Comparative Parasitology 68(2) 2001 - Peru State College

266 COMPARATIVE PARASITOLOGY, 68(2), JULY 2001
tion of both preparasitic and parasitic stages. For
such studies, it is critical that the cyathostomins
be identified and classified as consistently as
possible. Modern identification manuals exist
(Lichtenfels, 1975; Hartwich, 1986; Dvojnos
and Kharchenko, 1994), but problems in identifying
several species persist (Lichtenfels et al.,
1997). In 1997, workers convened an international
workshop to clarify the systematics of the
Cyathostominea (Sun City, Republic of South
Africa), and an agreement was reached on a consensus
recommendation for the taxonomy of 51
species as detailed in Lichtenfels et al. (1998).
Despite the importance of these parasites, information
is still lacking on species prevalence
in Britain, especially since the development of
widespread anthelmintic resistance. The last detailed
study of species prevalence and infection
intensity in the U.K. was in 1976 (Ogbourne,
1976). The present report describes the species
of cyathostomins present in the large intestine of
a population of ponies from western Scotland.
The nematodes were collected to provide DNA
sequence information for the development of diagnostic
tools and for phylogenetic analysis of
the nematodes.
Adult parasites were collected from intestinal
contents of 4 Welsh-Shetland cross ponies aged
from 9 to 15 mo originating from a local horse
population. The history of anthelmintic treatment
of the ponies is unknown. These animals
were euthanized at the University of Glasgow
Veterinary School for reasons other than parasite
infestation. Intestinal contents were coarse-filtered
with household plastic sieves. After sieving,
the contents were passed through a Baermann
apparatus with milk filters and then
through SS-jjim wire-mesh sieves. Individual
adult parasites were washed in sterile phosphatebuffered
saline (137 mM NaCl, 8.1 mM
Na2HPO4, 2.7 mM KC1, 1.47 mM KH2PO4, pH
7.2). Where possible, a total of 200 parasites
were collected from the ventral and dorsal colon;
however, the cecum often contained fewer
than 50 adult parasites. With the aid of a dissection
microscope, the heads were excised with a
scalpel because the bodies were subsequently
used for DNA extraction. The heads were stored
in 200 (JL! of 5% buffered formalin, then mounted
on glass slides in a few drops of phenolalcohol
(80% melted phenol crystals and 20%
absolute ethanol) to which glycerine had been
added at about 5% of the volume, and studied
Copyright © 2011, The Helminthological Society of Washington
with an Olympus BX50® differential interference
contrast microscope. The parasites were
identified according to the key of Lichtenfels
(1975), supplemented by more recent descriptions
of certain species (Lichtenfels and Klei,
1988; Kharchenko et al., 1997; Lichtenfels et al.,
1997, 1999). The taxonomy used in this report
follows the checklist of genera and species recommended
by the 1997 international workshop
(Lichtenfels et al., 1998). Representative heads
of 14 species of cyathostomins and Craterostomum
acuticaudatum and photomicrographs of 2
species of cyathostomins have been deposited in
the U.S. National Parasite Collection, U.S. Department
of Agriculture, Beltsville, Maryland
20705-2350 as accession numbers 90698-
90714. Two species of cyathostomins, Cylicocyclus
elongatus and Cylicocyclus radiatus, and
Gyalocephalus capitatus could not be documented
by either method.
Eighteen cyathostomin species, representing 5
genera, were identified. Table 1 shows the total
numbers of parasite species per animal identified
morphologically and the relative numbers of
each species collected from each animal. Eight
species occurred in all 4 ponies. One rare species,
Tridentoinfundibulum gobi, was found in
•Scotland for the first time. It had been reported
previously only in Asia and North America
(Lichtenfels et al., 1998). In addition, individuals
of the genera Craterostomum and Gyalocephalus
were isolated but in smaller numbers
than most of the cyathostomin species. The 7
most abundant cyathostomin species were, in
descending order, Cylicocyclus ashworthi, Cyathostomum
catinatum, Cylicostephanus longibursatus,
Cyclostephanus minutus, Cylicocyclus
nassatus, Cylicocyclus insigne, and Cylicostephanus
goldi. These species comprised over
94% of the total cyathostomin burden. These results
are similar to recent enumeration studies
performed in several geographically distinct regions,
for example in the U.S.A., Europe, and
Australia (Reinemeyer et al., 1984; Mfitilodze
and Hutchinson, 1985; Bucknell et al., 1995;
Gawor, 1995). In addition, in terms of local studies
performed previously in the U.K., the species
identified here were very similar to those reported
by Mathieson in Scotland (1964); Ogbourne
in southwest England (1976), and Love
and Duncan in Scotland (1992). Ogbourne
(1976) performed the most extensive study and
identified 21 species in 86 horses of various ages