Abstract:
Most leptospiral infections in horses are asymptomatic; however, acute disease manifestations as well
as reproductive failure and recurrent uveitis have been reported. In South Africa, the epidemiology of the
disease in horses is not well documented.Aserosurvey to determine what serovars were presentin horses
from Gauteng, KwaZulu-Natal and Western Cape Provinces and to get an estimate of the seroprevalence
of leptospirosis was carried out from January 2013 until April 2014 with the assistance of four large
equine hospitals located in these provinces. Furthermore, associations between potential risk factors and
both seropositive horses to the predominant serovar Bratislava and to Leptospira spp. were statistically
evaluated using univariate analysis and multivariable logistic regression models. A total of 663 horse sera
were collected and tested against a panel of 24 leptospiral serovars using the microscopic agglutination
test. The most predominant serovars in Gauteng were Bratislava [32%, 95% CI: 29–35%]; Djasiman [10.4%,
95% CI: 8–12%] and Arborea [8.9%, 95% CI: 7–11%], in the Western Cape Province, Bratislava [27.35%, 95%
CI: 23–32]; Djasiman [15.4%, 95% CI: 12–19%] and Arborea [14.5%, 95% CI: 11–18%] and in KwaZulu-Natal,
Bratislava [39.4%, 95% CI: 34–44%]; Arborea [9.6%, 95% CI: 7–13%]; and Tarassovi [7.7%, 95% CI: 5–10%]
respectively. Twenty one serovars representing 17 serogroups were detected with serovar Bratislava
being the most serodominant. The apparent prevalence to one or more serovars of Leptospira spp. at a
serum dilution of 1:100 in Gauteng, KwaZulu-Natal and Western Cape Provinces were 49%; 37% and 32%
respectively. The true prevalence was calculated for each province taking into account the clustering
effect during the sampling and was found to be between 24 and 74% in Gauteng; 26–39% in the Western
Cape and 20–54% in KwaZulu-Natal. Nooitgedacht (South African horse breed) horses were found to be
at greater risk of being seropositive to both serovar Bratislava (OR = 5.08) and Leptospira spp. (OR = 6.3).
Similarly, horses residing on properties with forestry in the vicinity were found to be at greater risk
of being seropositive to both serovar Bratislava (OR = 9.3) and Leptospira spp. (OR = 5.2). This study has
shown that a high proportion of horses in South Africa are exposed to a wide range of serovars, inferring
a complex epidemiology. It also describes for the first time new serovars of Leptospira in South African
horses that have not previously been reported.