Issue 50, July 2012
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New Alternatives to Antibiotics Help Keep Animals Healthy

When a bacterial infection threatens our health, our immune system kicks in to counter the threat, but sometimes the infection is too powerful to handle without help. In that situation, antibiotics may be needed to treat the illness. The same is true for animals.

Antibiotics have long been used to fight dangerous microorganisms like bacteria, fungi and parasites. They are essential for human and animal health and continue to save lives as well as enhance animal production and efficiency.

Over the years, concerns have increased about certain bacterial strains' ability to develop resistance to antibiotics. In response to these concerns, effective alternative technologies have been developed by Agricultural Research Service (ARS) scientists and others to help improve animal production and protect animal health and food safety.

Fighting Foodborne Bacteria with Organic Compounds

One alternative to antibiotics is a patented invention that uses organic compounds to combat foodborne bacterial pathogens in animals' intestines. Microbiologist Robin Anderson and his colleagues at the ARS Food and Feed Safety Research Unit in College Station, Texas, developed the technology. They demonstrated that chlorate (salt or sodium) and nitro compounds were successful in reducing and killing important foodborne pathogens like Escherichia coli O157:H7 and Salmonella. Nitro compounds are organic substances that contain one or more nitro groups, which consist of three atoms—one of nitrogen and two of oxygen—that act as one.

A chlorate-based compound mixed into feed or water was shown to be highly effective in reducing E. coli in cattle and Salmonella in turkeys and broiler chickens. However, chlorate has not been approved for commercial use in food animals by the U.S. Food and Drug Administration (FDA). Salmonella causes more than 1.3 million cases of human foodborne disease each year, resulting in about $2.4 billion in economic losses.

The most effective treatment was a combination of nitro and chlorate compounds, Anderson says.

"An attractive aspect of the nitro compound technology is that it also kills methane-producing bacteria that reside in the stomach of cattle and sheep," Anderson says. "This means it has the potential to not only reduce production costs, but also to reduce the release of an important animal-generated greenhouse gas into the environment."

The technology could also be used instead of specific antibiotics to treat diarrheal infections in young animals, according to Anderson.

Alternative Treatments for Poultry

Devising technologies that can used in poultry production without reliance on medications is part of the research efforts of scientists at the ARS Henry A. Wallace Beltsville Agricultural Research Center (BARC) in Beltsville, Md.

Avian immunologist Hyun Lillehoj has formed partnerships with industry leaders, university researchers, international scientists and her colleagues in the BARC Animal Parasitic Diseases Laboratory, which have led to the development of effective technologies that help control poultry diseases.

Lillehoj's research includes examining the effects of phytochemicals derived from safflower, plums, peppers, cinnamon, green tea and other plants in enhancing the immune system of chickens. She has also studied the beneficial effects of probiotics, which are live, nonpathogenic bacteria that promote health and balance of the intestinal tract.

In addition, Lillehoj investigates the capacity of host innate immune molecules and genetic markers to help fight parasitic diseases like coccidiosis, which causes annual losses of more than $600 million in the United States and $3.2 billion worldwide.

"We have identified several chicken genetic markers that influence parasitic diseases like coccidiosis," Lillehoj says. "We hope to eventually identify genetic markers that will make it possible to select and breed birds for enhanced disease resistance."

Scientists are looking at host innate immune molecules—produced by chickens during an infection—that have antimicrobial activity. These molecules can kill pathogens, improve host immune response and promote the growth of beneficial bacteria in the poultry gut.

The team has identified one such molecule called NK lysin.

"NK lysin proteins are produced by host lymphocytes that are activated by parasites during coccidiosis infection in the gut," Lillehoj says. "We made recombinant NK lysin proteins and demonstrated for the first time that this chicken recombinant antimicrobial protein not only kills chicken coccidia, Neospora and Cryptosporidia, which infect large animals and humans, respectively, but also shows bioactivity against avian leukosis virus-transformed tumor cells."

A Dose of Vitamin D to Ease Mastitis

The most costly and most common disease in dairy cattle may soon have a new treatment option. A natural remedy—vitamin D—has been shown to delay and reduce the severity of mastitis infection in animals.

Mastitis, which affects the mammary gland or udder, costs the U.S. economy an estimated $2 billion per year. The disease can lead to a reduction in milk production, milk quality and income for dairy producers. In some cases, infected cows must be removed from herds.

Scientists at the ARS National Animal Disease Center (NADC) in Ames, Iowa, examined the role of vitamin D in altering the response of the cow's immune system to Streptococcus uberis, a mastitis pathogen.

"Research shows that specific levels of vitamin D need to be in the blood stream to prevent conditions like rickets, or softening of the bones," says molecular biologist John Lippolis, in the NADC Ruminant Diseases and Immunology Research Unit. "A higher level needs to be in the blood for proper immune function, but generally, milk has very little vitamin D until it is fortified during processing."

Lippolis and his colleagues at NADC used a form of vitamin D called pre-hormone 25 hydroxyvitamin D that's found in blood, but not in milk. Animals treated with vitamin D had a significant reduction in bacteria counts and less clinical signs of severe infection compared to untreated cows. In the early stage of the infection, as vitamin D reduced the bacterial counts, milk production was greater in the treated animals.

Scientists also looked at bovine serum albumin (BSA) in milk, as well as somatic cell counts—immune cells that enter the mammary gland to fight infection.

"BSA is a protein in blood that becomes a marker in milk to indicate when an infection gets really bad," Lippolis says. "The barrier between the milk and the blood can become a little bit degraded, indicating the severity of the disease."

Results showed that vitamin D affects the immune system and suggested that it could help reduce the need for antibiotics in treating mastitis. Lippolis says that vitamin D also has the potential to decrease other bacterial and viral diseases such as respiratory tract infections.

For more information about animal disease research, contact Cyril Gay or Eileen Thacker, co-leaders of the ARS National Program #103, Animal Health. For food safety research, contact Mary Torrence, leader of ARS National Program #108, Food Safety (animal and plant products).