Veterinary diagnostics in Ireland (part 2)

In the Republic of Ireland, the Department of Agriculture, Food and the Marine (DAFM) operates a group of six veterinary diagnostic laboratories: one large central laboratory on the outskirts of Dublin city and five smaller regional laboratories near Athlone, Cork, Kilkenny, Limerick and Sligo.

Animal Health Ireland

Since the establishment of Animal Health Ireland in 2009, a not-for-profit partnership-based organisation providing leadership and co-ordination in the control of non-regulatory animal health issues in Ireland, a sub-group (Cellcheck) has focused on improving milk quality (www.animalhealthireland.ie/). Cellcheck has organised a large number of half-day farmer workshops which focus on a small number of areas pinpointed as being key to achieving the most effect on improving milk quality. Preparation of the teat prior to sampling and treatment is one of the topics covered in the workshop. The workshops have brought together small, expert teams which include a veterinary practitioner, dairy adviser, milking machine technician and milk processor representative, to deliver simple, clear and focused messages to the farmers.

Results

Figure 5 illustrates the breakdown of culture results from 2013. Staphylococcus aureus was the most commonly isolated bacterial pathogen from milk samples received. This does not mean of course that it is the most common cause of mastitis in Irish dairy cows. The fact is that many of the samples received are likely to be taken from cows that the farmers are finding hard to ‘cure’, have persistently high somatic cell counts, and/or have repeated cases of clinical mastitis in the same quarter.

Comparing the figures obtained here with those from laboratories in other countries, a few things stand out. Firstly, is the high isolation rate of Staphylococcus aureus, then the low isolation rate of Streptococcus agalactiae and fungal species. Mycoplasma bovis was isolated from a small number of the samples tested during 2013. This pathogen is not easily detected using the routine culture methods. The positive cases were detected using microaerophillic culture or polymerase chain reaction (PCR) testing, which was only carried out on selected samples.

Figure 5: Percentage breakdown of isolates from the milk samples received during 2013.
Figure 5: Percentage breakdown of isolates from the milk samples received during 2013.

Two panels of antimicrobials are used for sensitivity testing- a gram-positive and a gram-negative. Figure 6 illustrates the antimicrobial sensitivity results for the 2013 Staph. aureus isolates using the gram-positive panel. Resistance to cefoxitin is used as an indication of possible methicillin resistance, so any Staph. aureus isolates resistant to this are held and subjected to further testing.

Figure 6: The gram-positive antimicrobial panel used by the laboratories and the summary of the sensitivity results for Staphylococcus aureus.
Figure 6: The gram-positive antimicrobial panel used by the laboratories and the summary of the sensitivity results for Staphylococcus aureus.

A review of the antimicrobial panels used by the laboratories is carried out periodically. Feedback is received occasionally from veterinary practitioners to say that the panels do not fully represent the antimicrobials used in mastitis control at farm level. This is true to a certain extent and is because of the laboratories role in monitoring resistance patterns and trying to represent the wide range of antimicrobial groups. Figure 7 illustrates the antimicrobial sensitivity results for the 2013 Escherichia coli isolates using the gram-negative panel. Resistance to cefpodoxime is used as an indication of possible extended spectrum beta-lactamase (ESBL), so any E. coli isolates resistant to this are held and subjected to further testing.

Figure 7: The gram-negative antimicrobial panel used by the laboratories and the summary of the sensitivity results for Escherichia coli.
Figure 7: The gram-negative antimicrobial panel used by the laboratories and the summary of the sensitivity results for Escherichia coli.

 

Text & illustrations: Alan Johnson – Alan.Johnson@agriculture.gov.ie