What Is Typhoid Fever and How to Use the Typhoid Rapid Test Kit?
Responsible for more than 9 million cases and 110,000 deaths worldwide, typhoid fever remains a major threat to public health across the developing regions of the world. According to the World Health Organization (WHO), typhoid fever is endemic in many parts of Asia, Africa, and Latin America. It disproportionately affects children and young adults in communities with inadequate sanitation and limited access to clean water. Despite the availability of effective treatments and preventive measures, the widespread incidence and high global burden of typhoid fever highlight the urgent need for improved public health interventions and innovative diagnostic tools to control and eliminate the infection. Furthermore, since typhoid fever commonly presents with a range of nonspecific symptoms, such as fever, headache, malaise, and abdominal pain, its clinical diagnosis may be challenging. With the development of rapid chromatic immunoassays based on the principle of antibody detection, it has now become possible to detect typhoid fever in various point-of-care contexts, including remote and resource-limited areas. Although rapid detection kits, such as our Typhoid IgG/IgM Rapid Test Kit, are recommended to be used in adjunction to traditional methods and interpreted in the context of the patient’s clinical presentation and exposure history, the kit offers unique advantages from a public health standpoint, including rapid turnaround time, ease of use, affordability, and accessibility. Read along to learn more about typhoid fever, its symptoms, and how it is detected with the Typhoid Rapid Test Kit.
What is Typhoid Fever?
Typhoid fever is a bacterial infection caused by the bacterium Salmonella typhi. Salmonella typhi is a gram-negative, facultative anaerobic bacterium of the family Enterobacteriaceae. Salmonella typhi is primarily transmitted via the fecal-oral route, often via the consumption of contaminated food or water. In areas with poor sanitation, inadequate hygiene practices, and limited access to clean food and water, typhoid fever is a persistent threat as these bacteria can survive for several weeks in water, sewage, and soil.
Once ingested, Salmonella typhi targets the intestinal tract and penetrates the intestinal mucosa to enter the host bloodstream. Migrating via the bloodstream of the host, the bacteria cause a systemic infection. Then, the bacteria replicate within the phagocytic cells of the reticuloendothelial system, primarily in the liver, spleen, and bone marrow. The pathogenesis of Salmonella typhi depends on various factors, including the Vi antigen and the type III secretion system. The Vi antigen enhances the immune evasion ability of the bacteria. In contrast, the type III secretion system allows the bacteria to inject toxins into host cells and manipulate the immune responses of the host body. The severity of typhoid fever may range from a mild flu-like disease to a life-threatening illness with potentially life-threatening complications such as intestinal perforation, bleeding, and sepsis.
What are the Symptoms of Typhoid Fever?
The symptoms of typhoid fever can vary widely in severity and can be difficult to differentiate from similar febrile illnesses. The incubation period for the disease often ranges between 6 to 30 days, with an average of 8 to 14 days. The early symptoms of typhoid fever are usually non-specific and include a gradual onset of fever, headache, fatigue, and malaise. The development of common gastrointestinal symptoms, such as abdominal pain, constipation, diarrhea, nausea, and vomiting, follows these initial symptoms. Some patients may also present with a distinctive rose-colored rash on their trunk and abdomen. As the infection progresses, patients may experience neurological symptoms such as delirium or confusion and enter into a state of coma. Common complications of typhoid fever include intestinal perforation, gastrointestinal bleeding, and sepsis. If left untreated, these complications may result in the death of the patient.
What is the Typhoid Rapid Test Kit?
The Typhoid Fever Rapid Test Kit is a diagnostic tool designed to detect the presence of antibodies against Salmonella typhi in patient blood, serum, or plasma samples. Coming in a lateral flow test format, the test kit contains a nitrocellulose membrane coated with antigens specific to Salmonella typhi and a colored particle conjugate that binds to the antibodies that may be present in the tested sample. Once a sample is applied to the test strip, any antibodies against Salmonella typhi present in the sample will form antigen/antibody complexes with the antigens specific to Salmonella typhi coated on the nitrocellulose membrane. Then, the colored particle conjugate will bind to the antibodies on the membrane, which enables the development of colored lines on the test region (T) and control region (C) on the assay. The kit usually results in 15 to 20 minutes and incorporates a control line (C) that functions as a procedural control, confirming the validity of the results.
How to Use the Typhoid Rapid Test Kit?
Rapid test kits for the detection of typhoid fever most often come in the form of serological assays. The test procedure requires the collection of a blood, serum, or plasma sample by a healthcare professional via standard venipuncture or fingerstick techniques. If the test is not performed with a whole blood sample, the collected whole blood sample can be centrifuged to obtain a serum sample or placed into a tube with anticoagulants to obtain a plasma sample. When the required sample is ready, a few drops are added to the sample well (S) on the test strip. Then, a few drops of the included buffer solution or sample diluent are applied to the same well, and a timer is started. After a reaction period of approximately 15 to 20 minutes, the results should be ready to be read qualitatively on the test strip. If a colored line appears in the test line region (T), it indicates the presence of antibodies against Salmonella typhi. If no line appears in the test line region (T), the test result is considered negative. Regardless of the presence of the test line (T), the control line (C) should always appear as a confirmation of the validity of the results. If the control line (C) is absent at the end of the specified reaction period, the results are considered invalid, and the procedure should be repeated with a new test kit.
