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Abstract: A compulsory control program to control-eradicate Brucella infections was initiated 1985 in the Basque Country in Northern Spain. The program included both Brucella melitensis infection (ovine/caprine brucellosis), which were later included in a national plan, and Brucella ovis infection (ovine epididymitis), which was promoted by the local animal health authorities. Prevalences of these infections in small ruminant farms at that time were 10% and 60% of flocks, respectively. Since then, the flocks/herds have been tested annually and animals found to be infected by means of the tests employed were slaughtered. At the same time, a voluntary Small Ruminant Lentivirus infection control program also started in some sheep flocks of the region. Currently, prevalences of brucellosis have dropped to 0% for B. melitensis infection and <0.1% for B. ovis. This implies an overall rate reduction of 100% and 99.9%, respectively. The results for Small Ruminant Lentivirus infection have not been so good and only three of the eight flocks into the scheme have reached eradication. Good results have been obtained by local and national animal health authorities and farmers during the past 25 years for brucelosis control. Use of simple serological testing and culling has allowed reduction-eradication of the infection. Once advanced control is reached, an economic balance will be necessary, in order to optimize best use of resources, including allocating them to control other small ruminant problems. [Copyright &y& Elsevier]

Visna/Maedi is a disease of sheep caused by small ruminant lentivirus (SRLV) infection that is widespread throughout the world and that has been recognized to be present in the Basque Country (Spain) since the early 1980's. Nearly seven decades of studies have improved the knowledge on its clinical signs and epidemiology. However, its slow progressive nature, subclinical most of the time, makes difficult to assess its real impact on productive traits, a question of critical importance to balance out the economic costs it causes and the benefits of designing and deploying an eradication program. Development of a dairy breeding program since the 90 s in the local Latxa sheep population has provided data on milk productivity in several flocks where SRLV infection prevalence has been continuously monitored. This study analyses retrospectively the association between SRLV prevalence and production variables during ten yearly lactations in three Latxa dairy flocks with medium-high SRLV seroprevalence. Our results indicate that average standard lactation of seropositive sheep was 6.7 % lower than controls. The largest differences (p < 0.001) were observed at the ewe lifetime peak of production between second and fourth lactations. Lifelong milk and lamb production data indicated even a higher impact, with costs rising up to nearly 50 €/ewe/year. This substantial production decrease associated with subclinical SRLV infection in Latxa dairy sheep supports the benefit of establishing a SRLV control program. A rough cost-benefit analysis indicated that even in a medium-yielding breed, testing expenses would be largely covered by milk production improvement., (Copyright © 2020 Elsevier B.V. All rights reserved.)