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on methodical conference
department of infectious diseases and epidemiology
„____” ____________ 200 р.
Protocol № _____
Chief of Dept., professor __________ V.D. Moskaliuk
METHODOLOGICAL INSTRUCTIONS
to a fifth year student of the Faculty of Medicine
on independent preparation for practical training
Topic: BOTULISM
Subject:
Major:
Educational degree and qualification degree:
Year of study:
Hours:
Prepared by assistant professor
Infectious Diseases
Medicine
Specialist
5
2
Sydorchuk A.S.
Topic: Botulism
1. Lesson duration: 2 hours
2. Aims of the lesson:
3.1. Students are to know:
• etiology of botulism, types of pathogens, their principal properties;
• epidemiology of botulism;
• pathogenesis of botulismand morphology of organs afflicted by Clostridium botulinum;
• symptoms and development of typical and atypical botulism;
• clinical characteristic of botulism;
• complications of botulism;
• diagnosis of botulism;
• laboratory methods of examination at botulism;
• differential diagnosis of botulism including distinguishing between similar diseases;
• treatment of botulism with taking into account of course severity;
• prophylactic and antiepidemic measures at botulism.
3.2. Students are to be able:
• to question a patient in order for obtaining of information on disease history and
epidemiologic anamnesis;
• to perform clinical examination of a patient;
• to formulate and to substantiate the diagnosis of botulism;
• to prepare a plan of additional patient examination;
• to evaluate results of laboratory examination;
• to determinate a course severity;
• to make differential diagnosis to distinguish between similar diseases (Guillant-Barre
syndrome, poliomyelitis, stroke, myastenia gravis, tick paralysis, and poisoning due to curare
or belladonna alkaloids);
• to prescribe adequate pathogen and etiotropic treatment;
• to prepare a plan and organize prophylactic and antiepidemic measures.
3.3. Students are to acquire the following skills:
• to conduct clinical examination of a botulism patient and other acute intestinal diseases;
• to formulate and substantiate a clinical diagnosis;
• to prepare a plan of paraclinic patient examination;
• to take samples of material (stool, vomitory masses, suspicious food-stuffs, water after
irrigation of the stomach) for bacterioscopy and other quick analysis methods and
bacteriological examination for revealing of Clostridium botulinum;
and to take samples of material (blood) for PCR (polimerase chain reaction) and other quick
analysis methods (ELISA) and serological examination for revealing of toxin and the agent;
• to evaluate results of paraclinic patient examination;
• to organize hospitalization and treatment of a botulism patient (of a person suspected to have
botulism);
• to provide emergency aid at severe botulism;
• to plan and organize prophylactic measures against botulism;
• to plan and organize antiepidemic measures to localize and liquidate a botulism source,
especially during preparing of conservative food-stuffs.
4. Advice to students.
Botulism is a paralytic disease caused by the neurotoxins of Clostridium botulinum and
in rare cases, Clostridium butyricum and Clostridium baratii. These gram-positive sporeforming anaerobes can be found in soil samples and marine sediments throughout the world.
With a lethal dose to humans of less than 1 mcg, botulinum toxins are the most poisonous
substances known and pose a great threat as an agent of biological warfare. They are classified
by the Centers for Disease Control and Prevention (CDC) as one of the six highest-risk threat
agents for bioterrorism because of their high lethality, ease of production and transport, and
need for prolonged intensive care treatment.
Investigations of Clostridium neurotoxin as a biological weapon have been carried out
by various nations. The Japanese in World War II carried out human experiments on prisoners
in Manchuria. Also in World War II, the British secretly used a botulism-impregnated grenade
in the assassination of a German Gestapo officer. The United States studied botulinum toxin as
a military bioweapon until President Nixon signed the Biological and Toxin Weapons
Convention in 1972, ending all US biotoxin weapons research. Iraq and the Soviet Union
stockpiled neurotoxin, with Iraq admitting to weaponizing thousands of liters of toxin in
warheads after the 1991 Gulf War. An attempt at terrorist use of Clostridium toxin in the early
1990s by the Japanese Aum Shinryko cult against American military targets was unsuccessful.
The term botulus is derived from the Latin word for "sausage." An outbreak of
clostridial "sausage poisoning" in Europe in the late 1700s was responsible for many deaths. A
German physician, Dr. Justinus Kerner, published the first case descriptions of botulism in
1822, with experiments conducted on himself and laboratory animals.
Classification
Six forms of botulism are now described, depending on the route of acquisition.
The first form, food-borne botulism, follows the ingestion of preformed toxin in foods
that have not been canned or preserved properly.
Wound botulism, caused by systemic spread of toxin produced by organisms inhabiting
wounds, is associated with trauma, surgery, subcutaneous heroin injection, and sinusitis from
intranasal cocaine abuse.
Infant botulism results from intestinal colonization of organisms in infants younger than
1 year. In this age group, normal intestinal flora may not have developed to the degree that
prevents colonization by these organisms in healthy adults.
A fourth form, adult intestinal colonization botulism, has been described. Similar in
pathogenesis to infant botulism, this form occurs in older children and adults with abnormal
bowel, such as colitis, intestinal bypass procedures or, or in association with other conditions
that may create local or widespread disruption in the normal intestinal flora.
Injection-related botulism is a result of inadvertent misadventures with injection of
therapeutic pharmaceutical botulinum toxin.
Finally, inhalational botulism has recently been described. To date, the only human
cases have been the result of inadvertent inhalation of toxin by laboratory workers. However,
aerosolization and inhalation of botulinum toxin is considered a likely method for poison
delivery in a bioterrorist attack.
Differences in antigenicity among the toxins produced by different strains of botulismcausing organisms allow for separation of the organisms into 7 distinct types (A-G). Types A,
B, and E are the toxins most often responsible for disease in humans, while types C and D only
cause disease in other animals (eg, nonhuman mammals, birds, fish). In rare instances, a single
strain of organism may produce 2 toxins.
As alluded to earlier, clostridia other than C botulinum have been associated with a
handful of cases of botulism. These include reports of food-borne and infant botulism
associated with type E toxin produced by C butyricum. Adult and infant intestinal colonization
botulism, associated with type F toxin-producing C baratii, has been documented.
In addition, strains of C botulinum have been classified into 4 groups based on their
phenotypic characteristics and DNA homology.

Group I organisms are proteolytic and produce toxins A, B, or F.

Group II is nonproteolytic and can make toxins B, E, or F.

Group III organisms produce toxins C or D.

Group IV organisms, now identified as Clostridium argentinense, produce toxin type G,
which has not been shown to cause neuroparalytic illness but has been associated with
sudden death in Switzerland.
Epidemiology
Food-borne botulism, the first form of the disease to be identified, is responsible for
approximately 1000 reported annual cases worldwide. While European cases most commonly
are associated with type B contamination of home-processed meats, Alaskan, Canadian, and
Japanese outbreaks often involve type E toxin in preserved seafood. Chinese cases involve type
A toxin in home-processed bean products. A recently described case in Thailand was
associated with ingestion of home-preserved bamboo shoots.
Most cases in the continental US are associated with home-canned vegetable products
such as asparagus, green beans, and peppers. Of the average 30-40 food-borne US cases per
year, 60% are type A, 18% type B, and 22% type E. Alaska, California, Michigan, Washington,
New Mexico, Illinois, Oregon, and Colorado have the highest incidences of food-borne
botulism.
The toxin type most often responsible for food-borne illness corresponds well with the
geographic distribution of the toxigenic species. Type A is most common west of the
Mississippi, type B east of the Mississippi, and type E in Alaska. Toxin type A produces a
more severe illness than type B, which in turn is more severe than type E.
By far, home-processed foods are responsible for most (94%) outbreaks of food-borne
botulism in the continental US. In fact, of the 6% of outbreaks caused by mass-produced
commercial foods, most cases were attributed to consumer mishandling of commercial
products.
Infant botulism occurs in children younger than 1 year, with 95% of the cases occurring
in patients younger than 6 months. Peak susceptibility is in the 2- to 4-month range. In the 16
years following its identification in 1976, 1134 cases of infant botulism have been recorded in
the United States. With approximately 60 cases of infant botulism reported each year, it is now
the most frequently occurring form of botulism. The disease is most common in the western
part of the United States. One half of all annual cases are reported in California, where the
frequency of the toxin responsible is distributed equally between types A and B.
While the toxin types of food-borne botulism seem to reflect the distribution of
toxigenic strains in the environment, the frequency of type B toxin in infantile botulism is
disproportionately high. Although the case-fatality ratio for infant botulism in the US is less
than 2%, the disease is suspected to be responsible for up to 5% of sudden infant death
syndrome cases in California.
Although the ingestion of honey has been identified as a strong risk factor for the
disease, it is found in fewer than 20% of case histories (and only 5% of case histories in
California in recent years).
Other risk factors that have been reported include infants with higher birth weights and
mothers who were older and better educated than the general population. Another reported risk
factor was a decreased frequency of bowel movements (<1/d) for at least 2 months.
Breastfeeding was associated with older age at onset of illness in type B cases.
Through 1992, only 1-3 cases of wound botulism were reported in the US each year.
Two thirds of these cases were type A and almost one third were type B. One half of all cases
were reported from California. In recent years, the number of reported cases of wound botulism
has risen dramatically, with 11 cases in California in 1994 and 19 cases confirmed by the State
Department of Health Services during the first 11 months of 1995. All but 1 of 40 cases
reported in California, at this writing, involved drug abusers, many with subcutaneous injection
or skin-popping of heroin.
Cases of adult colonization botulism have been increasingly reported in the literature. In
some of these cases, C botulinum organisms, but no preformed toxin, could be found in foods
the patients had ingested. These cases were associated with a prolonged latent period of up to
47 days postingestion before onset of symptoms. In one study, 2 of 4 patients had surgical
alterations of the gastrointestinal tract that may have promoted colonization. Jejunoileal bypass,
surgery of the small intestine, and Crohn disease are among other reported factors predisposing
adult patients for intestinal colonization.
Only rare cases of injection-related botulism have been reported, despite the
increasingly common use of botulinum neurotoxin in neurology, ophthalmology, and
dermatology practices. The standard packaging mandated by the FDA contains doses that are
well below the human toxic level.
Pathogenesis
C botulinum is distributed widely throughout the environment and can be found in soil,
freshwater and saltwater sediments, household dust, and on the surfaces of many foods. The
toxins produced are cytoplasmic proteins (mass = 150 kDa) released as cells lyse. While the
spores survive 2 hours at 100°C (but die rapidly at 120°C), the exotoxin is heat labile. It
becomes inactivated after 1 minute at 85°C or 5 minutes at 80°C.
Although the mode of entry of toxin may differ between the different forms of diseases,
once the toxin enters the bloodstream, it acts in a similar manner to produce the clinical
symptoms. The toxin binds to receptors on presynaptic terminals of cholinergic synapses, is
internalized into vesicles, and then is translocated to the cytosol. In the cytosol, the toxin
mediates the proteolysis of components of the calcium-induced exocytosis apparatus (the
SNARE proteins) to interfere with acetylcholine release. Blockade of neurotransmitter release
at the terminal is permanent, and recovery only occurs when the axon sprouts a new terminal to
replace the toxin-damaged one.
The effects of the toxin are limited to blockade of peripheral cholinergic nerve
terminals, including those at neuromuscular junctions, postganglionic parasympathetic nerve
endings, and peripheral ganglia. This blockade produces a characteristic bilateral descending
paralysis of the muscles innervated by cranial, spinal, and cholinergic autonomic nerves but no
impairment of adrenergic or sensory nerves, and no central nervous impairment. The classic
syndrome of botulism is a symmetrical, descending motor paralysis in an alert patient, with no
sensory deficits.
Mortality/Morbidity:

For food-borne botulism, patients with an early onset of clinical symptoms (within 36 h
of toxin ingestion), index patients in food-borne cases, and patients older than 60 years
generally have a longer clinical course than their counterparts.

Deaths occurring within the first 2 weeks of botulism are most often due to failure to
recognize the severity of disease or from pulmonary or systemic infection. The average
duration of respiratory support for those requiring mechanical ventilation is 6-8 weeks
but may be as long as 7 months.

For food-borne botulism, severity of disease seems to be associated with toxin type.
Intubation is required for 67% of patients with type A botulism, 52% of patients with
type B, and 39% of patients with type E. In addition to being more likely to need
ventilatory support, patients with type A botulism tend to see a physician earlier and
have a longer course of illness than those with type B botulism. The case-fatality rate
for type A botulism is 10%, twice that of type B.

Ventilatory and upper airway muscle strength, along with exercise performance,
predominantly build within the first 12 weeks, and most patients are back to normal
within 1 year with type A botulism. Dyspnea, fatigue, and decreased maximal workload
are common 2 years after type B intoxication, although lung function tests have
returned to normal.

The overall case-fatality rate is approximately 7 - 10%. For patients over 60 years old,
the fatality rate is approximately doubled. The mortality rate is lower for patients who
receive prompt antitoxin, compared to those with delayed treatment.

Infant botulism progresses for 1-2 weeks and stabilizes for 2-3 weeks before recovery
begins. The average length of a hospital stay for infants is approximately 1 month,
although excretion of toxin and organisms may continue for more than 3 months
following discharge. The infant case-fatality rate (1.3%) is low compared to food-borne
illness, but a 5% relapse rate is associated with infant botulism after apparent resolution
of clinical symptoms.

The case-fatality rate of wound botulism is 10%, and survivors experience significant
morbidity requiring prolonged medical care.

The occurrence of an episode of botulism does not necessarily confer immunity toward
subsequent episodes. Immunization in the form of a pentavalent toxoid is available, but
it is used only for those in high-risk areas such as laboratory workers and certain
military personnel. It requires yearly boosters to remain protective.
History (Anamnesis):

Although laboratory confirmation is necessary for a definitive diagnosis, clinical
presentation, patient history, and physical examination (particularly neurologic exam)
can be used as strong indicators for the presence of botulism. Due to the delay in
laboratory confirmation, antitoxin should be begun in patients with highly suggestive
presentations.

Place special attention on eliciting a complete patient history, including the following:
o
History of foods eaten, and any ill contacts who ate the same foods.
o
History of intravenous drug abuse (especially "skin popping")
o
Recent surgery or trauma
o
Gastrointestinal problems or intestinal bypass surgery
Physical (Examination):

Food-borne botulism
o
The CDC suggests attention to the following cardinal features:


Patient is afebrile unless another infection is present.

Patient demonstrates symmetric neurologic symptomatology.

Patient remains responsive, with intact sensation (14% of patients report
some paresthesias or decreased sensation)

Patient has a normal or slow heart rate in the absence of hypotension.

Signs typically are not accompanied by sensory deficits, with the
exception of blurred vision.
o
The neurologic symptomatology often has been described as a progressive,
symmetric, descending weakness or paralysis that first affects muscles
innervated by the cranial nerves, then progresses to involve muscles of the neck,
arms, and legs. This occurs in an alert patient with intact sensorium and intact
sensation.
o
The typical progression of symptoms (in order of appearance) in a botulinum
neurotoxin poisoning can be summarized by the Dozen D's: dry mouth, diplopia,
dilated pupils, droopy eyes, droopy face, diminished gag reflex, dysphagia,
dysarthria, dysphonia, difficulty lifting head, descending paralysis, and
diaphragmatic paralysis.
o
Respiratory difficulty arises from airway obstruction and diaphragmatic
weakness. Diplopia, dysarthria, dry mouth, and generalized weakness are among
the most common presenting symptoms. Other symptoms that have been
associated with botulism include ptosis, dysphagia, sore throat, dysphonia,
nystagmus, ataxia, paresthesias, paralytic ileus, severe constipation, urinary
retention, and orthostatic hypotension.
o
Pupils are dilated or unreactive (ophthalmoplegia) in 50% of patients. Unless
secondary complications such as respiratory failure develop, patients are alert
and mental function is unimpaired.
o
Sensory deficits only have been reported in isolated cases. Neurologic
symptoms may appear from 6 hours to 10 days after ingestion of toxin, with a
median incubation period of 1 day.
o
Nausea, vomiting, and diarrhea often precede or accompany neurologic
manifestations; constipation typically follows after neurologic signs have
appeared. GI symptoms are more prominent in food-borne botulism and much
less pronounced in cases of wound botulism.
Infant botulism
o
The degree of involvement in this form of the disease can vary from
asymptomatic to paralysis to sudden death.
o
A prominent and common sign of the disease is constipation (defined as 3 or
more days without defecation). Other clinical features include listlessness,
lethargy, difficulty in sucking and swallowing, hypotonia, weak cry, poor
feeding, pooled oral secretions, generalized muscle weakness, and poor head
control, which gives the infant a characteristic floppy appearance.
o
Neurologic findings include ptosis, ophthalmoplegia, sluggish pupillary reaction
to light, flaccid expression, dysphagia, weak gag reflex, and poor anal sphincter
tone.

o
Respiratory failure occurs in approximately 50% of diagnosed patients.
o
The incubation period (between the time of spore ingestion and onset of
symptoms) associated with infant botulism varies from 3-30 days.
Wound botulism
o
Patients often present with much of the same symptomatology that is observed
in the food-borne form, including acute blurred vision, dysphagia, dysarthria,
generalized weakness (with or without absence of deep tendon reflexes), and
pupillary abnormalities. Gastrointestinal manifestations are absent.
o
The Clostridium-infected wound generally appears benign, without typical signs
of infection (unless also infected by other bacteria, in which case a fever also
may be present). In some cases, the wound is not apparent.
o
The average incubation period is 10 days.
Lab Studies:




Laboratory confirmation
o
Before treatment with antitoxin, obtain 10-15 mL of serum, 25-50 g of feces,
and possibly 25-50 mL of fluid from gastric aspiration. Collect and refrigerate
similar quantities of suspected food samples for testing. In constipated patients,
a gentle saline enema may be required to obtain fecal specimens.
o
Label each specimen container with the patient's name, specimen type, date of
collection, and medications being received, and send it to a state health
department-approved reference laboratory in insulated cold packs. Contact your
local health department for specific instructions.
o
Confirmation of the organism and/or toxin and toxin typing is obtained in
almost 75% of cases. Early cases are more likely to be diagnosed by toxin assay,
whereas later ones are more likely to have a positive culture. Laboratory
confirmation of toxin presence is via a mouse bioassay, and identification of the
toxin type is performed by a mouse toxin neutralization test.
Food-borne botulism
o
For food-borne botulism, toxin is found in serum samples 39% of the time and
in stools 24% of the time.
o
Organisms are found in cultures of stool samples 55% of the time.
o
Stool cultures generally are more sensitive than toxin detection for specimens
obtained later (>3 d postingestion) in the course of illness.
Infant botulism
o
In patients whom infant botulism is suspected, stools and enema fluids (with
minimal water added to limit dilution of toxin) are the specimens of choice, as
serum is only rarely toxin positive.
o
One also may wish to culture possible sources of clostridia, such as honey or
house dust.
Wound botulism: Wound botulism may be identified by detection of toxin in serum or
by culture of wound specimens.

Adult colonization botulism: Organisms may be detected in stool and toxin in serum for
up to 119 days following the onset of symptoms.

New methods of detection: In vitro methods of detection, including polymerase chain
reaction-based detection of clostridial genes and ELISA identification of toxin, but
these methods are not widely available outside of research institutions.
TREATMENT
Emergency Department Care: Antitoxin should be administered as soon as the
clinical diagnosis is established, as laboratory confirmation requires days. The early
administration of antitoxin will not reverse the course of the intoxication but will prevent
further progression of paralysis. This is the best method to prevent diaphragmatic involvement
and the need for mechanical ventilation. Antitoxin can only bind neurotoxin free in the blood.
Once in the neuron, it cannot be bound.

Food-borne botulism
o
Monitor asymptomatic individuals who have eaten food suspected of being
contaminated for the appearance of neurologic signs and symptoms.
o
Enemas and cathartics or whole-bowel irrigation may be used (if no ileus is
present) to purge the gut of toxin. If ingestion occurred within the past few
hours, emetics or gastric lavage may aid in the removal of toxin.

Infant botulism: Most cases progress to complete respiratory failure. Intubation is
required for a median of 16-23 days. Tracheostomy usually is not required.

Wound botulism

o
Wound botulism requires thorough debridement of the wound site, even if it
appears to be healing well.
o
Follow this by injection of 3% hydrogen peroxide to produce aerobic conditions.
Hydrogen peroxide itself is not innocuous to tissues, and some have advocated
using hyperbaric oxygen therapy if available.
o
Antitoxin may be injected directly into the wound site.
o
Urinary retention may require use of a catheter.
Respiratory concerns
o
In adults, botulism results in pulmonary complications in 81% of patients, with
ventilatory failure in one third.
o
Monitor spirometry, pulse oximetry, and arterial blood gas measurements, with
particular attention placed on serial measurements of maximal static inspiratory
pressure and respiratory vital capacity to help in predicting respiratory failure.
o
Strongly consider intubation and mechanical ventilation when vital capacity is
less than 30% of predicted (or <12 mL/kg), particularly when absolute or
relative hypercarbia and rapidly progressive paralysis with hypoxemia are
evident.
Consultations:

Pulmonology for respiratory sequelae

Surgery for wound care

Infectious disease specialist for management issues
The goals of pharmacotherapy are to reduce morbidity and prevent complications.
Medication commonly used in the treatment of botulism is described below. In addition to that
described, guanethidine and 4-aminopyridine have been used for the treatment of botulinum
paralysis but have not been shown to be effective.
The use of local antibiotics such as penicillin G or metronidazole may be helpful in
eradicating C botulinum in wound botulism. Antibiotic use is not recommended for infant
botulism because cell death and lysis may result in the release of more toxin. Aminoglycoside
antibiotics and tetracyclines, in particular, may increase the degree of neuromuscular blockade
by impairing neuronal calcium entry.
Drug Category: Antitoxin therapy -- Therapy consists of approximately 10,000 IU of
antibodies against toxin types A, B, and E to neutralize serum toxin
Drug Name
Trivalent equine botulism antitoxin -- CDC recommends administration of 1 vial of
antitoxin for adult patients with botulism as soon as diagnosis is made, without waiting for
laboratory confirmation; before administration of antitoxin, consider skin testing for sensitivity
to serum or antitoxin (see Contraindications, below).
1 vial of trivalent botulism antitoxin administered IV results in serum levels of type A,
B, and E antibodies capable of neutralizing serum toxin concentrations in substantial excess of
those reported for botulism patients; administration of 1 vial of antitoxin IV recommended and
need not be repeated (circulating antitoxins have a half-life of 5-8 d).
Antitoxin packages, which include instructions for skin or conjunctival testing for
hypersensitivity to horse serum and a regimen for desensitization, are available through the
CDC (emergency assistance number 770-488-7100); Antitoxin packages also may be obtained
through state health departments.
Antitoxin neutralizes toxin not yet bound to nerve terminals and has circulating half-life
of 5-8 d; patients who do not receive antitoxin treatment show free toxin in serum for up to 28
d. For infant botulism, IV Botulinum Immune Globulin (BIG) trials in California were
completed in early 1997; trials demonstrated safety and efficacy of human-derived botulinum
immune globulin and a reduced mean hospital stay from 5.5 wk to 2.5 wk. BIG is now FDA
approved and is only available from the California Department of Health Services.
Adult Dose 1 vial of antitoxin, diluted 1:10 with saline; administered IV over 30-60 min
Pediatric Dose Administer as in adults
Contraindications Documented hypersensitivity
Interactions
None reported
Pregnancy
C - Safety for use during pregnancy has not been established.
Precautions Adverse reactions include serum sickness (3.6%), urticaria (2.6%), and
anaphylaxis (1.9%)
Risk of a serum reaction or other allergic reaction must be weighed against very
substantial likelihood of progression to respiratory paralysis if untreated; appropriate
antianaphylactic medications and resuscitation equipment should be on hand during
administration
Further Inpatient Care:

Ventilatory support

Surgical debridement of wounds

Pediatric nutritional support: Intravenous feeding (hyperalimentation) is discouraged
because of its potential for secondary infection and because of the success with
nasogastric or nasojejunal tube feeding.
Deterrence/Prevention:

Inform the public about the hazards of improperly preserved or canned foods.

Inform expectant mothers not to administer honey to infants.
Complications:

Wound infection

Respiratory distress
Prognosis: Prognosis is generally good with early detection, early antitoxin administration, and
intensive supportive therapy.
5. Test questions.
1. What kind of an agent of botulism?
2. What is botulism pathogenesis?
3. How is botulism spread (transmitted)?
4. What are the symptoms of botulism?
5. How is botulism diagnosed?
6. What medications are used to treat botulism?
7. What can be done to prevent botulism?
8. What are the effects of alcohol on botulism course?
9. Tell about the first aid in case suspicious at botulism.
10. Tell about antitoxin serum administration.
6. Literature:
1. Harrison A. Internal Diseases. Part of Infectious Diseases.
2. Nikitin E., Andreychyn M., Servetskyy K., Kachor V., Holovchenko A., Usychenko
E. Infectious Diseases. – Ternopil: Ukrmedknyga, 2004. – P. 88-91.