Typhoid fever is caused by the bacterium Salmonella typhi, which only lives in humans.
It is usually spread through contaminated food or water, which, upon consumption, would lead to the bacteria multiplying and spreading into the human bloodstream.
Typhoid can also be spread by close contact with an infected person.
The transmission of typhoid is by the faecal-oral route, i.e. the bacteria is passed in the faeces, and sometimes, the urine, of the infected person.
This happens when a person eats food handled by someone with typhoid, who has not washed properly after going to the toilet, or by drinking water contaminated by the bacteria.
The bacteria continues to reside in the intestines or gallbladders of a small number of people who have recovered from typhoid, often for years.
These people, called chronic carriers, do not have the clinical features of typhoid, but they continue to shed the bacteria in their faeces, exposing others to the risk of infection.
Improved environmental conditions, and the availability of antibiotics and vaccinations, have led to a marked decrease in the illness and death rates of typhoid in high-income economies.
However, this disease continues to be a burden in developing and middle-income economies.
The World Health Organization (WHO) estimates that the global incidence is about 11-20 million cases annually, with about 128,000 to 161,000 deaths.
The incidence in Malaysia has decreased markedly in the last half-century and was 0.59 per 100,000 population in 2017, with a mortality of 0.02 per 100,000 population.
Typhoid is endemic in Malaysia with outbreaks reported periodically.
The disease burden of typhoid is increased by urbanisation, climate change and increasing resistance to antibiotics, which facilitates its spread in overcrowded populations, and inadequate and/or flooded water and sanitation systems.
The risk of typhoid is higher when access to safe water and sanitation is lacking.
In short, the poor and vulnerable groups, including children, are at high risk.
When you get it
The clinical features of typhoid include prolonged high fever, nausea, abdominal pain, constipation or diarrhoea, fatigue, headache and an occasional rash.
The common complications of untreated typhoid are intestinal bleeding and perforation, which are both life-threatening.
When intestinal perforation occurs, a hole develops in the intestine, causing the intestinal contents to leak into the abdominal cavity, resulting in severe pain, nausea, vomiting and bloodstream infection (sepsis).
Other complications of typhoid include inflammation of the heart (myocarditis), of its lining and valves (endocarditis), and of the pancreas (pancreatitis); infection of the lungs (pneumonia), of the membranes around the brain and spinal cord (meningitis), of the kidneys and of the bladder; and psychiatric problems.
Typhoid is treated with antibiotics, which – together with improved hygiene, water treatment and better public health management – resulted in control of the disease in high-income economies.
The indiscriminate use of antibiotics in economically-deprived communities, where poverty and poor infrastructure is prevalent, has encouraged the development of antibiotic resistance, so much so that antibiotic resistance in typhoid is now both a clinical and economic challenge.
Concomitantly, the patient has to practise safe hygiene, i.e. wash their hands with soap and water after using the toilet, and not prepare or serve food to other people.
This will reduce the likelihood of transmission of the infection.
Complications that occur are managed accordingly.
There are currently two types of typhoid vaccines available.
They are an injectable vaccine containing the S. typhi antigen, and a live attenuated oral vaccine.
The former can be administered to adults and children over two years of age.
The latter can be administered to adults and children over six years of age.
Neither of these vaccines are approved for children less than two years of age.
The injectable vaccine provides protection beginning about seven days after the injection.
It provides about 72% protection after one-and-a-half years, and 50% after three years.
Revaccination is recommended every three years to maintain protection against typhoid.
The duration of protection following the oral vaccine is unclear and may vary with vaccine dose, and possibly subsequent exposure to the bacteria.
WHO says: “In Australia and Europe, three tablets are given on days one, three and five; this series is repeated every year for individuals travelling from nonendemic to endemic countries, and every three years for individuals living in countries or areas at risk.
“In North America, four tablets are given on days one, three, five and seven, and revaccination is recommended only after seven years (Canada) or five years (United States) for all, regardless of typhoid fever risk in the country or area of residence.”
Our local authorities require all licensed food handlers to have vaccination against typhoid.
However, there is no data on compliance to this requirement.
For the young
The clinical trial of the first conjugate typhoid vaccine (TCV) in Nepal was published in the New England Journal of Medicine on Dec 5, 2019.
It involved 20,019 children aged nine months to 16 years.
The recipients of the TCV numbered 10,005, whilst the control group who received the meningococcal capsular group A conjugate vaccine (MenA) numbered 10,014.
Blood cultures confirmed typhoid in seven recipients of TCV, i.e. 79 cases per 100,000 person-years, and 38 recipients of MenA, i.e. 428 cases per 100,000 person-years.
The vaccine efficacy was 81.6%.
Both groups had similar complications or side effects, i.e. 61 cases in the TCV and 71 in the MenA groups respectively, in the first six months.
Fever, which was identified as vaccine-related, developed in 5% and 5.4% of the TCV and MenA groups respectively.
The development of typhoid antibodies (i.e. seroconversion) was 99% (677 of 683 participants) and 2% (8 of 380 participants) in the TCV and MenA groups respectively.
The authors concluded that: “A single dose of TCV was immunogenic and effective in reducing S. typhi bacteraemia in children nine months to 16 years of age.”
WHO prequalified the TCV in December 2017, on the rationale that it had longer-lasting immunity than the other vaccines, required fewer doses and can be given to children above six months of age.
The organisation recommends that a single dose of TCV be administered to children above six months of age and in adults up to 45 years in endemic regions.
Dr Milton Lum is a past president of the Federation of Private Medical Practitioners Associations and the Malaysian Medical Association. The views expressed do not represent that of organisations that the writer is associated with. The information provided is for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
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