Huvepharma organised its first International Veterinary Symposium in Albena, Bulgaria from 1-3 June. Important issues such as the current use of antibiotics and its effect on bacterial resistance caused a lot of discussion among the 200 veterinarians present.
By Emmy Koeleman
Prof. Christian Friis from Denmark kicked off the first day by giving an in-depth presentation on the prudent use of veterinary drugs. As a member of the CVMP - the European Board for Approving Veterinary Drugs on the market - he explained some factors that this board considers before selection of the drug. These are: Diagnosis of the microorganism, Drug potency against the pathogen(s), Drug distribution to the site of infection, Desirable drug concentration profile, Route of administration, Duration of therapy and intervals between treatment and Development of resistance. This is especially of high importance for diseases with a high incidence: respiratory tract infections, gastro-intestinal disorders, meningitis and arthritis. Friis addressed a few points from this list: Regarding drug distribution to the site of infection he said that it is very important to know if the drug gets to the right tissue and where the infection is (in which tissue). If the drug is administered orally or in the muscle this can have an effect on this and therefore needs to be considered per drug. Regarding duration of therapy and intervals between treatments Friis discussed a trial that had been done in 2005 in Denmark where they compared treatment of four times 5 mg with one treatment of 20 mg. The animals showed no clear differences in the dropping rate of the body temperature. He said that probably more studies need to be done to see if there are real benefits in giving a drug in intervals.
ESBL and MRSA
Prof. Peter Silley from the UK gave a lively speech on the current hot topics: ESBL producing bacteria and MRSA
bacteria in animals and humans. ESBL stands for Extended Spectrum Beta-Lactamase, which are enzymes that have developed a resistance to antibiotics like penicillin and capable of hydrolyzing what we now term extended spectrum antimicrobials, the 3rd and 4th generation cephalosporins. So why are ESBLs important? 3rd and 4th generation cephalosporins represent antimicrobials that are important in treatment of severe and invasive infections in humans. The first nosocomial outbreaks of resistant bacteria were described in the 1980s and since then occurrence of infections with bacteria resistant to 3rd and 4th generation cephalosporins e.g. Klebsiella pneumoniae, E. coli, Salmonella spp and Pseudomonas aeruginosa increased worldwide. An increased resistance implies either delayed adequate treatment or initial use of 2nd and 3rd line alternatives (higher risk of adverse reactions, e.g. aminoglycosides or increased toxicity e.g. colistin). Delayed adequate therapy can increase the burden of infection with bacteria resistant to 3rd and 4th generation cephalosporins. However, Silley addressed that whilst ESBLs are widely detected in the human population they are far less frequently reported in animals.
Preliminary results from a study in the Netherlands showed that the majority of ESBLs found in humans do not correspond with the ones found in chickens and the majority of ESBL infections are caused by human to human contacts. However, ESBLs are an important issue said Silley and more information is needed to find out where the infections actually come from. Regarding MRSA, Silley mentioned that during the period 1970-2000, MRSA has been sporadically isolated from animals, in particular cows, small companion animals and horses. With exception of some equine isolates, the nature of these cases suggested a human origin and with no epidemics reported (Leonard & Markey, 2008). Silley explained that until recently both the scientific community and policy makers were convinced that MRSA in human medicine had nothing to do with animal husbandry but was a problem solely based on the antimicrobial use in human medicine.
Definition of resistance
That we consider antibiotic use increases antibiotic resistance is a fact, but there is still some confusion over the term 'resistance'. There are different definitions used around the globe and what they find resistant in the US is different from the view in Europe. The ban on using Baytril in the US poultry industry for example had no effect at all on human health, explained Silley. Because there are no clear 'resistance values', it makes it difficult for veterinarians to actually get this resistance down, instead of just reducing the total kg of antibiotics used.
Because the volume should not be such an issue, it targets more the resistance issue and adapts current
antibiotic use to minimise this.Resistance is also not simply a fault of antibiotic use and it is a complex issue which not only should put pressure on veterinarians, according to Silley. According to Friis, fluruoquinolones and cephalosporins should still be alternatives for treatment of diseases in food producing animals but should be used with care. As a take home message Silley called for harmonisation across European surveillance systems so that data can be compared on a like for like basis. He addressed that resistance is not a disease but that we must relate the data to public health. “Care needs to be taken when evaluating the data by those developing and regulating drugs, we need to move away from a simple view of causality as we grapple with the total ecology of antimicrobial resistance. He also said that as we are facing new challenges we must not be bound by old paradigms.”
Respiratory diseases in swine
Prof. Dominiek Maes from Belgium started the pig workshop by giving a clear outline on the main respiratory diseases in swine and gave some facts that every veterinarian needs to know. Respiratory diseases are the most important diseases in pigs and are the major cause of antibiotic use on the farm, said Maes. However, studies showed that the prevalence of respiratory diseases have not gone down in the last 30 years, despite all the hygiene, health and management measures. Maes said that maybe the severity of the disease has gone down but that is difficult to say. He explained that M.hyo is caused mostly by trade of (subclinically) infected pigs and can be transmitted easily by air. Studies in the UK and Denmark showed that the pathogens can be transported by air for 3.2 km and 4.7 km respectively. He further addressed that M.hyo can be shredded for weeks or even months.
Another issue to consider is the interaction with other pathogens, according to Maes. When M.hyo and PRRS virus are present together, it was shown that M.hyo made the PRRS infection more severe and the symptoms in the animals were more severe than the sum of the two infections together. When M.hyo is present with influenza it was shown that the animals showed more severe coughing and pneumonia lasted longer. Also M.hyo and PCV2 showed (negative) synergestic effects on the clinical symptoms of the disease, for example a higher incidence of PMWS disease. When M.hyo was found with parasitic infections, also more severe pneumonia lesions were seen. Maes mentioned that respiratory problems can be tackled via medication and/or vaccination. Medication gives the vet more flexibility and can be used against more pathogens. A negative aspect of vaccination is that it can only be used against one pathogen. However, vaccination is a more long term strategy compared to medication and creates no resistance issues (which could be the case with applying medication). Maes added that vaccination against respiratory disease is not enough to reduce the transmission and infection levels in the herd.
Dose calculator for veterinarians
At the symposium, Alain Kanora - Global marketing director & international sales director affiliates for Huvepharma - introduced the dose calculator that can be used by pig and poultry vets.
This tool – developed by Henk Lecluyse from Huveparhama – looks like a normal calculator but can be used to calculate the correct dose of medication for the animals in mg/ kg body weight.
Antibiotic use in the UK
Prof. Peter Silley summed up a few statements on the current use of antibiotics in the UK. A report on the use of antimicrobials in people and animals in the UK in 2007 suggested over half the total tonnage of antimicrobials used was in people in contrast to the previous 2004 report where use in animals accounted for the larger share. Sales of veterinary medicines has fallen since figures published for 2004 and the amount of antimicrobials sold per tonne of liveweight of animal slaughtered for food decreased from 0.08 kg in 2004 to 0.06 kg in 2007. Silley also mentioned that 87% of antimicrobials used in animals in 2007 was in food producing animals, with tetracyclines accounting for 45% of total antimicrobial use in animals and β-lactams accounting for 19%. In contrast, in man, β-lactams accounted for 66% of antimicrobials used in the community in the UK and 77% of antimicrobials used in hospitals in England and Wales. Approximately 80% of antimicrobial prescriptions for people were for patients in the community. Compared to figures shown in the previous report, antimicrobial prescribing in the community seems to be on the increase again after a number of initiatives in the 1990s promoting prudent antimicrobial prescribing were successful in reducing number of prescriptions. However, during the same period, the UK population also increased by 1.1 million (1.9%). It's hard to draw comparisons with 2004 as data originate from a variety of sources and different methods may have been used to detect resistance. Notwithstanding these factors, it appears for a number of bacterial species that there have only been limited changes in the degree of antimicrobial resistance reported between 2004 and 2007.
Source: Pig Progress magazine Volume26 No. 6