Dear Sir:
We read with interest the study reported by Ayral and others1 entitled “Distribution of Leptospira serogroups in cattle herds and dogs in France.” Ayral and others1 concluded that the inventory of infecting Leptospira serogroups revealed that current vaccines in France are not fully capable of preventing leptospirosis. In total, 394 cattle were diagnosed with clinical leptospirosis, and the results suggested infection by serogroups Australis (43%), Sejroe (33%), and Grippotyphosa (17%).
We share our experience with bovine leptospirosis in Brazil and compare it with the scenario described in France. Infected cattle are commonly asymptomatic and may shed the bacterium in urine for long periods.2 Serology by microscopic agglutination test (MAT) is recommended as the primary diagnostic tool, although it is considered reliable only at the serogroup level.3 Although useful for a diagnosis at the herd level, serology is not adequate for the individual detection of carriers,4 which may impair control programs.5 For individuals, a rapid, sensitive, and reliable diagnostic tool, such as polymerase chain reaction (PCR), is required.
In a study conducted by our group in 2013, 208 cows were randomly selected in a slaughterhouse located close to Rio de Janeiro, Brazil. After clinical pre-slaughter examination, the animals were considered free of signs of leptospirosis. Blood samples (208) for serology (MAT)3 and urine samples (199) from direct puncture of the bladder for PCR-lipL325 and culture were obtained. Serology showed that 77 of 208 (37%) animals were reactive, with serogroup Sejroe by far the most frequent (62.3%) followed by Javanica (7.8%), Icterohaemorrhagiae (6.5%), Grippotyphosa (3.9%), and Tarassovi (3.9%). Urine PCR showed that 67 of 199 animals (33.6%) were positive. Additionally, 10 isolates were obtained in pure culture, including serogroups Sejroe, Shermani, and Grippotyphosa with 2 isolates each and Sarmin, Tarassovi, Autumnalis, and Panama with 1 isolate each. These results showed a high rate of asymptomatic shedding in cows. Members of serogroups Grippotyphosa, Autumnalis, and Panama are usually associated with environmental contamination and maintained by wildlife species. Serogroup Sejroe is the most common in ruminants worldwide as well as in Brazil.6 Serogroups Sarmin, Shermani, and Tarassovi have never previously been reported from cattle in Brazil and may have been neglected as agents of bovine leptospirosis.
Serogroup distribution differed between Brazil and France. In our study, both seronegative and seroreactive cows were shedding leptospires. Therefore, the direct detection of leptospires in urine by culturing or PCR is an important tool for the success of control programs in cattle. Additionally, an active surveillance approach should also include asymptomatic animals, because they may shed the bacterium to the environment and consequently, play an important role in the epidemiology of leptospirosis.
- 1.↑
Ayral FC, Bicout DJ, Pereira H, Artois M, Kodjo A, 2014. Distribution of Leptospira serogroups in cattle herds and dogs in France. Am J Trop Med Hyg 91: 209–210.
- 2.↑
Salgado M, Otto B, Sandoval E, Reinhardt G, Boqvist S, 2014. A cross sectional observational study to estimate herd level risk factors for Leptospira spp. serovars in small holder dairy cattle farms in southern Chile. BMC Vet Res 10: 126.
- 3.↑
Adler B, de la Peña Moctezuma A, 2010. Leptospira and leptospirosis. Vet Microbiol 140: 287–296.
- 4.↑
Gamage CD, Koizumi N, Perera AK, Muto M, Nwafor-Okoli C, Ranasinghe S, Kularatne SA, Rajapakse RP, Kanda K, Lee RB, Obayashi Y, Ohnishi M, Tamashiro H, 2014. Carrier status of leptospirosis among cattle in Sri Lanka: a zoonotic threat to public health. Transbound Emerg Dis 61: 91–96.
- 5.↑
Hamond C, Martins G, Loureiro AP, Pestana C, Lawson-Ferreira R, Medeiros MA, Lilenbaum W, 2014. Urinary PCR as an increasingly useful tool for an accurate diagnosis of leptospirosis in livestock. Vet Res Commun 38: 81–85.
- 6.↑
Cosate MR, Barouni AS, Moreira EC, Veloso IF, Gomes MT, Salas CE, 2012. Molecular characterization by LSSP-PCR and DNA sequencing of a pathogenic isolate of Leptospira interrogans from Brazil. Zoonoses Public Health 59: 379–388.