Today, we conclude our review of pathogens that may spread as a result of global warming and changes in precipitation levels, according to a new report from the Wildlife Conservation Society.
- Click here to read Part 1 of this story (overview).
- Click here to read Part 2 of this story (avian flu, babesiosis, cholera).
- Click here to read Part 3 of this story (Lyme disease, intestinal and external parasites, ebola).
As humans have moved cattle around the world, bovine tuberculosis has spread. It now has a global distribution and is especially problematic in Africa, where it was introduced by European livestock in the 1800s.
The disease infects vital wildlife populations, such as buffalo (above) and lions in Kruger National Park in South Africa, where tourism is an integral part of local economies. The disease also infects humans in southern Africa through the consumption of unpasteurized milk.
Human forms of tuberculosis can also infect wild animals. Droughts associated with climate change are likely to force contact between wildlife and livestock at limited water sources. This can lead to increased disease transmission among livestock and wildlife, as well as livestock and humans.
Harmful algal blooms off global coasts create toxins that are deadly to both humans and wildlife. These occurrences—commonly called “red tides”—cause mass fish kills, marine mammal strandings, penguin and seabird mortality, and human illness and death from a variety of toxins.
Similar events in freshwater are caused by a species of cyanobacteria and have resulted in animal die-offs in Africa. Altered temperatures or food-web dynamics resulting from climate change will have unpredictable impacts on the occurrences of this worldwide phenomenon. Effects of harmful algal blooms on sea life are often the first indicators that such an event is taking place.
Rift Valley Fever
Rift Valley fever virus (RVFV) is an emerging zoonotic disease of significant public health, food security and overall economic importance, particularly in Africa and the Middle East. In infected livestock like cattle, sheep, goats and camels, abortions and high death rates are common.
In humans—who can contract the virus from butchering infected animals—the disease can be fatal. Given the role of mosquitoes in virus transmission, climate change continues to be associated with concerns about the spread of RVFV.
Also known as trypanosomiasis, this disease affects humans and animals. It is caused by the protozoan Trypanosoma brucei and is transmitted by the tsetse fly.
The disease is endemic in certain regions of Sub-Saharan Africa, affecting 36 countries, with estimates of 300,000 new cases every year and more than 40,000 human deaths each year in eastern Africa.
Domestic cattle are a major source of the disease, but wildlife can be infected and maintain the disease in an area. Direct and indirect effects (such as human land-use patterns) of climate change on tsetse fly populations could play a role in the distribution of this deadly disease.
Found in the tropical regions of Africa and parts of Central and South America, this virus is carried by mosquitoes, which will spread into new areas as changes in temperatures and precipitation levels permit.
One type of the virus, jungle yellow fever, can be spread from primates to humans, and vice versa, via mosquitoes that feed on both hosts. Recent outbreaks in Brazil and Argentina have had devastating impacts on wild primate populations. In some South American countries, monitoring of wild primates has resulted in early detection of disease activity, allowing rapid implementation of vaccination programs to protect humans.
Plague (Yersinia pestis)—one of the oldest infectious diseases on record—still causes significant death rates in wildlife, domestic animals and humans in certain locations.
Plague is spread by rodents and their fleas. Alterations in temperatures and rainfall are expected to change the distribution of rodent populations around the globe, which would impact the range of rodent-borne diseases like plague.
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Photo by Julie Larsen Maher. © Wildlife Conservation Society.