Climate change’s impact on managing animal health

Vet Advice with Dr. Ron Clarke

I’m losing more arguments with grandchildren that our climate hasn’t changed significantly, prompted by signals that have only grown more evident through the last half of my lifetime. At one point, I convinced myself that climatic changes were part of a natural phenomenon — one of those things history would look upon and call an “age,” a period destined to be a global repeat of something that happened before. A hundred-year cycle perhaps, then everything would return to a point of equilibrium. Although it still could happen, veterinarians and those paid to manage animal health events must take heed.

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Close-up view of a brown and white Hereford cow's eye. Only part of the cow's head and ear are visible in this image

The late evolution of wisdom and delayed acquisition of knowledge had something to do with earlier pessimism. I saw a quote in a T-shirt shop the other day that made me think about the importance of knowing the difference. The quote: Knowledge is knowing that a tomato is a fruit. Wisdom is knowing not to put it in a fruit salad.

It’s important to accept climate change as far more than just weather-related incidents and that emergence of many infectious diseases have been directly correlated with climate change. West Nile virus, Chickungunya, Ebola, MERS, Nipah and Dengue are but a few examples that were not even recognized when I graduated. In the future, civilization will see many more diseases emerge as a direct result of climate’s effect on shifting habitats that bring wildlife and farm life, crops and humans into closer contact with more pathogens.

The spread of African swine fever in China and its appearance on the fringe of Europe is today’s biggest animal health story, one few talk about. China, the world’s largest producer and consumer of pork, hopelessly battles African swine fever within its borders. African swine fever is about to change the world’s trade in animal protein with global knock-on effects to corn and soy production. The global swine herd is roughly 250 million head. Roughly 50 to 55 per cent of that number of swine is produced in China with about 40 per cent of China’s swineherd categorized as “backyard” hogs. Curt Hudnutt, executive vice-president of rural banking, North America, at Rabobank, feels the ability to contain the spread of African swine fever in China is very low.

In September, officials in Belgium confirmed the presence of African swine fever in two wild boar in a town roughly 10 km from France. The presence of wild boar throughout the region stokes fear that African swine fever could spread into the Netherlands, then Germany and throughout the continent. Control of highly infectious disease across international borders represents one of the great challenges facing animal health professionals.

Habitats are being altered in arctic regions and have been drastically changed in areas like California, recently ravaged by fires that consumed upwards of 500 square miles of forests and nearly eliminated Paradise, a city of 27,000. Entire populations of animals become displaced through natural disasters of all types, including deforestation linked to human efforts to expand food production. Due to ancestral genetics of pathogens — some unchanged for millions of years — disease agents easily find new hosts when transported into new areas.

No feature of Earth is more complex, dynamic, and varied than the layer of living organisms that occupy its surfaces and its seas, and no feature is experiencing more dramatic change at the hands of humans than this extraordinary, singularly unique feature of Earth. Food, clean water, medicines and protection from natural hazards are important ingredients in maintaining our security and quality of life. Breathable air, potable water, fertile soils, productive lands, bountiful seas are manifestations of the workings of life. No one can escape the impact of biodiversity loss because reduced global diversity translates quite clearly into fewer new medicines, greater vulnerability to natural disasters and greater effects from global warming. — World Wildlife Fund

At least 40 per cent of the world’s economy and 80 per cent of the needs of the poor are derived from biological resources. Scientists worry about an “Insect Apocalypse.” In a New York Times article (2018/11/27), Brooke Jarvis outlines scientific concern that the population of monarch butterflies fell by 90 per cent in the last 20 years; the rusty-patched bumblebee, which once lived in 28 states, dropped by 87 per cent over the same period. A whole insect world might be quietly going missing, a loss of abundance that could alter the planet in unknowable ways — much of it linked to climate change.

Climate change has been implicated in the spread of arboviruses — viruses carried by arthropods such as mosquitoes, midges and ticks. While alterations in temperature and rainfall are important factors in making new territory hospitable to an invading arbovirus, many other forces also influence new patterns of viral emergence. Although you can’t disassociate arbovirus diseases from the climate, Texas Medical Branch at Galveston pathology professor Stephen Higgs and Oxford University professor Ernest A. Gould outline other factors. They include:

  • Genetic mutation, new mosquito species, the presence of immunologically vulnerable humans, numbers of humans and movement of infected individuals (Chikungunya virus).
  • Cyclic periods of high rainfall, modern irrigation projects, and livestock trade between Africa and southern Arabia (Rift Valley fever virus).
  • Modern air transport, the availability of compatible mosquito species and large numbers of virus-spreading migratory birds (West Nile virus).

Scientific evidence for warming of the climate system seems unequivocal. Oceans warm, ice sheets shrink, glaciers retreat, snow cover diminishes and ocean levels rise. The numbers of record high temperature events continue to increase, while the number of record low temperature events decrease. Climatic extremes create an increased number of intense rainfall occurrences and punishing drought. The “shifting baseline syndrome” has been described by hunters and fishermen: The fish get smaller and smaller, to the point where today’s prize catches were dwarfed by fish that in years past were piled up and ignored. But the smiles on the fishermen’s faces stay the same size. The world never feels fallen, because we grow accustomed to the fall. — Cabela’s

Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be sent to Canadian Cattlemen ([email protected]) or WCABP ([email protected]).

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Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be sent to Canadian Cattlemen ([email protected]) or WCABP ([email protected]).

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