THE OCCURRENCE OF AN UNRECORDED FILARID
       NEMATODE, ONCHOCERCA CERVICALIS RAILLIET
               AND HENRY, 1910, IN THE LIGAMENTUM
                         NUCHAE OF HORSES IN INDIA

                                                 BY

                         HAR DAYAL SRIVASTAVA, D. Sc.

                            Helminthologist (On special duty)

         Imperial Veterinary Research Institute, Mukteswar-Kumaun

                    (Received for publication on 25th May 1938.)

RAILLIET AND HENRY in a paper on the classification of the genus Oncho-
cerca Diesing [1841], published in 1910 established a new species, O. cervicalis,
which according to them was very common in France. Subsequently this
nematode, which is commonly known as the neck threadworm, has been re-
ported from equines in several countries,—Australia, England, United States
of America and Africa. The parasite has been suspected to be the cause of
fistulous withers and pole evil, having been found in a number of cases of
the disease. The etiological relationship, however, between the worms and
the disease has not yet been definitely established, as the parasite has
also been met with in apparently healthy animals. Recently, Datta [1936]
has demonstrated the invariable presence of an unsheathed microfilariae
in the sections of affected skin from over twenty cases of Lichen tropicus
in equines in this country. As in several other forms of Onchocercaciasis,
the microfilariae are not found in the blood of the diseased animals. Though
the condition known as khojlee or Lichen tropicus in equines has been known
in this country for a very long time, the occurrence of O. cervicalis in Indian
hosts has not been previously reported. Through the kindness of Capt.
Datta the author received some pieces of Ligamentum nuchae from cases of
Lichen tropicus for examination. Entire ligaments from cases of the
disease subjected to post mortem examination at this Institute were also
examined. In three cases large numbers of inextricably coiled, fine, shining
white worms were present. On a detailed examination all of them proved to
be specimens of O. cervicalis. The adult worms usually occur between two
lamellar portions of the Ligamentum nuchae. In situ the worms resemble
the fibres so closely that it is almost impossible to follow the course of
the parasite for any appreciable length during micro dissection. Small,
hard, calcareous nodules varying in size from a pin head to a pea were often
found associated with the parasite. Usually the anterior end was found
embedded in the nodule.

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