Symptoms and Diagnosis

The onset of botulism generally occurs twelve to thirty-six hours after the toxin is ingested. However, the incubation period may vary from a few hours to several days. Symptoms can range from mild to severe. Constipation is characteristically an early sign, reflecting formation of toxin within the GI tract, although this is frequently overlooked. There is a specialized test to detect toxin in serum by bioassay; however, this may be negative, particularly in wound and infant botulism. Therefore, tests that confirm the presence of the organism or its toxin in wounds, vomitus, gastric fluid, or stool are much more effective.

Foodborne Botulism

Cranial nerve involvement often marks the onset of symptoms of foodborne botulism. Symptoms may include dizziness, fatigue, headache, and the feeling of being agitated and/or anxious. The affected individual's mental status remains unaffected. Fever is usually minimal and may, in fact, be absent (afebrile). Affected individuals may experience generalized muscle weakness, often progressing rapidly from the head to involve the neck, arms, chest, and legs. The weakness is usually not the same on both sides of the body (asymmetric). Individuals may also experience nausea, vomiting, severe constipation or diarrhea, and/or urinary retention. Abdominal pain may precede or follow the onset of paralysis. Botulism may also produce progressive muscular paralysis possibly abdominal distention characterized by the absence of normal intestinal sounds. Paralytic obstruction of the intestines (ileus) may also occur.

Eye symptoms may include double vision (diplopia) and/or blurred vision, impaired functioning of the muscles of the eyes (ophthalmoplegia), droopy eyelids (ptosis), an abnormal intolerance of light (photophobia), dilation of the pupil (mydriasis), and an involuntary rapid movement of the eyeball (nystagmus).

Some individuals have difficulty speaking (dysphonia) or slurred speech (dysarthria). Symptoms may also include difficulty in swallowing (dysphagia), a dry mouth and very dry or sore throat. The gag reflex may be suppressed. Some individuals have a tongue that is swollen and "coated."

Weakening of the reflexes (hyporeflexia) may also be present. Pupillary reflexes may be depressed and deep tendon reflexes may be normal or decreased. Some individuals experience a sudden drop in blood pressure upon arising from a bed or chair (postural hypotension) or a rapid heartbeat (tachycardia). Difficulty breathing, irregular rate of respiration, and breathing characterized by rhythmic waxing and waning of the depth of respirations, which may be accompanied by periods of apnea (Cheyne-Stokes respiration), may also be present.

Wound Botulism

Wound botulism is characterized by the same neurological symptoms as foodborne botulism. However, the affected individual experiences no gastrointestinal symptoms nor is there any evidence implicating food as the cause. The skin must be carefully checked for wounds. Wound botulism is common after traumatic injury involving contamination with soil, after cesarean delivery, and in individuals with a chronic substance abuse problem. A fever due to infection from other bacteria may be present.

Infant Botulism

Infant botulism may occur in infants less than 12 months of age. Constipation is initially present in approximately two-thirds of these cases, followed by neuromuscular paralysis. The severity of the disease varies among affected infants. Affected individuals generally have been exposed to foods other than milk contaminated with spores which are common in the environment. Cases have been related to the ingestion of honey, vacuum cleaner dust, and soil that contains C. botulinum.

The differential diagnosis of infant botulism includes other causes of paralysis such as Guillan-Barré syndrome (symmetric ascending paralysis with an elevated CSF protein), poliomyelitits (asymmetric paralysis, fever, and CSF pleocytosis), and myasthenia gravis (muscle fatigability with reversal or ptosis with tensilon). In addition, bacterial sepsis and meningitis must always be excluded in any infant presenting with fever, lethargy, and poor feeding. The absence of a gag reflex, profound hypotonia, and hyporeflexia help to differentiate infant botulism from bacterial sepsis. EMG (if abnormal) typically show a pattern of brief duration, small-amplitude potentials with a decremental response at low repetitive (3-10Hz) stimulation and an incremental or “staircase” response at high repetitive stimulation.

The diagnosis is confirmed by the detection of the organism or its toxin in the infant’s stool. Toxin isolation and identification are accomplished via mouse lethality testing, with typing confirmed by neutralization of the toxin by specific sera.

Similar Paralytic Disorders

Symptoms of the following disorders can be similar to those of botulism. Comparisons may be useful for a differential diagnosis.

• Eaton-Lambert Syndrome is a neuromuscular disorder that may be an autoimmune disease. Major symptoms include muscle weakness and fatigue especially of the pelvic and thigh muscles. Other symptoms may include dryness of the mouth, impotence, pain in the thighs, and a pricking, tingling or creeping sensation on the skin (paresthesias) around the affected areas.
• Guillain-Barre Syndrome (acute idiopathic polyneuritis) is a very rare, rapidly progressive disorder causing inflammation of the nerves (polyneuritis) and paralysis. Although the precise cause of Guillain-Barre Syndrome is unknown, a viral or respiratory infection precedes the onset of the syndrome in about half of the cases. This has led to the theory that Guillain-Barre Syndrome may be an autoimmune disease (caused by the body's own immune system). Damage to the covering of nerve cells (myelin) and nerve axons (the extension of the nerve cell that conducts impulses away from the nerve cell body) results in delayed nerve signal transmission. There is a corresponding weakness in the muscles that are supplied with nerve impulses (innervated) by the affected nerves.
• Myasthenia Gravis is a chronic neuromuscular disease characterized by weakness and abnormally rapid fatigue of muscles, particularly those that are controlled by the brain stem (bulbar-innervated). The symptoms of Myasthenia Gravis typically improve following a period of rest. Any muscle may be affected by this disorder. However, the muscles around the eyes (extraocular) and those used in swallowing are most frequently affected by Myasthenia Gravis.

Prevention

It is essential that both home canned and commercially canned foods be prepared properly. To prevent botulism, these foods must be adequately heated before serving. Food that shows any sign of spoilage should be discarded. Unabsorbed toxin may be eliminated by induction of vomiting, gastric lavage, and purgation.

Clostridium botulinum spores are highly resistant to heat and may survive for several hours at tempatures of 100°C. Exposure to moist heat at 120° centigrade kills the spores. On the other hand, the toxins are readily destroyed by heat. Therefore cooking food at 80°C for 30 minutes protects against botulism. While home-canned food is the most common source for botulism, commercially prepared foods have been implicated in about ten percent of the cases. Vegetables, fish, fruits and condiments are the most commonly involved; however beef, dairy products, pork, poultry, and other foods have also been implicated. To reduce the risk of infant botulism it is recommended that honey not be fed to infants who are less than 12 months of age.

Medical Treatment

Since respiratory impairment and its complications may be life threatening, affected individuals should be hospitalized and closely supervised. Prolonged artificial respiration may be required.

Adult Care

Antibiotic therapy is not indicated for the treatment of foodborne or infant botulism. For wound botulism, antibiotic therapy may include agents such as penicillin G or metronidazole. Intravenous equine (made from horses) antitoxin, administered as early as possible in the course of illness, is the only specific treatment available for foodborne and wound botulism. Equine antitoxin can be toxic to babies with infantile botulism, however, so human botulism immune globuline is prepared for infants. Antitoxin will not reverse established neurological damage, but may prevent the progression of disease, shorten the duration of ventilatory failure, and reduce the period of hospitalization.

Trivalent antitoxin (A, B, E) is available on a 24-hour basis from the Centers for Disease Control in Atlanta, GA. They also supply a polyvalent antitoxin for specific outbreaks that are due to Types C, D, or F botulism. Treatment should be initiated as soon as possible. However, the risks of treatment must be weighed against potential benefits. The antitoxins are made from horse serum and there is the possibility, in some individuals, of anaphylaxis or serum sickness. It may even be beneficial to begin treatment even several weeks after ingestion of the toxin. While the use of antitoxin does not reverse preexisting neurological impairment or the binding of already bound toxin, it may possibly slow and halt further progression of the disease.

Infant Care

Aggressive respiratory and nutritional care (nasojejunal tube) are the mainstays of treatment. Many infants require intubation and prolonged mechanical ventilation. Continuous nasogastric feedings are preferred over bolus feedings to minimize the risk of aspiration. Small volumes increased over a few days are well tolerated and decrease the need for central hyperalimentation. Physical and occupational therapies are crucial in maintaining range of motion and functional positioning in patients. Antibiotics have not shown to ameliorate the course of the disease. Aminoglycosides such as gentamicin should be avoided for they may potentiate the neuromuscular blockade. The role of human botulism immune globulin to modify the course of the disease if administered early is being explored.

Prognosis for complete recovery is excellent with meticulous supportive care. Infant botulism is a self-limited disease lasting a total of 2 to 6 weeks with progressive symptoms for 1 to 2 weeks followed by gradual recovery of motor function over 3-4 weeks, as a result of the production of new nerve terminals and motor-end plates. Relapse has been reported after apparent recovery, thus necessitating close supervision and follow-up. It is universally recommended that honey and corn syrup not be fed to infants less than 1 year old to prevent the occurrence of infant botulism.

Investigational Therapies

Guanidine has been used in the treatment of some patients affected with botulism. However, reported results have been inconclusive and thus far the effectiveness of the drug remains unproven. More studies are needed to determine the long-term safety and effectiveness of this medication for the treatment of botulism.

Equine antitoxin is administered to individuals with wound botulism. The wound should be thoroughly explored and cleaned. An antibiotic, such as penicillin, should be given to eradicate C. botulinum from the site, even though the benefit of this therapy is unproven. The wound should be cultured and the results should help guide the use of other antibiotics. Metronidazole may be an effective alternative to penicillin.

There is an experimental botulism vaccine for laboratory workers.