102
Cutaneous Leishmaniasis in a Bullock in Assam
affecting man, and secondly, the cutaneous infection known as Oriental sore
due to Leishmania tropica affecting both man and the dog. As a result,
however, of the researches of Laveran and others [1917] the parasites of both
forms of the disease have been shown to be immunologically different, although
inoculation of L. donovani into laboratory animals, besides producing visceral
leishmaniasis, may also produce lesions characteristic of L. tropica, and vice
versa. Morphologically, no characteristic differences have been observed
between these two species, and the parasite observed in the present case
bears a close resemblance to the two known species.
Work on the specific identity of the parasite could not be undertaken
due to lack of laboratory facilities in Assam. However the epizootological
facts known regarding both forms of the disease as prevalent in India are
worthy of consideration. The geographical regions in which one form of
the disease prevails are entirely distinct from those in which the other occurs.
Thus according to Sinton [1925] only L. tropica infection prevails, both in
man and dog, in the western part of the country or in the region north-west
of a line joining Delhi and Bombay, while in parts south-east of this line
only L. donovani occurs. Further, the commonly recognised insect vector
of L. tropica, according to workers at Calcutta School of Tropical Medicine
[Knowles, 1928], is Phlebotomus sergenti, and, as Sinton [1925] has observed,
there is a co-relationship between the geographical distribution of P. sergenti
and of Oriental sore. Sinton records that he has never found P. sergenti
amongst sandflies collected in places south and east of a line joining Bombay
and Delhi; also that Oriental sore caused by L. tropica does not occur south
and east of this line. Although experimental infections with L. tropica have
been successfully set up with some certainty in dogs and monkeys, they
have failed in the hands of Chadwick and MacHattie [1927] in such animals
as horses, cattle, sheep, a pig, fowls and rabbits.
The available epizootological and experimental data make it very doubt-
ful if L. tropica happened to be the cause of the sores in the present case.
The possibility of L. donovani, being involved in the present case, has to be
judged in the light of the following established facts concerning this species :
(a) the occurrence of L. donovani south-east of the line joining Bombay and
Delhi, and the non-occurrence of a single case of Oriental sore caused by L.
tropica in man in this province, (b) the common insect vector of L. donovani,
Phlebotomus argentipes, is found abundantly in endemic centres of kala-azar
in Assam and Bengal where according to Lloyd, Napier and Smith [1925]
the fly prefers to feed on cattle rather than on man, (c) both in experimental
animals [Row, 1912, 1913 and 1914] and in man L. donovani may cause cuta-
neous lesions. In post-kala-azar cases [Brahmachari, 1922] and in those
having no previous history of kala-azar [Acton, 1926] dermal leishmaniasis
of various clinical types has been encountered and described. Napier and
Dasgupta [1934] and Smith and Haldar [1935] have described ulcerative
lesions in man in which L. donovani have been found.
The present case of ulcerative dermal leishmaniasis in a bullock in Assam
would thus appear to be strongly suggestive of a L. donovani infection.
Although only one case of this disease in a bovine is being described here