Occurrence of serological reactions for serogroup Sejroe (CTG and Prajtino) in female buffalo in the state of Pernambuco, Brazil

Seroprevalence and risk factors associated with the presence of bovine leptospirosis in the municipality of Sotaquirá, Colombia

Background

Bovine leptospirosis is a zoonotic, infectious, and cosmopolitan disease of worldwide distribution, caused by the spirochete Leptospira spp., which has been diagnosed in humans; domestic mammals, such as dogs, sheep, goats, swine, horses and cattle; and wild animals. It is considered a significant cause of economic losses in livestock because it causes infertility, abortion and reduced milk production.

Aim

To establish the prevalence and the main risk factors associated with Leptospira spp. in cattle in the municipality of Sotaquirá, Colombia.

Methods

An observational, descriptive, cross-sectional study with simple random sampling was carried out. 1,000 cattle of Ayrshire, Holstein, Jersey, Normande, Zebu, and crossbreeds were sampled. Blood samples were taken by coccygeal venipuncture and processed by microscopic agglutination technique; animals were considered positive when titers were ≥1:100. The data obtained were processed with the statistical program EpiInfo®.

Results

A general apparent prevalence (AP) of 16% (160/1,000) was established, where the crossbreeds (20.5% AP), the 2-4 years age group (17% AP), and the serovars Leptospira interrogans serogroup Pomona (5.1%) and L. interrogans serogroup Sjroe serovar Hardjo (3.4%) presented the highest seropositivity. The variables barnyard, artificial insemination, and use of certified semen were identified as protective factors against the disease, while diarrhea was considered a risk factor.

Conclusion

The prevalence in this study is within the range of those reported at the national level; however, it is essential to establish plans to control and prevent the disease.

Genetic basis underlying the serological affinity of leptospiral serovars from serogroups Sejroe, Mini and Hebdomadis

Leptospirosis is a widely distributed zoonosis caused by pathogenic strains of bacteria of the genus Leptospira (Phylum Spirochaetes). Its agents are commonly classified based on their antigenic characteristics into serogroups and serovars, which are relevant for epidemiologic studies and vaccine development. Serological tests are considered laborious and require a specialized infrastructure. Some molecular methods have been proposed to accelerate these procedures, but they still can not replace the immunological tests, thus requiring a further understanding of the genetic basis underlying the serological classification. In this work, we focused on elucidating the genetic factors determinant for the serogroup Sejroe, which is one of the most prevalent serogroups in livestock. For this, we conducted a comparative analysis using >700 leptospiral genomic samples available in the public database. The analysis showed that the genes comprising the rfb locus are the main genetic factors associated with the serological classification. Samples from the serogroup Sejroe have an rfb locus with a conserved gene composition that differs from most other serogroups. Hebdomadis and Mini were the only serogroups whose samples have an rfb locus with similar gene composition to those from serogroup Sejroe, corroborating with the serological affinity shared by them. Finally, we could determine a small region in the rfb locus in which each of those three serogroups can be distinguished by its gene composition. This is the first work that uses an extensive repertoire of genomic data of leptospiral samples to elucidate the molecular basis of the serological classification and open the road to more reliable strategies based on molecular methods for serodiagnosis.

Prevalence of Leptospira serogroups in buffaloes from the Brazilian Amazon

Although Brazil has one of the largest buffalo populations in the Americas, buffalo leptospirosis is still poorly explored when compared to that in bovines; thus, the aim of this research was to carry out a large serological study for leptospirosis in this species in the Brazilian Amazon. For this, we collected 1,405 serum samples from buffaloes raised in the Amazon delta region, which is considered a major area of buffalo production in Brazil. The test used was a microscopic agglutination test (MAT) adopting 34 Leptospira antigens, some of which have never been tested for buffaloes in Brazil, including autochthonous strains; in total, 20 serogroups were evaluated. From the total of 1,405 serum samples, 894 (63.6%) reacted in the MAT to at least one of the 20 serogroups, and 511 (36.4%) did not react. The serogroups Sejroe, Autumnalis and Pomona were the most prevalent, with titres ranging from 100 to 12,800, and the autochthonous strains used were not significant in relation to the reference serovars. Leptospirosis in buffaloes seems to have a serological profile similar to leptospirosis in cattle, mainly due to the prevalence of the Sejroe serogroup; however, the results of this study suggested that in the Brazilian Amazon, Leptospira strains that are serologically distinct from the autochthonous strains isolated in the southeastern region of Brazil may be circulating in these animals. Other serovars could also be inserted into the panel of antigens used in MAT for serological studies on buffaloes.