Massey research update

Livestock health and climate change: how prepared are we?

Emilie Vallee, Senior Lecturer in Veterinary Epidemiology at Massey University, and Masako Wada, Postdoctoral Fellow in Veterinary Epidemiology at the School of Veterinary Science, describe their research into diseases’ sensitivity to climate change – and the implications for New Zealand farms.

BACKGROUND

We now know that climate change is highly likely unescapable. The National Institute of Water and Atmospheric Research’s (NIWA’s) projections for New Zealand include a temperature increase of 0.8° Celsius by 2040 and 1.6° Celsius by 2110, a change in rainfall patterns and an increase in extreme weather events (Ministry for the Environment, 2017). However, these projections depict considerably varying climate futures depending on the different greenhouse gas emission scenarios based on human behaviours, so the current efforts should be continued or intensified.

In its 2019 Climate Change and Land report, the Intergovernmental Panel on Climate Change (IPCC) points out the role of intensive and inefficient farming in contributing to greenhouse gas emissions (IPCC, 2019). It is often overlooked that animals as well as farming communities will also be negatively affected by the consequences.

The expected direct effects on livestock welfare and health include heat stress and exposure to extreme weather events, and the indirect effects include changes in the distribution of arthropod vectors, intermediate hosts and pathogens, and an increased incidence of water-borne diseases. We have already seen evidence of this, such as the increase in Leptospira spp. prevalence in lambs after floods (Dorjee et al., 2008). We also know that the risk of ruminants being infected with liver fluke could increase by up to 186% by 2090 (Haydock et al., 2016) and that some regions in the South Island may become more environmentally suitable for Haemaphysalis longicornis, the vector of the Theileria orientalis parasite in New Zealand (Lawrence et al., 2017).

Most livestock diseases in New Zealand have some form of seasonality or climate sensitivity, although it is difficult to summarise and prioritise their importance. Our team, with funding from the Ministry for Primary Industries’ (MPI’s) Sustainable Land Management and Climate Change programme, reviewed the climate sensitivity of livestock diseases present and endemic in New Zealand, prioritised them, identified sources of animal health data that could be used for preparedness, and designed some scenarios for the top five diseases of importance. The team comprised (in addition to the authors) Naomi Cogger, Jackie Benschop and Jonathan Marshall from Massey University and Gregor Macara from NIWA.

METHODS

For this project we worked alongside a stakeholder and technical advisory group (STAG) comprising representatives from MPI, the NZVA, SPCA, Livestock Improvement Corporation, Beef + Lamb New Zealand and DairyNZ.

We began by creating a list of 41 diseases endemic in New Zealand livestock based on the research team’s knowledge, Massey’s undergraduate curriculum and the STAG’s input. We then systematically reviewed these diseases’ climate sensitivity with the help of undergraduate veterinary students from Massey University.

At a STAG workshop we established a list of criteria to score and rank the

diseases by asking “What does it mean for a disease to be important for climate change preparedness?”. The STAG was also asked to identify possible sources of longitudinal and cross-sectional animal health data.

For a case study for facial eczema, we used VetEnt’s seven years of spore count monitoring data (thanks to Emma Cuttance) to model the association between spore counts and climate by machine learning methods. We then used NIWA’s projections for Waikato to forecast the start and duration of spore seasons and the magnitude of spore peak. For another case study we used a crosssectional data set (Yupiana et al., 2019) to model the association between Leptospira shedding and seasonal profiles of the sampling locations, as well as weather conditions two weeks before sampling.

Finally, we conducted three qualitative scenarios (for salmonellosis, mastitis and barber’s pole), summarising the information by region.

RESULTS

The literature on the evidence of disease sensitivity to climate was highly variable between diseases, and tended to correlate with the extent of the research efforts. Generally, parasitic diseases with freeliving stages and infectious diseases caused by pathogens that can survive outside the hosts showed the greatest sensitivity, and were therefore more likely to be affected by climate change.

Using criteria relating to disease control, economic, social and welfare impacts, and climate sensitivity, the research determined that facial eczema, leptospirosis, salmonellosis, mastitis and barber’s pole were the top five livestock diseases of concern for New Zealand’s climate change preparedness.

The facial eczema models forecast an average increase in peak facial eczema spore counts of 2,000–3,000 spores/g each year, and an earlier start of alert-level spore counts (2.6 weeks earlier by 2100).

The existing data on the Leptospira models did not show any significant association between Leptospira shedding

AT A TIME WHEN FARMERS’ MENTAL HEALTH

IS ALREADY WORRYING, IT IS IMPORTANT FOR FARMERS, VETERINARIANS AND RESEARCHERS TO WORK TOGETHER TO ANTICIPATE THE IMPACTS OF CLIMATE CHANGE AND IMPROVE OUR RESILIENCE.

and climate variables, highlighting the need for longitudinal data to build quantitative scenarios.

We found that the risk of Salmonella brandenburg abortion in sheep was likely to increase with rising temperature and rainfall levels throughout the country. And we found that the incidence of mastitis was likely to increase with increasing temperature and similar or increasing rainfall, and that there may be indirect effects of climate change on mastitis, such as after a power outage caused by floods.

Finally and interestingly, the limiting factor for the barber’s pole worm (Haemonchus contortus) development cycle is currently low temperatures, but it is likely to become drought as average temperatures increase by 2100. This suggests a possible shift in seasonality by 2100, from a low-risk winter and spring to a low-risk dry season in the northern and eastern parts of the North Island.

RELEVANCE

At a time when farmers’ mental health is already worrying, it is important for farmers, veterinarians and researchers to work together to anticipate the impacts of climate change and improve our resilience.

More attention should be paid to climate change impacts and mitigation when discussing herd health plans. Veterinary practices may also need to adjust the timing of their support, such as by measuring spore counts earlier or adjusting drenching programmes. To help identify the risks linked with climate impacts and prescribe the necessary changes in management, we will provide the context and resources by sharing the findings of our review and models on a dedicated website that will be available later in the year.

We hope to keep this area of research growing by developing our networks, looking at more animal species and diseases in detail, and providing further advice on the role of veterinarians.

REFERENCES: Dorjee S, Heuer C, Jackson R, West DM, Collins

Emerson JM, Midwinter AC, Ridler AL. Prevalence of pathogenic Leptospira spp. in sheep in a sheep-only abattoir in New Zealand. New Zealand Veterinary Journal 56, 164–70, 2008

Haydock LAJ, Pomroy WE, Stevenson MA,

Lawrence KE. A growing degree-day model for determination of Fasciola hepatica infection risk in New Zealand with future predictions using climate change models. Veterinary Parasitology 228, 52–9, 2016

Intergovernmental Panel on Climate Change

(IPCC). Climate Change and Land. www.ipcc.ch/site/ assets/uploads/sites/4/2020/02/SRCCL-CompleteBOOK-LRES.pdf (accessed 19 March 2020). 2019

Lawrence KE, Summers SR, Heath ACG, McFadden AMJ, Pulford DJ, Tait AB, Pomroy

WE. Using a rule-based envelope model to predict the expansion of habitat suitability within New Zealand for the tick Haemaphysalis longicornis, with future projections based on two climate change scenarios. Veterinary Parasitology 243, 226–34, 2017 Ministry for the Environment. Climate Change Projections for New Zealand: Atmosphere Projections Based on Simulations from the IPCC Fifth Assessment. 2nd Edtn. Ministry for the Environment, Wellington, New Zealand, 2017

Yupiana Y, Vallee E, Wilson P, Collins-Emerson

J, Weston J, Benschop J, Heuer C. Emerging Leptospira strain poses public health risk for dairy farmers in New Zealand. Preventive Veterinary Medicine 170, 2019