Leptospira spp. in horses in southern Brazil: Seroprevalence, infection risk factors, and influence on reproduction
Introduction
Leptospirosis is a zoonotic bacterial disease caused by gram-negative spirochetes from the genus Leptospira. It affects animals and humans, especially in tropical areas [1] where the temperature and humidity conditions are ideal for the organism. They can live for two weeks in the soil and four weeks in water [2]. When there is contact with the epidermis or mucous membranes of vulnerable hosts, the spirochete penetrates and spreads hematogenously to target organs, where it can survive for several months [3]. The disease in animals expresses itself in several ways depending on the infected species [4]. In horses, reproductive disorders (neonatal deaths, embryonic absorption, and abortions) are frequent, causing economic losses [5,6]. Some breeds develop kidney disease [7], liver dysfunction [8] and recurrent equine uveitis [9,10].
In Brazil, leptospirosis is endemic among farm animals, being reported in pigs [11], sheep [12] goats [13], and cattle [14], with seroprevalences of 20–50%. Seroprevalence studies in horses are critical because these animals carry substantial economic value. There is substantial use of horses in the southern states of Brazil, whether as animal tractors, or in rodeos and riding. The maintenance of these animals in semi-urban areas and cohabitation with other susceptible domestic animals may increase the risk of infection by Leptospira spp. and become a zoonotic risk for contacts [15].
Given the importance of horses in the southern states, as well as the high seroprevalence of Leptospira spp. in other species, we hypothesized that there would be high seropositivity in horses as well. Therefore, the objective of this study was to determine the seroprevalence of Leptospira spp. in horses in southern Brazil, as well as to identify the risk factors for infection and consequences on reproduction.
Section snippets
Samples
Frozen horse serum samples (–20 °C) were obtained from 20 cites from a mountainous plateau, coastal regions and a small part of western Santa Catarina [16], Brazil (Fig. 1). According to IBGE in 2012, when the samples were collected, the horse herd in the state of Santa Catarina comprises 122,565 animals, with 32,450 living in the mountain mesoregion and 32,645 on the coast (mesoregions Vale do Itajaí and Florianópolis), representing 53.11% of the equine population of the state. We sampled 585
Serology
Among the 595 serum samples evaluated, 273 (45.9%) were positive for anti-Leptospira antibodies (Fig. 1). Among the positives, the numbers of samples with titers 1:100 were 159/273 (58.2%), and with at least one serovar with titer >1:100 there were 114/273 (41.8%). The numbers of horses with simple and mixed infections were 124/273 (45.4%) and 149/273 (54.6%), respectively. Mixed leptospiral infection was detailed in Supplementary material 1; as well as the number of seropositive animals for
Discussion
Seroprevalence of anti-Leptospira spp. was 45.9% in our study; that is, almost half of the animals evaluated had contact with the pathogen and developed immune response (antibodies) during their lifetimes. The farms that were part of this study kept animals for work or events (rodeos), so farmers use only vaccines when mandatory, in the same way that diagnostic tests were only carried out regularly for diseases of constant surveillance according to recommendations from the Brazilian Ministry of
Conclusion
The population of horses with antibodies (titration ≥1: 100) to Leptospira spp. corresponded to almost 50% of the herd, particularly animals seropositive for the serovars that are highly pathogenic to humans. We found that age of the animals was a risk factor for infection, that is, the greatest number of seropositive animals were over 6 years old; furthermore, females were more often infected than males; however, location, breeds, contact with dogs or other domestic animals and gender were not
Ethics committee
The present work was approved by the Committee of Ethics in Animal Experimentation (CEUA) of UDESC, protocol number 1.05/09.
Author contributions
Jaguezeski A.M., Lovato L.T. and Da Silva AS contributed to the design and implementation of the research, to the analysis of the results. Moura A.B. helped in the elaboration of the project and its execution and financing. Moura A.B and da Silva M.O. participated in the execution of the experiment and collection of samples and data. Laber I.F. and von
Declaration of Competing Interest
The authors declare that no conflict of interest exists.
Acknowledgments
Thanks to CAPES (Brazil) and CNPq (Brazil) for the financial support.
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