Validation of an indirect enzyme-linked immunosorbent assay for the detection of antibody against Brucella abortus in cattle sera using an automated ELISA workstation

An automated indirect enzyme-linked immunosorbent assay (I-ELISA) for the serological diagnosis of bovine brucellosis was developed and validated in-house. A total of 4803 cattle sera from South Africa ( n=3 643), Canada ( n=652), Germany ( n=240), France ( n=73) and the USA ( n=195) was used. The South African panel of sera represented 834 sera known to be positive by the Rose Bengal test (RBT), serum agglutination test (SAT) and complement fixation test (CFT), 2709 sera that were negative by CFT and 100 sera from animals vaccinated with a standard dose of Brucella abortus strain 19. Overseas sera were obtained from reference non-vaccinated brucella-free cattle ( n=834), naturally infected ( n=72), experimentally infected ( n=71) and vaccinated animals ( n=83). Also 100 sera collected from cattle in Canada and known to be positive by competitive ELISA (C-ELISA) were used. The intermediate ranges ("borderline" range for the interpretation of test results) were derived from two-graph receiver operating characteristics analysis. The lowest values of the misclassification cost-term analysis obtained from testing overseas panels covered lower I-ELISA cut-off PP values (0.02-3.0) than those from local panels (1.5-5.0). The relatively low cut-off PP values selected for I-ELISA were due to the fact that the positive control used represents a very strong standard compared to other reference positive sera. The greater overlap found between negative and positive cattle sera from South Africa than that between reference overseas panels was probably due to the different criteria used in classifying these panels as negative (sera from true non-diseased/non-infected animals) or positive (sera from true diseased/infected animals). The diagnostic sensitivity of the I-ELISA (at the optimum cutoff value) was 100% and of the CFT 83.3%. The diagnostic specificity of I-ELISA was 99.8% and of the CFT 100%. Estimate of Youden's index was higher for the I-ELISA (0.998) than that for the CFT (0.833). Analysis of distribution of PP values in sera from vaccinated and naturally infected cattle shows that in vaccinated animals all readings were below 31 PP where in infected ones these values represented 43%. Therefore, it appears that I-ELISA could be of use in identifying some naturally infected animals (with values >31 PP) but more sera from reference vaccinated and infected animals need to be tested to further substantiate this statistically. Of 834 sera positive by RBT, SAT and CFT, 825 (98.9%) were positive in the I-ELISA. Compared to C-ELISA the relative diagnostic sensitivity of the I-ELISA was 94% and of the CFT 88% when testing 100 Canadian cattle sera. Of 258 South African cattle sera, of which 183 (70.9%) were positive by the I-ELISA and 148 (57.4%) by the CFT, 197 (76.4%) were positive by C-ELISA when re-tested in Canada. One has to stress, however, that Canadian C-ELISA has not been optimised locally. Thus, the C-ELISA was probably not used at the best diagnostic threshold for testing South African cattle sera. This study shows that the I-ELISA performed on an automated ELISA workstation provides a rapid, simple, highly sensitive and specific diagnostic system for large-scale detection of antibodies against B. abortus. Based on the diagnostic accuracy of this assay reported here, the authors suggest that it could replace not only the currently used confirmatory CFT test, but also the two in-use screening tests, namely the RBT and SAT.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat v.9 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Isolation of Cowdria ruminantium by cellular affinity chromatography and detection by an enzyme-linked immunosorbent assay

The isolation of Cowdria ruminantium by means of wheat germ lectin affinity chromatography as described in this paper permits the recovery of partially purified viable organisms under mild conditions in short time. These conclusions are based upon results of analyses of column fractions by intravenous inoculation into sheep, protein determination, electronmicroscopy and enzyme-linked immunosorbent assay. The entire purification procedure could be completed in 4-5 hours using only either infected sheep tissue or nymphae as starting material.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Risk factors for Coronavirus disease 2019 (Covid-19) death in a population cohort study from the Western Cape province, South Africa

Risk factors for coronavirus disease 2019 (COVID-19) death in sub-Saharan Africa and the effects of human immunodeficiency virus (HIV) and tuberculosis on COVID-19 outcomes are unknown. We conducted a population cohort study using linked data from adults attending public-sector health facilities in the Western Cape, South Africa. We used Cox proportional hazards models, adjusted for age, sex, location, and comorbidities, to examine the associations between HIV, tuberculosis, and COVID-19 death from 1 March to 9 June 2020 among (1) public-sector “active patients” (≥1 visit in the 3 years before March 2020); (2) laboratory-diagnosed COVID-19 cases; and (3) hospitalized COVID-19 cases. We calculated the standardized mortality ratio (SMR) for COVID-19, comparing adults living with and without HIV using modeled population estimates.Among 3 460 932 patients (16% living with HIV), 22 308 were diagnosed with COVID-19, of whom 625 died. COVID19 death was associated with male sex, increasing age, diabetes, hypertension, and chronic kidney disease. HIV was associated with COVID-19 mortality (adjusted hazard ratio [aHR], 2.14; 95% confidence interval [CI], 1.70–2.70), with similar risks across strata of viral loads and immunosuppression. Current and previous diagnoses of tuberculosis were associated with COVID-19 death (aHR, 2.70 [95% CI, 1.81–4.04] and 1.51 [95% CI, 1.18–1.93], respectively). The SMR for COVID-19 death associated with HIV was 2.39 (95% CI, 1.96–2.86); population attributable fraction 8.5% (95% CI, 6.1–11.1)

Improved method for the generation and selection of homogeneous lumpy skin disease virus (SA-Neethling) recombinants

Please refer to abstract in articl

PCR-based detection of the transovarial transmission of Uruguayan Babesia bovis and Babesia bigemina vaccine strains

Bovine babesiosis is responsible for serious economic losses in Uruguay. Haemovaccines play an important role in disease prevention, but concern has been raised about their use. It is feared that the attenuated Babesia bovis and Babesia bigemina vaccine strains may be transmitted by the local tick vector Boophilus microplus, and that reversion to virulence could occur. We therefore investigated the possibility that these strains could be transmitted via the transovarial route in ticks using a Babesia species-specific polymerase chain reaction (PCR) assay. DNA was extracted from the developmental stages of the tick vector that had fed on calves immunized with the haemovaccine. It was possible to detect Babesia DNA not only in adult ticks, but also in their eggs and larvae. In addition, it was shown that calves infested with larvae derived from eggs laid by ticks fed on acutely infected calves, were positive for Babesia using PCR. Caution should therefore be shown with the distribution of the haemovaccine in marginal areas. It is still advisable that suitable tick control measures be used to prevent transovarial transmission and the potential risk of attenuated Babesia reverting to virulence.The articles have been scanned with a HP Scanjet 8300; 600dpi, saved in TIFF format. Adobe Acrobat v.9 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Generation and evaluation of a recombinant modified vaccinia virus Ankara vaccine for rabies

Modified vaccinia virus Ankara (MVA) has become a vaccine vector of choice for recombinant vaccine development. A MVA-based rabies vaccine would be advantageous for use as a vaccine for dogs (and wildlife), particularly if it proves innocuous and efficacious by the oral route. Here, the generation and immunological testing of a recombinant MVA expressing a rabies virus glycoprotein gene is described. In a murine model, higher dosages of recombinant MVA were needed to induce equivocal immune responses as with Vaccinia Copenhagen or Vaccinia Western Reserve recombinants, when administered by a parenteral route. The MVA recombinant was not immunogenic or efficacious when administered per os in naïve mice. The ability of the recombinant MVA to induce anamnestic responses in dogs and raccoons was also investigated. Recombinant MVA boosted humoral immune responses in these animals when administered peripherally, but not when administered orally.J.W. was supported by a Regular Fellowship (Level 42) at the CDC. This work was supported in part by grants from the U.S. National Vaccine Program Office and the National Research Foundation of South Africa

Heartwater : past, present and future : proceedings of a workshop held at Berg en Dal, Kruger National Park, on 8-16 September 1986

Numerous parameters affect the enzyme-linked immunosorbent assay activity and the assay conditions must therefore be carefully controlled to obtain reproducible results. These parameters include temperature, pH, ionic strength, buffer composition, cofactors, substrate depletion, product inhibition, increasing reversal of reaction as product concentration increases, adsorption of enzyme to solid supports, denaturation and non-enzymatic background rate. An ELISA was used to detect Cowdria ruminantium antibodies during the course of heartwater disease. lgM antibodies reached a maximum on the 4th day after infection and disappeard on the 7th day. IgG antibodies first appeared on the 8th day and continued to increase during the remainder of the observation period of 28 days. The presence of C. ruminantium in the blood fractions of diseased animals was demonstrated by an enzyme-linked immunosorbent assay. The earliest detection of C. ruminantium antigen was in plasma and serum on the 4th day after inoculation. Of all the blood fractions investigated, the red blood cell fraction showed the highest concentration and this reached a maximum on the 12th day after infection.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

Heartwater : past, present and future : proceedings of a workshop held at Berg en Dal, Kruger National Park, on 8-16 September 1986

A distinction is drawn between the non-specific resistance to heartwater of very young calves and that of cattle older than a year. The suckling-calf resistance is at its greatest during the first few weeks after birth and then gradually declines during the next 6-8 months. Aspects of its possible mechanism and significance are discussed. The role played by conglutinin in the natural resistance of older cattle to heartwater and in the epidemiology of the disease is discussed.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

Management of oral feeding following total laryngectomy around the world: YO‐IFOS international study

International audienceBackground: To analyze worldwide practices regarding the initiation of oral feeding after total laryngectomy (TL).Methods: Online survey.Results: Among the 332 responses received, 278 from 59 countries were analyzed. Our results showed that 45.6% of respondents started water and 45.1% started liquid diet between postoperative days 7 and 10. Semi-solid feeds were initiated between days 10 and 14 for 44.9% of respondents and a free diet was allowed after day 15 for 60.8% of respondents. This timing was significantly delayed in cases of laryngo-pharyngectomy and after prior radiotherapy (p < 0.001). A greater proportion of respondents in Africa and Oceania allowed early oral feeding before day 6 as compared with the rest of the world (p < 0.001).Conclusion: Despite increasing number of publications, there is still a lack of evidence to support early oral feeding. The majority of respondents preferred to delay its initiation until at least 7 days after surgery