Introduction

Botulism is a neuroparalytic condition caused by a neurotoxin (a substance that affects the nervous system) that is released by a bacterium called Clostridium botulinum. Clostridium botulinum is a gram-positive, rod-shaped bacterium, hence why it is classified as a bacillus type of bacteria. The key to Clostridium botulinum is that it is an obligate anaerobe, as it requires no oxygen to grow. This type of bacteria is widespread and worldwide, hence it can be found everywhere.¹

There are 8 strains of Clostridium botulinum, and they are defined as strain A, B, C, D, E, F, G and H, and all of these produce a different toxin. Botulism transmission can occur through a few different routes:

1. Ingestion: ingesting contaminated food that was improperly or inadequately stored, for example, homemade canned food that was not properly pressurised and heated to destroy the bacteria or the spores of the bacteria. The toxins do not have a particular smell or taste
2. Inhalation: Transmission through this route is extremely rare and can only occur in laboratory settings
3. Direct inoculation: This is essentially a puncture wound through which spores of the bacteria can enter, a process that is also quite rare
4. Infant botulism: The ingestion of clostridial spores that then colonise the host's gastrointestinal (Gl) tract and release toxin produced in vivo
5. Wound botulism: An infection of a wound by Clostridium botulinum, leading to the in vivo production of neurotoxin
6. Adult enteric infectious botulism, or adult infectious botulism of unknown source, is similar to infant botulism in that the toxin is produced in the gastrointestinal tract of the infected adult
7. GI tract of an infected adult host
8. Latrogenic botulism, though rare, occurs in patients who have received botulinum toxin for cosmetic purposes²

The spores of Clostridium botulinum will form under certain conditions, and they widely exist in the environment in underground soil, rivers and seawater. When Clostridium botulinum is under certain stresses, spores are produced, and these are metabolically inert and resistant to the environment to protect the bacterial genetic material inside. When these spores enter an environment favourable for the growth of the bacteria, they will revert back into the Clostridium botulinum bacteria. This bacterium itself produces the neurotoxin, the strongest toxin that has been discovered, which is then released into the surrounding environment. ³

Signs and symptoms

The symptoms of botulism vary from mild to severe and life-threatening. To add, their incubation periods (the time from when the person is infected with the bacteria till the signs and symptoms appear) vary depending on how you get infected and could range between a few hours and a few days. 

There are 3 types of botulism infections, and all three have signs and symptoms which are common:

• Symmetric descending paralysis - the paralysis is on both sides of the body, and it starts from the head and goes down toward the toes
• Ptosis (drooping of the upper eyelids)
• Shortness of breath
• Weakness and fatigue
• Visual issues (e.g. blurry vision) but no other sensory (related to the other senses) problems⁴

Diagnosis

Early diagnosis is very important because paralysis can reach the respiratory muscles and cause difficulty in breathing, which can cause death. 

To diagnose botulism, the doctor will check for signs of muscle weakness or paralysis, such as drooping eyelids and a weak voice. They will also ask about the intake of foods consumed in the last few days and if you have been exposed to the bacteria through a wound .Diagnosis of botulism can also be done through the detection of the toxin. This can be done in a variety of ways for example, blood can be checked, gastric contents to see if there are toxins in the stomach or by detecting toxins in a stool sample.⁵

Antitoxin treatment

Two types of antitoxin therapies are available for treating botulism. The equine serum heptavalent botulism antitoxin, containing antibodies for seven of the eight known toxin types (A through G), is used for children over one year old and adults. This heptavalent formulation, which replaced earlier versions, was approved by the FDA in 2013. It is stored in the Strategic National Stockpile and distributed via the CDC's drug service.⁶

Antibiotic therapy

Antibiotic treatment for wound botulism, though not confirmed by clinical trials, is commonly used and recommended after administering antitoxin. Penicillin G (3 million units IV every four hours for adults) is effective against other clostridial species and is often utilised. For patients allergic to penicillin, Metronidazole (500 mg IV every eight hours) is an alternative option. Given the risk of polymicrobial infection in wound botulism cases, patients should quickly receive antimicrobial therapy, particularly if they exhibit symptoms such as leukocytosis, fever, an abscess, or cellulitis. Treatment may need to be expanded to address other organisms found in the wound. However, the use of aminoglycosides is contraindicated, since they have been reported to induce neuromuscular blockade, potentiating the effects of the toxin in these patients. ⁷

For wound botulism, antibiotics are administered alongside proper debridement. The length of treatment varies based on the severity of the wound. For complicated wounds, consultation with an infectious disease specialist should be sought, as a doctor may need to surgically remove infected tissues.

Rehabilitation and Long-term Care

As recovery takes place, therapy may be required to improve speech, swallowing and other functions affected by the disease.

Preventative measures

Clostridium botulinum can be inactivated with high temperatures that are a minimum of 120 degrees celsius for at least 5-10 minutes. Hence, it is important that food is cooked and prepared properly, especially home-cooked canned foods or canned food. One should avoid eating canned food if the can is bulging, which means that there is air in the can that suggesting the presence of Clostridium botulinum. Clostridium botulinum can metabolise certain sugars that are in a can and can produce carbon dioxide.⁸

For children under the age of 1, it is best to avoid feeding them honey or corn syrup as there is some evidence that states that one may get infant botulism from eating honey under the age of 1.

For foodborne botulism, laxatives, enemas, or other cathartics may be administered if there is no significant ileus. Patients with wound botulism should receive thorough debridement, regardless of the wound's appearance. Additionally, patients should get a tetanus booster if their last immunisation was five or more years ago.⁸

Special considerations

Antibiotics are not advised for treating infant botulism or adults with suspected gastrointestinal botulism, as breaking down intraluminal C. botulinum could elevate the amount of toxin available for absorption.

If botulism occurs in a pregnant woman, it should be treated the same way as a non-pregnant woman. Data on maternal treatment with botulinum antitoxin are very limited but have not shown evidence of fetal harm, and where clinically indicated, treatment with the antidote should not be withheld on account of pregnancy. To ensure safety, additional fetal monitoring may be warranted in cases of maternal botulism, particularly if exposure is associated with maternal hypoxia.⁹

Conclusion

Botulism is a neuroparalytic condition caused by bacterial neurotoxin from spores of Clostridium botulinum. It can cause a variety of symptoms and side effects. Botulism can be fatal if left untreated. However, most people who receive a prompt diagnosis and treatment can make a full recovery from the illness. They return to normal functioning throughout their lives.

FAQs

What foods carry botulism?

The botulism toxin has been found in honey, garlic, and foods containing low acid levels, such as meat, seafood, some fruits and vegetables (figs, potatoes, corn, and green beans), canned cheese, carrot juice, and canned tomatoes.

Is botulism contagious from human to human?

Botulism is not contagious.