Leptospirosis: II. Investigation of clinical disease in dairy cattle in the Waikato district of New Zealand

Abstract

Investigations were carried out in 1975, 1976 and 1977 in 16 dairy herds where leptospiral abortions were suspected and in five other herds where clinical disease was not present. Both Leptospira interrogans serovars pomona and hardjo were isolated from cattle in herds with leptospirosis, but only pomona was recovered from those that had aborted. There was no evidence that hardjo caused clinical disease in dairy cattle in the Waikato district. It was found that 73% of the cows that aborted and 19% of other animals in the same herds had microscopic agglutination test titres to pomona of 1:2,000 or greater. By contrast, only 2% of cattle in herds without clinical evidence of leptospirosis had such titres. One cow retained a titre of 1:2,000 or greater to pomona for 7 months; titres of this order had a shorter duration in other cows. Leptospiruria occurred in 50% of cows that had aborted and in 9% of in-contact cows in the same herds. Only 0.7% of cows had leptospiruria in the herds with no clinical disease. Ten of 35 cows shedding pomona still had leptospiruria one month later. It was concluded that clinical leptospirosis should be diagnosed by testing a sample of the herd, rather than just individual cows, because of the variability and persistence of leptospiruria and serological titres in cows with and without clinical signs. Although hardjo is common in cattle in the Waikato district, it was not found to cause abortion in cattle.

Neglected zoonotic agents in cattle abortion: tackling the difficult to grow bacteria

“…antibodies was 21.4% and primarily due to serovar Hardjo (seroprevalence of 17.0%). The implication of a positive titer to serovar Hardjo on fetal loss remains controversial as many studies failed to show a causal association between seropositivity and abortion [ 22 , 45 – 48 ], while others described Hardjo as a cause of abortions [ 49 , 50 ]. The interpretation of the serological results for Leptospira spp.…”

On-farm risk factors associated withLeptospirashedding in New Zealand dairy cattle

“…However, Leptospira shedding was also identified in subclinically infected cattle [5,7,8]. Carter et al [5] and Cordes et al [7] found 0.7% and 0.4% of dairy cows, respectively, in Waikato farms were shedding Leptospira without showing any clinical signs. The true percentage of cattle shedding Leptospira might have been higher since the detection was based on microscopy and culture techniques.…”

“…During that period, clinical leptospirosis with leptospiruria in cattle was frequently diagnosed and largely associated with Pomona infection [5,6]. However, Leptospira shedding was also identified in subclinically infected cattle [5,7,8]. Carter et al [5] and Cordes et al [7] found 0.7% and 0.4% of dairy cows, respectively, in Waikato farms were shedding Leptospira without showing any clinical signs.…”

“…Before the introduction of extensive vaccination with bivalent (Hardjo and Pomona) vaccines in New Zealand dairy herds in the 1980s, human leptospirosis cases in dairy farm workers related to those serovars were commonplace with an average annual incidence of 1100 notified cases per 100 000 of the resident population in 1970–1979 [3, 4]. During that period, clinical leptospirosis with leptospiruria in cattle was frequently diagnosed and largely associated with Pomona infection [5, 6]. However, Leptospira shedding was also identified in subclinically infected cattle [5, 7, 8].…”

“…During that period, clinical leptospirosis with leptospiruria in cattle was frequently diagnosed and largely associated with Pomona infection [5, 6]. However, Leptospira shedding was also identified in subclinically infected cattle [5, 7, 8]. Carter et al .…”