Economic and epidemiological impact of different intervention strategies for subclinical and clinical mastitis

Abstract

The objective of this study was to evaluate and compare different combinations of intervention strategies forcontagious or opportunistic subclinical and clinical intramammary infections (IMI). We simulated two differentDanish dairy cattle herds with ten different intervention strategies focusing on cow-specific treatment or culling,including three baseline strategies without subclinical interventions. In one herd, the main causative pathogen ofIMI wasStaphylococcus (S.) aureus. In the other herd,Streptococcus (St.) agalactiaewas the main causative agent.For both herds, we investigated costs and effectiveness of all ten intervention strategies. Intervention strategiesconsisted of measures against clinical and subclinical IMI, with baselines given by purely clinical interventionstrategies. Our results showed that strategies including subclinical interventions were more cost-effective thanthe respective baseline strategies. Increase in income and reduction of IMI cases came at the cost of increasedantibiotic usage and an increased culling rate in relation to IMI. However, there were differences between theherds. In theSt. agalactiaeherd, the clinical intervention strategy did not seem to have a big impact on incomeand number of cases. However, intervention strategies which included cow-specific clinical interventions led to ahigher income and lower number of cases in theS. aureusherd. The results show that intervention strategiesincluding interventions against contagious or opportunistic clinical and subclinical IMI can be highly cost-ef-fective, but should be herd-specific.