Herd Level Antimicrobial Resistance in Beef Calves in Switzerland 1986 through 2011

The increasing emergence of antimicrobial resistance in food animals is a growing global concern and is closely linked to animal husbandry practices. In this study we describe the changement of antimicrobial resistance in beef calf production in Switzerland from 1986 through 2011. Data were collected from farms with known calf herd problems, such as diarrhoea or pneumonia, along with antimicrobial resistance from those herds. The Herd Health Section of the University of Zu-rich visited each farm. Samples were analysed for bacterial growth and resistance test commonly indicated in diseases such as calf pneumonia and diarrhoea. Each resistance test comprised of samples from at least three diseased animals. For diarrhoea, a faeces sample was used, for pneu-monia a deep nasal swab was taken. In nasal swabs, only batches yielding considerable bacterial growth in three individual animal samples were included for diagnosis. Other growth of bacteria was considered as contamination. The results consisted of bacterial resistance to antibiotics against defined diseases such as calf diarrhoea and calf pneumonia at herd level. This approach is reflecting the situation as found in practice when a calf has to be treated without delay and without results from further laboratory diagnostics. In diarrhoea cases, four antibiotics showed no bacterial resistance. Bacterial resistance of below 10% was observed to three antibiotics. Up to 20% bacterial resistance was found to two antibiotics. Eighty per cent and over was found to be six antibiotics. Bacterial resistance to two antibiotics was found in over 90% of samples and all samples were resistant to one antibiotic. In pneumonia three antibiotics showed no resistance;one was below 10%;four antibiotics were below 20%. Over 80% of samples were resistant to four antibiotics. One resistance was over 90% and all bacterial samples were resistant to two antibiotics. Differences in bacterial resistance between pneumonia and diarrhoea in two study periods with equal cases, i.e. 1986-2006 and 2007-2011 were found. A reduction in bacterial resistance can be found in 5 out of 7 cases, when the amount of the respective antibiotic was reduced over time. This finding raises the obvious question whether antibiotics should be removed from the marked ones by a period of about 10 years. This would help to control not only bacterial resistance but also the use of the limited amount of antimicrobial drugs available. Such a control program would need to be established by international and national drug agencies as well as the pharmaceutical industry. Such a program would require extensive international validation.

Evidence-Based Use of Antibiotics in Veal Calves with Diarrhea

Diarrhea is the leading cause of mortality in beef and dairy calves during the first week of life and results in substantial financial loss [1]. Diarrhea is a multifactorial disease and can be infectious or non-infectious. However, in the majority of calves, infectious organisms, especially Cryptosporidium parvum, rotavirus, coronavirus, and E. coli, are the primary cause [2]. The aim of this study was to generate a decision tree, based on prevalence, diagnostic testing and treatment and to estimate associated costs or risk. For each of the four main pathogens, two principal approaches are outlined and compared. The first approach relies on a detailed diagnostic workup and allows for specific etiological treatment. The second approach relies on the trial-and-error method, which involves the use of a first-choice antibiotic, followed by a second- and third-choice antibiotic if the previous ones failed to resolve the disease. In Switzerland, the prevalence of diarrheic calves infected with E. coli is approximately 1% suggesting that the use of antimicrobials for the treatment of scouring calves, in the absence of a diagnostic workup, is not always justified. However, for all four major pathogens, the trial-and-error method affords cheaper treatment compared with treatment based on an etiological diagnosis. This creates a quandary in view of the current worldwide efforts to reduce the use of antibiotics in animal agriculture.

Evidence-Based Use of Antibiotics in Meat Calves

Abuse of antibiotics is an increasing commonly feature in the media. Widespread preventive use of antibiotics without diagnostics in meat calf husbandry is a major public health concern. In this study, we compare a “trial and error” method, comprising of a first choice antibiotic, followed by a second and third choice (as recommended by the WHO), with a method which utilizes an antibiotic resistance test to first identify the best antibiotic out of first, second or third choice alternatives using decision tree analysis. Data were collected from farms with a known calf herd problem along with antibiograms from those herds. Samples were analysed for resistance to antibiotics against calf pneumonia on a herd level, rather than for resistance against specific antibiotics. Resistance tests were performed on batch samples composed of at least three diseased animals. A deep nasal swap was taken. In nasal swaps only ++ or +++ growth in all 3 samples were used for diagnosis. Other growth of bacteria was considered as contamination. A comparison of resistance rates across a range of antibiotics between farms with known calf pneumonia and calf diarrhoea issues was performed. The decision tree analysis presented provides strong support in favour of an evidence-based approach to antimicrobial treatment by using an antimicrobial resistance test, providing an advantage of 58% per meat calf against the “trial and error” method, giving a financial gain of some CHF 320.09 under Swiss economic circumstances.