The spores germinate at the site of entry into the tissues and then spread by the circulation to the lymphatics, where the bacteria multiply.The production of two powerful exotoxins and lethal toxin by the bacteria causes death. Veterinarians can often tell a possible anthrax-induced death by its sudden occurrence, and by the dark, nonclotting blood that oozes from the body orifices. Most anthrax bacteria inside the body after death are outcompeted and destroyed by anaerobic bacteria within minutes to hours post mortem. However, anthrax vegetative bacteria that escape the body via oozing blood or through the opening of the carcass may form hardy spores. These vegetative bacteria are not contagious. One spore forms per one vegetative bacterium. The triggers for spore formation are not yet known, though oxygen tension and lack of nutrients may play roles. Once formed, these spores are very hard to eradicate.The infection of herbivores (and occasionally humans) by the inhalational route normally begins with inhaled spores being transported through the air passages into the tiny air sacs (alveoli) in the lungs. The spores are then picked up by scavenger cells (macrophages) in the lungs and are transported through small vessels (lymphatics) to the lymph nodes in the central chest cavity (mediastinum). Damage caused by the anthrax spores and bacilli to the central chest cavity can cause chest pain and difficulty breathing.
TNF-alpha is a cytokine whose primary role is to regulate immune cells, as well as to induce inflammation and apoptosis or programmed cell death. Interleukin 1, beta is another cytokine that also regulates inflammation and apoptosis. The overproduction of TNF-alpha and IL1B ultimately leads to septic shock and death. However, recent evidence indicates anthrax also targets endothelial cells that line serous cavities such as the pericardial cavity, pleural cavity, and peritoneal cavity, lymph vessels, and blood vessels, causing vascular leakage of fluid and cells, and ultimately hypovolemic shock and septic shock. Diagnosis
Various techniques may be used for the direct identification of B. anthracis in clinical material. Firstly, specimens may be Gram stained. Bacillus spp. are quite large in size (3 to 4 μm long), they may grow in long chains, and they stain Gram-positive. To confirm the organism is B. anthracis, rapid diagnostic techniques such as polymerase chain reaction-based assays and immunofluorescence microscopy may be used.All Bacillus species grow well on 5% sheep blood agar and other routine culture media. Polymyxin-lysozyme-EDTA-thallous acetate can be used to isolate B. anthracis from contaminated specimens, and bicarbonate agar is used as an identification method to induce capsule formation. Bacillus spp. usually grow within 24 hours of incubation at 35 °C, in ambient air (room temperature) or in 5% CO2. If bicarbonate agar is used for identification, then the medium must be incubated in 5% CO2.