Dec provocation test (lymphatic filiarisis)

Diagnosis of LYMPHATIC FILARISIS
Hetrazan provocative test

1. Diethylcarbamazine (DEC) provocation test AJAY SUBEDI Janamaitri foundation institute of health sciences,Balaju,Kathmandu Diagnosis of LYMPHATIC FILARISIS

2. P eriodicity T he biological property of microfilariae to be present in the peripheral blood circulation during a particular period in the day or night.

3. Introduction Wuchereria bancrofti ,  Brugia malayi  and  Brugia timori  are the causative agents of Lymphatic filariasis (Elephantiasis ). Microfilariae of these nematodes show nocturnal periodicity. They appear in peripheral blood at night time between 10pm and 2 am. This periodicity is due to biological and evolutionary co-adaptation of the microfilariae to the feeding habit of the mosquito  Culex quinquefaciatus  i.e. the principle vector for transmission of this parasite.

4. Periodicity may also be related to the sleeping habits of the hosts. It has been reported that if the sleeping habits of the hosts are reversed over a period, the microfilariae change their periodicity from nocturnal to diurnal . Nocturnal periodic microfilariae are believed to spend the day time mainly in the capillaries of the lung and kidneys or in the heart and great vessels.

5. So, for the diagnosis of the lymphatic filariasis , blood specimen should be collected at late night.   It may be impractical to obtain blood from an OPD patient at night time. So, to make the microfilariae appear in the patient’s peripheral blood during day time, DEC provocation test is done.

6. Microfilariae are not found in the peripheral blood in : During early allergic manifestations . In Occult filariasis . Case of Elephantiasis – due to lymphatic obstruction After an attack of lymphangitis , due to death of adult worm.

7. DEC provocation test Also known as HETRAZAN PROVOCATIVE TEST .

8. procedure The patient is given with a tablet of DEC orally ( 2mg/kg). (the nocturnal microfilariae are stimulated and come to peripheral blood within 30-45 minutes). After 30min, the capillary blood is collected by finger prick for demonstration of microfilariae by direct wet mount or staining the blood smear.

9. Microfilaria of Wuchereria bancrofti : unstained preparation (wet mount of blood sample) low power 10×

10. Microfilariae begin to decrease 2 hours later.

11. sensitivity It has a sensitivity that is almost comparable to that of night blood surveys .

12. Contraindication This test is contraindicated in the areas where Loa loa or Onchocerca volvulus infections are also found because of Mazzotti reaction & blindness in onchocerciasis .(cause Subcutaneous filariasis ) consisting of pruritus, rash , lymphadenopathy, fever, hypotension.

13. Thank You