M Sc (Microbiologist) CIHSR, Dimapur
Did you know?
• Typhoid is caused by the bacteria, Salmonella species
• It is contracted by ingesting contaminated food (by carriers) or water (contaminated with feces) containing the bacteria.
• Symptoms include poor appetite, headaches, diarrhoea, generalized aches and pains, fever, and lethargy.
• It can be diagnosed using blood, blood serum, stool and urine. Typhoid can be confirmed by various investigations and each of them becomes positive at various times in the course of the disease. This can be remembered as BASU.
• Blood culture in the 1st week
• Antibody detection using blood serum (Widal test) in 2nd week
• Stool culture in the 3rd week
• Urine culture in the 4th week
• It can be treated using antibiotics
• It can be prevented by following these simple steps:
• Thoroughly wash hands with soap and warm water after going to the bathroom and before preparing food
• Always drink boiled or safe water
• Follow proper sanitation practices
Interpreting Widal Test
Widal test is a blood test which detects the presence of antibodies in patient’s serum to diagnose typhoid and paratyphoid fever caused by the bacteria, Salmonella Typhi, Paratyphi A and B. When facilitiesfor blood culture to confirm typhoid are not available, Widal test can be of value in the diagnosis of it. In places like India where typhoid is prevalent, healthy individuals may also show some levels of antibodies in their blood. So, just the mere presence of antibodies in an individual’s blood does not imply that he is having typhoidal fever. Also, a negative Widal test does not rule out typhoid fever. Therefore, interpreting the results of Widal test require taking into account the following:
• The stage of the disease when blood was taken- Antibodies in the blood against the bacteria appear by the end of the first week, so blood taken earlier may give a negative result.
• Obtain a baseline antibody level- It is important to know the cut off (baseline) antibody levels in normal population of that area (by doing a study) so that any levels below the baseline level, will be considered as negative.
• Prior infection or immunisation
• Patients who are already on antibiotics may show poor response
Widal is widely used all over India and is helpful for diagnosing typhoid, but if not interpreted correctly, can lead to wrong diagnosis and ultimately, wrong treatment.