Q: I read that there have been cases of botulism in Pennsylvania. Isn’t this a third world disease?
A: Although botulism is a rare condition in the United States — with about 110 cases reported annually — it can and does occur worldwide.
Botulism is caused by a toxin made by the bacteria Clostridium botulinum, which is common and may be found in soil and untreated water throughout the world. The bacteria make spores which can survive for long periods of time, however, if the spores are heated to 250 degrees for at least five minutes they are destroyed, so proper food preparation (for example, for home canning) is important.
People get sick from botulism toxin in one of three ways:
* Infants may ingest the bacteria, most commonly from being given honey or corn syrup (sometimes on their pacifier). The bacteria may then take up residence in the intestines and produce toxin. Almost three quarters of the cases of botulism in the U.S. are in infants, with the highest incidence in Utah, Pennsylvania and California, where Clostridium botulinum spore counts in the soil are high. It is very unlikely for adults to get botulism in this way since most normal adults’ intestines are resistant to colonization with this bacterium.
* The botulism toxin can be directly ingested from improperly prepared foods. In fact, there are occasional outbreaks of botulism from poorly prepared home-canned foods, improperly cured meats, smoked or raw fish, honey or corn syrup. About a quarter of the botulism cases in the U.S. are from this type of food poisoning. Although the toxin itself has no taste or smell, some (but not all) strains of Clostridium botulinum “spoil” the food, making it smell and/or taste bad and even causing the can it is stored in to bulge.
* A small number of cases of wound botulism — where the toxin enters the body through a break in the skin — are reported every year in the U.S. Once inside the body, the toxin enters the bloodstream and then binds to part of a specific type of nerve (the presynaptic terminal in cholinergic nerves). This binding permanently disrupts the function of these nerves; it takes months for them to produce new normally functioning synapses.
Since this is a poisoning and not an infection, there is no fever with this condition. If it occurs from ingestion of the toxin or the bacteria, gastrointestinal symptoms can occur.
The nerves affected can be those responsible for making the eyes move and the pupils dilate or constrict, so vision problems are common.
Other nerves — such as those responsible for speech, swallowing or making the facial muscles move — may be affected. As the toxin begins to involve the nerves going to the muscles, the patient develops paralysis.
This is a descending paralysis with the arms affected before the legs. When the muscles that allow the patient to breathe are affected, respiratory failure can occur.
Depending on the amount of toxin present in the patient’s system, symptoms may progress from mild to severe (and life-threatening) over hours, days or even weeks.
The first step in diagnosing botulism is considering the possibility; a descending paralysis raises suspicion of this condition, as does respiratory failure in an otherwise healthy infant. The diagnosis is confirmed by demonstration of the toxin in the patient’s blood. Even if this test is negative in infants, finding spores in their stool confirms the diagnosis. Finding the bacteria in a wound confirms the diagnosis in patients with wound botulism.
Since the disease can progress rapidly, treatment for botulism is initiated even without confirmatory tests when the suspicion is high.
* The first step is supportive care; patients with respiratory failure require intubation (a tube placed in their airway and a machine used to breathe for them).
* Although wound botulism may benefit from antibiotics, the other types do not and antibiotics are not indicated.
* Human antibody antitoxin is recommended for infants, and horse serum antitoxin for those over age 1. The antitoxins may prevent more nerves from being affected, but since the nerve damage is irreversible once it has occurred, the patient will need supportive care until the nerves repair themselves, often for months.
Less than 10 percent of treated adults die. The prognosis is even better in appropriately treated infants, with less than a 1 percent mortality rate. The milder the disease, the more likely the patient will completely recover back to their baseline.
In order to prevent botulism, do not give honey or corn syrup to infants. Be sure to prepare home-canned foods and home-cured meats correctly. Throw away spoiled foods. Seek emergency treatment if you develop symptoms suggestive of botulism poisoning.
Jeff Hersh, Ph.D., M.D., F.A.A.P., F.A.C.P., F.A.A.E.P