New Insight into Pathogenic E. coli

Avian Pathogenic Escherichia coli (APEC) continues to cause major economic losses to the poultry industry worldwide, said Dr Rikke Heidemann Olsen on the University of Copenhagen in Denmark.

Conventional wisdom is that APEC is a secondary pathogen, which takes advantage of viral infections. However, her studies using new molecular methods show the E. coli acting as a primary pathogen and providing the opportunity for colonisation by another pathogen, histomonas (blackhead disease).

Dr Olsen said that control of APEC relies on high biosecurity, epidemiological investigations that identify the source of infection (which may be the hatchery or parent stock) and the development of an effective vaccine.

Histomoniasis

Histomoniasis (blackhead) is a protozoal disease of turkeys, chickens and other galliform birds, according to Keith Warner of Minster Vets in Hereford, UK. He reported to the conference experience from his practice of the disease on turkey farms over the last few years.

From these, he concluded that biosecurity can protect housed turkeys on concrete floors but it is not sufficient as the only control method. Changing boots can help to prevent contamination of a 'clean' house, he said.

However, when infection is present, there are no authorised medications currently available for successful treatment, a situation about which veterinarians - especially those covering 'minor species' including turkeys - often express concerns. Rapid use of fenbendazole has some beneficial effects, said Mr Warner, and it is used successfully in preventative programmes.

On the very limited number of treatment options for what can be a very costly disease, the UK industry has requested authorisation to use dimetridazole in breeding birds not destined for human consumption. The UK government opposes this without absolute guarantees of traceability as the drug is classified as a carcinogen.

Paramomycin (Histobloc) has been considered for approval by the EU authorities but, according to Mr Warner, more work is required on post-marketing monitoring. In the meantime, it may be used if PCR tests confirm the presence of histomonads on a flock-by-flock basis but this leads to a delay in starting treatment that reduces its efficacy. The product works well when given in feed as a preventative programme, he said.

Looking to the future, Mr Warner mentioned that the vaccine developed by Dr Michael Hess of the Veterinary University of Vienna looks promising.

Emerging Issues on Antimicrobial Resistance in Turkeys

Three issues on antibiotic resistance in turkeys were identified and described by Christopher Teale of the Animal Health Veterinary Laboratories Agency (AHVLA) in Shrewsbury, UK.

On Salmonella, he said that some serovars have much greater propensity to develop resistance than others. Of the common foodborne types, for example, Salmonella Typhimurium tends to be much more resistant that Salmonella Enteritidis. Salmonella Kentucky, which was previously associated with human infections following international travel, has subsequently been detected in European poultry. Salmonella Saintpaul is the fourth most frequently reported serovar in European turkeys and isolates were shown in a recent study to display resistance to six antibiotics.

An EFSA report from 2012 revealed turkey flocks in Germany and Hungary to be positive for Methicillin-Resistant Staphylococcus aureus (MRSA). Another study in Germany looking in detail at 20 turkey flocks found turkeys in 18 flocks to be positive, as were many of the farm workers who cared for them. The types of MRSA found were mostly the clonal complex (CC) 398 type, which is generally associated with livestock, particularly pigs. It has been known rarely to cause illness in farm-workers but it is different from the types that pose a serious threat to humans in hospitals and the community.

Finally, on E.coli, Mr Teale said that normal commensal bacteria in turkeys are not pathogenic to the birds or humans. However, they do represent a possible reservoir of resistant genes and a recent UK study has confirmed that commensal E. coli from turkeys carry genes for extended-spectrum beta-lactamase (ESBL) resistance.

Further Reading Find out more information on the diseases mentioned in this article by clicking here.

May 2013