Lawmakers urge EPA to rethink use of antibiotics on citrus trees

Citrus greening disease
Citrus greening disease

emarys / iStock

US lawmakers are urging the Environmental Protection Agency (EPA) to rethink its position on the use of two medically important antibiotics to treat a disease affecting citrus production.

In a letter to EPA Administrator Andrew Wheeler, JD, MBA, yesterday, Rep. Jackie Speier (D-CA) and Sen. Elizabeth Warren (D-MA) said the EPA's proposals to significantly expand the application of oxytetracycline and streptomycin on citrus trees to prevent citrus greening disease—a bacterial infection—will exacerbate the problem of antimicrobial resistance.

The two requested that the agency not authorize expanded use of the antibiotics until it can be determined that such use will not harm human health.

The letter, which was signed by five other lawmakers, also argues that the EPA has ignored other federal agencies and scientific evidence in its decision-making process.

The EPA approved emergency use of the antibiotics on citrus trees in Florida in 2016 to combat the disease, then said it would allow expanded use of oxytetracycline on roughly 700,000 acres of citrus farms in Florida and California in December 2018. The agency is currently reviewing the request for expanded use of streptomycin.

"Antibiotics are life-saving medicines and, except in extraordinary circumstances, should only be used to treat specific illnesses in people and animals," the lawmakers wrote. "EPA's assessments appear to ignore scientific evidence, violate the principle of judicious antibiotic use, and could create unnecessary harm to human health by authorizing an unprecedented amount of medically important antibiotics to be used for plant agriculture."

Questions about human health impact

Citrus greening is caused by a bacterium—Candidatus Liberibacter asiaticus—spread by an insect called the Asian citrus psyllid. When citrus trees are infected, they produce fruits that are green, small, misshapen, and bitter and can't be sold. Most infected trees eventually die within a few years. According to the US Department of Agriculture's Animal and Plant Health Inspection Service, the disease has devastated millions of acres of citrus crops across the United States since 2005. In Florida, as much as 90% of citrus acreage has been affected.

Seeking protection against the disease, the Florida Department of Agriculture and Consumer Services asked the EPA for permission to spray oxytetracycline and streptomycin on orange trees in 2016, then renewed that request in 2017. Spraying has not solved the problem, but has slowed the spread of the disease. The Florida Department of Citrus considers antibiotic spraying to be a short-term response to citrus greening.

The proposals for expanded use of the drugs would allow citrus growers to use 338,000 pounds of oxytetracycline and 650,000 pounds of streptomycin a year. Those amounts dwarf the amounts of oxytetracycline and streptomycin used in people.

Public health and environmental advocacy groups have expressed concern about widespread application of oxytetracycline and streptomycin to control plant disease, as the drugs are used to treat a variety of human bacterial infections and are considered "highly important" and "critically important" to human health by the World Health Organization. The concern is that spraying massive amounts of the antibiotics on citrus trees could spur antibiotic resistance in bacteria in the soil, and that resistant pathogens in the soil could ultimately find their way into people and cause drug-resistant infections.

"The EPA is gambling with our life-saving antibiotics in its proposal to massively expand their use in citrus production," Matt Wellington, antibiotics campaign director for US PIRG (Public Interest Research Groups), told CIDRAP News. "Spraying thousands of pounds of a medically important antibiotic on citrus trees violates the basic principle that these drugs should be used as little as possible, and only when necessary."

"We're using more of these antibiotics on fruit trees than to treat disease in humans," Nathan Donley, a senior scientist at the Center for Biological Diversity, said in a December 2018 press release from the group, after the EPA approved expanded use of oxytetracycline. "Citrus greening is a serious issue, but using important antibiotics with limited effectiveness against the disease isn't the solution,"

In March, the Center for Biological Diversity, US PIRG, and other public health and environmental groups delivered more than 45,000 petition signatures to the EPA asking the agency to deny expanded use of streptomycin on citrus fields.

CDC, FDA concerns

The Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) have also expressed concern. In a 2017 report to the EPA obtained by the Center for Biological Diversity through a Freedom of Information Act request, the CDC concluded, based on its own testing, that antibiotics used as pesticides have the potential to select for antibiotic-resistant bacteria in the environment, including bacteria that cause human disease.

In their letter to the EPA, Speier and Warren said the agency has downplayed and ignored these concerns, and has even ignored the advice of its own experts.

According to the letter, the EPA modeled its risk analysis for the use of oxytetracycline and streptomycin off of FDA Guidance for Industry (GFI) #152, which requires the agency to determine whether a new antibiotic intended for use in food-producing animals is safe with regard to human health. The FDA considers a new antibiotic safe if there is reasonable certainty of no harm to human health from the proposed use.

Even though the EPA found that the proposed use of oxytetracycline and streptomycin created a risk of antimicrobial resistance in humans, the letter states, it failed to follow the recommended standard for approval outlined by GFI #152. The letter also says the EPA failed to follow its own recommendation that baseline data be established on oxytetracycline and streptomycin resistance and on the presence of bacteria that could affect human health in citrus orchards.

The letter also cites recent research, conducted by scientists at the University of Florida and published in the journal Phytopathology, that found that spraying oxytetracycline on citrus trees had no significant effects on citrus greening.

"Taken all together, your agency should have sought greater assurances and a better understanding of the human—and environmental—risks to expanded pesticide use," Speier and Warren wrote. "EPA's failure to fully consider these risks is especially troubling in light of the fact that the proposed technique of spraying massive quantities of these antibiotics has never proven to be effective, and indeed has now been shown in a study by citrus researchers at the University of Florida to have no demonstrable effect."

In addition to asking the EPA to reconsider its decisions on oxytetracycline and streptomycin, the lawmakers also requested written answers to a series of questions about how the agency made those decisions, including why it ignored CDC and FDA guidance on the issue, along with written or electronic communications regarding the decision-making process.

In an emailed statement, the EPA said it would respond to the lawmakers "through the proper channels." But it also cited a statement issued in June, which said that the agency had been working closely with the CDC, FDA, and USDA on the issue, and that the terms of approval of expanded use of oxytetracycline were based on guidance from those agencies and included "numerous requirements to minimize the likelihood of antibiotic resistance developing from its use in agriculture."

 See also:

Aug 28 Letter to EPA Administrator Andrew Wheeler

Aug 1 Phytopathology abstract

Dec 6, 2018, Center for Biological Diversity press release

May 11, 2017, CDC report to EPA

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