Detection of Leishmania infantum in dogs by PCR with lymph node aspirates and blood

The PCR technique was applied to the diagnosis of leishmaniasis in dogs, bo th serologically negative and positive. DNA was taken from lymph node aspir ates and blood. The primers 13a and 13b, derived from Leishmania amazonies and Leishmania braziliensis kinetoplast DNA (kDNA), also amplified Leishman ia infantum IPT1 constant region of minicircle kDNA. The amplified fragment is 116 bp long. It was cloned and the sequence was determined. A 70-bp inn er fragment was designed and used as a probe in dot blot hybridization, A g roup of 124 dogs was examined, 37 of which showed typical symptoms of disea se. PCR was performed on 124 blood samples and 52 lymph node aspirates. Usi ng microscopic examination as the "gold standard," we calculated sensitivit y, specificity, and positive and negative predictive values of 100% using l ymph node aspirates and values of 85, 80, 95, and 57%, respectively, using blood samples. We found that 40% of the animals without lesions and 38% of the animals with clinical signs gave false-negative results by indirect imm unofluorescence antibody testing. These animals could contribute to the spr eading of infection among dogs, and represent a potential risk for human he alth as well.