What is Botulism?
Botulism is a rare but sometimes deadly condition where the body experiences widespread weak and floppy muscle movements. This is due to a toxin known as botulinum neurotoxin (BoNT), produced by a bacterium called Clostridium botulinum. This condition was first recognized as foodborne illness, meaning it originated from consumed food, in Germany and Belgium in the 1800s. Since then, different ways of contracting botulism have been found, including through wounds, medical treatments, and inhalation.
Although an antitoxin can be given to patients affected by the botulinum neurotoxin to lessen the condition’s impact, there is no perfect cure yet. Treatment still depends on methods such as mechanical ventilation, where a machine helps a patient breathe, and other intensive therapies for weeks. These treatments help while the body’s own mechanisms for signaling muscle movement recover.
The botulinum neurotoxin is the most powerful poison known to us, and it’s relatively easy to manufacture, store, and spread. Therefore, it’s a subject of significant concern for defense organizations worldwide as they strive to protect against its potential misuse.
What Causes Botulism?
Botulism is a condition that affects the nerves and causes paralysis. It comes from a powerful poison made by a specific type of bacteria called Clostridium botulinum. Other related bacteria, such as Clostridium butyricum and Clostridium baratii, occasionally also produce this toxin. These bacteria are widely spread in the environment, found in places like soil, seawater sediment, seafood, fruits, and vegetables. They form hardy spores that can survive in harsh conditions. When the conditions are right, these spores turn into bacteria that produce the toxin.
The poison that the bacteria produce, called botulinum neurotoxin, is considered the most lethal toxin known. It is extremely potent, with only a tiny amount – measured in nanograms, which are a billionth of a gram – needed to be harmful. For reference, the lethal dose, or the amount that can kill half of those exposed, is between 1 and 3 nanograms per kilogram of body mass.
The paralysis in botulism happens because this toxin stops a chemical called acetylcholine from being released in our bodies. This chemical is important because it helps our muscles move. When it’s blocked, the nerves can’t signal the muscles to contract, which leads to paralysis.
There are a few ways a person can get botulism. The most common way is by eating food that has not been stored properly and contains the bacteria, which can release the toxin. It can also get into the body through a contaminated injection, or in theory, can be used as a biological weapon. In some cases, infants and people who have wounds can also get it if the bacteria multiply and release the toxin inside their bodies.
Risk Factors and Frequency for Botulism
Since 1973, the Centers for Disease Control and Prevention, or CDC, has been monitoring cases of botulism – a serious illness caused by bacteria – in the United States via the National Botulism Surveillance System. Between 2011 and 2015, there was an average of 162 cases of botulism reported each year. Botulism can occur in various forms, and the rate of each type has been consistent over recent years:
- Infant botulism: 71%-88% of cases
- Foodborne botulism: 1%-20% of cases
- Wound botulism: 5%-10% of cases
- Botulism of other or unknown origin: 1%-4% of cases
Though unusual, there have been instances of large outbreaks of botulism. An example includes a 2015 outbreak in Ohio that resulted in 27 cases. Thankfully, there have been no reported instances of botulism resulting from bioterrorism in the United States. There was only one case of botulism that occurred due to the use of an unlicensed, highly concentrated form of BoNT.
The number of deaths due to botulism is low compared to the overall number of cases. In the 1950s, the mortality rate of foodborne botulism was between 60-70%. However, from 1975-2009, the overall mortality rate dropped to 3.0%. Out of 3,618 botulism cases, there were 109 deaths reported. These deaths varied by the type of botulism:
- Infant botulism: less than 1% of cases resulted in death (18 deaths from 2,352 cases)
- Foodborne botulism: 7.1% of cases resulted in death (61 deaths from 854 cases)
- Wound botulism: 5.0% of cases resulted in death (18 deaths from 359 cases)
- Botulism of other or unknown origin: 22.6% of cases resulted in death (12 deaths from 53 cases)
Signs and Symptoms of Botulism
Botulism is a serious illness that starts with problems related to certain nerves involved in muscle control, particularly those in your face and throat. This leads to symptoms like:
- Visual disturbances (diplopia)
- Difficulty swallowing (dysphagia)
- Voice changes (dysphonia)
- Slurred speech (dysarthria)
These symptoms occur because botulism affects certain nerves in your body. As the disease progresses, it affects other parts of the body leading to weakness and in severe cases, paralysis. Patients may also experience blurred vision and, occasionally, abnormal physical sensations (paresthesias). If botulism affects the diaphragm – the muscle that controls breathing – it can cause respiratory failure, which may require a breathing tube and ventilation machine. Other symptoms include constipation and difficulty urinating. If you get botulism from eating contaminated food, you might also experience abdominal pain, nausea, and vomiting starting 12 to 72 hours after eating the contaminated food.
Infant botulism can vary in how it presents and its severity. Common early symptoms in infants include constipation, weakness, difficulty feeding, a weak cry, and excessive drooling. If an infant is unusually floppy and has low muscle tone, they might need immediate medical care including a breathing tube and ventilation machine.
Wound botulism can happen if the botulism bacteria get into a wound. This is often associated with illegal drug use. Symptoms are similar to other forms of botulism, but can also include fever and signs of an infection, such as redness and swelling around a wound. This usually happens 5 to 15 days after the bacteria enter the body.
Testing for Botulism
If you’re suspected of having botulism, a type of food poisoning, your doctor might treat you before the lab test results come back, because the disease can progress quickly and it takes a few days to confirm. The doctor will base their initial diagnosis on your medical history and a physical exam. They might also perform an electromyogram, which is a test that checks the health of the muscles and the nerves that control the muscles, to support their suspicion.
Once the lab results come back, they can confirm botulism. The scientists in the lab will check your blood and stool samples for botulinum toxin, which is the toxin that causes botulism. They can also look for spores in your stool sample and, if you have a wound, they may take a swab for cultures. A traditional way to test for botulism is the mouse lethality assay, where a live mouse is injected with your sample, and then watched for signs of botulism. Unfortunately, other tests that have been developed to detect botulism, like ELISA and electrochemiluminescence, often have low sensitivity due to poor quality antibodies and other factors in samples like stool and blood. Endopeptidase assays are another type of test that is being developed to detect botulinum toxin and have high sensitivity and specificity.
Treatment Options for Botulism
Treating botulism, a rare but serious illness caused by toxins, covers a few key steps. These include giving the patient a special medicine called an antitoxin, admitting them to the hospital for close monitoring, providing help with breathing if necessary, and cleaning the wound and treating it with antibiotics if the botulism comes from a wound.
All patients with symptoms that might indicate botulism should be admitted to the hospital straightaway so their condition can be closely monitored. The specific antitoxin therapy given to patients can come in two forms. One is a medicine made from horse serum, recommended for patients over a year old. The other is a medicine made from human antibodies, designed for infants under one year of age. These antitoxin treatments aim to counteract the toxins causing botulism.
If healthcare providers believe a patient may have botulism, they should immediately reach out for help. They can contact regional Poison Control Centers, State Health Departments, or even the national Centers for Disease Control and Prevention (CDC). If the symptoms seem to be progressing rapidly, the patient should be given an antitoxin as soon as possible.
Constant monitoring involves regular checks of the patient’s breathing (ventilation), blood flow (perfusion), and their ability to keep their airway open. It also involves the use of equipment to continually measure their oxygen levels in the blood, their breathing capacity, and their blood gases. If a patient’s ability to breathe is compromised or their ability to use their lungs is less than 30% of what is expected, doctors may need to put a tube down their throat to help them breathe (intubation).
If botulism is caused by a wound, the wound needs to be cleaned (debridement), and the patient given antibiotics after the antitoxin. Suitable antibiotics could include Penicillin G or metronidazole, depending on the patient’s possible allergies. However, some antibiotics are not advisable: Aminoglycosides can sometimes make the effects of botulism worse, and antibiotics should not be used in infants with botulism due to the risk of toxin release.
Additional treatment could include feeding the patient through an IV if they have severe illness affecting the digestive system (severe ileus), and flushing the intestines with a solution to remove toxins in case of foodborne botulism without severe ileus.
Lastly, the patient should be cared for in an intensive care unit (ICU) setting with special attention to their airway and breathing, since breathing failure is a common problem in botulism. Other considerations may include intubation if there are signs of respiratory distress; a tracheostomy, a surgical procedure to create an opening through the neck into the windpipe to manage secretions; monitoring urinary output by inserting a catheter; and taking measures to prevent stomach ulcers caused by stress. Finally, doctors should avoid giving the patient magnesium salts as these can worsen the muscle weakness caused by botulism.
What else can Botulism be?
Here are some medical conditions that may be considered when diagnosing patients:
- Basilar artery stroke
- Diphtheria
- Encephalitis
- Familial Mediterranean fever
- Hypermagnesemia
- Hyperthyroidism and thyrotoxicosis
- Neurasthenia
- Poliomyelitis
- Tick paralysis
- Cerebrovascular disease of the brainstem
Possible Complications When Diagnosed with Botulism
Hospital-acquired infections, often referred to as nosocomial infections, are very common and need to be avoided. Other complications that can arise include urinary tract infections (UTI), inflammation of a vein – often in the leg (thrombophlebitis), and a type of blood clot that forms in the deeper veins, commonly the legs (deep vein thrombosis).
Additional adverse outcomes include bed sores from prolonged pressure on the skin (pressure sores), the stiffening of muscles or joints (contractures), and a lack of adequate growth or development (failure to thrive).
Possible Complications:
- Hospital-Acquired Infections (nosocomial)
- Urinary Tract Infections (UTI)
- Inflammation of a Vein (Thrombophlebitis)
- Blood Clot in the Deep Vein (Deep Vein Thrombosis)
- Bed Sores (Pressure Sores)
- Stiffening of Muscles or Joints (Contractures)
- Lack of Adequate Growth or Development (Failure to Thrive)
