Botulism
Overview
Botulism is rare and serious, unusual and notorious, dangerous and indiscriminate. It is caused by a nerve toxin known as botulinum, which is produced by a bacteria called Chlostridium botulinum¸ and which has the distinction of being considered potentially the most lethal substance known to humankind. In our daily lives, botulism seems to exist mainly as a cautionary spectre, looming over us as we examine canned food in supermarkets for evidence of bulging or crushing that might mean botulism! Despite the relatively low incidence of botulism - about 110 reported cases in the United States every year - it is more than worth watching out for, as its effects can be devastating, ranging from temporary muscle paralysis to respiratory failure and death.
Chlostridium botulinum, the source of the toxin, is actually a group of bacteria, commonly found in soil, and other low-oxygen breeding grounds. Under the microscope, they are rod-shaped. As the bacteria form spores, they become able to survive in a dormant state until they are exposed to conditions that can support their growth.
Although there are technically seven varieties of botulism toxin, only four of them cause illness in humans, and the illness falls into three main types of botulism - categorized by science according to the three ways the disease can be acquired.
The first is known as food-borne botulism, and it accounts for approximately 25% of botulism cases in the United States. Unsurprisingly, this designation refers to cases of botulism resulting from the ingestion of foods contaminated with the botulinum toxin. This form of botulism is particularly dangerous in that small amounts of contaminated food can infect large numbers of people, and its possibilities in terms of biological warfare have been a point of concern for some time. A botulism outbreak is a considered public health emergency, and is reportable to the U.S. government.
Wound botulism, which is the least common form of the disease and accounts for less than 1% of reported cases, is nonetheless a risk associated with any infected wound. If a wound becomes infected, physicians will generally monitor any associated symptoms that might indicate a contamination of Chlostridium botulinum, as opposed to a more common wound-related disease such as tetnus. Wound botulism is also obviously among the risks associated with injectable drugs.
The third type of botulism is the most common - accounting for about 75% of reported cases in the United States - and perhaps the most tragic. Infant botulism is overwhelmingly more common than food-borne botulism because a human infant, unlike an adult, can become infected by consuming the dormant spores of the botulinum bacteria. The bacteria then grows in the favorable conditions of the intestines, and the toxin is released there.
Intestinal infection very rarely occurs in adults, or in children more than a year old. It is the fragility of the newborn system that permits the spores to mature in the intestine, and virtually all reported cases of intestinal infection of botulism in adults have been related to abdominal surgical procedures.
All forms of botulism have the potential to be fatal, and are considered true medical emergencies.
Symptoms
The most devastating effect of botulinum toxin on the human system is that it paralyzes the nerves, so the muscles cannot contract. Muscle paralysis is the major symptom of botulism, and an indication that the disease is progressing. It is also the condition most associated with botulism, and most feared in regard to it. It is important to acknowledge, however, that there are less dramatic symptoms - many of which indicate the critical early stages of a botulism episode, during which long-term paralysis or death may be effectively prevented.
The classic symptoms of botulism, in fact, are all small indicators of muscular failure. They include problems with the optic musculature (double vision or blurred vision, for example, or unavoidably “drooping” eyelids); a decrease in control over oral muscles (slurred speech, difficulty swallowing, dry mouth, decreased gag reflex); and a general sense of muscle weakness. Common neurological tests like the knee-jerk reaction often show a decrease in, or absence of, normal muscular reflex.
In the case of infant botulism, a baby infected will generally seem abnormally weak and lethargic. Infant botulism often causes infants to lose their ability to eat, as the muscles which make eating possible are so newly developing, and constipation is also a symptom, similarly due to the toxin’s attack on specific muscles that have not been used much.
All symptoms of botulism are truly symptoms of the muscle paralysis caused by the bacterial toxin. This is why medical attention is so crucial during the early stages of botulism; if the condition is untreated, these symptoms may progress to more severe manifestations of paralysis, threatening the continued use of the arm, leg, trunk, and breathing muscles.
The symptoms of botulism, in the food-borne form of the diease, generally appear 18 to 36 hours after the consumption of contaminated food. There have, however, been reported cases wherein the first symptoms appeared as soon as six hours, or as late as ten days, after eating.
Diagnosis and Treatment
Botulism, like many other conditions, shares many symptoms, and can be mistaken for other things. Conditions such as stroke and Guillian-Barre Syndrome also involve muscle paralysis and can, conversely, be mistaken for botulism. Often, a healthcare provider who suspects botulism will conduct tests such as brain scans, spinal fluid evaluations, and nerve conductions (EMG), in order to rule out such other muscle paralysis diseases.
In some cases, botulism may be detected through the use of the somewhat distasteful “mouse inoculation test,” wherein the patient’s blood serum or stool is injected into a laboratory mouse, which is then monitored for signs of botulism.
Once identified, the first step in the treatment of botulism is often the removal of any contaminated food left in the stomach or intestines. Under the instruction of a physician, the patient may be given enemas to clean the digestive system. Inducing vomiting may also be employed toward this end. Wounds that have become infected with botulism are often surgically treated, to remove the source of the toxin-producing bacteria.
Because severe botulism tends to effect the respiratory system, and can lead to respiratory paralysis, patients suffering from advanced botulism may be put on a ventilator for some time until the paralysis, with ongoing medical care and therapy, begins to improve. The leading cause of death from botulism is respiratory failure, but reassuringly, the disease is not as deadly as it once was. Since 1950, the botulism death rate has fallen from 50% to 8%.
Like many other neurological afflictions (such as lyme disease), botulism can linger in the system long after its major symptoms have been effectively treated. Patients who survive a botulism infection sometimes experience episodes of fatigue and shortness of breath for years afterwards, and many require long-term medical care and therapy.
Because food-borne botulism often comes from canned foods, it is a sound preventative measure to avoid eating food from cans which have a “bulge” in them, or which seem strangely warped. People who can their own foods at home should adhere to strict hygienic procedures to avoid the contamination of their food. (The USDA’s Home Canning Guide is the official resource.) Because the botulism toxin is destroyed at high temperatures, home-canned foods are always safest when boiled before eaten. Naturally, any canned food product that has an abnormal smell should be discarded.
It is perhaps not as universally understood as it should be that one should never give honey to a child less than one year old. Honey is a significant cause of infant botulism, because it sometimes can contain spores of Clostridium botulinum. The amount that can exist in honey is not enough to effect an older child or an adult, but newborns and infants can be severely infected.
With the benefit of a timely diagnosis during the early stages, food-borne and wound botulism can often be treated with an antitoxin that blocks the action of the toxin circulating in the blood. Although the antitoxin can prevent the condition from growing worse, true recovery can still take several weeks. In the case of infant botulism, the antitoxin cannot usually be administered safely, although there is much hope for an infant-safe application of the antitoxin in the near future.
Additional Resources