Development of a dipstick test for the diagnosis of animal leptospirosis

Abstract

Leptospirosis is an infectious bacterial disease of acute or chronic course, caused by spirochetes of the genus Leptospira of zoonotic and cosmopolitan character that affects humans and domestic and wild animals. It can be directly transmitted by contact with fluids (blood or urine) containing leptospires, through placenta, hematogenous, genital routes and breast feeding; or indirectly by contact with an environment contaminated with leptospires which were originated from the urine of sick, convalescent or infected animals. The acknowledgement of the infection severity, geographic distribution, involved risk factors and the circulating strains is of extreme importance to the goal of establishing the regional epidemiology of this disease and the improvement of preventive measures. The information about leptospirosis epidemiology has its roots on the results obtained by serological reaction Microscopic Agglutination Test (MAT), proof of reference recommended by the World Health Organization. However, the incoherences and limitations of this diagnostic technique are evident. Although MAT establishes some degree of serogroup / serovar specificity involved, this test has the disadvantage of being very sensitive when concerning time and the high concentration of antibodies needed for issuing the signal. Moreover and at various occasions, this test is not discriminatory of previous and active infection or vaccine reaction. Therefore, serology does not necessarily reflect the state of the leptospires carrier or disposer. Other methods such as PCR have also been used to enhance the early diagnosis of the disease. However, acquiring the information about the involved leptospira infecting strain through PCR is impossible, and such data is of epidemiological importance to the identification of the reservoirs. Although the bacterial isolation is a definitive diagnosis of the disease, this method has low sensitivity, requiring newly harvested samples to be observed for a minimum period of 30 days. Thus, the development of simpler, faster and more efficient diagnostic methods becomes increasingly more necessary. In this work, we intend to evaluate the use of recombinant proteins of Leptospira spp. as antigens in the development of a rapid immunochromatographic assay based on the type dipstick as a possible diagnostic tool for leptospirosis. (AU)