Climate crisis, food production and the rising risk of pandemics

Could climate change be impacting the spread of diseases?

Australia is already feeling the effects of the climate crisis through rising temperatures, drought and major bushfires.

Meanwhile, governments are loosening environmental laws and agribusiness farming is damaging the habitat of native and introduced species.

All of this is changing the environment in which animals, including humans, live. But could it also be impacting on the spread of diseases?

There has been a rapid rise in the number of flying foxes in Coffs Harbour, in mid-north coast New South Wales. The clearing of hundreds of hectares of trees for blueberry cultivation, along with run-off from pesticides, has apparently damaged their native food supply. Seeking new food sources, these bat have begun moving into urban areas.

But there are health warnings associated with flying foxes and micro bats, as they carry the Australian bat lyssavirus, which is similar to rabies.

Pathogens

Diseases are caused by an organism know as a pathogen. All a pathogen needs to thrive and survive is a host. Once it sets itself up in the host’s body, it manages the body’s immune responses and uses it to replicate itself before spreading to a new host.

Depending on the type of pathogen, it can be transmitted in several ways: skin contact, bodily fluids, airborne particles, contact with faeces or a surface touched by an infected species.

The most typical pathogens are bacteria, fungi, parasites and viruses, such as lyssavirus.

There have already been 89 incidents of people requiring treatment to guard against lyssavirus after been bitten or scratched by flying foxes in the Coffs Harbour region.

Lyssavirus can also be passed on to humans indirectly. In the Brisbane suburb of Hendra, which is close to two major racecourses, the virus spread to horses via food that had been contaminated by flying fox bodily fluids. Known as the Hendra virus, it was subsequently passed on to humans involved in caring for these horses.

In horses, this virus can generate a fever, increased heart rate and rapid deterioration of respiratory and/or nervous system signs. However, there is a vaccine for horses.

In humans, it can cause fever, cough, sore throat, tiredness and, later, meningitis or inflammation of the brain and sometimes convulsions and coma. It can be fatal and there is no human vaccine currently available.

A pandemic refers to a large-scale spread of a particular disease for which there are no vaccines or known treatment. Perhaps the best-known pandemic was the worldwide spread of human influenza towards the end of World War I.

The pandemic took place in three waves: March 1918, where the mortality rate mirrored previous influenza outbreaks and their effects on the elderly and very young; September 1918; and early 1919, where it became extensively fatal. It is estimated that, worldwide, about 500 million people were infected and 50-100 million people died as a result of the pandemic.

Analyses of samples from second wave frozen corpses indicated the disease had migrated across species, most likely from bird-to-swine, then swine-to-human and finally human-to-human.

Food production

Since then there has been a rise in the speed with which various influenza viruses have spread. This has been linked to post-World War II changes in food production.

Global agribusiness meat production is based on the Taylorist time-and-motion factory model, in which maximum profitability shapes productivity. It revolves around shaping the type of animal best suited for quick development and fast delivery to market at the lowest possible cost.

At a national level, agribusiness production is generally structured vertically; that is, a single company owns and controls every stage of the process. When an avian or swine flu outbreak occurs in one country, the company moves to source its supply from another location.

In 1997, a deadly bird flu swept through poultry on two farms in Hong Kong. Two months later, a child died of the same highly pathogenic strain that had apparently jumped the species barrier. This was followed later by a small number of infections and deaths linked to handling of poultry.

By the end of the year birds begin to rapidly die in the city’s markets and authorities were forced to step in, ordering the destruction of all 1.5 million poultry.

Infected birds died from the inside out, imploding from internal organ damage. Humans similarly suffered organ breakdown and collapse, especially of the lungs, which often led to patients effectively drowning in their own fluid within days of infection.

In 2009, an outbreak of a new strain of swine flu in Mexico spread globally through human-to-human contact. Within a month, the World Health Organisation had reported 15,510 official cases of swine flu and 99 recorded deaths in 53 countries.

Since flu can transmit before symptoms appear, it had all the earmarks of a pandemic. But while the flu spread quickly, its virulence was not much more than that of a bad seasonal flu.

Profits

Pandemics do not just affect human populations.

At present, there is a pandemic of African Swine Fever (ASF) that has spread to more than 50 countries and has particularly devastated China, home to half of the world’s 1.3 billion pig population.

ASF has been identified in Eastern Europe, where the current outbreak began in 2014, Southeast Asia (Vietnam, South Korea, Laos, the Philippines), Western Europe (Belgium) and, more recently, in East Timor.

While the virus does not spread to human beings, it is virtually 100% fatal once established in a pig population. Infected pigs die in a similar manner to animals infected with bird flu.

The severity of the crisis has meant global prices have risen substantially in intensive or semi-intensive pork producing countries not yet infected, such as the United States and Canada.

Australia, is taking steps to deal with the $2 billion threat ASF poses to the industry here.

Federal agricultural minister Bridget McKenzie announced the creation of a national feral-pig coordinator on November 8. There are an estimated 25 million feral pigs in Australia that are already responsible for annual loses of $14.5 million in agricultural production.

However, if the government’s only strategy for dealing with ASF is feral pig control, then it is almost certain that the disease will gain entry through other methods of transmission.

ASF can be transmitted through direct contact with infected animals, either wild or domestic, and parasites, such as ticks.

The virus can also survive several months in processed meat and several years in frozen carcasses. In July, meat containing the virus was found by port authorities in Northern Ireland. While Australian pig production is mainly for fresh pork products, the vast majority of bacon, ham and other cured pork products are still imported.

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