Health care: Why Malarial Parasite usually not found in PBF

Malaria –Its Misdiagnosis

Malaria is a very common cause of fever in tropical countries.¹ It is one of the major public health problems in Bangladesh. Out of 64 districts, 13 bordering districts in the east and northeast facing the Indian states of Assam, Tripura and Meghalaya and part of Myanmar belong to the high-risk malaria zone. ²

Internationally, about 3.3 billion people - half of the world's population - are at risk of malaria. Every year, this leads to about 250 million malaria cases and nearly one million deaths.³ In 2008, there were 247 million cases of malaria and nearly one million deaths – mostly among children living in Africa. In Africa a child dies every 45 seconds of Malaria, the disease accounts for 20% of all childhood deaths.^4,

Early diagnosis of malaria and its effective and timely treatment reduces morbidity and prevents death from malaria. Prompt and accurate parasitological confirmation of malaria is essential for effective disease management and malaria surveillance. ³ Clinically, the first symptoms of malaria (most often fever, chills, sweats, headaches, muscle pains, nausea and vomiting) are often not specific and are also found in other diseases.⁴ In Europe and North America, imported malaria have been misdiagnosed as influenza, viral hepatitis, viral encephalitis, or traveler’s diarrhoea, sometimes with fatal consequences.⁵ In Africa, 70% cases of malaria are diagnosed in the home and in some areas three-quarters of patients with fever are advised to take anti-malarial drugs for non-malarial illness.⁶

It appears to be a common issue of failure to demonstrate malarial parasite in peripheral blood in clinically suspected cases of malaria. The causes of this failure usually may be due to over diagnosis, misdiagnosis, inappropriate timing during blood collection and other causes:

1. Common diseases of misdiagnosis are:

a. UTI (urinary tract infection) - fever in UTI case usually associated with shivering and sweating. There might not be any symptoms of burning or frequency micturition when it affects the upper part of urinary tract. In this case (upper UTI) if the physician overlooks the patient’s abdominal or back pain it would misguide in the diagnosis.

b. Viral infection: - Viral infection is the commonest cause of febrile illnesses. Most people in our country initially use few doses of paracetamol before seeking advice from physician. Physician finds history of shivering and sweating in these cases but it is due to the effect of paracetamol.

c. Tuberculosis: Usually extra pulmonary cases may be confused with malaria due to rise of temperature at the evening time and associated with drenching sweating typically at night. ^{1, 5} Tuberculin test should help in the diagnosis of tuberculosis.⁷

d. Meningitis: Although headache may be severe in meningitis, so can be confused with malaria, there is no neck stiffness or photophobia resembling that in meningitis. Acute sinusitis, dengue fever or leptospirosis, some times can confuse with malarial infection due to chills mayalgia. ¹

2. Use of some antibiotics can also prevent appearance MP in peripheral blood- like fluoroquinolones (e.g., ciprofloxacin), cotrimoxazole, and tetracycline etc.⁸

3. Collection of blood: After excluding the above causes of fever if diagnosis goes in favour of malaria, still malarial parasite may not be found in peripheral blood due to

a. Blood examined at early stage of malarial infection - Particularly in first week of illness number of infected RBC may be too low that MP can not be seen even after searching for longer period.

b. Time of collection- Some physicians may advice to collect blood at the height of temperature for malarial parasite. But this should be a misleading idea. Fever in malaria synchronizes with rupture of infected RBC at the end of erythrocytic schizogony releasing a chemical called hemozoin, a febrile toxin. So at the height of temperature there should not be any intact infected RBC containing MP for demonstration in peripheral blood unless double cycles or multiple cycles on malarial infection run simultaneously, which is also not very rare. So, it is better to collect blood 1 to 2 hours or like before the onset of fever. When a fever subsides blood should to be collected at least 10-12 hours after an attack of fever because this time is needed to develop a ring form of malarial parasite inside newly recruited red cells.⁸

Serology does not detect current infection but rather measures past exposure. However, antibody detection may be useful for, screening blood donors or testing a patient who has been recently treated for malaria but in whom the diagnosis is questioned.³

References:

1. Nicholas J, White, Joel G. Breman.Malaria. In Harrison’s Principles of Internal Medicine. Seventeen Editions, 2008. Page 744.

2. Communicable Disease: World Health Organization. http://www.whoban.org/communicable_dis_malaria.html

3. Malaria: Diagnosis and treatment. World Health Organization. http://www.who.int/malaria/diagnosis_treatment/en/

4. Malaria Diagnosis (U.S.) – Serology. Center for Disease Diagnosis and Prevention. http://www.cdc.gov/malaria/

5. D J Bradley,David A. Warrell. Malaria: In Oxford Text Book of Medicine.4^th edition; Volume I, 2003, Page 721-748.

6. Malaria Knowledge Programme. www.liv.ac.uk/istm/majorprog/malaria/outputs.htm/

7. SI Patrick. Value of the Tuberculin Test. N Engl J Med 1959; 261:723-724 October 1, 1959

8. K.D. Chattergee. Malarial Parasites of Man. In Parasitology. 12 the Edition.. 1980. Page 72-103.