ANTHRAX
Agent. Bacillus anthracis is a large, nonmotile, gram-positive rod that forms environmentally resistant endospores when exposed to air.
Reservoirs. Sheep, goats, cows, and other domestic and wild ruminants.
Occurrence. Incidence is worldwide except for the far north and some South Pacific islands, but it varies greatly by region. Anthrax in animals occurs sporadically in Eurasia, North America, and Australia but is endemic in Africa, the Middle East, India, Southeast Asia, Mexico, and parts of South America. Warm, humid areas tend to have anthrax “hot spots” because heat stress lowers animals’ resistance and the climate encourages sporulation of shed organisms.
Estimates of human anthrax cases range from 20,000 to 100,000 per year, with most occurring in Africa, South America, Europe, the Middle East, and the former Soviet Union. In the United States, human anthrax is very rare, with only three cases reported between 1984 and 1993. Most cases of anthrax are occupationally acquired; people at greatest risk are veterinarians and animal care workers, abattoir workers, hide tanners, wool processors, and bonemeal producers.
Transmission. Infected animals shed the organism via hemorrages that occur at death, thus contaminating soil with endospores that can remain viable for years. Other animals can become infected by grazing in the contaminated areas. Biting flies may be involved in mechanical transmission of the bacteria.
There are two forms of human anthrax that are occupationally associated: cutaneous and inhalation. Cutaneous anthrax is acquired when organisms enter broken skin, usually on the hands, arms, or face. Direct contact with tissues or body fluids of diseased animals and exposure to contaminated soil are the most common means of transmission. Inhalation anthrax results from inhaling viable spores that may be present in wool and processed hides of infected animals. A third form, gastrointestinal anthrax, results from eating contaminated undercooked meat and is not associated with any particular occupational exposure.
(snipped some info concerning Disease in Animals)
Disease in Humans.
Signs and Symptoms. Cutaneous anthrax accounts for more than 95% of cases. Within 1 week of inoculation a small, painless, reddish, pruritic papule forms and develops into a fluid-filled vesicle. The area surrounding the lesion becomes edematous, and secondary vesicles may form around the initial site. The typical lesion of cutaneous anthrax is a black eschar that develops after a vesicle ruptures and ulcerates. Most patients recover within 10 days of onset, but in some cases cutaneous anthrax progresses to systemic disease. Disseminated anthrax is rapidly fatal if untreated.
Inhalation anthrax is almost always fatal. It begins with mild, nonspecific upper respiratory signs, but within 3 to 5 days the patient become acutely ill, with fever, shock, and rapidly progressing respiratory distress. Death occurs within 24 hours of onset of the acute phase.
Diagnosis. Cutaneous anthrax is easily diagnosed if the disease is considered among the possibilities. Gram staining of the vesicular fluid often reveals large, gram-positive rods, and cultures of the fluid are usually positive for B. anthracis if specimens are collected before antibiotic therapy is begun.
The diagnosis of inhalation anthrax is much more difficult because early signs mimic a mild, influenza-like infection. Death usually occurs before the diagnosis is made.
Treatment. Cutaneous anthrax responds well to antibiotic treatment. Inhalation anthrax, however, is often diagnosed too late in the course of teh disease for even massive doses of antibiotics to be effective.