Anthrax in the United States
Introduction
- Anthrax, which means 'coal' in Greek, is a severe disease caused by the bacteria Bacillus anthracis, which stays alive in its surroundings by sporulating. Because of this protective measure, the disease itself is fairly old and can be found naturally on all continents, including Asia, southern Europe, sub-Sahelian Africa and Australia. Anthrax can be contracted by humans and herbivorous animals, though other infected mammals and birds have been found.
Besides being a threat to the human population, anthrax has also been used in acts of biological warfare.
http://www.who.int/csr/disease/Anthrax/anthraxfaq/en/
Description of Anthrax
- Anthrax can infect both humans and animals, and although human contact does not spread the disease, humans can get infected from touching or inhaling spores from contaminated animal products. Even eating rare meat from an infected animal is enough to cause anthrax. Symptoms will generally appear within 7 days after infection. The infection can affect the skin, respiratory tract, and gastrointestinal tract.
Cutaneous Anthrax
- The most common type of anthrax, cutaneous (skin) anthrax, happens when a person has a cut of some type on the skin, allowing the bacteria to enter. An itchy lesion usually forms at this site, but after 1-2 days, it turns into a vesicle, and later, an ulcer. The surrounding lymph nodes are may also be subject to swelling. The ulcer, generally 1-3cm in diameter, contains a black necrotic (dead) center and is typically painless. However, if left untreated, approximately 20% of cutaneous anthrax cases can lead to death.
http://emergency.cdc.gov/agent/anthrax/needtoknow.asp
Respiratory (Pulmonary) Anthrax
- The most common type, cutaneous (skin) anthrax, happens when a person has a cut of some type on the skin, allowing the bacteria to enter. An itchy lesion usually forms at this site, but after 1-2 days, it turns into a vesicle, and later, an ulcer. The surrounding lymph nodes are may also be subject to swelling. The ulcer, generally 1-3cm in diameter, contains a black necrotic (dead) center and is typically painless. However, if left untreated, approximately 20% of cutaneous anthrax cases can lead to death.
Gastrointestinal Anthrax
- Gastrointestinal anthrax usually results from eating infected meat. The infection severely inflames the intestines, causing severe diarrhea and vomiting of blood, initially preceded by nausea, decreased appetite, and fever. If it goes untreated for long enough, toxaemia and shock will occur, leading to death. Gastrointestinal anthrax can also occur in the oropharyngeal – the symptoms then become a sore throat, difficulty in swallowing, fever, swollen lymph nodes, and toxaemia. Even with treatment, about 50% of oropharyngeal anthrax infections are fatal.
http://www.who.int/mediacentre/factsheets/fs264/en/
Description of the microbe
Bacillus anthracis is a Gram-positive bacterium that is responsible for the acute disease, anthrax. In 1887, Robert Koch showed that Bacillus anthracis could form endospores, and caused anthrax when injected into animals. It was also the first organism used to develop a vaccine with a weakened strain. (http://www.ncbi.nlm.nih.gov/sites/entrez?db=genomeprj&cmd=Retrieve&dopt=Overview&list_uids=13855)
Gram-positive cells share cell walls made of peptidoglycan, techoic acids, lipoteichoic acids, capsular polysaccharides, and S-layer crystalline proteins for their cell structure, but Bacillus anthracis differs by being surrounded by its poly-D-glutamate capsule instead of a polysaccharide capsule, having no techoic acid, and having non-glycosylated S-layer proteins. (http://www.jbc.org/cgi/content/full/281/38/27932)
It is large and rod shaped and about 1-1.2um wide, and 3-5 um long. It is capable of growing both in aerobic and anaerobic conditions. It is similar to Bacillus cereus and Bacillus thuringiensis both genotypically and phenotypically, and all are able to form spores. (http://textbookofbacteriology.net/Anthrax.html)
The difference being that Bacillus anthracis has the ability to synthesize virulence factors.(http://www.ncbi.nlm.nih.gov/sites/entrez?db=genomeprj&cmd=Retrieve&dopt=Overview&list_uids=13855)
Also capable of forming biofilm which allows it to be resistant to the host immune system and antibiotics. (http://mic.sgmjournals.org/cgi/content/full/153/6/1693?view=long&pmid=17526827)
When faced with starvation, Bacillus anthracis is capable endospore formation. Spores are capable of resisting heat, cold, dessication, radiation, and disinfectant. This allows the spores to survive in inhospitable environments and germinate when conditions are more favorable. (http://textbookofbacteriology.net/Anthrax.html)
Virulence factors pXO1, anthrax toxin, and pXO2, capsule gene, are responsible for the pathogenicity. They are both required for the virulence of Bacillus anthracis. The capsule is made up of a poly-D-glutamate polypeptide. The capsule is either “smooth” or “rough”, which is not virulent. The capsule gene both protects against phagocytosis and mediates the bacterial infection of the bloodstream. Bacillus anthracis capsule and anthrax toxin grow in response to increased atmospheric Co2. (http://textbookofbacteriology.net/Anthrax.html)
Three components contribute to the anthrax toxin, the edema factor (EF), protective antigen (PA), and the lethal factor (LF). The edema factor increases fluid build up in the cells while the lethal factor promotes cell death and bacterium release. (http://www.ncbi.nlm.nih.gov/sites/entrez?db=genomeprj&cmd=Retrieve&dopt=Overview&list_uids=13855)
Combinations of these factors cause these results in experimental animals:
PA+LF is lethal EF+PA causes edema EF+LF is inactive PA+LF+EF causes edema and necrosis, and is lethal (http://textbookofbacteriology.net/Anthrax.html)
Transmission of disease
How is it transmitted? Is there a vector (animal/insect)?
Problems with Anthrax in America
Outbreak of anthrax in the United States
Although human anthrax was historically known to be contracted from high exposures to animals and animal products that were infected with Bacillus Anthracis spores, the spread of human anthrax in the United States took on a different approach. The problem arises during early October to November in 2001, as the United States of America announced its first ten confirmed cases of human anthrax from bioterrorism. The outbreak of this disease was caused by inhalation of anthrax from exposure of the disease.
Spread of anthrax in the U.S.
Intentional contaminated letters and packages were mailed to various districts of the U.S., targeted victims remained helpless and vulnerable to the Bacillus anthracis spores upon opening and handling. As a result from this event, the U.S. postal office was affected drastically as all of the initial patients were either employees of the postal office, mail handlers and sorters.
Effects of anthrax on the U.S. citizens
The problem caused by this hazardous disease in America results in various health issues along with social disruption and an economic crisis. Victims experienced chills, a fever, difficulty coughing, constant sweats, fatigue, and typical feelings of morning sickness; nausea and vomiting. As an outcome of the ten initially infected citizens, all displayed abnormal chest x-rays; infiltrates, mediastinal widening, and pleural effusion. With efforts to restore health to the ten patients, methods of multiple drug antibiotics were used along with guidance and supportive care, however only 60% of the patients survived.
Prevention
In the United States, the primary way to reduce the risk of exposure is through controlling the livestock. Proper disposal of anthrax infected carcasses and vaccination of at risk herds can help reduce exposure. The most effective and proper way of eliminating the exposure is through incineration of the contaminated soil. Patients that have died from anthrax should be isolated and contaminated materials should be properly disposed of through incineration. It is important that following the first detection of an anthrax infection in a herd, the surrounding animals should be removed and isolated from the field. The animals will then need to be monitored for a period of time and all the animals should be vaccinated if needed.
Vaccines
Vaccines can be used to prevent the disease in humans and animals. In the United States however, only high-risk groups such as military personnel are given the vaccine. Vaccine is not recommended for public use in the United States as anthrax cases are very rare and potential adverse side effects have been reported in some patients.
Anthrax Vaccine Adsorbed(AVA)
Anthrax Vaccine Adsorbed (AVA) is the only licensed human vaccine in the United States. The vaccine does not contain any dead or living bacteria cells but rather anthrax protective antigen protein so that vaccine cannot give an infection to the person. In a controlled study in which 379 employees received the vaccines, 414 received placebo, and 340 received neither vaccines or placebo, the study documented a vaccine efficacy of 92.5% for protection against anthrax (cutaneous and pulmonary). The duration of this protection is unknown in humans but in animals it has been known to have an effect from one to two years after two doses.
Treatment
Antibiotics
Antibiotics can be used before and after the patient has come in contact with the disease. This therapy is shown to result in a substantial recovery in individuals and animals infected with anthrax if taken immediately. Antibiotics can also be used for prevention and treatment in asymptomatic patients that may have been in exposed to the anthrax but have shown to have less of an effect on the spore form of the disease. It is important to note that antibiotics can kill the bacteria, but do not have an effect on anthrax toxins so late treatment of the infection can be detrimental.
What else could be done to address this problem
Are there solutions that could be successful but haven't been implemented due to political or economic reasons? Are there successful efforts in other countries? Are there reasons why these efforts may or may not be successful in the country you've focused on? etc. etc.
References
Edited by Kevin Kuo, Maggie Chan, Miya Yoshida, Eric Ku, Stephen Chin, students of Rachel Larsen
