September 5, 2017 at 3:32 p.m.
Hemorrhagic Bowel Syndrome research reported
The disease has become a growing concern in cattle operations. Past, unproven, theories pointed toward Aspergillus fumigatus, Clostridium perfringens, Salmonella spp., and bovine viral diarrhea virus (BVD) as possible causes.
Tager discussed HBS symptoms, recent research on possible causes, and a newly emerged preventative feeding solution to prevent HBS.
Disease symptoms include depression, lack of appetite, dehydration, bloody stool or no stool, fever in the front end, cold hind end, and elevated heart and breathing rate. The disease is highly fatal, resulting in death in 85 to 100 percent of cases within 24 to 48 hours. Investigation has shown massive hemorrhaging of the jejunum (middle section of small intestine) and blockage of the intestine with resulting blood clots.
Suspected contributing factors include fermentable carbohydrates, season, and stage of lactation. Cows in early lactation are more susceptible and 94 percent of cases are second lactation cows or older. While forage quality and the presence of Aspergillus fumigatus and pathogen challenges from Clostridium perfringens, type A, are the most pointed to causes of the disease, they were not proven in research studies. One study, conducted in Iran, found that C. perfringens was present in most, but not all, cultured HBS tissues. In a second study, 12 healthy cows were inoculated with C. perfringens, Type A, but none developed clinical signs of HBS.
Another study proposed that an alternate pathogen (like A. Fumigatus) may be responsible for the initiation of the disease by first disrupting the lining of the gut to allow C. perfringens in.
When five dairy farms in southern Alberta, Canada experienced weekly cow deaths due to HBS in 2011, Agriculture and Agri-Foods Canada (similar to the U.S. Department of Agriculture) was contacted to investigate. Jejunal samples were taken from HBS cows, as well as non-HBS cows. Common pathologies were present in the jejunal samples from the HBS cows - inflamed Peyers Patches, severe hemorrhaging, complete loss of mucosal structures, and large blood clots. The non-HBS cows had none of those symptoms.
Bacterial analysis found that the primary pathogen was E. Coli, with both O157:H7 and non-O157:H7 shiga toxin producing strains in tissues and digesta. There were no Clostridia or Salmonella and only one isolate of non-pathogenic Listeria grayii.
Tager noted that the O157:H7 toxin is the same one that has caused problems with food-and-mouth in Europe and Canada.
Dairy cattle are the main reservoir of Escherichia coli O157:H7. The toxin naturally exists in the gut, but is kept under control by other competing microbial populations and is not usually harmful in cattle - but is detrimental to humans. Some strains create shiga toxins that cause mild to severe pathological symptoms in cattle, among them diarrhea and/or hemorrhaging.
O15:H7 disrupts the bowel by attaching to the surface of epithelia, disrupting the membrane and beginning to "colonize" epithelial cells. That causes the cells to change and form lesions. The colonies/lesions produce toxins that then cause diarrhea or hemorrhaging.
Although there are no effective treatments for HBS, new approaches to managing pathogen issues in livestock using prebiotics and probiotics are gaining support.
With that in mind, Tager addressed whether feed additives could help prevent the problem. She cited several studies that found that probiotics can decrease the binding and lesion formation of E. coli O157:H7 in human epithelial cells. Another study showed that beneficial microbes in the gut can use prebiotic sugars - Sorbitol, L-arabinose, trehalose and rhamnose - as nutrients, but that E. coli O157:H7 cannot. The theory is that good microbes will thrive on these nutrients and "competitively exclude" E. coli O157:H7.
Tager also noted that the Vi-COR product, Celmanax Liquid, can act as a prebiotic to help reduce E. coli O157:H7 in cattle. Celmanax components block the attachment and infiltration of E. coli O157:H7 into the intestine.
To test the efficacy of Celmanax Liquid in preventing pathogen adhesion to intestinal cells, jejunal sections were harvested from healthy steers and cultured in vitro. Aliquots of E. coli O157:H7 were added to the jejunal cells in the presence or absence of 0.01 percent to 1 percent Celmanax Liquid. The samples were incubated, then washed to remove unattached bacteria. The number of cells was counted.
The study found that Celmanax, at 0.01 percent, led to a 10-fold reduction in E. coli attaching to explants of jejunum. At 1 percent, Celmanax decreased E. coli attachment by 100-fold.
Feed samples from the Canadian study farms also contained high amounts of mold, including pockets of white, blue, pink, or dark red mold. Samples of stored forages - corn silage, barley silage, and dry hay - were collected from the farms and evaluated for the presence of mycotoxigenic fungi. Various fungi, including Aspergillus fumigatus, were isolated from the forages. They were also isolated from tissues and digesta taken from HBS cows.
Jejunal samples from healthy steers were incubated with an extract of moldy forage or pure mycotoxins, with or without Celmanax. The results showed that Celmanax eliminated the cytotoxic effects of fungal extracts and purified mycotoxin standards.
Further studies showed that, when Celmanax was added to the diets on the farms, the incidence of HBS cases dropped to none.
In conclusion, Tager summed up what has been learned thus far. Those findings indicate that HBS is not caused by one specific organism. Differences may be due to geography.
HBS may need a "perfect storm" of mycotoxins, toxin producing pathogens, and other factors.
"It may need to have several other factors. It could be weather, age of cattle, and location. It happens when they all come together - and it happens fast," Tager concluded.[[In-content Ad]]
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