Surveillance for brucellosis in Ireland 2018
Background
Brucellosis in cattle was officially eradicated from Ireland in 2009. Up to that point bovine brucellosis caused substantial production losses related to poor fertility and foetal loss in cattle. Other negative consequences of bovine brucellosis were testing costs incurred by both farmers and the state, and human illness, mainly in farmers and vets.
Ireland is now free of both Brucella abortus (which causes brucellosis in cattle) and Brucella melitensis (which causes brucellosis in sheep and goats). To demonstrate freedom to trading partners, Ireland carries out extensive testing on its cattle and sheep populations each year.
Active surveillance
To demonstrate freedom from brucellosis in cattle, Ireland tests cull cows which are sampled as they pass through slaughter plants. Cull cows are considered a high risk group for brucellosis if it is present in a country, and so are considered an appropriate category to test. 129,469 cull cows were tested for brucellosis using a screening ELISA test, and an additional confirmatory CFT test in a small number of cases, during 2018. Testing was carried out by the Department of Agriculture, Food and the Marine (DAFM) in its Blood Testing Laboratory in Cork. All cull cow samples tested negative for Brucella abortus, and Ireland was able to demonstrate freedom from the disease on that basis.
To demonstrate freedom from brucellosis in sheep for the same period, DAFM sampled 7,544 sheep on farm in 392 separate flocks which are spread out countrywide. All tested negative for Brucella melitensis on a screening test carried out at the Cork Blood Testing Laboratory. Again, this demonstrated freedom from brucellosis in sheep.
Passive surveillance
It should be noted that the active surveillance outlined above is supplementary to the passive surveillance which Ireland regards as its mainstay in detecting incursions of exotic disease.
Both Brucella abortus and Brucella melitensis are notifiable diseases in Ireland, meaning that anyone who suspects that an animal may have the disease is legally obliged to notify DAFM. In addition, it is a legal requirement to notify DAFM of any case of abortion in a bovine animal; abortion is the most common clinical sign of infection with Brucella abortus.
Beyond disease reporting, DAFM operates a network of regional veterinary laboratories, strategically located around the country. Farmers and private veterinary practitioners (PVPs) submit large numbers of samples, including aborted foetuses, to the laboratories every week, and therefore DAFM can be confident that in the event that disease reporting was not effective in detecting an incursion of brucellosis, then laboratory-based passive surveillance would achieve this result instead.
Farmers are encouraged to have their PVP examine and test cows and sheep which have aborted, to report suspicions of brucellosis in either species to their local Regional Veterinary office, and to make use of their local Regional Veterinary Laboratory to aid with diagnosis of disease conditions.
Thanks to the Cork Blood Testing Laboratory for providing the data on the numbers of samples tested under the brucellosis testing programmes.