Tetanus

by Zandra Starlin

Etiologic Agent

            Tetanus is caused by the exotoxin produced by Clostridium tetani.

Transmission

            Tetanus is the only vaccine-preventable non-contagious disease.  Transmission happens through open wounds where the bacilli enter and produce exotoxins.  Transmissions may appear following surgery or through open wounds such as those produced from burns.  Transmission may also happen from very minor wounds that did not require medical attention.  Dental abrasions, pregnancy, abortion, and animal bites are also known means of transmission.

Reservoirs

            Soil containing fecal matter containing C. tetani tends to be the leading cause of infection.  C. tetani is normal flora in the intestinal tract of humans and animals.  Therefore, it is also a normal inhabitant in soil, especially in areas where animals tend to defecate.  Humans and animals may be infected by this disease.

Characteristics of C. tetani

            C. tetani is a gram-positive spore producing bacillus.  It is an obligate anaerobe and produces toxin tetanospasmin which is carried through the blood stream and in turn damages the central nervous system in locations throughout the body.  There are no subspecies, C. tetani has no serotypes.  It is shaped like a tennis racquet and is typically mobile, using flagellum as its means of motility.  Only the nontoxic form of C. tetani may not be motile and may not have flagellum.

Identification

            C. tetani is only detectable in about one-third of specimens taken from the wound.  For this reason, and because C. tetani can be found in samples taken from people without tetanus, it can be complicated to diagnose through lab testing.  C. tetani tests indole positive, glucose negative, and has spherical spores.  However, this does not provide proper laboratory identification for diagnosis of tetanus.  Tetanus diagnosis typically occurs through observable symptoms (see Signs and Symptoms).  It is very important to try to identify tetanus before there is neurological damage.

Signs and Symptoms

            Symptoms of tetanus become apparent after exotoxins excreted from C. tetani damage the nervous system.  Fever, sweating, elevated heart rate, and elevated blood pressure may occur.  Symptoms of tetanus usually begin around the upper regions of the body and work their way down.  Muscle spasms often happen at the sight of infection.  Then lockjaw may set in. As the symptoms move down the body, the neck and other parts of the body may become rigid or spasmodic, and pain at the infection sight is evident.  Often opisthotonos, an involuntary rigid leaning back of feet and head with abdomen protruding out, sets in.  In cases that are further along, the victim may experience seizures, inability to swallow, bone fractures, cardiac complications, and brain damage.

Historical Background

            Possible cases of patients with tetanus symptoms seem to date back to 5th century BCE.  However, Carle and Rattone discovered the etiology of tetanus in 1884 by injecting pus of a human tetanus case into animals.  In 1889, Nicolaier discovered that C. tetani could be found in the soil by injecting animals with soil.  Nocard then developed an antitoxin for passive immunization in 1897 that treated men in World War I.  He was later followed by Ramon who developed an inactivated form of the toxin using formaldehyde in 1920 and then was utilized by Descombey to create the tetanus toxoid in 1924 which was used for treatment and prevention in World War II.

Virulence

            Incubation for this infection is normally between 3 and 21 days.  There are three different types of tetanus that can occur:  cephalic, local, and generalized.  Cephalic tetanus is very rare and occurs when there is a head injury or from ear infection with C. tetani.  This may cause neurological damage and highly impacts muscles in the face.  Local tetanus is also rare and is contracted through a lesion which may be followed by muscle spasms for that persist for many weeks.  Local tetanus is extremely rarely fatal, but it can turn into generalized tetanus.  General tetanus is the most common form of tetanus and carries most of the symptoms described previously.  Complete recovery often takes months and spasms continue for typically about a month.  Neonatal tetanus is a form of generalized tetanus found in newborns.  This can often be transmitted through nonsterile medical equipment and is often contracted through the stump left from the umbilical cord.

Control and Treatment

            Patients diagnosed with tetanus are most often treated with Tetanus Immune Globulin (TIG).  This injection is administered as a single dose into the muscular tissue.  It only kills off toxin that has not attached to nerve endings.  Another type of treatment that may be used is Intravenous Immune Globulin (IVIG).  Both of these treatments contain the antitoxin for tetanospasmin.

Prevention

Prevention is possible through a simple vaccine that is given in 3 to 4 doses which must then be followed up by a booster every ten years.  The vaccination may be administered for infants as young as six weeks old.  There are many forms of the vaccine available and any of them are efficient in prevention of tetanus.  The different forms are for different ages and some forms also provide vaccination for other types of illness.  These vaccines include:  DTaP, DT, Td, or Tdap.  All vaccines include the toxoid diphtheria which is the formalin-inactivated tetanus toxin.  Contraction of tetanus after proper administration of vaccine is extremely rare.  Efficacy of the vaccine is virtually 100%. 

Incidence

            The tetanus vaccine was introduced into the childhood immunization schedule in the United States in the 1940.  There had already been a huge decrease in cases from early 1900s to the 1940s due to the discovery of vaccination.  In the 1940s there were about 0.4 cases per 100,000 people, which decreased continuously until the 1970s at which point there were only about 0.05 cases per 100,000 people.  In 2009, there were only about 0.01 cases per 100,000 people in the United States.  Most cases are found in people older than 40 years of age.  However, there has been a shift to an increasing percentage of people younger than 40 years old because of drug usage.  Heroin users are at risk because quinine, which is used to dilute heroin, may harbor C. tetani.  Incidence tends to be highest in highly populated damp, warm climate locations where organic material in the soil is highest.

References

Centers for Disease Control and Prevention. “Tetanus.” Epidemiology and Prevention of Vaccine-Preventable Diseases. 12th Edition, Eds. Atkinson W, Wolfe S, Hamborsky J. Washington DC: Public Health Foundation, 2011. 291-300.

Health Tree. HealthTree.com. 21 July, 2010. Web. 6 May, 2011.   http://www.healthtree.com/articles/childhood-diseases/rare/tetanus/

Massachusetts Department of Public Health. “Tetanus (also known as lockjaw).” Guide to Surveillance, Reporting and Control. Bureau of Communicable Disease Control. June, 2006. Web. 6 May, 2011.      http://www.mass.gov/Eeohhs2/docs/dph/disease_reporting/guide/tetanus.pdf

“The Terms and Conditions of Tetanus.” The Bacterial Diseases. The Bacterial Diseases, 27 October, 2010. Web. 6 May, 2011.  http://www.thebacterialdiseases.com/tetanus.html

Wells, C.L., Wilkins, T.D. “Chapter 18:  Clostridia: Sporeforming Anaerobic Bacilli.” NCBI. National Center for Biotechnology Information, U.S. National Library of Medicine, 1996. Web. 6 May, 2011  http://www.ncbi.nlm.nih.gov/books/NBK8219/#A1060