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PROCEEDINGS OF THE HELMINTHOLOG1CAL SOCIETY
The Synonymy of the Ruminant Parasites Nematodirus oiratianus
Raevskaia, 1929 and Nematodirus lanceolatus Ault, 19441
KAY S. SAMSON
USDA, Agricultural Research Service, Animal Disease and
Parasite Research Division, Las Cruces, New Mexico
Nematodirus oiratianus Raevskaia, 1929 (see
Raevskaia, 1931) was first described from
Altai wapiti (Cervus canadensis asiaticus) and
domestic sheep (Ovis aries) in Asiatic Russia.
It has since been recovered from other ruminant hosts in several localities in the USSR.
The Index Catalog of Medical and Veterinary
Zoology lists the following host records: water
buffalo (Bos bubalis), bezoar goat (Capra
aegagrus), domestic goat (C. hircus), Siberian
mountain goat (C. sibirica), roe deer (Capreolus capreolns) and (C. pygargus bedfordi),
European red deer (Cervus elaphus xanthopygus), sika (C. nippon), Dzeren antelope
(Gazella siibgutturosa), Siberian argali (Ovis
ammon), Armenian mouflon (O. ophion armeniana), chamois (Rupicapra rupicapra caucasica), and Saiga antelope (Saiga tatarica).
The males of N. oiratianus can be distinguished by the characteristic shape of the
terminal ends of their spicules. Each spicule
divides and the resulting rod-shaped parts
fuse distally to form a lancet-shaped structure,
the point of which extends completely to the
posterior border of a surrounding membranous
expansion. The spicules illustrated by Raevskaia (1931) had a retrograde prong at the
site of their junction. The females contained
unusually large eggs (0.255-0.272 mm long
and 0.119-0.153 mm wide).
Ault (1944) discovered nematodes similar
to N. oiratianus in domestic sheep in Argentina, but because of differences he considered
significant, Ault named his species N. lanceolatus. Type specimens of N. oiratianus were
not available to him for comparison, so his
conclusions were based on the description
given iii Travassos (1937). Ault observed in
his specimens that the externo-dorsal rays were
1 A portion of a thesis submitted in partial fulfillment of
the requirements for the degree of Master of Science, New
Mexico State University, Las Cruces.
This work was carried out in cooperation with the New
Mexico Agricultural Experiment Station and is a contribution to the Western Regional Project W-35—Nematocle
Parasites of Ruminants.
closer to the edge of the bursa than in N.
oiratianus and that a retrograde prong between
the spicules was lacking. Also, he was unable
to find eggs as large as those described for
N. oiratianus.
The first report of N. lanceolatus from North
America was that of Gilmore and Allen (1960)
who found it in pronghorn antelope in New
Mexico. They identified their specimens tentatively as N. lanceolatus because the measurements of the spicules more nearly corresponded
to those described for that species than to
N. oiratianus. This same tentative identification was given to specimens from domestic
sheep and Barbary sheep in New Mexico
(Allen, 1959 and unpublished data) and to
specimens from Colorado bighorn sheep (Pillmore, 1961). Becklund and Senger (1967)
recorded N. lanceolatus from Montana bighorn. Apparently there is no published record
of this species from cattle.
To clarify the apparent taxonomic confusion
concerning N. oiratianus and N. lanceolatus,
the author undertook the studies on morphology described in this report. Since females
in the genus Nematodirus have few characters
of taxonomic value, this study involved males
principally. Detailed comparisons were made
of 77 males from domestic sheep in New
Mexico, four from the same host in Argentina,
that were supplied by Dr. C. N. Ault, and a
total of 51 from Siberian mountain goats,
Siberian argali, domestic sheep, and domestic
cattle in the USSR. The Russian specimens
were kindly supplied by Dr. S. N. Boev, Institute of Zoology, Academy of Sciences of the
Kazakh, Alma-Ata, USSR.
The structure of the distal ends of the spicules was carefully noted, as was the location
of the externo-dorsal rays of the bursa. Other
characters examined were length of body,
width of anterior end, length of esophagus,
width in front of bursa, length of spicules including terminal ends, size of lateral lobes of
Copyright © 2011, The Helminthological Society of Washington
OF WASHINGTON, VOLUME 35, NUMBER 1, JANUARY 1968
bursa, and length of dorsal rays. Comparisons
were first made of all specimens from domestic
sheep. Next, measurements of specimens from
domestic sheep were compared with measurements obtained from specimens from cattle and
wild ruminants in Siberia. The measurements
of all specimens obtained for this study were
then compared with the original measurements
given for N. oiratianiis by Raevskaia and those
given for N. lanceolatus by Ault. Some of the
data were treated by analysis of variance.
A comparison of the spicules of the various
specimens revealed no important differences.
The retrograde prong which Ault mentioned
as being present in the illustration of IV. oiratianiis was not discerned in any of the spicules.
The externo-dorsal rays of the four specimens from domestic sheep in Argentina were
situated somewhat closer to the edge of the
bursa than the rays in specimens from both
domestic and wild ruminants in Siberia and
domestic sheep in New Mexico, but this difference alone is not considered sufficient to
warrant placing the Argentina forms in a
separate species. Total lengths of specimens
varied considerably as might be expected, and
in some cases these differences were statistically significant. There is, however, some
difficulty in measuring total lengths of males
because they are invariably coiled. The greatest difference in average total lengths was
between Siberian cattle (8.77 mm) and Siberian mountain goats (12.51 mm), with the
specimens from other sources ranging between
these two. It is of interest, though, that
Raevskaia (1931) gives a maximum total
length of 16.5 mm and that a specimen from
New Mexico domestic sheep measured only
7.38 mm. In our collection of males from
pronghorn antelope in New Mexico, there are
some specimens as short as 7.20 mm. Despite
this wide variation in total lengths of the
worms, differences in lengths of spicules were
small and in no case significant, regardless of
host and geographical source.
The differences observed between the speci-
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mens examined in this study are considered
minor and within the bounds of intraspecific
variation. Therefore, it is the opinion of the
author that N. lanceolatus Ault, 1944, should
be placed in synonymy with N. oiratianiis
Raevskaia, 1929. This opinion is supported by
recent observations by Samson (1966) that
large eggs comparable in size with those in the
original description of N. oiratianiis are occasionally associated with both natural and experimental infections in domestic sheep in New
Mexico.
Literature Cited
Allen, R. W. 1959. The occurrence of Nematodirus lanceolatus in domestic sheep in the
United States. J. Colo.-Wyo. Aeacl. Sci. 4
(11): 53.
Ault, C. N. 1944. Nematodes parasitos de los
bovinos y ovinos en la Argentina (Segunda
nota). Rev. Med. Vet., Buenos Aires, 26:
497-509.
Becklund, W. W., and C. M. Senger. 1967.
Parasites of Ovis canadensis canadensis in
Montana, with a checklist of the internal and
external parasites of the Rocky Mountain bighorn sheep in North America. J. Parasit. 53:
157-165.
Gilmore, R. E., and R. W. Allen. 1960. Helminth parasites of pronghorn antelope (Antilocapra americana) in New Mexico with new
host records. Proc. Helm. Soc. Wash. 27:
69-73.
Pillmore, R. E. 1961. General investigations of
diseases and parasites. Quar. Rept. Colo. Dept.
Game and Fish, Oct., p. 101-102.
Raevskaia, Z. A. 1931. Zur Charakteristik der
Nematoden der Gattung Nematodinis, Ransom 1907. (Versuch einer monographischen
Bearbeitung). Ztschr. Infektionskr. Haustiere.
40: 112-136.
Samson, K. S. 1966. Preliminary studies on the
life history of Nematodirus oiratianiis, an intestinal parasite of ruminants. Program 42.
Ann. Meet. Southwest, and Rocky Mountain
Div. Am. As. Adv. Sci. p. 35-36.
Travassos, L. P.
1937. Revisao da Familia
Trichostrongylidae Leiper, 1912. Monogr.
Inst. Oswalclo Cruz. No. 1, 512 p.
Copyright © 2011, The Helminthological Society of Washington