An increase in the size of the national dairy herd in recent years is considered a likely factor in the number of herds infected with bovine TD reaching a six-year peak in 2019.
Department of Agriculture figures show 4,060 herds were infected with the disease last year.
The national herd incidence, where at least one animal tested positive for bovine TB, rose for the third year in a row to reach 3.72% of all herds – up from 3.47% in 2017 and the highest recorded level since 2013.
“It is likely that the expansion of the dairy herd since 2015 has played a role in this, since dairy herds, larger herds and herds which introduce more cattle are all more at risk of bovine TB breakdowns,” the department said.
It noted that dairy herds account for 52% of all infected cattle last year.
Over 8.8 million tests were conducted for bovine TB on the national herd of 6.4 million cattle during 2019. While incidence of the disease overall is low in many areas, some very high levels were recorded in the north-east of the country as well as parts of Clare, Cork and Wicklow.
The incidence rate reached over double the national average in Monaghan at 7.02%, while it was 6.12% in Cork North – both areas with some of the highest cattle densities in the country.
Although Wicklow had the highest incidence rate of the disease at 12.33% of all herds in the county, the number of infected cattle at 380 was relatively small as Wicklow accounts for only 0.5% of the national herd. Limerick and Longford had the lowest herd incidence at 2.06% and 2.21% respectively.
A total of 17,058 cattle tested positive last year through a combination of skin testing and gamma interferon testing (GIF). It represented a 2.5 reduction on 2018 figures.
Cork North had the highest number with 1.993 testing positive followed by Monaghan (1,336) and Clare (1,190).
The Department of Agriculture said GIF testing is able to identify infected animals at an earlier stage than the skin test and, if used appropriately, could reduce the chances of leaving residual infection in a herd after restrictions on cattle were removed.
“We expect by removing more infected cattle earlier the risk of re-infection will fall,” the Department of Agriculture said.
However, the department acknowledged that continuing efforts were needed from all stakeholders to reverse recent increases in the incidence of the disease.
“Risks must be addressed by national policy changes and by actions at farm level,” it added and acknowledged the recent upturn in bovine TB figures was “multifactorial” and often related to local issues.
The department said a report presented by the TB 2030 stakeholder forum last year contained a set of proposals which could have a significant impact on the reduction of bovine TB in the year ahead.
In addition it said a spending review of a bovine TB eradication programme which was published last October would also inform future policy consideration.
However, the Irish Farmers’ Association has warned that the review’s findings, which recommended limits on financial supports to farmers with herds affected by bovine TB, could jeopardise the ongoing support of their members for the programme.
10% since 2015 despite no increase in the incidence of the disease in cattle herds.