Leptospira PCR

Leptospira PCR

Species: Ovine, cervine, bovine, caprine, llamoid, canine, equine, porcine

Specimen: Whole blood, urine

Container: EDTA tube, sterile pottle 

Collection protocol: Venepuncture, mid-stream urine or cystocentesis

Special handling/shipping requirements:  Double bagged in a leak proof container as this is a zoonotic disease and can be spread to humans through breaks in the skin

General information about the disease:

:  Leptospirosis is a zoonosis caused by one of the many pathogenic serotypes of the genus Leptospira, a spirochete that is transmitted by direct contact of abraded skin or mucous membranes with urine or tissues of an infected animal or, more commonly, by indirect contact with mud or water contaminated by urine of infected animals. Rodents are the most common carrier of Leptospira. Most mammals are considered as carriers of the bacteria but the most commonly encountered domestic animal carriers are pigs and cattle.

The bacteria are spread through the urine of infected animals due to a chronic infection of the renal tubules. The clinical signs of infection can be influenced by factors such as inoculation dose, immune status and age of the animal. Severity ranges from the inapparent to severe. Some of the clinical signs associated with acute disease include high fever, jaundice, haemoglobinuria, pulmonary congestion and death. The clinical signs most associated with chronic infections tend to be infertility and reproductive failure. Agalactia can be associated with clinical signs of the disease, particularly in dairy cattle.

General information about when this test is indicated:

PCR allows rapid specific and sensitive diagnosis of clinical leptospirosis. The assay can detect DNA from as few as 1-10 organisms per ml of urine sample. Using PCR, it is possible to quantify the amount of template and therefore the number of target organisms. The PCR test also paves the way for screening of sub-clinical shedders of the organism in situations where there is a significant health and safety risk, e.g. dairy sheds, piggeries, sheep farms and abattoirs. Currently PCR is unable to identify the infecting serovar.

Comparison with other related tests:

PCR has a very high positive and negative predictive value but only determines if pathogenic leptospires are present or not. Confirmation of the serotype requires blood sampling of surviving and/or contact animals. Confirmatory tests include serologic testing such as MAT to detect antibody production to leptospira. Very high antibody titres are suggestive of infection, but paired serum titres produce more reliable prognostic information. Direct detection of the bacterium may be done by culture of urine or blood culture, identification of leptospiral DNA, fluorescent antibody staining of urine, or urine dark-field microscopy. Culture of Leptospira spp. can be difficult and time-consuming. Early in the course of infection, PCR tests on the blood and slightly later the urine will be positive but at this time antibody titres will be negative. Antibody takes a week to ten days to start to develop and then longer for high diagnostic titres to occur. Where late in the course of the disease, urine can be PCR negative while the animal will be antibody positive. The time taken for development of antibody titres varies depending on innate factors within the individual animal, infective dose, infective organisms, etc. To detect animals shedding Leptospires submit urine samples. An EDTA blood sample from an acutely infected animal may identify Leptospiraemic animals. Body fluids from aborted fetuses can be submitted where leptospirosis is suspected.