18The benefits and efficacy of control programs for herds infected with Mycobacterium avium 19 subsp. paratuberculosis (MAP) have been investigated under various contexts. However, most 20 previous research investigated paratuberculosis control programs in isolation, without modeling 21 the potential association with other dairy diseases. This paper evaluated the benefits of MAP 22 control programs when the herd is also affected by mastitis, a common disease causing the 23 largest losses in dairy production. The effect of typically suggested MAP controls were estimated 24 under the assumption that MAP infection increased the rate of clinical mastitis. We evaluated 25 one hundred twenty three control strategies comprising various combinations of testing, culling, 26 and hygiene, and found that the association of paratuberculosis with mastitis alters the ranking of 27 specific MAP control programs, but only slightly alters the cost-effectiveness of particular MAP 28 control components, as measured by the distribution of net present value of a representative U.S. 29 dairy operation. In particular, although testing and culling for MAP resulted in a reduction in 30 MAP incidence, that control led to lower net present value (NPV) per cow. When testing was 31 used, ELISA was more cost-effective than alternative testing regimes, especially if mastitis was 32 explicitly modeled as more likely in MAP-infected animals, but ELISA testing was only 33 significantly associated with higher NPV if mastitis was not included in the model at all. 34Additional hygiene was associated with a lower NPV per cow, although it lowered MAP 35 prevalence. Overall, the addition of an increased risk of mastitis in MAP-infected animals did not 36 change model recommendations as much as failing to consider mastitis at all. 37 Paratuberculosis, or Johne's Disease, is a chronic intestinal disease of ruminants caused by 40 infection with Mycobacterium avium subsp. paratuberculosis (MAP). Animals are usually 41 infected at a young age, with a variable and often extended latent period [1]. Infected animals 42 have lower milk production [2-9], decreased reproductive performance in later stages of disease 43 [6,10-12], and are often culled early [5,13]. It is difficult to control MAP in dairy herds; many 44 tests have poor diagnostic sensitivity [14], MAP persists in the environment for long periods of 45 time [15], paratuberculosis symptoms are slow to develop [16], and the available vaccines are 46 limited in distribution due to their cross-reaction with tuberculosis diagnostics [17]. 47 The debate over the economically optimal control method for MAP results from a wide range of 48 models and assumptions. Some studies have found test and culling to be consistently cost-49 effective [18,19], while others have found that cost-efficacy of test and cull required subsidized 50 testing costs [20] or only culling of animals with decreased milk production during MAP latency 51 [21]. Simulation models have identified cost-effective programs, such as q...