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Barwick, R. S., Mohammed, H. O., McDonough, P. L., & White, M. E. (1998). Epidemiologic features of equine Leptospira interrogans of human significance. Prev Vet Med, 36(2), 153–165.
Abstract: Leptospirosis is a zoonotic bacterial disease caused by Leptospira interrogans. There is a serologic evidence that horses are exposed to L. interrogans and, as a shedder of these organisms, can be a threat to humans. We examined risk factors associated with the risk of testing seropositive to three L. interrogans serovars (L. icterohaemorrhagiae, L. grippotyphosa, and L. canicola) in the horses of New York State, in order to understand the epidemiology of the disease and suggest strategies to control and prevent equine leptospirosis. To carry out this study, blood samples were collected from a random sample of 2551 horses and tested for the presence of antibodies to the above serovars using the microscopic agglutination test. Samples with a titer $100 were considered positive. Clinical and demographic data were collected on each horse, the farms' management practices and ecology. Logistic regression analysis was used to develop a multivariate indexing system and to identify factors significantly associated with the risk of leptospirosis. Four indices were developed based on the possible sources of exposure: rodent exposure index; wildlife exposure index; soil and water index; and management index. The soil and water index was significantly associated with the risk of exposure to all three serovars. Management was positively associated with L. icterohaemorrhagiae and L. canicola. Density of horses turned out together was positively associated with the risk of exposure to L. grippotyphosa. We concluded that indirect exposure of horses to L. interrogans through contaminated soil and water appears to be significantly associated with the risk of exposure to all three serovars. Management appears to play an important role in the exposure to L. interrogans. Modification of management practices might reduce the horses' risk of exposure and hopefully minimize the human hazards.
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McDonough, P., Kindig, C. A., Ramsel, C., Poole, D. C., & Erickson, H. H. (2002). The effect of treadmill incline on maximal oxygen uptake, gas exchange and the metabolic response to exercise in the horse. Experimental Physiology, 87(04), 499–506 M3– null.
Abstract: In healthy man, conditions that change muscle O2 delivery affect the achievable maximum rate of O2 uptake (V[dot above]O2,max) as well as the metabolic (e.g. lactate threshold, LT) and gas exchange (e.g. gas exchange threshold, Tge) responses to incremental exercise. Inclined (I) compared to level (L) running increases locomotory muscle EMG at a given speed in the horse, indicative of elevated metabolic demand. To our knowledge, the effect of treadmill incline on V[dot above]O2,max, LT and Tge has not been addressed in the exercising quadruped. We used blood sampling and breath-by-breath expired gas analysis to test the hypothesis that I (10 % gradient) would increase V[dot above]O2,max and the rate of O2 uptake (V[dot above]O2) at LT and Tge in six Thoroughbred horses during incremental running to volitional fatigue. V[dot above]O2,max was significantly higher for I (I, 77.8 ± 4.1; L, 65.5 ± 5.3 l min-1; P < 0.05), but peak plasma lactate concentration was not (I, 28.0 ± 3.7; L, 25.9 ± 3.0 mM). Arterial PCO2 increased to 62.1 ± 3.3 and 57.9 ± 2.7 Torr (I vs. L; P < 0.05), yet despite this relative hypoventilation, a distinct Tge was present. This Tge occurred at a significantly different absolute (I, 49.6 ± 3.2; L, 42.4 ± 3.2 l min-1; P < 0.05), but nearly identical relative V[dot above]O2 (I, 63.6 ± 1.2; L, 63.9 ± 1.6 % V[dot above]O2,max) in I and L. Similarly, LT occurred at a significantly greater absolute V[dot above]O2 (I, 37.3 ± 2.8; L, 26.9 ± 2.1 l min-1), but a relative V[dot above]O2 that was not different (I, 47.9 ± 2.1; L, 43.9 ± 4.5 % V[dot above]O2,max). In addition, Tge occurred at a significantly higher (P [less-than-or-equal] 0.05) absolute and relative V[dot above]O2 than LT for both I and L tests. In conclusion, V[dot above]O2,max is higher during inclined than level running and both LT and Tge in the horse occur at a similar percentage of V[dot above]O2,max irrespective of the absolute level of V[dot above]O2,max. In contrast to humans, LT is a poor analogue of Tge in the horse.
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