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SOME FACTS ABOUT ANTHRAX

by: Stephen B. Blezinger
Ph.D, PAS

By now, Anthrax has become a household word. Interestingly, up to a few weeks ago, few people outside of livestock producers and military personnel, especially veterans of the Gulf War had ever heard of the disease. In the livestock industry, we hear of it very sporadically, most of the time with reports coming in conjunction with some climatic extreme (flooding or drought).

While we have be deluged with information concerning the various cases of the disease and the positive testing of postal locations as related to suspected terroristic attacks at the WTC and Pentagon on 9/11, it might be of interest to note that cases of Anthrax were reported by the Associated Press on September 8. This particular situation was related to a family eating contaminated meat and developing “Anthrx-like” symptoms shortly thereafter. An important point to understand and remember here is that there is NO threat to the public from eating contaminated meat when meat is processed commercially for sale. Commercial meat production is inspected diligently. The cow consumed by the family was raised on their own farm and processed at a small custom slaughterhouse where consumers can have their own animals processed for personal use. Unfortunately, with all the hysterics in the News media, a lot of misinformation is also going around concerning the consumption of beef, the potential danger, etc.

Let's take a look at this disease and some of the facts surrounding it. Being better informed can help you wade through some of the muck and mire that you are faced with on a daily basis at this most challenging time.

Anthrax – Some History

As reported by the Center for Disease Control, Anthrax is one of the great infectious diseases of antiquity. The fifth and sixth plagues in the Bible's book of Exodus may have been outbreaks of anthrax in cattle and humans, respectively. The "Black Bane," a disease that swept through Europe in the 1600s causing large numbers of human and animal deaths, was likely anthrax. In 1876, anthrax became the first disease to fulfill Koch's postulates (i.e., the first disease for which a microbial etiology was firmly established), and five years later, in 1881, the first bacterial disease for which immunization was available. Large anthrax outbreaks in humans have occurred throughout the modern era—more than 6,000 (mostly cutaneous) cases occurred in Zimbabwe between October 1979 and March 1980, and 25 cutaneous cases occurred in Paraguay in 1987 after the slaughter of a single infected cow.

Anthrax, in the minds of most military and counterterrorism planners, represents the single greatest biological warfare threat. A World Health Organization report estimated that three days after the release of 50 kg of anthrax spores along a 2-km line upwind of a city of 500,000 population, 125,000 infections would occur, producing 95,000 deaths. This number represents far more deaths than predicted in any other scenario of agent release. Moreover, it has been estimated that an aerial spray of anthrax along a 100-km line under ideal meteorologic conditions could produce 50 percent lethality rates as far as 160 km downwind. Remember these are projections and are at best, educated guesses. Finally, the United States chose to include anthrax in the now-defunct offensive biological weapons program of the 1950s, and the Soviet Union and Iraq also admitted to possessing anthrax weapons. An accident at a Soviet military compound in Sverdlovsk in 1979 resulted in at least 66 deaths due to inhalational anthrax, an inadvertent demonstration of the viability of this weapon. The epidemiology of this inadvertent release was unusual and unexpected. None of the persons affected were children. Whether this is due to differences in susceptibility between children and adults or purely to epidemiologic factors (children may not have been outdoors at the time of release) is unclear.

One of the reasons there is some interest in this particular disease for use in biological warfare is due to it's survivability. The spore form of this organism can survive in the environment for many decades under a wide variety of conditions. Certain environmental conditions appear to produce "anthrax zones," areas wherein the soil is heavily contaminated with anthrax spores. One thing for all producers and the average citizen to understand is that Anthrax spores occur in many areas under many conditions and only become a problem when ingested in a sufficiently large concentration so as to create an infection. Conditions where the spores can readily exist include soil rich in organic matter (pH <6.0) and dramatic changes in climate, such as abundant rainfall following a prolonged drought. Partly because of its persistence in soil, anthrax is a rather important veterinary disease, especially of domestic herbivores (cattle, sheep, horses, goats). In addition to encountering anthrax while grazing in areas of high soil contamination, these herbivores may also acquire the disease from the bite of certain flies. Vultures/buzzards may mechanically spread the organism in the environment. Anthrax zones in the United States closely parallel the cattle drive trails of the 1800s.

Heath and Medical Implications

As noted and outlined by the United States Department of Agriculture, Anthrax is a disease of most if not all, mammals, including humans, is caused by a spore-forming bacterium called Bacillus anthracis. Anthrax has an almost worldwide distribution and is a zoonotic disease, meaning it may spread from animals to humans. All mammals appear to be susceptible to anthrax to some degree, but ruminants such as cattle, sheep, and goats are the most susceptible and commonly affected, followed by horses, and then swine.

The U.S. Department of Agricultures main diagnostics laboratory in Ames, Iowa, the National Veterinary Services Laboratories, maintains small quantities of anthrax to use as reference material in making confirmatory anthrax diagnoses in animals. USDA's Animal and Plant Health Inspection Service maintains that laboratory as part of fulfilling its mission to protect American agriculture.

Disease Epidemiology

Anthrax is endemic to the United States, occurring sporadically throughout the country as environmental conditions allow. The Del Rio, Texas, region has reported ongoing outbreaks of anthrax in deer and livestock this summer. The most recent outbreak there occurred on September 21, 2001. Other recent outbreaks include an outbreak in cattle and horses in Minnesota in June-July 2000; in cattle, horses, and bison in North Dakota in August 2000; and in cattle in Nebraska in January 2001.

During their vegetative stage, cells of the anthrax agent multiply in the lymph nodes of susceptible animals, including humans. When cells of B. anthracis escape from the animal's body and are exposed to oxygen, they form spores. These spores are highly resistant to heat, cold, chemical disinfectants, and long dry periods. B. anthracis spores are reported to survive for years in the environment. Environmental persistence may be related to a number of factors, including high levels of soil nitrogen and organic content, alkaline soil (a pH level higher than 6.0), and ambient temperatures higher than 60oF.

The anthrax organism may be spread within an area by streams, insects, wild animals and birds, and contamination from wastes of infected animals. Anthrax may be perpetuated in nature by hosts such as a wildlife reservoir, which in turn spills over into the livestock population. Animals are usually infected by ingesting soilborne spores, such as in contaminated food or water. Spores can be picked up directly from the soil through grazing or from feed grown on infected soil. When periods of drought cause livestock to forage much closer to the ground, animals may ingest spores in soil they accidentally eat along with forage. After flooding, the concentration of spores caught in standing water increases when preexisting or transitory ponds begin to evaporate. Spores may also be present in bonemeal, protein concentrates, excreta, and tissue and body fluids of infected carcasses.

Although rare, it is possible for animals to inhale dust harboring anthrax spores. Bites from flies and other insects that may harbor vegetative anthrax have also been reported to be vehicles for mechanical transmission.

Clinical Signs

Disease occurs when spores enter the body, germinate, multiply, and release toxins. The incubation period of natural infection in animals is typically 3 to 7 days with a range of 1 to 14 days, or more. In cattle and sheep, the course of illness may last about 1 to 2 hours. Clinical signs, such as fever up to 107 degrees Fahrenheit, muscle tremors, respiratory distress, and convulsions, often go unnoticed. After death, there may be bloody discharges from the natural openings of the body, rapid bloating, a lack of rigor mortis, and the presence of unclotted blood. This failure of blood to clot is due to a toxin released by B. anthracis.

Anthrax in horses and related animals is acute and can last up to 96 hours. Clinical manifestations depend upon how the infection occurred. If due to ingestion of spores, as in cattle, septicemia, fever, colic, and enteritis are prominent. Anthrax due to insect bite introduction (mechanical transmission) is characterized by localized hot, painful, edematous, and subcutaneous swellings at the bite location that spread to the throat, lower neck, floor of the thorax, abdomen, prepuce, and mammary glands. These horses may have a high fever and dyspnea due to swelling of the throat or colic due to intestinal involvement.

Swine, dogs, and cats usually show a characteristic swelling of the neck secondary to regional lymph node involvement, which causes dysphagia and dyspnea following ingestion of the bacteria. An intestinal form of anthrax with severe enteritis sometimes occurs in these species. Many carnivores apparently have a natural resistance, and recovery is not uncommon.

So What Does This Tell Us?

First it tells us that Anthrax is a fairly nasty disease and can result in a fairly high mortality rate. More importantly it tells us a number of other things as well:

1) Anthrax has been around for a long time in many, if not most parts of the world. Because it has been around quite some time, we have a fairly good understanding of it.

2) One of the primary reasons for it's apparent use in terrorism is it's viability.       It holds up under a number of conditions.

3) It can be treated and cured if caught soon enough. Symptoms in humans are flu-like. This is one of those times NOT to delay in going to the Doctor if symptoms appear.

4) Despite the various projections, the success of infection to this point has ben very limited much to the senders chagrin I am sure.

5) Nothing beats common sense and a cool head in a situation like this. If you suspect a problem in your livestock, you need to call the vet as soon as possible. At this point, the likelihood will be VERY small that the average producer will encounter the disease.

6) The likelihood of contracting the disease from consumption of infected meat will be very small, especially if all the meat you consume is from a commercial source where it has been inspected extensively.

Conclusions

The average person and average cattle producer has a very small chance of being exposed to Anthrax. However, in this day and time I would encourage everyone to be extremely watchful and careful. Be informed and help your friends and neighbors to be informed as well.

Dr. Steve Blezinger is a management and nutrition consultant with an office in Sulphur Springs, TX. He can be reached at P. O. Box 653 Sulphur Springs, TX 75484, by phone at (903) 885-7992 or by e-mail at sblez @peoplescom.net

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