Poor sanitary conditions and limited awareness are common issues associated with the spread of emerging human diseases like typhoid, giardiasis, and dysentery. Whenever bacteria or viruses find opportunities, they threaten humans, haunting them for years. Like other diseases, typhoid is one of the water-borne infections caused by Salmonella typhi. Typhoid is an insidious illness that is responsible for numerous diseases and mortalities in the past.
What is Typhoid?
Typhoid, also known as typhoid fever, is a gastrointestinal tract infection, notably affecting the small intestine. Salmonella typhi, the serotype of Salmonella enterica, is the causative agent of typhoid fever. Serotypes are groups of microorganisms belonging to the same species, but structural differences exist among them. Serovar is just another term used for serotype.
There are approximately 1400 serovars of Salmonella enterica species, and Salmonella typhi is among those serotypes that are human pathogens. After the species’ name, typhoid fever is also called enteric fever. Morphologically, Salmonella typhi is a Gram-negative, rod-shaped, motile, and intracellular bacteria. Although other Salmonella strains also infect animals, Salmonella typhi cannot affect animals; it specifically affects humans. This bacteria is named after an American veterinary surgeon, Daniel Elmer Salmon.
How Common is Typhoid Fever?
As developing countries lack proper sanitation systems, Salmonella typhi is commonly found in these countries, including South and Southeast Asian, African countries, and the Caribbean, with frequent outbreaks. Every year, approximately 11 to 21 million people catch this infection. The United States, United Kingdom, Japan, Canada, Australia, and Western Europe have reported a few typhoid cases, mainly due to infected people traveling to these countries bringing the infection. According to the Centers for Disease Control and Prevention, 5,700 Salmonella typhi cases are reported yearly in the United States. Similarly, 300 cases are reported each year in the United Kingdom. Moreover, infections caused by Salmonella typhi are more prevalent among children than adults, which may be attributed to their weak immune system, although only mild symptoms appear in children.
Transmission of Salmonella typhi
The four F concept is responsible for transmitting Salmonella typhi; the four F represents the flies, the fingers, the feces, and the fomites. Salmonella typhi follows the fecal-oral route.
- Since no animal is found to be the reservoir of the bacteria, the transmission only occurs from human to human. The bacteria infect the host’s intestines and can easily pass out along with feces expelled by the host. In this case, if infected feces contaminate the drinking water, it may result in the transmission of bacterium from one person to another via the consumption of unclean water.
- Similarly, suppose an infected person touches food without washing his hands after using the washroom. In that case, it will also spread typhoid fever from one person to another. The objects that infected persons use can also spread this infection.
- Likewise, asymptomatic carriers are also the source of transmitting Salmonella typhi. An asymptomatic carrier is a person who has recovered from typhoid infection but continues shedding bacteria through feces for up to one year.
Pathogenesis of Salmonella typhi
Consuming food or water contaminated with bacteria causes it to enter your body. The bacteria enter from the mouth, move to the stomach, and then enter the ileum, a part of the small intestine. It stays in the intestine for 1 to 3 weeks. The bacterium in the intestine releases some chemicals that cause ulcers in the intestinal walls. The common symptoms associated with intestinal inflammation are diarrhea and abdominal pain. If the host’s defense mechanisms are strong enough, it can somehow limit the infection in the intestine; otherwise, the pathogen escapes into the bloodstream and finds its way to lymph nodes, the spleen, the gall bladder, bones, and other body parts.
Symptoms of Typhoid Fever
- Headache
- fever of 40 degrees Celsius
- chills
- abdominal pain
- loss of appetite
- vomiting
- diarrhea
- myalgia or muscle pain
- bradycardia
slow heartbeat is a common symptom of infection with Salmonella typhi.
- The first stage consists of gradually increasing fever after the incubation time of the pathogen.
- In the next stage, the bacteria invade and multiply in the Peyer’s patches in the intestine. Peyer’s patches are the follicles present in the lining of the ileum.
- This stage is characterized by diarrhea or constipation and abdominal pain.
- Small red or pink spots known as rose spots also appear on the chest and stomach.
- At this time, if the infection is left untreated, it starts spreading to other body parts, including the brain, spleen, and gall bladder, leading to encephalitis and intestinal bleeding.
- Afterwards, the recovery period starts, but in some cases, bacteria can live in the gall bladder in a dormant stage, meaning that the infected person does not experience any symptoms during this infection stage.
Complications of Typhoid Fever Include
- Intestinal bleeding
- Swollen or perforated gallbladder
- Meningitis
- Bronchitis, pneumonia, or other respiratory tract infections
- Bone and heart inflammation
- Kidney failure
- Miscarriage
Diagnosis of Typhoid Fever
Blood, urine, and stool samples can be analyzed to identify Salmonella typhi. The following tests can be used to analyze the samples above:
Widal test
The principle of this test is to detect the antibodies produced against Salmonella typhi. This test involves analyzing a patient’s serum, extracted from a blood sample and poured onto the suspension containing specific antigens. Suppose the patient’s immune system has produced antibodies to encounter infection. In that case, the serum under analysis will contain these antibodies, binding to specific antigens in the suspension, forming antigen-antibody clumps. The formation of clumps is visible to the naked eye and thus indicates a positive test. However, this test is time-consuming and often produces false positive results.
Typhidot
It is a type of rapid diagnostic test. This test detects the presence of IgM and IgG antibodies in the patient’s serum. Whenever a person gets infected with Salmonella typhi, IgM and IgG antibodies are produced in the blood. A specific Typhidot test kit is used to analyze these antibodies. These kits contain a cellulose nitrate membrane coated with the outer membrane protein (OMP) of Salmonella typhi. This OMP is a specific antigen that binds with the IgM and IgG antibodies if present in the blood serum. Two bands are produced upon binding of antibodies with OMP, indicating a positive test result. Otherwise, a single-band appearance indicates a negative test.
TUBEX test
This test utilizes brown and blue colored magnetic particles. The brown magnetic particles are coated with antigen, while the blue magnetic particles are coated with O9 antibody. Blue magnetic particles act as indicators of the reaction. The antibodies in the patient’s serum attach to brown magnetic particles and settle at the base. The test will be perceived as positive if blue indicator particles in the solution emit a blue color. However, a negative test will produce a colorless solution.
Treatment of Typhoid Fever
Oral rehydration therapy
Oral rehydration therapy involves consuming water with optimum sugars, sodium, and potassium concentrations. It is an effective way to relieve symptoms of diarrhea.
Antibiotics
Antibiotics such as ciprofloxacin, cefixime, azithromycin, and carbapenems are recommended as drugs of choice. However, vaccination is the best option due to the continuously emerging antibiotic resistance in bacterial pathogens. Sometimes, typhoid fever bacteria can cause recurrent infection even after the patient recovers. This recurrence is termed typhoid relapse. However, typhoid relapse causes milder symptoms than the initial infection for the first time.
Prevention of Typhoid Fever
Preventing typhoid fever usually involves two essential measures: vaccination and food safety.
Vaccination
There are two approved typhoid vaccines available to prevent infection. The oral vaccine Ty21a, in the form of tablets, is sold as Vivotif by Crucell Switzerland. However, it has not been available since December 2020. Another vaccine is an injectable typhoid polysaccharide vaccine. Sanofi Pasteur sells it as Typhim Vi, while GlaxoSmithKline named it Typherix. The injectable vaccine requires a booster dose after every two years.
Food safety measures
- Wash your hands after using the toilets.
- Wash utensils and other objects after an infected person touches them.
- Avoid eating undercooked food, particularly meat.
- Always use appropriately packaged and sterilized preserved foods.
- If you suspect the water is contaminated, use bottled water for drinking and cooking.
Final Thoughts
Typhoid fever was first discovered by Karl Joseph Eberth in 1880. It is caused by the bacterium Salmonella typhi, which is spread by contaminated food or water. An affected person by typhoid may experience high fever, stomach pain, and severe headache. The prevalence report of this disease indicates that an estimated 9 million people are affected by this disease, and among them, 110000 people die annually throughout the world.
Frequently Asked Questions – FAQs
How many days does a typhoid fever last?
Typhoid fever lasts for about 7 to 10 days when treatment is started immediately after the appearance of the symptoms.
What is the effective treatment of typhoid fever?
After early diagnosis of typhoid fever, some antibiotic tablets are recommended to patients. These tablets must be utilized for 7 to 14 days.
Can drinking water be an effective way to prevent typhoid?
A lot of preventive measures could be adopted to prevent typhoid fever, but drinking water, sanitization, and proper hygiene are the key points.
About the author
Dr Madilyn Adams is a PhD in molecular medicine from Harvard University and has been working as a medical blogger for seven years.
References
- https://www.who.int/news-room/fact-sheets/detail/typhoid#:~:text=Overview,and%20spread%20into%20the%20bloodstream.
- https://www.mayoclinic.org/diseases-conditions/typhoid-fever/symptoms-causes/syc-20378661
- https://www.medicalnewstoday.com/articles/156859
- https://www.cdc.gov/typhoid-fever/index.html
- https://my.clevelandclinic.org/health/diseases/17730-typhoid-fever
