Generality
Abdominal typhus - or typhoid fever - is a systemic infectious disease (involving the entire organism), caused by the bacterium Salmonella enterica serotype typhi .
The agent responsible for typhus is present in the urine and faeces of infected people, and can be transmitted from man to man via faecal-oral route through the ingestion of contaminated food or drink.
Typhoid fever is common in less industrialized countries, mainly due to limited access to drinking water, inadequate disposal of waste water, and flooding. Because of the way the infection spreads, typhoid fever is more common in some parts of the world that have low levels of sanitation. The annual incidence of typhoid fever is estimated at around 17 million cases worldwide.
Salmonella typhi
The causative agent of typhoid fever is Salmonella typhi, whose vector can only be human. Therefore, the infection is always transmitted from one human being, sick or healthy carrier of the bacterium, to another. The incubation period may vary depending on the infecting dose, but is usually 1-3 weeks.
After ingesting contaminated food or water, the bacteria invade the small intestine and enter the bloodstream temporarily. Salmonella typhi initially multiplies in the cells of the liver, spleen and bone marrow, and then returns to the blood. When the organism spreads into the bloodstream, patients develop symptoms, including fever. The bacteria invade the gallbladder, the biliary tract and the lymphoid tissue associated with the intestine. Here, they multiply in large numbers to then pass into the intestinal tract. In this phase the pathogens can be identified, for diagnosis, in stool cultures tested in the laboratory.
Contagion
Generally, typhoid fever contracts with the ingestion of bacteria present in contaminated food or water.
Salmonella typhi has a remarkable resistance in the external environment, especially if contained in organic materials: bacteria can survive for weeks even in sewage and mud.
Patients with illness can contaminate water through feces, which during the acute phase of infection contain a high concentration of bacteria. The bacterial pollution of the water network can, in turn, contaminate the food supply. If a healthy person eats food or drinks that have been contaminated with a small amount of faeces or urine in which Salmonella typhi is present, he can contract the infection.
Furthermore, if infected patients do not wash their hands properly after going to the bathroom, they can contaminate the food or surfaces they touch, contributing to the spread of the infection.
Other ways typhoid fever can be contracted are:
- Eat shellfish or seafood from a water source that has been contaminated with infected faeces or urine;
- Have sexual intercourse (oral or anal) with a person carrying Salmonella typhi .
Healthy carrier status may follow acute illness. If typhoid fever is not treated, it is estimated that one person in 20 will become a carrier of the long-term condition, even if asymptomatic. This means that the excretion of Salmonella typhi from the body of chronic carriers can continue and last for more than 1 year.
Symptoms
To learn more: Symptoms Typhus
If the infection is not treated, the symptoms develop over the course of four weeks, with continuous worsening manifestations. As the condition progresses, the risk of developing complications increases. With treatment, symptoms should improve rapidly within 3-5 days.
First week
The symptoms that appear during the first week of infection are:
- High fever (39-40 ° C);
- Abdominal pain;
- Constipation (more common in adults) or diarrhea (in children);
- He retched;
- Dry cough;
- Headache;
- Papular exantheum in the skin (pink spots 1-4cm wide located on the trunk and distributed in less than five points);
- General malaise.
Second week
In the unlikely event that you are unable to undergo treatment, the symptoms listed above will become more severe in the second week of illness, and may be associated with severe swelling of the abdomen and bradycardia (slowing of the pulse).
Third week
During the third week, they can introduce themselves:
- Anorexia (lack of appetite) and weight loss;
- Physical exhaustion;
- Attacks of malodorous, watery and yellow-green diarrhea;
- Deterioration of the mental state, with serious confusion, apathy and, in some cases, psychosis (the person is not able to understand the difference between reality and fantasy).
Complications often develop during this period.
Fourth seventh
By the end of the third week, fever tends to gradually decrease (defervescence phase). This process ends in the fourth and last week. The signs and symptoms of the disease may recur 10 days after the fever has subsided.
Diagnosis
The causative agent can be identified in blood, bone marrow, faeces or urine samples. The diagnosis of typhoid fever can usually be formulated by:
- blood culture and Widal serum agglutination test - during the first week;
- co-culture and blood antigen research - during the second and third week.
Faecal cultures are sensitive in the early and late stages of the disease, but often need to be supplemented with a culture test for definitive diagnosis. The analysis of a bone marrow sample is a more accurate way to confirm Salmonella typhi infection, however it is only used if the other tests are inconclusive. If the outcome is positive due to the presence of Salmonella typhi, it is advisable to extend the medical assessment to other members of the patient's family.
Treatment
Typhoid fever requires immediate treatment with antibiotics and convalescence lasts for some time. If diagnosed in its early stages, it is likely that the infection is mild and can usually be treated for 7 -14 days. Symptoms should start to improve already within 48-72 hours of starting therapy, but it is still essential to finish the treatment, following the medical indications. The most severe cases of typhoid fever require hospitalization and administration of antibiotics and intravenous fluids. Hospitalization is usually recommended if the patient complains of persistent vomiting, swollen abdomen and severe diarrhea.
Several antibiotics are effective for the treatment of typhoid fever. Chloramphenicol has been the drug of choice for many years, but due to serious side effects (albeit rare), it has been replaced by other antibiotics. Some strains of Salmonella typhi have developed resistance to one or more types of these drugs, so a combination of different antibiotics can be prescribed. The choice of therapy must be guided by the identification of the geographical region where the infection was contracted and the result of the available cultures (multi-resistant strains of S. typhi have become common in some areas of the world, such as in the Indian subcontinent and in the Arabian peninsula). Ciprofloxacin is the most frequently used drug, while ceftriaxone is an alternative for pregnant patients. Other antibiotics that can be prescribed are ampicillin and trimethoprim / sulfamethoxazole, although some resistance has been observed in recent years. Surgery may be necessary to correct life-threatening complications, such as internal bleeding or bowel perforation. However, this is a very rare occurrence in people treated with antibiotics.
- Recurrences. If the treatment does not completely resolve the infection, the symptoms of typhoid fever may recur: about one in 20 people undergoes a relapse, with re-presentation of symptoms one week after the end of the antibiotic treatment. However, in relapse, symptoms tend to be milder and last for a limited amount of time. Usually, further antibiotic therapy is recommended.
- Long-term carriers. The healthy carrier status can be managed with longer therapy. Often, removal of the gall bladder, a site of chronic infection (together with the intestinal tract), manages to eradicate the infection. At the end of the therapy, the patient should undergo a coproculture to check if Salmonella typhi is still present in the faeces. If the result is positive, it means that the subject is a carrier of typhoid fever and will have to undergo further treatment with antibiotics.
Until the test results are negativised, showing that the samples are free from bacteria, the patient should avoid handling or preparing food, in addition to washing his hands with particular care after going to the bathroom.
Complications
Complications usually affect people who have not been treated with antibiotics, appearing in the third week after the onset of symptoms.
The most common complications that can occur in untreated typhoid fever are:
- Intestinal hemorrhage;
- Intestinal perforation.
Intestinal perforation is a very serious complication, as it spreads the infection to neighboring tissues and can cause peritonitis. If this happens, the infection can spread quickly in the blood, before spreading to other organs. This carries the risk of multiple organ failure and, if left untreated, can be fatal.
Vaccination
Vaccination is recommended for people who intend to travel to parts of the world where typhoid is widespread. The countries with the highest rates of typhoid fever are: Bangladesh, China, India, Indonesia, Laos, Nepal, Pakistan and Vietnam.
- Travelers in areas where there is a recognized risk of exposure to Salmonella typhi . The risk is greater if the destination is a developing country (for example, Latin America, Asia and Africa);
- People who must work or live in parts of the world where the infection is present, in close contact with the local population, exposing themselves frequently or in a prolonged manner to poor sanitary conditions.
However, the vaccines provide only limited protection and the conferred immunity can be overwhelmed by high concentrations of S. typhi . In addition, travelers should be warned that typhoid vaccination cannot replace a careful selection of food and drink, which is always essential. Therefore, when traveling to countries where typhoid fever is present, it is important to follow some precautions:
- Drink only bottled water (properly sealed);
- Don't eat raw vegetables, peeled fruits, seafood or salads;
- Don't eat ice cream, ice cubes or drink fruit juice from street vendors;
Two vaccines are available for typhoid prevention:
| ViCPS vaccine | Ty21a vaccine |
75% effective against typhoid fever in the first year after vaccination | Effective 50-60% against typhoid fever in the first year after vaccination |
Administered by injection (parenteral use); number of doses needed: 1 | Available in oral form (capsules); number of doses needed: 4 |
Inactivated vaccine | Live attenuated vaccine produced by the Ty21a strain of Salmonella typhi, a characteristic that makes it contraindicated in immunocompromised patients or people taking antibiotics at the time of vaccination. |
Primary vaccination must be carried out at least one month before the trip | Before a possible exposure, the immunization must be completed within a week |
The protective effect of the vaccine lasts about 2 years, after which a booster vaccination will be necessary | The vaccine is effective for about 5 years, after which a recall is necessary |
- The typhoid fever vaccine is not suitable for children under the age of two.
- The distribution of the heat-phenol-inactivated parenteral vaccine, widely used for many years, has been discontinued.
Side effects
After vaccination against typhoid fever, some people experience temporary pain, redness or swelling at the injection site. About 1% of people experience an increase in body temperature (38 ° C), while the less common side effects include abdominal pain, headache, nausea and diarrhea. Serious reactions are rare.
