insect proboscis and are transferred to the human host. Little is known of the portion of
the life cycle from larva to adult worm.
The incubation period is long and the clinical course uncertain.
Symptoms of infection may appear 3 months or longer after the
transmitting mosquito bite, but microfilariae do not appear in the blood for
at least 9 months.
These early symptoms include fever and inflammation of the lymphatic
system and genital structures.
If not adequately treated, filariasis persists for years.
Repeated or prolonged infections are manifested by lymphatic congestion
and elephantiasis (an enlargement and thickening of the tissues), particularly of the
lower limbs and the scrotum.
Proof of diagnosis consists in demonstrating microfilariae or adult worms in certain
tissues and organs and is difficult, especially in acute cases. Specific therapy consists
of the use of diethylcarbamazine (Hetrazan, Banozide).
In endemic areas, mass administration of diethylcarbamazine once per month produces
a profound and prolonged reduction of microfilariae and thereby interrupts the
transmission cycle. Nevertheless, measures directed toward the control of mosquito
vectors afford the simplest approach (para 5-12), and any use of drug prophylaxis
should be in conjunction with mosquito control measures.
Section VII. FLYBORNE DISEASES
5-28. FILTH FLIES
a. General. Filth flies (that is, houseflies, blow flies, flesh flies) are two-winged
flying insects found all over the world, but more abundantly in warmer climates. They
are frequently found in kitchens and dining areas. Filth flies breed in filth, feed on it, and
transmit it to man along with whatever pathogens may be in it. Typically, the common
housefly, Musca domestica, goes through a 4-stage life cycle (Figure 5-9), which from
egg to adult takes about 15 days.