# Seroprevalence of seven climate-sensitive zoonoses in Greenland and northern Sweden (1998–2017): High antibody prevalence against Rickettsia and Leptospira, with Leptospira possibly linked to global warming

## TL;DR

This study found high rates of antibodies against Rickettsia and Leptospira in Greenland and northern Sweden, with Leptospira cases possibly increasing due to climate change.

## Contribution

The study reports the first evidence of rising Leptospira seroprevalence in Greenland, potentially linked to global warming.

## Key findings

- Leptospira seroprevalence in Greenland increased significantly from 1998 to 2013.
- Rickettsia seroprevalence remained consistently high in both Greenland and northern Sweden.
- Tick-borne pathogens like B. burgdorferi and TBEV showed higher seroprevalence in northern Sweden.

## Abstract

Climate change may alter zoonotic disease patterns in the Arctic, yet knowledge remains limited.

Antibodies to seven zoonotic pathogens were analyzed in 660 unselected human sera drawn from serum banks from Greenland (n = 460) and Northern Sweden (n = 200) (1998–2017), frequency-matched with respect to sex, age, ethnicity and place of living. Greenlandic samples were tested for Francisella tularensis, Brucella melitensis, Brucella abortus, Coxiella burnetii, Rickettsia spp., and Leptospira spp., while Swedish samples also included Borrelia burgdorferi sensu lato (Bbsl) and tick-borne encephalitis virus (TBEV).

Leptospira seroprevalence was higher in Greenland 2013 (18 %, 95 % CI 13–24 %) than in Sweden 2012–2017 (4 %, 95 % CI 2–8 %) and increased significantly over time in West Greenland (1998: 2.5 %, 95 % CI 0.8–6 %; 2013: 30 %, 95 % CI 18–45 %, p < 0.001, OR 16.7, 95 % CI 5.7–48.9). Rickettsia seroprevalence remained stable over time (12 %, 95 % CI 5–24 %). Seroprevalence of F. tularensis and B. melitensis/abortus in Greenland 2013 was less than 1 %. In Sweden, seroprevalence was 1 % (95 % CI 0.1–4 %) for B. melitensis/abortus, 2 % (95 % CI 0.1–5 %) for Bbsl, 3 % (95 % CI 1–6 %) for F. tularensis, and 5 % (95 % CI 2–9 %) for TBEV. Antibodies to C. burnetii were not detected in any sample. Two of 81 polar bear samples from East Greenland (2016–2023) were seropositive for Leptospira spp.

This first report on human Leptospira infection in Greenland highlights rising seroprevalence, possibly linked to contaminated water and global warming. Findings emphasize widespread Rickettsia exposure in northern regions and tick-borne pathogens in Sweden, underscoring the need for updated public health data to inform public health planning.

•Baseline seroprevalence of 7 zoonoses in humans from Greenland & N. Sweden, 1998–2017.•Most of these microorganisms addressed for the first time in Greenland.•Leptospira seropositivity seen for first time in Greenland; rates rising over time.•Rickettsia exposure is widespread in Greenland and Northern Sweden.•Tick-borne pathogen exposure is high in Northern Sweden.

Baseline seroprevalence of 7 zoonoses in humans from Greenland & N. Sweden, 1998–2017.

Most of these microorganisms addressed for the first time in Greenland.

Leptospira seropositivity seen for first time in Greenland; rates rising over time.

Rickettsia exposure is widespread in Greenland and Northern Sweden.

Tick-borne pathogen exposure is high in Northern Sweden.