Risk factors related to seropositivity for Leptospira spp. in horses in the Serra Catarinense region

Fatores de risco relacionados a soropositividade para Leptospira spp. em equinos na região da Serra Catarinense

Deise Keli Farias Gabriela Dick Silvério Bunn André Thaler Neto Carolina Rech Álvaro Menin Mere Erika Saito About the authors

ABSTRACT:

Leptospirosis is a zoonotic infectious disease caused by the bacterium Leptospira spp. The consequences of infection in horses are unclear, and the serogroups involved vary depending on the region. This study aimed to evaluate the seropositivity of unvaccinated horses in the Serra Catarinense region and the possible risk factors associated with the infection. We used 207 horses from 26 properties, with no clinical history of infection and unvaccinated for leptospirosis. We submitted serum samples to the microscopic agglutination serum (SAM) to obtain the main reference serogroups. We considered animals with titre ≥100 as infected. The results of the serology revealed seropositivity in 45.4% (94/207) of the animals studied. The most frequent antibodies reportedwere those against the serogroups Australis 16.9% (35/207), Ichterhaemorrhagiae 14.4% (30/207), and Grippotyphosa 5.31% (11/207). Among the primary risk factors associated with the infection we reported extensive rearing system (OR = 1.27; P<0.05) and the presence of other animal species such as cattle (OR = 3.85; P<0.01) and capybaras (OR = 2.07; P=0.06). The findings presented in this study showed that leptospirosis is endemic in horses in the Serra Catarinense region, and revealed the need for emergency surveillance and control measures specific to this important zoonosis.

Key words:
diagnosis; animal health; infectious diseases

RESUMO:

A leptospirose é uma doença infecciosa zoonótica, causada pela bactéria Leptospira spp. Em equinos, as consequências da infecção não são claras e os sorogrupos envolvidos variam dependendo da região. Sendo assim, este trabalho objetivou avaliar a soropositividade de Leptospira spp. em equinos não vacinados na região serrana Catarinense e estimar os possíveis fatores de risco associados à infecção. Para tal, foram estudados 207 equinos, de 26 propriedades, sem histórico clínico da infecção e não vacinados para leptospirose. As amostras de soro foram submetidas ao ensaio de soro aglutinação microscópica (SAM) para os principais sorogrupos de referência. Animais com título ≥100 foram considerados reagentes. Os resultados da sorologia revelaram uma soropositividade de 45,4% (94/207) para os animais estudados. Com maior frequência foram observados anticorpos contra os sorogrupos Australis 16,9% (35/207), Icterohaemorrhagiae 14,4% (30/207), e Grippotyphosa 5,31% (11/207). Dentre os principais fatores de risco associados à infecção observados, foram o sistema de criação extensivo (OR=1,27; P<0,05) e a presença de outras espécies animais como bovinos (OR=3,85; P<0,01) e capivaras (OR=2,07; P=0,06). Os achados apresentados neste estudo mostraram que a leptospirose em equinos é endêmica na região da serra Catarinense, e revelam a necessidade de medidas emergenciais de vigilância e controle específicas para esta importante zoonose.

Palavras-chave:
diagnóstico; sanidade animal; doenças infecciosas

INTRODUCTION:

Leptospirosis is a zoonotic infectious disease highly important for global public health. It is caused by pathogenic species of the Leptospira spp. genus (DE BRITO et al., 2018DE BRITO, T. et al. Pathology and pathogenesis of human leptospirosis: a commented review. Revista do Instituto de Medicina Tropical de São Paulo, v.60, n.23, p.1-10, 2018. Available from: <Available from: http://dx.doi.org/10.1590/S1678-9946201860023 >. Accessed: Nov. 06, 2018. doi: 10.1590/S1678-9946201860023.
http://dx.doi.org/10.1590/S1678-99462018...
). In horses, the infection is associated with recurrent uveitis (VERMA & STEVENSON, 2012VERMA, A.; STEVENSON, B. Leptospiral uveitis - there is more to it than meets the eye! Zoonoses and Public Health, v.59 Suppl 2, p.132-41, 2012. Available from: <Available from: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1863-2378.2011.01445.x >. Accessed: May, 04, 2019. doi: 10.1111/j.1863-2378.2011.01445.x.
https://onlinelibrary.wiley.com/doi/full...
), abortions, stillbirths, or weak neonate foals (BROUX et al., 2012BROUX, B. et al. Acute respiratory failure caused by Leptospira spp. in 5 foals. Journal Veterinary Internal Medice, v.26, n.3, p.684-7, 2012. Available from: <Available from: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1939-1676.2012.00902.x >. Accessed: Nov. 10, 2018. doi: 10.1111/j.1939-1676.2012.00902.x.
https://onlinelibrary.wiley.com/doi/full...
; HAMOND et al., 2013HAMOND, C. et al. The role of leptospirosis in reproductive disorders in horses. Tropical Animal Health Production, v.46, n.1, p. 1-10, 2013. Available from: <Available from: https://link.springer.com/article/10.1007%2Fs11250-013-0459-3 >. Accessed: Dec. 04, 2018. doi: 10.1007/s11250-013-0459-3.
https://link.springer.com/article/10.100...
; PINNA et al., 2014PINNA, A. et al. Potential differences between Leptospira serovars, host-adapted (Bratislava) and incidental (Copenhageni), in determining reproductive disorders in embryo transfer recipient mares in Brazil. Veterinary Record, v.24, p.1-4, 2014. Available from: <Available from: https://veterinaryrecord.bmj.com/content/174/21/531.long >. Accessed: Jul. 20, 2017. doi: 10.1136/vr.101444.
https://veterinaryrecord.bmj.com/content...
). Horses are incidental hosts for most serovars of Leptospira sp., such as Icterohaemorrhagiae, Canicola, Pomona, and Grippotyphosa (ELLIS, 2015ELLIS, W. A. Animal leptospirosis. Current Topics Microbiology Immunology, v.387, p.99-137, 2015. Available from: <Available from: https://link.springer.com/chapter/10.1007/978-3-662-45059-8_6 >. Accessed: Apr. 03, 2019. doi: 10.1007/978-3-662-45059-8_6.
https://link.springer.com/chapter/10.100...
), considered reservoirs for the serovar of Bratislava (PINNA et al., 2014) 2012.

Infections in horses generally occurred by direct contact with contaminated urine or placenta fluids of infected animals or indirectly from a contaminated environment (FAISAL et al., 2012FAISAL, S. M. et al. Leptospira: invasion, pathogenesis and persistence. In: ME, E. (Ed.). The pathogenic spirochetes: strategies for evasion of host immunity and persistence. New York, NY: Springer Science, p.143-172, 2012. Available from: <Available from: https://www.springer.com/gp/book/9781461454038 >. Accessed: May, 04, 2019. doi: 10.1007/978-1-4614-5404-5_8.
https://www.springer.com/gp/book/9781461...
). Even with an intense humoral response, the agent can survive and multiply, being eliminated through the urine for up to three months (YAN et al., 2010YAN, W. et al. Experimental Leptospira interrogans serovar Kennewicki infection of horses. Journal of Veterinary Internal Medicine, v.24, n.4, p.912-7, 2010. Available from: <Available from: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1939-1676.2010.00507.x >. Accessed: Jan. 31, 2019. doi: 10.1111/j.1939-1676.2010.00507.x.
https://onlinelibrary.wiley.com/doi/full...
). In this context, leptospirosis in horses can represent a neglected zoonosis since horses of most regions are pets, presenting a very close relationship with humans of different age groups. In 2018, 237 cases of leptospirosis were confirmed in the State of Santa Catarina, Brazil, with five deaths, most involving men resident in urban areas (DIVE, 2019DIVE, Diretoria de Vigilância Epidemiológica. 2019. Available from: <Available from: http://www.dive.sc.gov.br >. Accessed: May, 30, 2019.
http://www.dive.sc.gov.br...
).

The seroprevalence of leptospirosis in horses varies considerably depending on the geographic location, risk factors, and studies serovars (CASELANI et al., 2012CASELANI, K. et al. Leptospirosis seroepidemiological study in horses used for urban traction. Revista do Instituto Adolfo Lutz, v.71, n.3, p.582-587, 2012. Available from: <Available from: http://periodicos.ses.sp.bvs.br/pdf/rial/v71n3/v71n3a20.pdf >. Accessed: May, 17, 2015.
http://periodicos.ses.sp.bvs.br/pdf/rial...
; LASTA et al., 2013LASTA, C. S. et al. Pesquisa de aglutininas anti-Leptospira em soros de equinos de tração em Porto Alegre, Brasil. Revista Brasileira de Ciência Veterinária, v.20, n.1, p.23-25, 2013. Available from: <Available from: https://www.ufrgs.br/lacvet/site/wp-content/uploads/2013/05/lasta_carroceiros-lepto.pdf >. Accessed: Nov. 06, 2018.
https://www.ufrgs.br/lacvet/site/wp-cont...
; FINGER et al., 2014FINGER, M. A. et al. Serological and molecular survey of Leptospira spp. among cart horses from an endemic area of human leptospirosis in Curitiba, southern Brazil. Revista do Instituto de Medicina Tropical de São Paulo, v.56, p.473-476, 2014. Available from: <Available from: http://www.scielo.br/scielo.php?pid=S003646652014000600473&script=sci_abstract >. Accessed: Nov. 11, 2018. doi: 10.1590/S0036-46652014000600003.
http://www.scielo.br/scielo.php?pid=S003...
). The prevalence and serovars involved depend on the reservoirs present (PETRAKOVSKY et al., 2014PETRAKOVSKY, J. et al. Animal leptospirosis in Latin America and the Caribbean countries: reported outbreaks and literature review (2002-2014). International Journal Environmental Research and Public Health, v.11, n.10, p.10770-89, 2014. Available from: <Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4211005/ >. Accessed: Feb. 07, 2019. doi: 10.3390/ijerph111010770.
https://www.ncbi.nlm.nih.gov/pmc/article...
) since they might undergo regional variations, which undoubtedly contributes to the difference between the data on prevalence between countries or regions (LOUREIRO et al., 2013LOUREIRO, A. P. et al. Leptospirosis in horses. Veterinay Record, v.172, n.18, p.479-80, 2013. Available from: <Available from: https://veterinaryrecord.bmj.com/content/172/18/479.3 >. Accessed: Jun. 06, 2015. doi: 10.1136/vr.f2824.
https://veterinaryrecord.bmj.com/content...
).

The primary control strategy for leptospirosis in all endemic regions is diagnosis followed by vaccination of the animals. However, serogroup-specific immunity, the diversity of serovars, and the absence of seroepidemiological data from endemic areas represent a challenge for defining vaccinal antigens (MARTINS et al., 2017MARTINS, M. et al. Humoral response in naturally exposed horses after leptospiral vaccination. Journal of Equine Veterinary Science, v.57, p.5, 2017. Available from: <Available from: https://www.sciencedirect.com/science/article/abs/pii/S0737080617301119 >. Accessed: Nov. 08, 2018. doi: 10.1016/j.jevs.2017.06.005.
https://www.sciencedirect.com/science/ar...
).

In this context, the knowledge on prevalent serovars is essential to understand the epidemiology of the disease, allowing the discovery of new carriers and possible reservoirs, and aid in defining vaccinal antigens to be used in the immunoprophylaxis strategies (ALVES et al., 2016ALVES, J. R. A. et al. Epidemiological characterization of leptospirosis in horses in the state of Pernambuco, northeastern Brazil. Arquivos do Instituto Biológico, v.83, p.1-5, 2016. Available from: <Available from: http://www.scielo.br/pdf/aib/v83/1808-1657-aib-83-e1032014.pdf >. Accessed: May, 04, 2019. doi: 10.1590/1808-1657001032014.
http://www.scielo.br/pdf/aib/v83/1808-16...
; VIEIRA et al., 2018VIEIRA, A. S. et al. A systematic review of leptospirosis on wild animals in Latin America. Tropical Animal Health Production, v.50, n.2, p.229-238, 2018. Available from: <Available from: https://link.springer.com/article/10.1007%2Fs11250-017-1429-y >. Accessed: Nov. 22, 2018. doi: 10.1007/s11250-017-1429-y.
https://link.springer.com/article/10.100...
). In Santa Catarina, there haven’t yet been any studies on the prevalence of leptospirosis in horses, making it difficult to update the vaccinal strains to be used in infection control programs. Therefore, this study aimed to evaluate the presence of anti-L. interrogans antibodies in serum samples of unvaccinated horses, identify the primary serogroups circulating in the Serra Catarinense region and investigate the possible risk factors associated with the infection.

MATERIALS AND METHODS:

Animals and samples

The total number of horses in the State of Santa Catarina is of approximately 112,766, 32,451 (28.77%) located in the Serra Catarinense region (IBGE, 2017IBGE. Instituto Brasileiro de Geografia e Estatística. 2017. Available from: <Available from: https://www.ibge.gov.br >. Accessed: May, 15, 2019.
https://www.ibge.gov.br...
) and with 3,314 properties registered in the official organ (CIDASC). We estimated the sampling according to the methodology proposed by THRUSFIELD (1997THRUSFIELD, M. Statistics in epidemiology: methods, techniques, and applications. Preventive Veterinary Medicine, v.32, n.1-2, p.149-151, 1997.). The calculation was done using the Epi Info statistical package, version 7.1.5. (CDC, 2015), based on the estimation of the horse herd of the Serra Catarinense region (n=32.451) for an expected prevalence of P<5%, based on preliminary regional studies on the population of unvaccinated animals.

For this study, we evaluated 207 serum samples from unvaccinated horses with no clinical signs or history of the disease from 26 herds of the Serra Catarinense region. The herds used originated from collaborating owners from different areas, with samples of at most ten animals from each property. The samplings occurred from November of 2017 to March of 2018. We collected the blood samples through venipuncture of the jugular vein using vacuum tubes with no anticoagulant, maintaining the samples under refrigeration at 10 ºC. We subsequently centrifuged the samples, dividing them into serum aliquots and freezing them at -20 ºC until analysis.

Serological test

We assessed the samples for the presence of anti-Leptospira spp. antibodies through a microscopic agglutination test (MAT) using live antigens cultivated in liquid medium (EMJH), according to OIE (2015)OIE. Dourine. In: Manual of Diagnostic Tests and Vaccines for Terrestrial Animals 2015. 2015. ed. [s.l.] OIE, 2015. p. 500.. We obtained a panel of antigens with 14 serogroups (18 reference serovars) from the Laboratory of Veterinary Microbiology of the Universidade Federal Fluminense (UFF/RJ). The panel consisted of serogroups (serovars) Australis (Bratislava, Australis), Autumnalis (Autumnalis), Cynopteri (Cynopteri), Bataviae (Bataviae), Canicola (Canicola), Grippotyphosa (Grippotyphosa), Panama (Panama), Icterohaemorrhagiae (Copenhageni, Icterohaemorrhagiae), Lousiana (Lousiana), Pomona (Pomona), Sejroe (Guaricura, Hardjobovis; Wolffi), Pyrogenes (Pyrogenes), Tarassovi (Tarassovi), and Ballum (Castellonis).

In summary, we added the antigenic suspension of live leptospires obtained from the respective serovars to serum diluted in series and incubated. The agglutination was examined using dark field microscopy (100 ×). We estimated the titers to be the highest serum dilution that agglutinated at least 50% of leptospires. We considered animals with a titre ≥100 as seroreagent. MAT was performed at the Laboratory of Animal Infectious Diseases of the Universidade Federal de Santa Catarina - UFSC, Curitibanos/SC.

Epidemiological data

We obtained the epidemiological data through a questionnaire applied to horse owners including information on the herd and possible risk factors associated with infection by Leptospira spp., such as animal breed, sex, rearing place (urban/rural), rearing system (extensive/semi-intensive/intensive), presence of rodents (yes/no), contact with wild animals (yes/no), contact with capybaras (Hydrochoerus hydrochaeris) (yes/no), contact with wild boars (yes/no), contact with cattle (yes/no), contact with sheep (yes/no), contact with pigs (yes/no), contact with dogs (yes/no), history of reproductive problems, uveitis or clinical disease diagnosed, or suspected of leptospirosis (yes/no), vaccination against leptospirosis (yes/no).

Statistical analysis

We recorded and analyzed the data generated by the interviews (independent variables) and the MAT (response variable) using the SAS statistical package (version 9.3, SAS Institute Inc., Cary, NC). Subsequently, we used descriptive statistics on all independent variables applied to the individual and tracked based on the response variable (positive or negative MAT). To estimate the risk of infection associated with the independent variables (qualitative variables), we used the logistic regression model (HOSMER & LEMESHOW, 1989HOSMER, D. W.; LEMESHOW, S. Applied Logistic Regression. New York: John Wiley & Sons, 1989.) and multiple analysis. We presented the values for p and considered them statistically significant when P<0.05.

RESULTS:

The data from this study showed that 80% (21/26) of the studied herds were positive (with at least one seropositive animal) for infection by Leptospira spp. Although, previous regional studies by the present working group indicated an estimated prevalence of leptospirosis of 5% (unpublished data), the detailed study of this population revealed that 45.4% (94/207) of the horses were seropositive for Leptospira spp. The serogroups most frequently diagnosed MAT were Australis (Bratislava) 16.9% (35/207), Icterohaemorrhagiae (Icterohaemorrhagiae and Copenhageni) 14.4% (30/207), Grippotyphosa (Grippotyphosa) 5.31% (11/207), Sejroe (Hardjobovis and Guaricura) 3.8% (8/207), Ballum (Castellonis) 3.4% (7/207), Autumnalis (Autumnalis) 2.4% (5/207) Canicola (Canicola ) 1.4% (3/207), Pomona (Pomona) 0.9% (2/207), and Tarassovi (Tarassovi) 0.5% (1/207), with titrations ranging from 100 (232 - 100%), 200 (45 - 19.40%) to 400 (4 - 1.72%) (Figure 1).

Figure 1
Prevalence of Leptospira spp. in horses of the Serra Catarinense region in the State of Santa Catarina, Brazil. Samples of horse serum (n=207) collected from November of 2017 to March of 2018 and tested for 14 Leptospira spp. serogroups.

The logistic regression analysis showed an association between seropositivity for Leptospira spp. and qualitative variables, such as extensive rearing system (OR = 1.27; P<0.05), history of abortions or other clinical forms (OR = 2.56; P<0.01), and the presence of cattle (OR = 3.85; P<0.01) and capybaras (OR = 2.56; P = 0.06) (Table 1). When evaluating specific serovars, there was an association between the presence of capybaras (OR = 14.0; P<0.001) and pigs (OR = 21.76; P<0.001) with seropositivity to Australis (Bratislava). In animals seropositive to Icterohaemorrhagiae (Copenhageni and Icterohaemorrhagiae) there was an association with the history of abortion or other clinical forms (OR = 31.11, P<0.001) and the presence of sheep (OR = 9.28, P<0.001) (Table 1).

Table 1
Risk factors associated with infection by Leptospira spp. in horses of the Serra Catarinense region I the state of Santa Catarina, Brazil. Samples of horse serum (n=207) collected from November of 2017 to March of 2018. The odds ratio (OR) and interval of confidence (IC) values are presented for horses with positive serology for Leptospira spp. and infection by the Australis or Icterohaemorrhagiae serogroups.

DISCUSSION:

The data of this study showed 45.4% (94/207) of seropositivity of the horses tested for Leptospira spp., 80% (21/26) of the evaluated herds had at least one seropositive animal (titer ≥100). Considering that the samples were obtained from urban and rural properties, and equestrian leisure activities increasingly involve humans of different age groups (MENY et al., 2019MENY, P. et al. Seroprevalence of leptospirosis in human groups at risk due to environmental, labor or social conditions. Revista Argentina de Microbiologia, p.0-10, 2019. Available from: <Available from: https://www.researchgate.net/publication/332309260_Seroprevalence_of_leptospirosis_in_human_groups_at_risk_due_to_environmental_labor_or_social_conditions >. Accessed: May, 06, 2019. doi: 10.1016/j.ram.2019.01.005.
https://www.researchgate.net/publication...
), these data showed that leptospirosis is a neglected zoonosis due to the absence of specific control programs.

Other studies conducted in Brazil have shown substantial differences in the prevalence of serovars according to the geographic region (FINGER et al., 2014FINGER, M. A. et al. Serological and molecular survey of Leptospira spp. among cart horses from an endemic area of human leptospirosis in Curitiba, southern Brazil. Revista do Instituto de Medicina Tropical de São Paulo, v.56, p.473-476, 2014. Available from: <Available from: http://www.scielo.br/scielo.php?pid=S003646652014000600473&script=sci_abstract >. Accessed: Nov. 11, 2018. doi: 10.1590/S0036-46652014000600003.
http://www.scielo.br/scielo.php?pid=S003...
; OLIVEIRA FILHO et al., 2014OLIVEIRA FILHO, R. B. et al. Spatial characterization of Leptospira spp. infection in equids from the Brejo Paraibano micro-region in Brazil. Geospatial Health, v.8, n.2, p.463-9, 2014. Available from: <Available from: https://geospatialhealth.net/index.php/gh/article/view/35 >. Accessed: Dec. 05, 2018. doi: 10.4081/gh.2014.35.
https://geospatialhealth.net/index.php/g...
; ALVES et al., 2016ALVES, J. R. A. et al. Epidemiological characterization of leptospirosis in horses in the state of Pernambuco, northeastern Brazil. Arquivos do Instituto Biológico, v.83, p.1-5, 2016. Available from: <Available from: http://www.scielo.br/pdf/aib/v83/1808-1657-aib-83-e1032014.pdf >. Accessed: May, 04, 2019. doi: 10.1590/1808-1657001032014.
http://www.scielo.br/pdf/aib/v83/1808-16...
). According to FINGER et al. (2014), the most prevalent serogroup in the region of Curitiba (southern Brazil) was Icterohaemorrhagiae. OLIVEIRA FILHO et al. (2014) observed a higher prevalence of the serogroup Panama in the Paraíba region (Northeast Brazil) when they evaluated horses used in the study.

The most frequent serogroups diagnosed in the present study were Australis 16.9% (35/207), Icterohaemorrhagiae 14.4% (30/207), and Grippotyphosa 5.31% (11/207). The diversity of circulating serovars directly impacts vaccination programs since most commercial vaccines do not include all serogroups to which animals are exposed. Commercial vaccines included only the serogroups most frequently diagnosed, coinciding with those with the highest prevalence reported in the present study. However, when comparing the serogroups reported with those present in a complete commercial vaccine, indicated for Equidae, we found that it does not include serogroups Sejroe, Autumnalis, and Castellonis.

We also demonstrated in this study that horses reared extensively (OR = 1.27; p <0.05) and in contact with cattle (OR = 3.85; p <0.01) are more likely to have seropositivity for leptospirosis. ELLIS (2015ELLIS, W. A. Animal leptospirosis. Current Topics Microbiology Immunology, v.387, p.99-137, 2015. Available from: <Available from: https://link.springer.com/chapter/10.1007/978-3-662-45059-8_6 >. Accessed: Apr. 03, 2019. doi: 10.1007/978-3-662-45059-8_6.
https://link.springer.com/chapter/10.100...
) reported that cattle are considered the primary hosts of serovars Hardjo, Pomona, and Grippotyphosa, representing a reservoir and potential risk factor for infection of other animal species, such as sheep and horses that often cohabit in the same environments (COUSINS et al., 1989COUSINS, D. V. et al. Evidence for sheep as a maintenance host for Leptospira interrogans serovar hardjo. Veterinary Record, v.124, n.5, p.123-4, 1989.; SILVA et al., 2007SILVA, E. F. et al. Isolation of Leptospira noguchii from sheep. Veterinary Microbiology, v.121, n.1-2, p.144-9, 2007. Available from: <Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1868676/ >. Accessed: Jul. 04, 2018. doi: 10.1016/j.vetmic.2006.11.010.
https://www.ncbi.nlm.nih.gov/pmc/article...
).

Despite considering leptospirosis as subclinical in horses (HAMOND et al., 2012HAMOND, C. et al. Subclinical leptospirosis may impair athletic performance in racing horses. Tropical Animal Health Production, v.44, n.8, p.1927-30, 2012. Available from: <Available from: https://link.springer.com/article/10.1007%2Fs11250-012-0158-5 >. Accessed: Nov. 06, 2018. doi: 10.1007/s11250-012-0158-5.
https://link.springer.com/article/10.100...
), the data in this study showed that there is a higher risk of infection (OR = 2.56; p <0.01) in properties with a history of clinical signs of the disease, such as abortion, the birth of weak foals, and repetition of heat, especially when considering the serogroup Icterohaemorrhagiae (OR = 9.28; p <0.001). PINNA et al. (2014PINNA, A. et al. Potential differences between Leptospira serovars, host-adapted (Bratislava) and incidental (Copenhageni), in determining reproductive disorders in embryo transfer recipient mares in Brazil. Veterinary Record, v.24, p.1-4, 2014. Available from: <Available from: https://veterinaryrecord.bmj.com/content/174/21/531.long >. Accessed: Jul. 20, 2017. doi: 10.1136/vr.101444.
https://veterinaryrecord.bmj.com/content...
) also observed a higher risk of infection for seropositive animals to serogroups Icterohaemorrhagiae and Australis in a study conducted in horses with a history of reproductive problems.

PETRAKOVSKY et al. (2014PETRAKOVSKY, J. et al. Animal leptospirosis in Latin America and the Caribbean countries: reported outbreaks and literature review (2002-2014). International Journal Environmental Research and Public Health, v.11, n.10, p.10770-89, 2014. Available from: <Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4211005/ >. Accessed: Feb. 07, 2019. doi: 10.3390/ijerph111010770.
https://www.ncbi.nlm.nih.gov/pmc/article...
) reported that a wider variety of serogroups circulating in a region is associated with a more diverse fauna when compared to an area with few animal hosts. In this study, we found animals reagent to a wide variety of serogroups such as Australis, Icterohaemorrhagiae, Grippotyphosa, Sejroe, Ballum, Autumnalis, Canicola, Pomona, and Tarassovi, suggesting that there are several species potentially reservoirs to Leptospira spp. in the region.

The results reported in this study showed a higher risk of the disease in horses in contact with capybaras (OR = 2.07; p = 0.06). Despite the many species of wild animals acting as reservoirs for leptospires, their role as a source of infection for animals and humans is still unclear (VIEIRA et al., 2018VIEIRA, A. S. et al. A systematic review of leptospirosis on wild animals in Latin America. Tropical Animal Health Production, v.50, n.2, p.229-238, 2018. Available from: <Available from: https://link.springer.com/article/10.1007%2Fs11250-017-1429-y >. Accessed: Nov. 22, 2018. doi: 10.1007/s11250-017-1429-y.
https://link.springer.com/article/10.100...
). The capybaras in the Serra Catarinense region have intense proliferation due to low predation, found even in an urban area. In Brazil, capybaras are also studied as reservoirs to leptospires, having already been identified as seroreagent to different serovars, such as Icterohaemorrhagiae, Copenhageni, Pomona, Castellonis, Grippotyphosa, Hardjo, Canicola, and Bratislava (LANGONI et al., 2016LANGONI, H. et al. Anti-leptospirosis agglutinins in Brazilian capybaras (hydrochoerus hydrochaeris). Journal of Venomous Animals and Toxins Including Tropical Diseases, v.22, p.4, 2016. Available from: <Available from: http://www.scielo.br/scielo.php?pid=S1678-91992016000100304&script=sci_abstract >. Accessed: Nov. 06, 2018. doi: 10.1186/s40409-016-0059-6.
http://www.scielo.br/scielo.php?pid=S167...
).

Results of this study showed that contact with pigs (OR = 21.76; p <0.001) and sheep (OR = 9.28; p <0.001) increased the chance of seroreagent horses by representatives of the Australis and Icterohaemorrhagiae serogroup, respectively. According to PINTO et al. (2016PINTO, P. S. et al. A systematic review of leptospirosis on dogs, pigs, and horses in Latin America. Tropical Anim Health Production, v.49, n.2, p.231-238, 2016. Available from: <Available from: https://link.springer.com/article/10.1007%2Fs11250-016-1201-8 >. Accessed: May, 06, 2019. doi: 10.1007/s11250-016-1201-8.
https://link.springer.com/article/10.100...
), the Bratislava serovar (Australis serogroup) is considered adapted and maintained by horses and pigs, allowing the determination of reproductive alterations, or present as subclinical. Sheep, in turn, can act as maintenance or accidental hosts, depending on the region and rearing conditions, mainly for serovars Hardjo, Autumnalis, lcterohaemorrhagiae, and Pomona; and consequently, representing a source of infection to cattle and horses (MELO et al., 2010MELO, L. S. S. et al. Main aspects of Leptospira sp infection in sheep. Ciência Rural, v.40, n.5, p.1235-1241, 2010. Available from: <Available from: http://www.scielo.br/pdf/cr/v40n5/a569cr2881.pdf >. Accessed: Jul. 04, 2019.
http://www.scielo.br/pdf/cr/v40n5/a569cr...
).

We did not include the presence of rodents (rats, mice) and dogs as risk factors in the analysis because they are present in all properties. In the case of dogs, PINTO et al. (2016PINTO, P. S. et al. A systematic review of leptospirosis on dogs, pigs, and horses in Latin America. Tropical Anim Health Production, v.49, n.2, p.231-238, 2016. Available from: <Available from: https://link.springer.com/article/10.1007%2Fs11250-016-1201-8 >. Accessed: May, 06, 2019. doi: 10.1007/s11250-016-1201-8.
https://link.springer.com/article/10.100...
) identified that the most frequent serovars are Canicola and lcterohaemorrhagiae; and therefore, may represent a possible agent reservoir for horses and humans both in urban and rural areas. Rodents should always be considered in the transmission chain since they represent an important reservoir for different Leptospira spp. in nature, especially for serogroups lcterohaemorrhagiae and Ballum (FAISAL et al., 2012FAISAL, S. M. et al. Leptospira: invasion, pathogenesis and persistence. In: ME, E. (Ed.). The pathogenic spirochetes: strategies for evasion of host immunity and persistence. New York, NY: Springer Science, p.143-172, 2012. Available from: <Available from: https://www.springer.com/gp/book/9781461454038 >. Accessed: May, 04, 2019. doi: 10.1007/978-1-4614-5404-5_8.
https://www.springer.com/gp/book/9781461...
; HOUWERS et al., 2011HOUWERS, D. J. et al. Agglutinating antibodies against pathogenic Leptospira in healthy dogs and horses indicate common exposure and regular occurrence of subclinical infections. Veterinary Microbiology, v.148, n.2-4, p.449-51, 2011. Available from: <Available from: https://www.sciencedirect.com/science/article/pii/S0378113510004074?via%3Dihub >. Accessed: Nov. 18, 2018. doi: 10.1016/j.vetmic.2010.08.020.
https://www.sciencedirect.com/science/ar...
).

CONCLUSION:

The findings presented in this study showed a high frequency of horses reagent to Leptospira spp. in the Serra Catarinense region, revealing the need for emergency vigilance measures to control this important zoonosis in horse herds. Furthermore, the presence of different animal species occupying the same spaces suggests the environment as a determining factor in the infection epizootiology and variability of circulating serovars. The research also highlighted the need for new studies focusing on updating the vaccinal strains commercially used, given that most do not contemplate all serovars circulating in all regions.

ACKNOWLEDGMENTS

This study was supported by the Fundação de Amparo à Pesquisa e Inovação do Estado de Santa Catarina (FAPESC), infrastructure support project for Universidade do Estado de Santa Catarina (UDESC) research groups, grants number 2017TR640 and for granting a scholarship for Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).

REFERENCES

  • CR-2019-0483.R1

BIOETHICS AND BIOSECURITY COMMITTEE APPROVAL

  • This research follows the norms issued by the National Council on Animal Experimentation Control (CONCEA) and was previously approved by the Ethics Commission on Animal Use by the Universidade do Estado de Santa Catarina (CEUA/UDESC), with CEUA protocol nº 4299250816.

Publication Dates

  • Publication in this collection
    18 May 2020
  • Date of issue
    2020

History

  • Received
    27 June 2019
  • Accepted
    01 Apr 2020
  • Reviewed
    29 Apr 2020
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