ANTHRAX IN AMERICA 2001-2003: Microbiology of Anthrax
Microbiology of Anthrax
B. anthracis is a large aerobic, gram-positive, spore-forming, nonmotile Bacillus species (1-1.5 |xm x 3-10 |im). Spores grow on ordinary lab media at 37°C and resemble a “jointed bamboo- rod” appearance and a “curled-hair” colonial appearance. B. anthracis forms a prominent capsule in tissue in vivo and in vitro in the presence of bicarbonate and carbon dioxide. Germination occurs when the bacillus is exposed to an environment rich in amino acids, nucleosides, and glucose. Spore formation (sporulation) will occur when the infected body is opened and exposed to air. These spores can survive for decades in ambient conditions.
Anthrax is a zoonotic disease that predominantly occurs in domesticated and wild animals. Contact with infected animals or animal products can result in human infection. There are three main forms of anthrax infection: 1) inhalation, 2) cutaneous, and 3) oropharyngeal/gastrointestinal. Other forms of anthrax infection include meningococcal and oropharyngeal. Natural infection occurs predominantly by the cutaneous route. prescription drugs online canada
Inhalation anthrax occurs when spores are inhaled. It is the most lethal form with mortality greater than 80%. The spores must be 1-2 \xm in length to stay in the lungs. Spores that are greater than 5 microns in size pose a minimal threat to the lungs, since they are trapped in the nasopharynx or cleared by the mucociliary escalator system. Cutaneous anthrax infection occurs when spores enter the body through an abrasion. This may occur when handling animal hides, wool, leather, or hair from infected animals. Gastrointestinal anthrax follows consumption of grossly contaminated and undercooked food. This is characterized by acute inflammation of the intestinal tract. Oropharyngeal anthrax is a milder form of gastrointestinal anthrax and has a mild course. B. anthracis can also cause meningitis. The most common portal of entry is thought to be the skin. However, inhalation and gastrointestinal anthrax can also lead to meningitis. In all of these cases, it is felt to be fatal if untreated.
Epidemiology
B. anthracis is found worldwide. It is a normal part of the soil flora and periodically undergoes bursts of multiplication that are not well understood. Conditions for multiplication are favorable when the soil pH is above 6.0, rich in organic matter, and when a dramatic change occurs in the soil environment, such as a drought or abundance of rainfall. Epizootics continue to occur in highly endemic areas, such as Iran, Iraq, Turkey, Pakistan, and sub-Saharan Africa. It is reported that anthrax killed over one million sheep in Iran in 1945. Herbivores can be infected while grazing. It has been suggested that spread from animals to animals occurs by biting flies, and to different environments by vultures and nonbiting flies. Animal vaccination programs have helped in some areas; nevertheless, epizootics still occur. For example, in 2000, over 30 farms in North Dakota were quarantined during an anthrax epidemic in which 157 animals died.
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Anthrax in humans occurs following the exposure of agricultural or industrial workers to contaminated animals. From 1900 to 1976, under natural conditions in the USA, only 18 cases of inhalation anthrax had been reported, and they were related to textiles manufactured from imported goat hair. The largest epidemic of inhalation anthrax occurred in 1979 in Sverdlovsk, Russia, where it is believed that there may have been 250 cases, with as many as 100 deaths.
Cutaneous anthrax is more common; there were 224 cases reported between 1944 and 1994 in the United States. Outside the United States, the largest epidemic of human anthrax occurred between 1978-1980 in Zimbabwe, where about 10,000 cases were reported—all mostly cutaneous. Although there is little data to accurately measure the incidence of gastrointestinal anthrax, it is still reported in Africa and Asia, mostly resulting from undercooked food. buy kamagra oral jelly
Recently in the United States, there have been 22 cases of anthrax of unnatural cause, including two cases in which the source of death is still unknown. One is a 61-year-old stock room employee in New York City, and the other is a 94-year-old woman from rural Connecticut.