The impact of climate change on horse health

Although the fight against global warming is at the heart of the concerns of a majority of citizens and the arguments of all political parties, the problem is not new. The first scientific findings were made in 1850. Since then, this disruption - which cannot be summed up as "simple" global warming - has grown in scale, and the consequences for human and animal health, as well as biodiversity, have been demonstrated. Horses are no exception to the rule, and today suffer from disorders and pathologies directly attributable to climate disruption.

The 6th IPCC report: risks on the rise

The IPCC (Intergovernmental Panel on Climate Change) released its latest conclusions on March 20, 2023. Its report⁽¹⁾ shows a global temperature rise of 1.1°C since pre-industrial times, with a forecast of +1.5°C by 2030. In connection with this, scientists note an increase in the risk of natural phenomena that are set to worsen: heat waves, droughts, extreme increases in precipitation, and so on.

They are also observing a change in the behavior of many species, notably the displacement and extinction of some, and the invasion of exotic species. In order to slow down this phenomenon, which can no longer be countered, France is working on 4 major axes: energy sobriety, energy efficiency, accelerating the development of renewable energies and revitalizing the country's nuclear industry. The plan to combat global warming has now become the National Climate Change Adaptation Plan (PNACC).

Irreversible consequences for humans, animals and plants

Irreversible climate change is having an inescapable impact on all forms of life: plant, animal and human. The decline in biodiversity, coupled with the destruction of habitats by farming, hunting and fishing, is contributing to the gradual disappearance of plants and species. A third of them could disappear by 2070⁽²⁾.

In humans, eradicated diseases such as tuberculosis, malaria and cholera are reappearing, while numerous zoonoses (diseases transmissible between humans and animals) are responsible for epidemics⁽³⁾. Aside from infectious aspects, climatic disruption disrupts animal physiology: heat stress leads to disorders (dehydration, reproductive problems, etc.) and changes in behavior. The movement of animal populations also activates interspecies viral transmissions.

Global warming and horse health

Scientific work on the direct consequences of climate change on living beings has yet to be fleshed out to establish a direct link between certain current disorders or pathologies and the climate. However, certain conditions are already scientifically considered to be the result of this phenomenon.

Pollen allergies on the rise

Climate change, combined with air pollution, is recognized as a source of increased pollen allergy, but also of intensified symptoms and longer risk periods⁽⁴⁾. The higher concentration of CO2 in the atmosphere increases pollen production, while pollution, by deforming certain grains, facilitates their penetration into the deep respiratory tract.

Horses, like humans, are therefore more prone to rhinitis, asthma attacks and conjunctivitis. In its 2023 report⁽⁵⁾, the RNSA (Réseau national de surveillance aérobiologique) notes an early pollen season in January, linked to abnormally high temperatures in December 2022. This led to an acceleration in the flowering of hazelnut and alder trees, and greater pollen production than in previous years.

RNSA notes that "this early season has been observed on several occasions in the past, but is becoming increasingly frequent due to climate change". This year, 2023, a high concentration of hornbeam pollen was also observed in March-April, with a high allergenic potential. From late April to late June, warm weather "favored the emission and dissemination of grass pollen in the air, reaching a higher peak of symptoms than in previous years". An anti-UV mask with a muffler can limit pollen allergies and protect weakened eyes..

Development of infectious diseases through an increase in arthropod vectors

The "One Health" conference held on April 4, 2024 in Tours⁽⁶⁾ featured veterinary virologist Dr Stephan Zientara⁽⁷⁾, tick specialist Dr Laurence Malandrin⁽⁸⁾ and infectiologist Dr Aymeric SEVE⁽⁹⁾. These eminent specialists presented their studies at this symposium on the "Influence of global warming on human and animal vector-borne diseases".

As a result of climate change, they are witnessing a proliferation of arthropods (mosquitoes, midges, ticks) carrying viruses (arboviruses), bacteria and parasites, which are moving around as a result of globalization (transport of animals and plants). Some pathogens affect animals, others humans, and some both. Among animal diseases, Dr. Zientara mentions African horse disease, which he describes as African horse sickness.

It's a hemorrhagic fever that causes 90% mortality in infected horses. Present in Africa, the pathology arrived in Europe (Spain and Portugal) in 1987 via zebras from Namibia, and may soon make its way to France. The specialist points out that, while in the past, the insects carrying the disease passed through international trade, they did not survive in Europe. With global warming, they are now able to do so.

Vector-borne diseases can also be transmitted by ticks. Dr. Malandrin points out that 20% of France's meadows and forests are infested with ticks. Ticks are potential carriers of bacteria, viruses and piroplasmas. The species most present in pastures is Dermacentor reticulatus, followed by Ixodés ricidus and 6 other listed species. The tick population is increasing, and during the autumn-winter season, they remain active. Only during the summer (June-July-August) are they inactive, as the heat is too strong.

The establishment of the Hyalomma marginatum species in the Mediterranean and south-western basins is a direct consequence of global warming. Brought to Europe by birds from Africa, the Mediterranean climate now provides ideal conditions for its proliferation.

This tick, responsible for transmitting the Crimean-Congo haemorrhagic fever virus, is currently being observed on a few cattle farms in the south of France, and is the focus of every vigilance. This pathology, like other vector-borne diseases, affects both humans and animals, requiring, as Dr Aymeric Seve points out, constant dialogue between human and veterinary medicine.

Increased risk of obesity and laminitis

Climate change has a direct impact on horse nutrition, increasing the risk of obesity. As early as 2019, British veterinary surgeon Gillies Moffat linked the abundance of grass in pastures, linked to global warming, to overfeeding in horses⁽¹⁰⁾.

Similar observations have been made by other veterinarians in the past, such as Dr. Joe Mackinder, who notes the increasingly frequent appearance of obesity-related laminitis in horses⁽¹¹⁾. The unfortunate consequence is often euthanasia of the animal, hence the need to make owners aware of this abundant phenomenon, which needs to be regulated.

Global warming and the equine industry

Climate change impacts all environments, and the equine industry in particular. It is therefore essential to implement various measures to adapt to the new climate data. Agata Rzekęć, agricultural engineer and environment/sustainable development project manager for the equine industry at IFCE, details these areas of adaptation⁽¹²⁾.

Availability of forage and cereals

Climate change is having an impact on crop yields and forage harvesting dates: the risks are a lack of grass in summer and a smaller recovery in autumn. Forage stocks will therefore need to be built up in both summer and winter. As for cereals, prices will rise as a result of transport difficulties and geopolitical events.

Feed availability must therefore be established on the basis of a ration balance, i.e. adapting the ration to the needs of the horses to avoid excess and wastage. It is also crucial to improve grazing management to increase productivity and regulate carbon emissions. Onehectare of grassland represents 70 tonnes of carbon, with a storage capacity of 110 to 210 kg/year.

Limiting carbon footprint

Concrete actions help to limit the industry's carbon footprint: avoid holding competitions in remote locations, reduce carbon dioxide emissions by optimizing horse transport, offset emissions by planting trees.

Reorganization of equestrian events

Given the impact of rising temperatures on horses and riders, events are likely to be scheduled earlier in the day and some cancelled during periods of heatwave or torrential rain.

Stable layout

It is crucial to rework the layout of buildings, moving towards eco-design (materials selected for their insulating properties). The architecture of buildings must also be reviewed to encourage watering, create shaded areas outside, reduce solar radiation, improve natural ventilation or, failing that, mechanical ventilation, recover rainwater, etc.

Water restrictions

With water shortages on the increase, watering of quarries will be limited, as will horse showers and the use of misters in the stables. Alternative solutions will have to be developed (rainwater harvesters).

Climate change, which is more than just global warming, has a direct and irreversible impact on living organisms - plants, animals and humans alike. Alterations in the health of horses are now being observed, requiring the implementation of the necessary measures (such as the wearing of masks) to guarantee a good quality of life.