Epidemiology and control of filariasis

1. Epidemiology and
Control of Filariasis
ABU UBAIDA FAZAA
ABDULRAZZAQ
DONE BY:

2. What is Lymphatic Filariasis

3. What is Lymphatic Filariasis
 Lymphatic filariasis is a vector-borne
parasitic disease that is endemic in
many tropical and subtropical
countries. The disease is caused by
thread-like, parasitic filarial worms:
Wuchereria bancrofti, Brugia
malayi, and Brugia timori.
 W. bancrofti is most widely spread
and is responsible for more than 90%
of the infections.

4. Classification
Can be classified depending on their
habitat in human tissues
Lymphatic
filariasis
Body cavity
filariasis
Connective
tissue
filariasis

5. Most Important Filariae
Species
Geographic
distribution
Pathogenicity
site of
infection
Microfilariae
(characteristics)
Vector
Wuchereria
bancrofti
Asia, Pacific,
Tropical Africa,
Americas
Lymphangitis,
fever,
elephantiasis
hydrocoele,
and
chyluria
Lymphatics
Found in blood,
sheathed,
periodicity
variable
Culicidae
(mosquitoes)
Brugia malayi
South and East
Asia
Lymphagitis,
fever, and
Elephantiasis
Lymphatics
Found in blood,
sheathed,
nocturnally
periodic or
subperiodic
Culicidae
(mosquitoes)

6. LIFE CYCLE
 The adult worms (macrofilaria) are located in the lymphatic system
of the human host, where they live for 5-10 years.
 During their lifespan, after mating, female worms bring millions of
immature microfilariae (mf) into the blood.
 Some of these mf may be engorged by mosquitoes taking a blood
meal.
 Inside a mosquito, mf develop in about 12 days into L3 stage larvae
(L3). These L3 are infectious to human: they can enter the human
body when a mosquito takes a blood meal. Some will migrate to the
lymphatic system and develop into mature worms.

7. LIFE CYCLE
 Maturation takes 6-12 months.
 Mf cannot develop into adult worms without
passing through the developmental stages in
the mosquito.
 life span of mf in the human body is estimated at
6-24 months.

9. WHY FILARIASIS NEVER CAUSES EXPLOSIVE
EPIDEMICS
There are three reasons
1- The parasite does not multiply in the insect vector.
2- The infective larvae do not multiply in the human host.
3- The life cycle of the parasite is relatively long, 15 years or more.
These factors favor the success of a control program.

10. Symptoms
 Most people infected with Brugian or
Bancroftian filariasis in endemic areas
are asymptomatic, since the
development of symptoms relates to
the cumulative acquisition of
increasing numbers of worms.
 The clinical course of lymphatic
filariasis includes three distinct phases:
1. Asymptomatic microfilaremia.
2. Acute episodes of adenolymphangitis
(ADL). Which is reversible.
3. Chronic lymphedema disease
(irreversible lymphedema), which is
often superimposed upon repeated
episodes of ADL.

11. Axillary
lymph
nodes
Inguinal
lymph
nodes

12. Parasites
 White, slender, roundworms.
 Three types. the most common are:
 Wuchereria bancrofti.
 Brugia malayi.
 Brugia timori.
 Live for 5-7 years, produce millions of
microfilaria.

13. EPIDEMIOLOGY
 W. bancrofti occurs in the following regions:
Africa, Southeast Asia, the Indian subcontinent,
many of the Pacific islands, and focal areas in
Latin America.
 B. malayi occurs mainly in China, India, Malaysia,
the Philippines, Indonesia, and various Pacific
islands.
 B. timori is limited to the Timor Island of Indonesia.

14. EPIDEMIOLOGY
 It is estimated that more than 120 million people
worldwide are infected with one of these three
microfilariae.
 More than 90 percent of these infections are due to W.
bancrofti, and the remainder are mostly due to B. malayi.
 Estimates suggest that more than 40 million infected
individuals are seriously incapacitated and disfigured by
the disease.

15. Infected regions

16. Control
 How can the menace of filariasis be controlled?
 Addition of DEC to salt for mass treatment: It is also a cheap and safe
method. Common salt medicated with 1–4 g of DEC per kg.
 Mosquito control measures: This is achieved by spraying insecticides which
are lethal to the larvae of the mosquitoes.
 Environmental issues in the control of filariasis: The filariasis problem largely
arises as a result of poor sanitation and hygiene. The emphasis should be on
improving existing sanitary conditions. In the case of Mansonia mosquitoes,
breeding is best controlled by removing supporting aquatic vegetation
such as the Pistia plant from all water collections and converting the ponds
to fish or lotus culture. Larvicidal operations are complemented activities
such as filling up of ditches and cesspools, drainage of stagnant water,
adequate maintenance of septic tanks and soakage pits etc.

17. Control
 Filarial Surveys: Firstly, in order to control the disease, an estimate of
the problem by conducting surveys has to be undertaken. There are
many elements in the survey. The survey can either entail the
examination of patients for the symptoms of filariasis, or the
examination of blood samples, particularly at night time to
demonstrate the parasite. Many times, the parasite is difficult to
detect in the blood, and tests which measure antibodies against the
parasite may have to be employed.
 Entomological survey: This comprises general mosquito collection
from houses, dissection of female vector species for detection of
developmental forms of the parasite, a study of the extent and type
of breeding places. The data is assembled, analyzed and used for
the compilation of certain filarial statistics.

18. Control
Preventive measures for travelers:
 Avoid outbreaks: Travelers should avoid known
foci of epidemic disease transmission.
 Be aware of peak exposure times and places.
 Wear appropriate clothing: Travelers can
minimize areas of exposed skin by wearing long-
sleeved shirts, long pants, boots, and hats.

19. Control
 Check for ticks: Travelers should inspect themselves and
their clothing for ticks during outdoor activity and at the
end of the day.
 Bed nets: Bed nets are essential in providing protection
and reducing discomfort caused by biting insects.
 Insecticides and spatial repellents: These products,
containing active ingredients that help kill the mosquitos.
 Optimum protection can be provided by applying the
repellents to the exposed skin.

20. TREATMENT
 Diethylcarbamazine — DEC with or without corticosteroieds.
 Ivermectin — Studies have established that ivermectin given as a
single dose in Bancroftian filariasis reduces microfilaremia by
approximately 90 percent even one year after treatment.
 Albendazole — has also been used in filarial infections. Prolonged
courses of high dose albendazole have a significant macrofilaricidal
effect and result in a gradual decrease in microfilarial levels.
 Doxycycline — Initial studies suggested that doxycycline, which has
good activity against filaria spp, leads to sterility of adult worms.

21. THANK
YOU