Estimation of the burden of leptospirosis in New Zealand

Abstract

Background Human leptospirosis mainly affects people in close occupational contact with domestic livestock and their products in New Zealand. The disease has an unquantified impact on both human health and animal production in the country. This study aimed to estimate the burden of leptospirosis in terms of disability‐adjusted life years (DALYs) and cost associated with loss due to absence from work, treatment of disease, animal production loss and cost of vaccination. Methods Previously published studies of abattoir workers farmers, and veterinarians, reporting annual risks of influenza‐like illness attributable to Leptospira infection, were used to estimate the expected number of cases in a year. The cost of lost animal production was based on results of observational studies in beef cattle, sheep and deer conducted in New Zealand. Results Expected median annual number of severe and mild cases of human leptospirosis was 2,025 (95% probability interval [95% PI] 1,138–3,422). Median annual DALYs were 0.42 (95% PI: 0.06–2.40) per 100,000 people for the entire population, and 15.82 (95% PI: 2.09–90.80) per 100,000 people working in at‐risk occupations (i.e. abattoir workers, farmers and veterinarians). Human infection resulted in a median cost of 4.42 (95% PI: 2.04–8.62) million US dollars (USD) due to absence from work and disease treatment. Median production loss cost in beef cattle, sheep and deer was USD 7.92 (95% PI: 3.75–15.48) million, while median vaccination cost in cattle, (including dairy), sheep and deer was USD 6.15 (95% PI: 5.30–7.03) million. Total annual cost of leptospirosis plus vaccination was USD 18.80 (95% PI: 13.47–27.15) million, equivalent to USD 440,000 (95% PI: 320,000–640,000) per 100,000 people. Conclusion This study provides an estimate of the disease burden and cost of leptospirosis in New Zealand that could support occupational health authorities and livestock industries in assessing interventions for this disease.

Risk Factors for Hospitalisation amongst Leptospirosis Patients in New Zealand

“…In NZ, the dry stock are pasture-grazed beef cattle, sheep, and deer farmed for meat, wool, and velvet production [ 42 ]. While the ongoing vaccination of all dairy herds [ 8 ] and commercial pig herds remains crucial, efficacious vaccines [ 43 , 44 ] are available for other classes of dry stock in NZ, such as sheep and beef cattle, but their uptake in these classes of stock is limited [ 45 ]. The vaccination of all classes of livestock is an important preventative measure against severe human cases of leptospirosis; however, the choice of available vaccine should also reflect on the most commonly identified serovars in both humans and livestock.…”

Of Mice, Cattle, and Men: A Review of the Eco-Epidemiology of Leptospira borgpetersenii Serovar Ballum

“…There is probably a bias in notification towards these occupations, but even so, the total number of severe cases was estimated to be approximately three times higher than the notifications. When mild human leptospirosis cases—that are more likely to be missed—were taken in consideration, this under-ascertainment factor increased to 22-fold [ 162 ].…”

Seroprevalence of Leptospira in Racehorses and Broodmares in New Zealand

“…Leptospirosis is a zoonotic disease that is of increasing concern within the public health in New Zealand [ 1 ]. The incidence of human cases notified in New Zealand over the last five years (2014–2018) increased from 1.2 cases per 100,000 in 2014 to 2.3 cases per 100,000 in 2018, peaking at 2.9 cases per 100,000 in 2017 [ 2 ].…”