Urine shedding patterns of pathogenic Leptospira spp. in dairy cows

Abstract

Pathogenic Leptospira spp. are zoonotic bacteria that infect wild and domestic animals. Humans contract leptospirosis directly through contact with infected animals or indirectly from contaminated water or soil. In mammalian reservoirs, the pathogen can colonize renal tubules for lengthy periods and persistently contaminate the environment through urine. Cattle have been reported to shed several serovars; with Hardjo the most common serovar found in cattle. Without clinical manifestations, the infection can spread within a herd, impairing productivity, and putting workers like farmers, abattoir operators and veterinarians at risk. The dynamics of pathogenic Leptospira shedding was studied in six dairy herds in southern Chile. Various intermittent urine shedding patterns were found, with elimination periods between 79 and 259 days and bacterial loads ranging from 3 × 10⁴ to 4.4 × 10⁴ bacteria/mL. The current study was the first to assess the various urine shedding patterns and loads of pathogenic leptospires shed through urine of naturally-infected dairy cows. In addition, the study suggests that vaccination does not prevent cattle infection, although it influences loads of pathogenic leptospires excreted in urine. Our study provides a great awareness of asymptomatic animal carriers in an endemic area and will contribute to improving disease control and designing better prevention strategies.

Keywords: Leptospirosis; cattle; dairy cows; transmission; urine shedding.

Figure 1

Distribution of urine shedding patterns in dairy cows from Chile, for non-vaccinated and vaccinated herds. %: is percentage of leptospirosis urine-shedders animals. Definitions: Not Persistent (NP); Short Persistent (SP); High Persistent (HP); Intermittent (I); Multiple Patterns (MP). ** means that there is a statistically significant (P<0.05) difference between vaccinated vs non-vaccinated group for a given pattern.

Figure 2

Distribution of pathogenic leptospire burden (GE/μL) according to different shedding patterns; data obtained from dairy cattle in southern Chile. Group 1: < 1000 (GE/μL), group 2: 1000 to < 10³ (GE/μL), group 3: 10³ to < 10⁴ (GE/μL), group 4: 10⁴ to 10⁵ (GE/μL), group 5: > 10⁵ (GE/μL).

Figure 3

Distribution of pathogenic leptospire burden (GE/μL) according to vaccination status of the animals; data obtained from dairy cattle in southern Chile. Group 1: < 1000 (GE/μL), group 2: 1000 to < 10³ (GE/μL), group 3: 10³ to < 10⁴ (GE/μL), group 4: 10⁴ to 10⁵ (GE/μL), group 5: > 10⁵ (GE/μL).