22            STUDIES ON NASAL SCHISTOSOMIASIS           [Vol. XXIV, Part I,

mosquitoes and their breeding grounds', which is already being worked out in
several malarious areas of the country. It needs a special contigent of some trained
labour with a supervisory staff to spray or broadcast the molluscicidal chemical in
proper strength over the snail-infected water. It must be planned systematically,
taking up groups of villages at a time along with the treatment of infected animals
as discussed earlier, without omitting any infected foci. Copper sulphate, owing
to its cheapness and easy availability, provides a good choice and the necessary
molluscicidal concentration should be worked out. Some Japanese workers [Hunter
Freytag, Ritchie, Pan, Yokagawa and Potts, 1952] have tried Santobrite (Sodium
pentachlorophenate) in Japan as a molluscicidal agent, using 30 lb. of the chemical
per acre (current price of the chemical is about $0.25 per lb. according to these
authors) in the dilution of approximately 1:200, with encouraging results.

The infective foci or the molluscan habitats are no doubt very many in the
area but are not very extensive and can be easily controlled.

(b)  Weeding out the snails by netting or hand-picking and destroying them
may not be physically possible.

(c)  Rearing of ducks and other snail-feeding birds does not appear to be a
practical proposition.

(d)  Some authorities have also suggested that by removing the vegetation
from the infected ponds, etc. the snails would automatically be starved and rooted
out.

(e)  Channelling the area and draining off the water-logged places is another
devise to control the incidence of the disease.

                                        FASCIOLIASIS

                              Fasciola indica Varma, 1953

Like other helminthic infections, particularly those caused by the trematodes,
this parasite has also found its habitat chiefly in the low-lying marshy regions of the
districts of Darbhanga, Saharsa, Purnea and parts of Monghyr and Bhagalpur lying
north of the river Ganges. The entire area constitutes almost a consolidated block,
bounded on the north by the territory of Nepal, on the south by the river Ganges,
on the west merging into the district of Mazaffarpur and on the east extending as far
as the eastern boundary of the State.

                                        TOPOGRAPHY

This region of fascioliasis lies wholly in the North Gangetic plain, between
latitudes 25.25' N & 26.50' N and longitudes 85.75' E & 88.25' E and is mostly
watered by the most notorious river Kosi with its many bifurcating and interlacing
off-shoots and tributaries, notable amongst them are the Kamla-Tiljuga, the Old
Baghmati and the Ghugri. The river Mahanadi with its several tributaries waters
the eastern portion of the district of Purnea.

The Kosi takes its origin somewhere in the territory of Nepal and all its seven
streams (called 'Sapta Kosi') join together before the river enters the plains.