Update on the status of leptospirosis in New Zealand

Abstract

Leptospirosis is a zoonotic disease that poses public health and ecological threats worldwide. In New Zealand (NZ), incidence of the disease is relatively high compared to other developed countries. The aim of this review was to describe the epidemiological status, ecological risk of leptospirosis and prevention in NZ. Disease notification data for leptospirosis in humans in NZ from 2010 to 2015 were collected from the Institute of Environmental Science and Research database. These data were supported by a literature review of epidemiological studies in human and animal populations. During this six-year period, exotic serovars of Leptospira interrogans sv Australis and Leptospira kirschneri sv Grippotyphosa were identified in patients who had travelled abroad to Samoa (Pacific Ocean) and Thailand, respectively. Most cases of leptospirosis were recorded in New Zealanders of European ethnicity, followed by Māori people. Males had a nine-fold increased risk compared to females mostly due to occupation. The risk of leptospirosis increased gradually with the age, with a peak in the 40 to 49-year-old age group, after which it decreased. Workers in meat-processing and farming industries appeared at highest-risk of occupational exposure compared with other risky occupations such as hunters, veterinarians, technicians, stock truck drivers and lake workers. Other cases were also attributed to outdoor exposures or travelling overseas. Highest disease notification rates occurred in the West Coast region of the South Island (average annual incidence 9.7 per 100,000 people), followed by Whanganui region (8.2 per 100,000) and Hawke's Bay region (8 per 100,000) in the North Island. Vaccines currently available for animals are specific for cattle, sheep, deer and dogs and do protect against all serovars present in NZ. The development and use of molecular diagnostics is crucial for specific identification of Leptospira isolates and informing deployment of efficient vaccines.