Rs. Barwick et al., RISK-FACTORS ASSOCIATED WITH THE LIKELIHOOD OF LEPTOSPIRAL SEROPOSITIVITY IN HORSES IN THE STATE OF NEW-YORK, American journal of veterinary research, 58(10), 1997, pp. 1097-1103
Objective-To determine and quantify risk factors associated with expos
ure of horses to the following serovars of Leptospira interrogans: pom
ona, autumnalis, and bratislava. Animals-2,551 horses were randomly se
lected from a target population during the period of May 1991 to Augus
t 1993. Procedures-Blood was collected from the horses and tested for
antibodies to serovars, using the microscopic agglutination test. A ti
ter greater than or equal to 1:100 indicated seropositivity. Informati
on was collected on each horse, its environment, and each farm's manag
ement practices. Logistic regression analysis was used to develop a mu
ltidimensional indexing system for indices of exposure and to identify
factors significantly associated with the risk of seropositivity. The
se indices were: 1) rodent exposure; 2) wildlife exposure; 3) soil and
water; and 4) management. Results-Rodent exposure index value was ass
ociated with the risk of exposure to all 3 serovars, Management index
value was positively associated with the risk of exposure to serovars
pomona and bratislava, but not with risk of exposure to serovar autumn
alis. Soil and water index value had a positive association with risk
of exposure to serovars pomona and autumnalis, but not to serovar brat
islava. The wildlife index value and the population density of horses
turned out together were associated with the risk of exposure to serov
ar autumnalis. Age of horse in years was associated nonlinearly (years
(2)) and linearly (years) with the risk of exposure to serovars autumn
alis and bratislava, and only linearly with the risk of exposure to se
rovar pomona. Conclusion-Risk of seropositivity to the 3 serovars of L
interrogans varies according to age, management practices, population
density of horses turned out together, and the values of the rodent e
xposure, wildlife exposure, and soil and water indices.