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New Zealand

Introduction

It is not known when pathogenic leptospires first became established in New Zealand. The first land mammals to arrive in this country about 1,200 years ago were human beings, dogs and the kiore, Rattus exulans. It cannot be determined if leptospirosis also arrived at that time. It is more likely that most, if not all pathogenic leptospires arrived with intentional and unintentional mammalian imports in the late 18th and 19th centuries.

The history of leptospirosis research in New Zealand is one which has traced the pattern of infection from overt animal and human disease through to the epidemiology of in apparent carrier states in both domestic and feral animals. We now know that these carriers represent reservoirs of infection. The causal organisms are fragile and can be difficult to grow. Serological testing has sometimes been useful in diagnosis but in earlier days serology created confusion because of cross-reactions among types (serovars) of leptospires. For example early studies suggested that the hedgehog,Erinaceus europaeus occidentalis, might be a carrier of infection byserovar pomona, but subsequent work showed that serovar ballumwas the most common serovar in that host. Another very practical deficiency of reliance on serological diagnosis was the absence of antibody in the early stages of acute disease.

The first confirmed occurrence of leptospirosis in domesticated animals in New Zealand was in 1950 when Leptospira pomona(later known as L. interrogans serovar pomona) was isolated from a calf with haemoglobinuria at Wallaceville Animal Research Station(Anonymous 1951), but 1953 was the seminal year for publications on leptospirosis. At a meeting of the Northland Branch of the New Zealand Veterinary Association, Ensor (1953) reported that in Northland during the 1952 season, 76 farms reported outbreaks of redwater which were attributed to leptospirosis. At the same meeting McClure (1953) reported the clinical and postmortem characteristics of the disease in young calves. He also gave the opinion that “Investigation into the relationship of Leptospirapomona and bovine abortion in New Zealand would be of value.”There was not long to wait because 7 months later Te Punga and Bishop (1953) recorded an outbreak of bovine abortion in the Waikato district which was established as being due to serovar pomona.

 Interestingly, the paper contains the earliest colour illustrations to appear in the New Zealand Veterinary Journal, including an excellent photomicrograph showing a silver-stained leptospiralorganism in a foetal kidney. The colour plates also illustrate the contrast between the clear-cut severe lesions of placentitis due to Brucella abort us, which was present in New Zealand at that time,and the mildness of changes in the placenta associated with leptospiral abortion. We now know that the latter “lesions” are largely autolytic or putrefactive in nature and associated with intrauterine death of the bovine conceptus. (Marshall and Manktelov 2002)

 

 RB Marshall & BW Manktelow (2002) Fifty years of leptospirosis research in New Zealand: a perspective, New Zealand Veterinary Journal, 50:sup3, 61-63 more details here