT-PCR with a CT value <27 collected from 26 June to 17 October 2021 at the University of Vermont Medical Center Clinical Laboratory for which vaccination records were available were included. Partially vaccinated and individuals <18 years of age were excluded. Infectious viral litres were determined using a micro-focus forming assay under BSL-3 containment. Results: In total, 119 specimens from 22 unvaccinated and 97 vaccinated individuals met all inclusion criteria and had sufficient residual volume to undergo viral titring. A negative correlation between RT-PCR CT values and viral litres was observed in both unvaccinated and vaccinated groups. No difference in mean CT value or viral titre was detected between vaccinated and unvaccinated groups. Viral litres did not change as a function of time since vaccination. Conclusions: Our results add to the growing body of knowledge regarding the correlation of SARS-CoV-2 RNA levels and levels of infectious virus. At similar CT values, vaccination does not appear to impact an individual's potential infectivity when infected with the Delta variant.

Assessment of shock index in healthy dogs and dogs in hemorrhagic shock.

OBJECTIVE: To compare the shock index (SI) in a population of healthy dogs to a population of dogs with confirmed hemorrhagic shock. DESIGN: Retrospective analysis of data collected prospectively from 2 previous studies. SETTING: University teaching hospital. ANIMALS: Seventy-eight healthy control dogs enrolled in a study to establish a reference interval for a tissue oxygen monitor; 38 dogs with confirmed hemorrhagic shock enrolled in a study to evaluate the tissue oxygen monitor in hemorrhagic shock. The heart rate and systolic blood pressure obtained during the respective studies were used to calculate the SI. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Shock index was significantly higher in the hemorrhage group (median 1.37, range 0.78-4.35) than the control group (median 0.91, range 0.57-1.53); 92% of the dogs in hemorrhagic shock had an SI of >0.91. Compared with controls, dogs in hemorrhagic shock had significantly lower body temperatures (median 38.3°C, range 35.6-39.9°C versus median 38.7°C, range 37.5-39.9°C), higher heart rates (median 150/min, range 120-220/min versus median 110/min range 80-150/min), lower systolic blood pressures (mean 112 mm Hg, SD ±35.8 mm Hg versus mean 125 mm Hg, SD ±21.5 mm Hg), higher lactate concentrations (median 0.51 mmol/L, range 0.078-1.41 mmol/L versus median 0.11 mmol/L, range 0.033-0.33 mmol/L), and lower hemoglobin concentrations (median 81 g/L, range 56-183 g/L versus median 162.5 g/L, range 133-198 g/L). CONCLUSIONS: Shock index is a simple and easy calculation that can be used as an additional triage tool and should prompt further investigation for hemorrhage if the values are >0.9.

Phenylpropanolamine toxicosis in dogs: 170 cases (2004?2009).

OBJECTIVE: To evaluate signalment, clinical signs, dose ingested, treatment requirements, duration of hospitalization, and outcome of dogs exposed to phenylpropanolamine. DESIGN: Retrospective case series. ANIMALS: 170 dogs with potential PPA toxicosis evaluated between 2004 and 2009. PROCEDURES: Dogs with potential PPA toxicosis were identified by reviewing the electronic database of an animal poison control center. RESULTS: 66 of the 170 (39%) dogs reportedly did not develop any clinical signs. Clinical signs reported in the remaining 104 (61%) dogs included agitation (n = 40), vomiting (27), mydriasis (19), lethargy (17), tremor or twitching (16), panting (15), bradycardia (13), tachycardia (12), hypertension (11), and erythema (8). Median dose ingested for all dogs was 29 mg/kg (13.2 mg/lb). Dogs developing clinical signs had a significantly higher median dose ingested (373 mg/kg [170 mg/lb]) than did dogs that did not develop clinical signs (18 mg/kg [8.2 mg/lb]). Likewise, median dose ingested for the 123 dogs treated as inpatients (36.9 mg/kg [16.8 mg/lb]) was significantly higher than the median dose for the 14 dogs treated as outpatients (20.5 mg/kg [9.3 mg/lb]). Median duration of hospitalization was 18 hours (range, 4 to 72 hours), and hospitalization time increased as the dose ingested increased. Survival rate was 99.4% (169/170); the dog that died had ingested a dose of 145 mg/kg (65.9 mg/lb). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that with supportive care, the prognosis for dogs that had ingested an overdose of phenylpropanolamine was excellent.