This document discusses the diethylcarbamazine (DEC) provocation test used to diagnose lymphatic filariasis. It notes that the parasites that cause lymphatic filariasis (Wuchereria bancrofti, Brugia malayi, and Brugia timori) show nocturnal periodicity, appearing in blood between 10pm-2am. The DEC test stimulates these microfilariae, causing them to appear in peripheral blood within 30-45 minutes of an oral DEC dose, allowing diagnosis during the day instead of collecting a night blood sample. The test has high sensitivity, but is contraindicated where Loa loa or Onchocerca volvulus infections

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

2. Periodicity
• The biological property of microfilariae to be
present in the peripheral blood circulation
during a particular period in the day or night.

4. 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.

5. • 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.

6. • 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.

7. • 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.

8. DEC provocation test
• Also known as HETRAZAN PROVOCATIVE TEST.

9. 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.

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

12. • Microfilariae begin to decrease 2 hours later.

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

14. 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.

15. Thank You