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Expected health impacts of climate change in Aotearoa New Zealand
Part 2: Vector-Borne, Zoonotic, and Allergic Diseases
Aotearoa New Zealand is a country that ranges across latitude zones, has prevailing westerly winds, is completely surrounded by ocean and has a large mountain chain affecting east-bound weather systems. With a climate that varies from the subtropical to subantarctic, the country is in a unique position to experience a great number of health impacts from climate change.
Vector-borne diseases
Vectors are living organisms that transmit disease and infectious pathogens across animals and humans. Common vectors include bloodsucking insects like mosquitos, that spread disease by transmitting microorganisms from an infected host to a new host.
Anthropogenic (resulting from human activity) environmental change has led to highly modified habitats across Aotearoa New Zealand. These habitats can provide suitable environments for the introduction and establishment of species including vectors.
The higher temperatures resulting from climate change mean that vectors will be able to survive for longer periods of the year providing more opportunity to spread disease. Currently the introduced mosquito species Culex quinquefasciatus is predominantly restricted to northern parts of the country due to the specific climate required to survive. Increased temperatures mean that more of the country will have the right conditions for migration of species into areas that have traditionally been too cold.
There have been five mosquito-borne diseases detected in Aotearoa New Zealand since 2019. Four viruses (Chikungunya, Dengue Fever, Ross River Virus, Zika) and one parasite (Malaria). These were imported from travel to the Pacific, Asia, and Africa. Each disease affects different demographics across age, ethnicity, region, and socio-economy.
Zoonotic diseases
Disease and infections that can be spread from animals to humans are known as zoonotic. Animals can also act as amplifying hosts to vector-borne diseases. Up to 60% of existing pathogens and 75% of emerging pathogens are zoonotic in nature.
Farming is an integral industry in Aotearoa New Zealand. The wake of Cyclone Gabrielle, one of several severe weather events of 2023, saw Beef and Lamb New Zealand issuing reminders to farmers to watch for salmonella and leptospirosis with farmers advised to wear PPE to protect themselves from water contaminated by their animals.
For those living in cities, leptospirosis can also be spread by brown rats with the bacteria able to survive in water and soil for several days. The 2023 weather events resulted in an increase in cases of leptospirosis in Auckland.
Geographic isolation and strict border control measures favour Aotearoa New Zealand when it comes to the import of new vector species that help the spread of zoonotic diseases. The most recent and devastating example of a zoonotic disease imported into the country is COVID-19. However, many zoonotic diseases are already present in the country and can be spread by household pets.
Allergic diseases
Allergic diseases including asthma will be impacted by climate change. Rising temperatures can lead to longer allergy seasons and the release of pollens. Like vectors, the warmer climate will impact plant species responsible for allergies by allowing them to grow outside of their traditional environs. In Aotearoa New Zealand these species include grasses, ragweed and plantains which are known to be allergy triggers.
There has been a lack of comprehensive monitoring of airborne pollen since the summer of 1988/99 which means that over 30 years of potential data has been uncollected. This uncollected data could have been integral to the prediction of future trends for allergic diseases.
Asthma triggered by thunderstorms has been rare in Aotearoa New Zealand, however severe weather events in the past few years has led to a growth of this phenomenon. Thunderstorm conditions coupled with a high presence of airborne allergens has seen a rise in Thunderstorm Asthma (TA) across Australasia in summer months. Warmer temperatures could see an increase of TA throughout the year.
Explore the impacts of climate on vector-borne and zoonotic diseases here and check out part three for the impact of climate change on housing, health, and the indoor environment.