March, 1954]
A.
K.
VARMA
19
the greater percentage of incidence of the disease in these animals. Further, all
ages were found to contract the disease when exposed to infection; but the younger
calves, that are kept more confined to the villages near dwelling places, were generally
found free. Thus, the age and sex incidence of this bilharzial disease appears to be
actually influenced by the increased or reduced opportunities of exposure of
susceptible animals to infection and there seems hardly any acquired partial or
total immunity on the part of any particular category of susceptible animals. Some
data worked out in this connection to substantiate these deductions more positively
are given in Table IV. These figures indicate greater incidence of the disease in
older animals and in males, both of which are more exposed to contacts with the
foci of infection.
In order to find out the probable concentrations of the parasite elsewhere in
the intestinal and vesical veins, besides the usual nasal veins, about 100 samples of
faeces and 20 of urine, collected from positively infected cases in different areas,
were examined for the presence of eggs, but the results were all negative, which
confirms the findings of previous investigators in this connection. It is quite probable
that the parasites, as they grow to maturity, find it physiologically more suitable to
migrate to the nasal veins to settle down there to lay their eggs for their final dis-
charge to the exterior. This peculiar selective habitat of S. nasale, unlike other
schistosomes parasitising intestinal and vesical veins, needs further investigation
to throw more light on the bionomics and pathogenicity of the parasite in order to
estimate the harm caused to the host.
The writer was unable to obtain a single positively infected animal for post-
mortem examination. An opportunity was, however, afforded to examine some
freshly slaughtered cattle and buffaloes as well as some goats (eight cattle, six
buffaloes and 18 goats) in this area at Patna, Biharsharif, Nawada and Arrah,
but no schistosome could be recovered from any of these carcases, although a very
close search was made for them in the mesenteric veins, liver and also the nasal
veins. The owners of these animals reported that none of them was infected with
nasal schistosomiasis, which is locally known as 'Nakra' or 'Sunsuna'. Moreover,
most of the animals slaughtered in these abattoirs are brought from other places,
because they are cheaper and not available in the locality owing to the religious
prejudices of the people, who do not usually sell cattle for slaughter purposes.
MOLLUSCAN FAUNA
No attempt seems to have been made so far to ascertain the potential molluscan
intermediary of the parasite in this State. Rao [1933] demonstrated that Limnaea
luteola (Lamarck) and Indoplanorbis exustus (Desh.) were the intermediate vectors
of S. nasale in Madras. Existence of many most favoured habitats of aquatic
snails in the areas surveyed has already been pointed out and it was interesting to
find that in areas lying over routes (1), (2) and (3) Limnaea luteola predominated
strikingly over other types. Some of the ponds and water-logged areas were found
very badly infested with these Limnaea, which, unlike Planorbis, were found to
favour clean, shallow, sluggish-moving water, where they were moving freely on
the surface of the water in an inverted position. Some Planorbis were also re-
covered from more or less stagnating water in some ponds covered with vegetation,
8 AR/53
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