The impact of climate change on horse health

While the fight against global warming is a key concern for most citizens and a central theme in the arguments of all political parties, climate change is not a new phenomenon. In fact, the first scientific observations were made in 1850. Since then, this disruption, which is not limited to "simple" warming, has grown in scale and its consequences for human and animal health and biodiversity have been demonstrated. Horses are no exception to the rule and today suffer from disorders and diseases that are directly attributable to climate change.

The IPCC's sixth report: increasing risks

The IPCC (Intergovernmental Panel on Climate Change) released its latest findings on March 20, 2023. Its report⁽¹⁾ notes a 1.1°C increase in global temperatures since the pre-industrial period and a forecast of +1.5°C by 2030. In connection with this, scientists are observing an increase in the risk of natural phenomena that will continue to worsen: heat waves, droughts, extreme increases in precipitation, etc.

They are also observing changes in the behavior of many species, including the displacement and extinction of some and the invasion of exotic species. In order to slow down this phenomenon, which can no longer be reversed, France is working on four major areas: energy conservation, energy efficiency, accelerating the development of renewable energies, and reviving 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 has an inevitable impact on all forms of life: plant, animal, and human. The decline in biodiversity, combined with the destruction of habitats linked to agricultural exploitation, hunting, and fishing, is contributing to the gradual disappearance of plants and species. One-third of these 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⁾. Apart from any infectious aspects, climate change disrupts animal physiology: heat stress causes disorders (dehydration, reproductive disorders, etc.) and behavioral changes. We are also seeing shifts in animal populations, which activates inter-species viral transmission.

Global warming and horse health

Scientific research on the direct consequences of climate change on living beings still needs to be expanded in order to establish a direct link between certain current disorders or pathologies and the climate. However, some conditions are already scientifically considered to be the result of this phenomenon.

Resurgence of pollen allergies

Climate change, combined with air pollution, is recognized as a cause of increased pollen allergies, as well as more severe symptoms and longer periods of risk⁽⁴⁾. Higher CO2 concentrations in the atmosphere increase pollen production, while pollution deforms certain grains, making it easier for them to penetrate deep into the respiratory tract.

Horses, like humans, are therefore more prone to rhinitis, asthma attacks, and conjunctivitis. In its 2023 report⁽⁵⁾, the RNSA (National Aerobiological Surveillance Network) notes that the pollen season began early in January due to abnormally high temperatures in December 2022. This caused hazel and alder trees to flower earlier than usual and produce more pollen than in previous years.

The RNSA notes that "this early season has been observed several times in the past, but it is becoming increasingly frequent due to climate change." In 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 "promoted the release and spread of grass pollen in the air, reaching a higher peak of symptoms than in previous years." A UV-protective mask with a nose cover can help limit pollen allergies and protect sensitive eyes.

Development of infectious diseases due to an increase in disease-carrying arthropods

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

They have observed that climate change is causing a proliferation of arthropods (mosquitoes, gnats, ticks) that carry viruses (arboviruses), bacteria, and parasites, which are spreading in particular through globalization (transportation of animals and plants). Some pathogens affect animals, others affect humans, and some affect both. Among animal diseases, Dr. Zientara mentions African horse sickness, which he describes as equine plague.

It is a hemorrhagic fever with a mortality rate of 90% in infected horses. Present in Africa, the disease arrived in Europe (Spain and Portugal) in 1987 via zebras from Namibia and may soon reach France. The specialist points out that, although insect carriers have been transported internationally in the past, 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. These ticks are potential carriers of bacteria, viruses, and piroplasms. The most common species found in pastures is Dermacentor reticulatus , followed by Ixodes ricidus , ahead of six other listed species. The tick population is growing, and they now remain active during the fall and winter seasons. They are only inactive during the summer months (June, July, and August) when the heat is too intense.

The establishment of the Hyalomma marginatum species in the Mediterranean basin and the southwestern basin is a direct consequence of global warming. Brought to Europe by birds from Africa, it now finds ideal conditions for proliferation in the Mediterranean climate.

This tick, responsible for transmitting the Crimean-Congo hemorrhagic fever virus, has been observed in a few cattle farms in the south and is currently under close surveillance. This disease, like other vector-borne diseases, affects both humans and animals, which requires, 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 and increases the risk of obesity. In 2019, British veterinarian Gillies Moffat linked the abundance of grass in pastures, caused by global warming, to overeating in horses⁽¹⁰⁾.

Similar observations have been made by other veterinarians in the past, such as Dr. Joe Mackinder, who has noted an increase in the incidence of obesity-related laminitis in horses⁽¹¹⁾. Unfortunately, this often results in the euthanasia of the animal, hence the need to raise awareness among owners about this phenomenon of overfeeding, which must be regulated.

Global warming and the horse industry

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

Availability of forage and grain

Climate change is impacting agricultural yields and forage harvest dates: the risks are a lack of grass in summer and a less significant recovery in autumn. Forage stocks will therefore need to be planned for in both summer and winter. As for cereals, they will see a rise in prices as a result of transportation difficulties and geopolitical events.

Feed availability must therefore be determined on the basis of a ration assessment, i.e., adapting the ration to the horses' needs in order to avoid excess and waste. It is also crucial to improve pasture management in order to increase productivity and regulate carbon emissions. It should be borne in mind thatone hectare of grassland represents 70 tons of carbon, with storage of 110 to 210 kg/year.

Limiting the carbon footprint

Concrete actions can help limit the sector's carbon footprint: avoiding holding competitions in remote locations, reducing carbon dioxide emissions by optimizing horse transport, and offsetting emissions by planting trees.

Reorganization of equestrian events

Given the impact of rising temperatures on horses and riders, events will likely be scheduled earlier in the day and some may be canceled during periods of extreme heat or heavy rain.

Stable layout

It is crucial to rethink building design by moving towards eco-design (materials selected for their insulating properties). Building architecture must also be reviewed in order to promote watering, create shaded outdoor areas, reduce solar radiation, improve natural or, failing that, mechanical ventilation, collect rainwater, etc.

Water restriction

As water shortages become more acute, watering of quarries will be limited, as will showering horses and the use of misters in stables. Alternative solutions will have to be developed (rainwater collectors).

Climate change, which is not limited to global warming, has a direct and irreversible impact on living organisms, plants, animals, and humans. Changes in horse health are now being observed, requiring the implementation of necessary measures (such as wearing masks) to ensure a good quality of life.