Guidance

Botulism: clinical and public health management

Updated 17 July 2025

This guidance is for healthcare professionals who are managing patients with suspected botulism. It provides a summary of the different types of botulism, their clinical presentation, risk factors, clinical management advice and reporting and public health investigation actions.  

Botulism is a rare but potentially life-threatening clinical syndrome caused by a potent neurotoxin, botulinum neurotoxin (BoNT). This is produced by a spore-forming anaerobic bacterium Clostridium botulinum (C. botulinum), which is naturally present in soil, water and marine sediments.

Exposure to botulinum toxin can occur through ingestion or injection of C. botulinum spores or botulinum toxin, and through bacterial wound infections.

Once in the body, botulinum toxin is transported to the neuromuscular junction where it inhibits release of the neurotransmitter acetylcholine, causing neuromuscular paralysis. Botulism results in a characteristic bilateral symmetrical descending flaccid paralysis starting with the cranial nerves and descending to the limbs.

Botulism can be treated with antitoxin; however antitoxin only binds to and neutralises circulating toxin, and not toxin already bound at the neuromuscular junction. This means that antitoxin does not reverse symptoms when administered.

The Botulism Service at UK Health Security Agency (UKHSA), Colindale can be contacted to discuss clinical management of cases and arrange for delivery of botulism antitoxin who can be contacted through the Colindale duty doctor on 0208 200 4400 both in and out of hours.

Infant botulism

Infant botulism is a rare disease that affects infants less than one year of age. It is caused by C. botulinum spores from the environment or food being ingested and germinating in the infant’s large intestine, producing botulinum neurotoxin.

Clinical features

Clinical features of infant botulism are often non-specific and include:

• constipation
• feeble cry
• poor sucking reflex
• feeding difficulties
• decreased gag reflex
• listlessness
• lethargy
• droopy eyelids
• loss of head control
• muscle weakness (arm, neck, leg)
• floppy baby syndrome

Clinical management

Prompt diagnosis and treatment with antitoxin – for infant botulism this should be human derived Botulism immune Globulin (BabyBiG®) available from the Infant Botulism Treatment and Prevention Program (IBTPP) California USA; (510) 231-7600. Successful management of infant botulism also depends on supportive care including artificial ventilation where necessary. Botulism is a clinical diagnosis and treatment with antitoxin should not be delayed for the results of laboratory investigations.

During and out of office hours medical advice can be obtained through the UKHSA duty doctor on 0208 200 4400.

Laboratory diagnosis

Confirmation of a clinical diagnosis is by detection of botulinum toxin or isolation of C. botulinum from infant faecal specimen or rectal wash out.

Clinical specimens:

• 1 gram (g) (pea size) faeces or rectal wash out inoculated into cooked meat broth or other anaerobic medium for rapid PCR detection of C. botulinum and 1g faeces or rectal wash out for toxin detection

All specimens should be sent directly to the Gastrointestinal Bacteria Reference Unit , Colindale with the sender’s name and address clearly marked. The reference laboratory should be telephoned prior to sending the sample on 0208 200 4400.

Risk factors

Infants regularly come into contact with C. botulinum spores as they are naturally present in soil and dust, but infant botulism is extremely rare in the UK. It is believed that some sort of disturbance of the normal bacteria in the infant intestine provides the opportunity for C. botulinum spores, if present, to grow and produce toxin.

In most cases of infant botulism the source of spores is not identified and they are assumed to be swallowed from the environment. Honey and peanut butter are foods that have been linked with infant botulism in the UK. Other risk factors noted in cases in the UK include exposure to pets like terrapins, building works and dust, herbal remedies and international travel. In Argentina and some southern Mediterranean countries infant botulism has been associated with feeding infants herbal infusions or teas.

Foodborne botulism

Foodborne botulism is a rare disease caused by ingestion of preformed toxin in food. C. botulinum spores germinate and multiply in food, producing botulinum toxin which when ingested causes acute illness. The incubation period can vary from a few hours up to 8 days, but is usually within 12 to 36 hours.

Foodborne botulism is considered a public health emergency because contaminated food may be available to other people.

Clinical features

Botulism is characterised by an acute afebrile descending symmetrical paralysis. In foodborne botulism, gastrointestinal symptoms such as nausea, vomiting and diarrhoea may precede neurological symptoms, but are not always present.

Neurological symptoms include:

• disturbances to vision, such as blurred vision, double vision, drooping eyelids and dilated pupils
• difficulty in swallowing and talking, slurred speech, dry mouth
• descending muscle weakness
• respiratory difficulty or failure due to respiratory muscle paralysis
• constipation

Clinical management

Prompt diagnosis and treatment with botulinum antitoxin to neutralise circulating toxin, together with supportive therapy and symptomatic treatment. Botulism is a clinical diagnosis and treatment with antitoxin should not be delayed for the results of laboratory investigations. Intubation and mechanical ventilation may be required in severe cases. Recovery can take several weeks.

Antitoxin can be obtained by contacting the UKHSA duty doctor on 020 8200 4400.

 Laboratory diagnosis

Confirmation of a clinical diagnosis is by detection of botulinum toxin in serum or faecal specimens or detection and isolation of C. botulinum from faeces or food samples.

Clinical specimens:

• 10 millilitres (ml) serum taken prior to antitoxin treatment
• 10g faeces or rectal wash out for toxin detection, and a pea sized portion inoculated into cooked meat broth for rapid PCR detection of C. botulinum

Food samples:

• 10g portion of suspected food to be sent refrigerated

All specimens should be sent directly to the Gastrointestinal Bacteria Reference Unit with the sender’s name and address clearly marked. The reference laboratory should be telephoned ahead of sending the sample on 0208 200 4400.

Risk factors

Foodborne botulism is usually caused by a fault during food processing or storage which enables C. botulinum to grow and produce toxin in food. Spores of C. botulinum are widely distributed in the environment and may be present in food but are usually unable to grow as they require certain conditions to do so, including the absence of oxygen. However, if the right conditions do exist, the spores can germinate, grow and produce toxin.

Foods that have been associated with foodborne botulism include home preserved foods, tinned and bottled foods, foods preserved in oil and food packed in airtight containers. Although most cases of foodborne botulism are caused by home preserved foods there have been rare incidents involving commercially prepared food. Botulinum neurotoxin is heat labile and destroyed by normal cooking procedures.

Wound botulism cases associated with injecting drug use

Wound botulism occurs when C. botulinum spores present in contaminated heroin (or injected drug) germinate under anaerobic conditions in a wound and produce botulinum toxin. People who inject drugs (PWIDs), specifically skin and muscle poppers are at risk of developing wound botulism. The toxin is produced locally in the wound and gets absorbed into the blood stream producing the clinical syndrome. If onset is very rapid there may be no symptoms before sudden respiratory paralysis occurs.

In recent years there have been an average of 2 reports of probable or confirmed cases of wound botulism in England per year among people who inject drugs. Reported cases of wound botulism associated with injecting drug use are published in the ‘Shooting Up’ report.

Clinical features

The main clinical syndrome produced by botulinum toxin is an afebrile, descending, flaccid paralysis. Patients with botulism typically present with difficulty speaking, seeing and/or swallowing. They may have:

• double vision
• blurred vision
• drooping eyelids
• slurred speech
• difficulty swallowing
• muscle weakness

If untreated, paralysis may progress to the arms, legs, trunk and respiratory muscles.

There is usually no fever, no loss of sensation and no loss of awareness. There may also be autonomic signs with dry mouth, fixed or dilated pupils, and cardiovascular, gastrointestinal and urinary autonomic dysfunction. If onset is very rapid, there may be no symptoms before sudden respiratory paralysis occurs, which may be fatal. Recovery can take months. Clinicians should suspect botulism in any patient with an afebrile, descending, flaccid paralysis.

Clinical management

Botulinum antitoxin is effective in reducing the severity of symptoms if administered early in the course of the disease. C. botulinum is sensitive to benzyl penicillin and metronidazole. In cases of wound infection, antimicrobial therapy can rupture the bacilli causing further worsening of symptoms. As far as possible antitoxin should be administered before starting antibiotics and surgical debridement undertaken for source control. Where there is definite clinical suspicion of botulism, treatment with antitoxin should not be delayed for the results of laboratory investigations.

Antitoxin can be obtained from the Colindale site by contacting the duty doctor on 020 8200 4400.

Laboratory diagnosis

Confirmation of the clinical diagnosis is by the demonstration of botulinum toxin in blood samples or, in the case of wound botulism, by the identification of C. botulinum in wound specimens. Routine laboratory tests are not helpful, and specimens should therefore be sent to the reference laboratory.

Samples to be taken from acutely ill patients include:

• serum: at least 10ml - serum samples must be collected before antitoxin is administered
• wound pus: as much as possible in a sterile container - if pus is not available, a swab of the lesion should be taken and put immediately into a transport medium for anaerobic culture
• biopsy tissues: if surgical debridement is performed, biopsy tissues should be placed immediately into a sterile container
• post-mortem specimens: 10ml heart blood, if not haemolysed, should be sent for serum collection - specimens from infected wounds (pus or wound swab) may also be useful

All samples must be kept refrigerated after collection.

All specimens should be sent directly to the Gastrointestinal Bacteria Reference Unit , Colindale with the sender’s name and address clearly marked. The reference laboratory should be telephoned prior to sending the sample on 0208 200 4400 in hours or through the duty doctor out of hours.

Preventive measures

The risk of death in individuals presenting with wound botulism may be reduced if supportive therapy and antitoxin are provided promptly. Increased awareness amongst clinicians and drug users may facilitate prompt diagnosis and treatment.

Wound botulism is thought to occur in people who inject drugs when heroin (or potentially other drugs) contaminated with C. botulinum spores is injected into sites that encourage anaerobic conditions. There is no way of telling if a supply of heroin (or other drugs) is contaminated with C. botulinum spores.

UKHSA has produced advice for ‘Botulism infection in those who inject drugs’.

Iatrogenic botulism

Iatrogenic botulism is caused by a therapeutic or cosmetic procedure involving the injection of botulinum toxin, where excess toxin enters the blood stream and the toxin’s effects extend beyond the intended area of treatment.

The incubation period varies: it is commonly between 4 and 8 days, but may be as short as 1 day or as long as several weeks following the procedure.

Clinical features

Iatrogenic botulism is characterised by symptoms presenting beyond the local sites of injection including:

• difficulty breathing or shortness of breath
• difficulty swallowing or talking; slurred speech or change in voice
• muscle weakness

Localised adverse effects following the injection of botulinum toxin can be common and will vary dependent on the site of the procedure. Commonly reported adverse effects from injection of botulinum toxin in the face from cosmetic procedures include:

• localised pain, swelling, redness of the injection site
• ptosis (drooping eyelids)
• disturbance to vision; blurred vision, double vision, dilated pupils
• headaches

Localised side effects that are not progressing in severity or accompanied by systemic neurological symptoms would not indicate iatrogenic botulism and therefore do not require treatment.

Clinical management

Management of patients with iatrogenic botulism is supported by prompt diagnosis and treatment with botulinum antitoxin to neutralise circulating toxin, together with supportive therapy and symptomatic treatment. Intubation and mechanical ventilation may be required in severe cases. Depending on the severity of symptoms, recovery following administration of botulinum antitoxin can take several hours to several weeks.

In patients presenting with only localised side effects where administration of botulinum antitoxin is not indicated, it may be necessary to monitor for further progression of symptoms and presentation of systemic neurological symptoms.

Where there is strong clinical suspicion of iatrogenic botulism, administration of botulism antitoxin should not be delayed for the results of laboratory investigations.  

Antitoxin can be obtained from the Colindale site by contacting the UKHSA duty doctor on 020 8200 4400 both in and out of hours.

Laboratory diagnosis

Confirmation of the clinical diagnosis is by the demonstration of botulinum toxin in blood (serum) samples.

• serum: at least 10ml. Serum samples must be collected before antitoxin is administered

Iatrogenic botulism cases may present a long time after initial exposure. Due to low levels of circulating toxin in these cases, confirmation of iatrogenic botulism via laboratory assay can have low sensitivity. Not all samples sent to the laboratory will be tested and the decision to test will be assessed on a case-by-case basis.

Routine laboratory tests are not helpful in cases of iatrogenic botulism. All specimens should be sent directly to the Gastrointestinal Bacteria Reference Unit with the sender’s name and address clearly marked.

Reporting and public health investigation

Since foodborne botulism constitutes a public health emergency, food must be excluded as a source for all cases of botulism. UKHSA has prepared a botulism reporting questionnaire that consultants in communicable disease control (CCDCs) can use to obtain information on clinical presentation, food history, botulinum toxin procedures and injecting behavior from all suspected cases of botulism.

Food samples associated with suspected cases of foodborne botulism must be obtained as a matter of extreme urgency in order to prevent further cases and sent refrigerated to the Gastrointestinal Bacteria Reference Unit.

For iatrogenic botulism, identifying the brand of the product and the administering practitioner’s contact details to support investigations that may be needed to limit any ongoing risk to the public.

Samples of heroin or other injectable drugs can be tested by UKHSA for the presence of microbial contamination. If the police are in possession of illicit drugs believed to be associated with suspected cases of wound botulism, contact Gastrointestinal Bacteria Reference Unit on 020 8200 4400 to discuss arrangements for microbial testing.

Clinicians and CCDCs are asked to report any suspected cases of botulism to UKHSA Colindale duty doctor on 020 8200 4400 both in and out of hours.