Use of the c-terminal coding region of Ligb for the molecular diagnosis (Ligbct PCR) of bovine leptospirosis in serum

Abstract

Argentina is an endemic country with epidemic outbreaks of leptospirosis. In lives tock, reproductive failures are knowing. A recent study considers that Leptospira is the second most common abortigenic pathogen and is responsible for more than US$ 7 million of losses in the cattle and dairy industry, respectively (1). In this context, it is essential to have sensitive and specific tools in order to effectively control the disease the spread. Molecular tools are widely used in different biological samples In this work, LigBct PCR which amplifies a 756 bp region of the C-terminal end of the conserved LigB protein (2) (ligbct) was used to detect leptospiral DNA in bovine serum. We used 134 bovine sera from the Leptospirosis Laboratory of INTA Castelar (OMSA Reference Laboratory) which arrived with a suspected diagnosis of Leptospirosis. All sera were classified by MAT (Microagglutination Test) as positive (n: 89) or non-de tectable ND (n: 45) with a cut-off point equal to 1/200. LigBct PCR was performed according to the protocol standardized by Saraullo et al (3). LigBct PCR was able to detect leptospiral DNA in 78.65% of positive sera, and in 42.22% of sera classified as ND by MAT. In the face of positive titers by MAT, remanent leptospiral DNA in the bloodstream can still be detected by LigBct PCR. However, leptospiral DNA was also detected in 42.22% of samples where antibodies were ND by MAT. High MAT titers infer infection as opposed to lower titers or ND, often without visible symptomato logy. Animals may not present symptoms compatible with leptospirosis, have low or undetectable titers with TMA, but be carriers and disseminate the bacteria through urine infecting the environment, other animals, and humans; therefore, the present technique could be serve to detect carrier animals. It is considered that LigBct PCR could be a complementary tool to detect leptospiral DNA in serum. The development of new diagnostic methods is of utmost importance in order to carry out an ade quate diagnosis of leptospirosis in Argentina and thus contribute to the reduction of the great economic losses associated with this important zoonotic disease.