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Foddai A.,Risk Analysis Group | Foddai A.,Technical University of Denmark | Nielsen L.R.,Copenhagen University | Krogh K.,Knowledge Center for Agriculture | Alban L.,Risk Analysis Group
Preventive Veterinary Medicine | Year: 2015

Denmark has been recognized as officially free (OTF) from bovine tuberculosis (bTB) since 1980. In this study, we estimated the annual probability (PIntro) of introducing Mycobacterium bovis into the Danish cattle population, through (a) imports of cattle and (b) foreign personnel working in Danish cattle herds. Data from 2000 to 2013 with date, number and origin of imported live cattle were obtained from the Danish Cattle Federation. Information on immigrants working in Danish cattle herds was obtained through a questionnaire sent by email to a sample of Danish cattle farmers (N = 460). Inputs obtained from data analysis, expert opinion, the questionnaire and literature were fed into three stochastic scenario tree models used to simulate the effect of import trade patterns, and contact between immigrant workers and cattle. We also investigated the opportunity of testing animals imported from OTF countries by tuberculin skin test and animals from non-OTF countries by interferon-γ test (IFN-γ), exemplified by using year 2009 where the number of imported animals was higher than usual.Results showed that PIntro is driven mainly by importation of live cattle. The combined median annual probability of introducing M. bovis into the Danish cattle population by either imported live cattle or infectious immigrant workers, ranged from 0.3% (90% prediction interval (P.I.): 0.04%:1.4%) in 2001 to 4.9% (90% P.I.: 0.6%; 19.2%) in 2009. The median of the median PIntro estimates from the 14 years was 0.7% (median of 90% P.I.: 0.08%; 3.5%). Hence, on average, at least one introduction each 143 years could be expected, if the annual number of imported animals does not change remarkably in the future.If the number of imported animals increases, compared to the years we analyzed, additional testing of imported cattle might be considered. For example, in 2009, PIntro would have been reduced from 4.9% to 0.8% (90% P.I.: 0.1%; 4.7%) if animals from OTF countries had been tested with the tuberculin skin test and animals from non-OTF countries had been tested with the IFN-γ test.The presented model could be used easily in other countries with similar bTB status to Denmark, where wildlife represents a negligible probability of infection for domestic cattle and where the imported live cattle represent the main pathway of bTB introduction into the local cattle population. © 2015 Elsevier B.V. Source


Foddai A.,Risk Analysis Group | Foddai A.,Technical University of Denmark | Nielsen L.R.,Copenhagen University | Krogh K.,Knowledge Center for Agriculture | Alban L.,Risk Analysis Group
Preventive Veterinary Medicine | Year: 2015

Tuberculosis is a zoonosis caused by Mycobacterium spp. International trade in cattle is regulated with respect to Mycobacterium bovis (M. bovis) but not Mycobacterium tuberculosis (M. tuberculosis), despite that cattle can become infected with both species. In this study we estimated the annual probability (PIntro) of introducing M. tuberculosis into the Danish cattle population, by the import of cattle and/or by immigrants working in Danish cattle herds. Data from 2013 with date, number, and origin of imported live cattle were obtained from the Danish cattle database. Information on immigrants working in Danish cattle herds was obtained through a questionnaire sent to Danish cattle farmers. The gained inputs were fed into three stochastic scenario trees to assess the PIntro for the current and alternative test-and-manage strategies, such as testing of imported animals and/or testing immigrant workers with the tuberculin skin test. We considered the population of Danish farmers and practitioners free of tuberculosis, because in Denmark, the incidence of the disease in humans is low and primarily related to immigrants and socially disadvantaged people.The median annual probability of introducing M. tuberculosis into the Danish cattle population due to imported live cattle was 0.008% (90% P.I.: 0.0007%; 0.03%), while the probability due to immigrant workers was 4.1% (90% P.I.: 0.8%; 12.1%). The median combined probability (PIntro) due to imported cattle plus workers was 4.1% (90% P.I.: 0.8%; 12.6%). Hence, on average at least one introduction each 24 (90% P.I.: 8; 125) years could be expected. Imported live cattle appeared to play a marginal role on the overall annual PIntro, because they represented only approximately 0.2% of the median annual probability. By testing immigrant workers the overall annual PIntro could be reduced to 0.2% (90% P.I.: 0.04%; 0.7%). Thus, testing of immigrant workers could be considered as a risk mitigation strategy to markedly reduce the likelihood of introducing M. tuberculosis into the Danish cattle population, if the risk is considered unacceptable by the veterinary public health authorities. © 2015 Elsevier B.V.. Source


Calvo-Artavia F.F.,Copenhagen University | Nielsen L.R.,Copenhagen University | Alban L.,Risk Analysis Group
Preventive Veterinary Medicine | Year: 2013

Under the current EU meat inspection regulation, every single carcase from all bovines above 6 weeks of age has to be examined for bovine cysticercosis (BC). This is time-consuming, costly, and is of limited value in countries with low prevalence. The aim of this study was to develop a stochastic simulation model for analysis of tentative risk-based meat inspection systems for BC in Danish cattle with regard to system sensitivity (SSSe), specificity and potential monetary benefits compared to the current system, which has an estimated SSSe of 15%. The relevant risk factors used to construct three alternative scenario trees were identified from previous Danish risk factor studies (1) gender, (2) grazing and (3) access to risky water sources. Thus, females, animals that had been grazing or animals with access to risky water sources were considered high-risk and would be subjected to invasive inspection at meat inspection. All animals in the low-risk groups (i.e. males, non-grazing or no access to risky water sources, respectively) would be subjected to visual inspection only. It was assumed that half of the cattle were slaughtered in abattoirs that would be able to reorganise the work at the slaughterline, allowing them to do with one meat inspector less. All abattoirs would gain on the price of sold uncut beef from the masseter muscles from visually inspected cattle. Under these assumptions, using gender and grazing were preferable due to them having SSSe only slightly lower than the current system, and highest effectiveness ratios, but they had a lower net economic effect (NEE) than the scenario using risky water sources. Using gender to differentiate high and low-risk groups was judged preferable over grazing due to feasibility, because the information is readily available at the slaughter line. The exact total NEE for the cattle sector depends on how many and which of the abattoirs that would be able to reorganise the work at the slaughter line to save money on inspection of the head of carcases. Overall, the SSSe was low in all scenarios leading to undetected BC-positive cattle both in the current meat inspection and under the investigated risk-based meat inspection systems. Therefore, improving the sensitivity of the methods used for inspection of high-risk cattle would be beneficial. © 2012 Elsevier B.V. Source


Calvo-Artavia F.F.,Copenhagen University | Nielsen L.R.,Copenhagen University | Dahl J.,Risk Analysis Group | Clausen D.M.,Copenhagen University | And 2 more authors.
Zoonoses and Public Health | Year: 2013

Bovine cysticercosis (BC) is a zoonotic, parasitic infection in cattle. Under the current EU meat inspection regulation, every single carcass from all bovines above 6weeks of age is examined for BC. This method is costly and makes more sense in countries with higher number of BC-infected animals than in countries with few lightly infected cases per year. The aim of the present case-control study was to quantify associations between potential herd-level risk factors and BC in Danish cattle herds. Risk factors can be used in the design of a risk-based meat inspection system targeted towards the animals with the highest risk of BC. Cases (n=77) included herds that hosted at least one animal diagnosed with BC at meat inspection, from 2006 to 2010. Control herds (n=231) consisted of randomly selected herds that had not hosted any animals diagnosed with BC between 2004 and 2010. The answers from a questionnaire and register data from the Danish Cattle Database were grouped into meaningful variables and used to investigate the risk factors for BC using a multivariable logistic regression model. Case herds were almost three times more likely than control herds to let all or most animals out grazing. Case herds were more than five times more likely than control herds to allow their animals access to risky water sources with sewage treatment plant effluent in proximity. Case herds were also more likely to share machinery or hire contractors than control herds. The risk decreased with increasing herd size probably because the larger herds generally tend to keep cattle indoors in Denmark. The results are useful to guide future data recording that can be supplied by the farmer as food chain information and then be used for differentiated meat inspection in low- and high-risk groups, enabling development of risk-based meat inspection systems. © 2012 Blackwell Verlag GmbH. Source


Foddai A.,Risk Analysis Group | Foddai A.,Technical University of Denmark | Nielsen L.R.,Copenhagen University | Willeberg P.,Technical University of Denmark | And 2 more authors.
Preventive Veterinary Medicine | Year: 2015

We compared two published studies based on different output-based surveillance models, which were used for evaluating the performance of two meat inspection systems in cattle and to substantiate freedom from bovine tuberculosis (bTB) in Denmark. The systems were the current meat inspection methods (CMI) vs. the visual-only inspection (VOI). In one study, the surveillance system sensitivity (SSe) was estimated to substantiate the bTB free status. The other study used SSe in the estimation of the probability of freedom (PFree), based on the epidemiological concept of negative predictive value to substantiate the bTB free status. Both studies found that changing from CMI to VOI would markedly decrease the SSe. However, the two studies reported diverging conclusions regarding the effect on the substantiation of Denmark as a bTB free country, if VOI were to be introduced.The objectives of this work were: (a) to investigate the reasons why conclusions based on the two models differed, and (b) to create a hybrid model based on elements from both studies to evaluate the impact of a change from CMI to VOI. The hybrid model was based on the PFree approach to substantiate freedom from bTB and was parametrized with inputs according to the newest available information. The PFree was updated on an annual basis for each of 42 years of test-negative surveillance data (1995-2037), while assuming a low (<1%) annual probability of introduction of bTB into Danish cattle herds.The most important reasons for the difference between the study conclusions were: the approach chosen to substantiate the bTB free status (SSe vs. PFree) and the number of years of surveillance data considered.With the hybrid model, the PFree reached a level >95% after the first year of surveillance and remained ≥96% with both the CMI and VOI systems until the end of the analyzed period. It is appropriate to use the PFree of the surveillance system to substantiate confidence in bTB free status, when test-negative surveillance results can be documented over an extended period of time, while maintaining a low probability of introduction of bTB into the cattle population. For Denmark, the probability of introduction of bTB should be kept <1% on an annual basis to sustain the high confidence in freedom over time. The results could be considered when deciding if the CMI can be replaced by VOI in cattle abattoirs of countries for which bTB freedom can be demonstrated. © 2015 Elsevier B.V.. Source

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