Second round of an interlaboratory comparison of SARS-CoV2 molecular detection assays used by 45 veterinary diagnostic laboratories in the United States

The COVID-19 pandemic presents a continued public health challenge. Veterinary diagnostic laboratories in the United States use RT-rtPCR for animal testing, and many laboratories are certified for testing human samples; hence, ensuring that laboratories have sensitive and specific SARS-CoV2 testing methods is a critical component of the pandemic response. In 2020, the FDA Veterinary Laboratory Investigation and Response Network (Vet-LIRN) led an interlaboratory comparison (ILC1) to help laboratories evaluate their existing RT-rtPCR methods for detecting SARS-CoV2. All participating laboratories were able to detect the viral RNA spiked in buffer and PrimeStore molecular transport medium (MTM). With ILC2, Vet-LIRN extended ILC1 by evaluating analytical sensitivity and specificity of the methods used by participating laboratories to detect 3 SARS-CoV2 variants (B.1; B.1.1.7 [Alpha]; B.1.351 [Beta]) at various copy levels. We analyzed 57 sets of results from 45 laboratories qualitatively and quantitatively according to the principles of ISO 16140-2:2016. More than 95% of analysts detected the SARS-CoV2 RNA in MTM at ≥500 copies for all 3 variants. In addition, for nucleocapsid markers N1 and N2, 81% and 92% of the analysts detected ≤20 copies in the assays, respectively. The analytical specificity of the evaluated methods was >99%. Participating laboratories were able to assess their current method performance, identify possible limitations, and recognize method strengths as part of a continuous learning environment to support the critical need for the reliable diagnosis of COVID-19 in potentially infected animals and humans.     

Oral transmission of transmissible gastroenteritis virus by muscle and lymph node from slaughtered pigs

A study was conducted in the USA to determine whether transmissible gastroenteritis (TGE) virus could be transmitted from carcases of slaughtered pigs. Transmissible gastroenteritis virus was transmitted to 6-day-old piglets by dosing with homogenates of muscle and lymph node collected from 500 clinically normal pigs at the time of slaughter. All piglets in 2 separately housed litters showed clinical signs of TGE with 5 piglets dying within 10 d of oral dosing with homogenates. Transmissible gastroenteritis virus was isolated from 2 of these piglets and all piglets developed TGE antibody. Transmissible gastroenteritis virus was not isolated in tissue culture from muscle and lymph node homogenates, but was isolated from 4 (0.8%) of 500 tonsil samples collected from the same pigs. A survey of 250 serum samples provided an estimate of the prevalence of slaughtered pigs with TGE antibody of 34.8% in the sample population. The results indicate that carcases of some pigs from TGE endemic areas contain viable TGE virus, and that there would be a substantial risk of introducing TGE virus into Australia by the importation of uncooked pig meat from these areas.     

Adhesion of Staphylococcus aureus and Escherichia coli to bovine udder epithelial cells

An assay for the adhesion of tritiated thymidine-labelled Staphylococcus aureus and Escherichia coli to bovine mammary ductular epithelial cell lines was developed. The relative adhesion of 15 strains of S. aureus to these cell lines was examined. Four strains did not adhere and the remaining 11 adhered at variable levels. Adhesion to different cell lines was generally similar. Adhesion to freshly collected bovine mammary epithelial cells was significantly greater than that to cells maintained in tissue culture. The system described was demonstrated to be a suitable model for studying adhesion of mastitis-causing organisms to bovine mammary epithelial cells.     

The Effect of Storage on Ammonia Concentration in Canine Packed Red Blood Cells.

Objective: To determine the effect of storage on ammonia concentration in canine packed red blood cell (pRBC) units.
Design: In vitro and in vivo study.
Setting: University Veterinary Teaching Hospital.
Interventions: Ammonia concentration was measured in 7 units of canine pRBC prepared in citrate-phosphate-dextrose (CPD) and Adsol^a on Days 1 and 35 of storage. Ammonia was measured in 4 additional units of canine pRBC on Days 0, 7, 14, 21, 28, and 35. Plasma ammonia was also determined in 5 anemic dogs receiving pRBC.
Measurements and Main Results: Ammonia concentration increased from 73 ± 15 mmol/L (mean ± SD) on Day 1 to 800 ± 275 mmpl/L on Day (p<0.001). When measured every 7 days in 4 units of canine pRBC, ammonia concentration increased from 23 ± 8 mmol/L on Day 0 to 179 ± 13 mmol/L (Day 7), 276 ± 56 mmol/L (Day 14). 383 ± 47 mmol/L (Day21), 466 ± 30 mmol/L (Day 28), and 562 ± 27 mmol/L (Day 35) (p<0.05 for all comparisons). In a preliminary study, plasma ammonia concentration measured in blood samples from 5 anemic dogs without primary liver disease immediately before and after transfusion with 5–10 ml/kg of stored pRBC remained in the normal reference range.
Conclusions: The ammonia concentration in stored canine pRBC increased markedly with time. In this preliminary study, ammonia concentrations in dogs without primary liver disease did not increase above the reference range after transfusion with pRBC.     

The laboratory culture of Dichelobacter nodosus in a footrot eradication program

SUMMARY As part of a program to eradicate virulent footrot from Western Australia, 2745 isolates of Dichelobacter nodosus were isolated from 5263 specimens from 1883 submissions. The virulence of each isolate was assessed using protease thermostability and isoenzyme zymogram. We describe changes to the materials and methods required to handle these specimens and to reduce the interval between submission and report to 8 days.     

Treatment of rupture of suspensory ligament and superficial flexor tendon in a bull

Rupture of the suspensory ligament at the insertions on the proximal sesamoid bones, and of the superficial flexor tendon of the left fore limb, occurred in an adult Angus bull as a result of fighting. There was severe hyperextension of the metacarpophalangeal (MCP) joint with the dewclaws almost touching the ground. Radiographs revealed severe hyper-extension of the MCP joint with the sesamoid bones aligned directly distal to the metacarpus. Initially, a full length fiberglass cast was applied with the limb partially flexed within the cast and the heels elevated. The cast was replaced twice. The cast was removed after 136 days and the bull was bearing full weight on the limb. Prolonged immobilisation of the limb produced new bone in the area (a normal response in cattle) to cause ankylosis of the traumatized MCP joint and partial ankylosis of the carpus. The bull was being used for pasture breeding one year after the injury.