Emerging zoonotic diseases: New type of filaria causing concern

By Syed Akbar
Hyderabad: Even as sustained efforts are on to eliminate the
common filariasis, a new type of filaria, human dirofilariasis, is now
emerging as a health issue in certain parts of the country including
Andhra Pradesh.

Dirofilariasis, which was hitherto limited to dogs and other animals,
is occasionally reported in human beings. Human dirofilariasis, like
the normal filarial infection, is transmitted by mosquitoes. Since the
reservoir of dirofilariasis is mostly dogs, the disease is carried to
human beings when mosquitoes that feed on infected canines bite them.

Analysis of medical data by scientists at the Vector Control Research
Centre, Puducherry, shows that cases of human dirofilariasis, caused
by Dirofilaria immitis and Dirofilaria repens, are more common in
areas where stray dog and cats live in large numbers. The analysis was
published in the scientific journal, Tropical Parasitology.
Dirofilaria are small nematode worms. But unlike the common filaria,
most of the cases of dirofilariasis are not properly reported.

“Since classical cases of filariasis are common, they are dealt at
epidemiologic scales. Uncommon infections are largely neglected and
reported rarely. When one searches for the reports in the literature,
it is not uncommon to find a few thousands of such reports. This is
only a tip of iceberg and indicates the occurrence of large number of
cases that go unreported,” points out VCRC senior scientist Dr SL Hoti.

He suggests that data on such cases should be generated in a
systematic epidemiologic study, as it will help in assessing the
dimension of the problem and devising strategies for the control.

Dirofilariasis is an emerging zoonosis (disease transmitted by animals
to man). This worm is capable of causing subconjunctival infection. It
is present in the form of periorbital and subconjunctival cysts. The
common filarial worm causes elephantiasis leading to swelling of lymph
glands, mostly those in the legs.

The emergence of dirofilariasis may thwart the attempts of health
planners to eliminate the common lymphatic filariasis caused by mostly
by W bancrofti. India accounts for 40 per cent of lymphatic filarial
cases in the world.