MALARIA PARASITE AND WIDAL TESTS
The Widal test is one method that may be used to help make a presumptive diagnosis of enteric fever, also known as typhoid fever. Although the test is no longer commonly performed in the developed countries, it is still in use in many emerging nations where enteric fever is endemic and limited resources require the use of rapid, affordable testing alternatives. The method is easy to perform, however concerns remain about the reliability of this test apparently because it is not specific for typhoid fever and can be positive even when a person does not have the infection.
Enteric (typhoid) fever is a life-threatening illness that is caused by infection with the bacterium Salmonella enterica serotype Typhi (S. typhi), transmitted largely through food and drinks contaminated with fecal matter. Its symptoms include high fever, fatigue, headache, abdominal pain, diarrhea or constipation, weight loss, and also a rash known as rose spots. Early diagnosis and treatment are important because serious complications, including severe intestinal bleeding or perforation, can develop within weeks.
The testing for enteric fever usually involves a blood culture to detect the bacteria during the first week of fever. A stool, urine or bone marrow culture may also be performed. A blood culture, however, can be both labor and time-intensive in areas that lack the resources for automated equipment. In developing countries, the Widal test continues to be used instead of cultures because it is quicker, simpler, and less costly to perform.
WHAT IS A WIDAL TEST?
Typhidot (or Widal test) is a rapid serological test for the diagnosis of typhoid fever. Typhidot test is a dot ELISA kit that detects antibodies that fight against the outer membrane protein (OMP) of the Salmonella typhi. The Typhidot test becomes positive within 2-3 days of infection and separately identifies both the IgM and IgG antibodies. The test is actually based on the presence of specific IgM and IgG antibodies to a specific 50KD OMP.
Typhoid fever is typically accompanied by diarrhea, progressive fever and rose colored rashes. There are two commonly used screening tests which detect antibodies to the bacterium. The Widal test is both quantitative as well as qualitative and it can tell the titres of specific antibodies. The Typhidot separately identifies IgM and IgG antibodies against the bacteria. IgM shows recent infection whereas IgG signifies remote infection.
WHAT IS THE WIDAL TEST USED FOR?
The typhoid screening test is used in the identification, diagnosis & monitoring of fever and other salmonella infections. The test is conducted to detect antibodies against the infection.
WHY TAKE THE WIDAL/TYPHOID TEST?
Typhoid fever as an infection, is characterized by;
- Headaches
- Gastroenteritis
- Non-bloody diarrhea
- Excessive sweating
- Relatively abnormal slow heart beat
- Enlarged liver and spleen
- Coughs
- Gradual increase in fever (with body temperatures as high as 40 °C)
- Distended abdomen
- In severe cases, Intestinal hemorrhage
SAMPLE REQUIRED FOR TEST
Type of specimen is Serum (Blood Sample). The procedure for specimen collection is Venipuncture (Collection of blood from a vein) usually from the arm.
The results of this test is either positive or negative.
MALARIA PARASITE TESTS
When a mosquito with malaria bites, a parasite gets into the blood and destroys oxygen-carrying red blood cells. One will usually feel sick within days or weeks. However some parasites can live in the body for a year without any problem.
The initial symptoms of malaria often looks like the flu or a virus. Because of this, most people may not get help right away. A delay in treatment can lead to death. Early tests gives the best shot at recovery.
Types of Tests
- Thick and thin blood smears - The most common and accurate malaria tests. A lab technician, doctor, or nurse will take some blood and send it to a lab to be stained to enable any parasites show clearly. The technician will spread it on a glass slide and look at it under a microscope. A thin blood smear, also called a blood film, is one drop of blood spread across most of the slide. A thick smear drops the blood on a small area. A normal test will do two of each smear.
The number of malaria parasites in a person’s blood can change each day. So the test might return negative for malaria even if he/she has it. A person will therefore need his/her blood drawn several times over 2 to 3 days for the best results.
- Rapid diagnostic test – Variously referred to as RDT or antigen testing, this is a quick fix option when blood draws and smears aren't available. In this test, blood is taken from a prick on the finger, put on a test strip that changes color to show whether the patient has malaria or not. This test however cannot tell which of the four common species of malaria parasites caused the infection. It can also not tell whether the infection is minor or major.
- Molecular test – Otherwise known as polymerase chain reaction test. This can identify the particular type of parasite that has caused the infection, which goes to help the doctor decide which drugs to prescribe. This test is a good choice if the blood sample has a low number of parasites.
- Antibody test - Doctors use this to find out if you've had malaria in the past. It looks for antibodies that show up in the blood after an infection.
- Drug resistance test - Some malaria parasites are resistant to drugs. But doctors can test your blood to see if certain drugs will work.
- Blood test - In addition to other tests, you may also have your blood drawn for a blood count and chemistry panel. This can tell your doctor how serious your infection is and if it's causing other problems, like anemia or kidney failure.
The treatment of malaria is determined by the type of Plasmodium causing the infection, the geographical area in which the infection was acquired and sometimes local patterns of drug resistance, not forgetting how sick the person is.
Pregnant and breastfeeding women and children require special consideration. People with uncomplicated malaria can be treated with oral medication; however, more severe disease requires that medication be administered intravenous (directly into a vein).
