Passalurus ambiguus
Esther van Praag, Ph.D.
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This
parasite is also known under the name Oxyuris
ambigua. It is a common, cosmopolitan parasite
that infests wild or pet rabbits cottontails and hares.
In the USA, the presence of P. nonanulatus
has also sometimes been observed in rabbits. Auto-infection is common through
ingestion of the eggs with the food. The juvenile stages of Passalurus sp. are rather found in the mucosa of
the small intestine and the cecum, while the adult worms are located in the
anterior part of the cecum and the large intestine of rabbits. Passalurus ambiguus is specific to lagomorphs and does not
represent a public health danger. The life cycle of Passalurus
sp. is direct: the eggs are ingested by the animal. The eggs have typically a
flat side and measure about 100*43 mm.
During their development, resistance against dehydration increases. The
larvae will emerge from the eggs and develop in the mucous layer of the small
intestine and the cecum, where they will develop into mature adults. Two
molts are reported, the first after 24 hours, and the second on the 3rd
day.
The adult worms have different sizes, the
males being smaller (± 5 mm) than the females (± 10 mm). The females,
characterized by a long and narrow tale, are marked with about 40 circular, cuticular striations. It seems that the female worms
deposit the eggs around the anus. The worms live about 106 days. Clinical signs
Passalurus sp. parasites are non-pathologic and their presence
remains asymptomatic, even when the infestation is severe. A rabbit may be
infested with over 1000 parasitic worms. Eggs and occasionally live adult
worms can be observed in freshly excreted feces. Once out of the rabbit body,
the worms will dry quickly and cannot be seen anymore after 5 minutes. It is interesting to note that the female
worms emerging from the anus of rabbits contain eggs in the gastrula stage
that are able to develop into an infective stage in the environment. The
presence of mucus in the droppings, frequently as threads, is an indication
that a rabbit may be infested by intestinal worms. This should be
differentiated from mucoid enteritis. An
overpopulation of the nematode worms in the digestive tract can lead to
stasis and cecal impaction, pain and gas
production. If not treated, the stasis can become chronic, with a bout every
4 to 6 weeks. At necropsy, Passalurus
sp. worms have been found in the lumen of the cecum, as well as in the
crypts and mucosa of the colon. The site where the worms were located was
inflammatory and presented dystrophic modifications. The most profound
inflammatory and dystrophic changes were found in the cecum. Signs of vascular
dystrophy were furthermore observed in the hepatic and renal parenchyma.
Diagnosis
The
presence of intestinal parasites is determined by a fecal flotation test. In rare
cases, the fecal flotation test result of heavily infested rabbit can return
negative. When left untreated, the presence of worms can often be observed in
the droppings Treatment
Further Information
H. Boecker (1953) Die Entwicklung des
Kaninchen Oxyuren Passalurus ambiguus.
Zeitschrift für Parasitenkunde 15: 491-518. S. Brown (1993) Rabbit Drug Dosages.
Rabbit Health News 10: 6-7 J. Burke (1994) Clinical Care and Medecine of Pet Rabbits. In: Proceedings of the Michigan
Veterinary Conference, pp 49-77. D. Duwel
and K. Brech (1981) Control of Oxyuriasis
in Rabbits by Fenbendazole. Lab. Anim. Sci. 15: 101-105. A.B. Erickson (1944) Helminth
Infection in Relation to Population Fluctuations in Snowshoe Hares. J. Wildl. Manage. 8: 134-153. E.V. Hillyer,
K.E. Quesenberry (1997) Ferrets, Rabbits, and
Rodents. Clinical Medicine and Surgery. W.B.
Saunders Company pp. J.P. Hugot
(1984) L’Insémination Traumatique chez les Oxyures de Dermpotères
et de Léporidés. Etude Morphologique Comparée. Ann. de Parasitologie Humaine
et Comparée 59: 379-385. M.A. Palimpsestov, R.S. Chebotarev
(1935) Zur Frage des Therapie bei Passalurose (Passalarus ambiguus) des Kaninchen. Tierärtzliche Rundschau 41:
709-711. N.M. Patton, K.W. Hagen, J.R. Gorham,
R.E Flatt (1986) “Domestic Rabbits: Diseases and Parasites. “Pacific
Northwest Extension Publ. Oregon, Idaho, and Washington. K.I. Skrjabin,
N.P. Shikhobalova, E.A. Lagodovskaya
(1960) Oxyurata of Animals and Man. Part I. Oxyuroidea. In: Skrjabin,
K.I. (ed.), Essentials of Nematology, The Academy of Sciences of the
U.S.S.R., Moscow (published by the Israel Program for Scientist Translations,
Jerusalem, 1974). J. Theodoris (1979) Contribution to the
study of parasites in the rabbits of Northern Greece. hellinike Kteniatrike (Hellenii Veterinary Medecine)
22: 181-183. T.L.H Tsui
and N.M. Patton (1991) Comparative Efficiency of Subcutaneous Injection Doses
of Invermectin against Passalurus ambiguous in rabbits J. Appl. Rabbit Res. 14: 266-269. N.B. Walden (1999) Rabbits: a
Compendium (The T.G. Hungerford VADE MECUM series for Domestic Animals:
Series C.13). Post Graduate Foundation in Veterinary Science, University of
Sydney, Sydney. J.P. Wiggins, M. Cosgrove, H. Rothenbacher (1980) Gastrointestinal Parasites of Eastern
Cottontail Rabbits (Sylvilagus floridanus)
in Central Pennssylvania. J. Wildl.
Dis. 16:541-544. Fujiwara H, Uchida K, Takahashi M.
[Occurrence of granulomatous appendicitis in rabbits] Jikken Dobutsu. 1987; 36(3):277-80. Shirokova EP, Grishina EA. [Microstructural changes in the organs of
the rabbit with passaluriasis] Med Parazitol (Mosk) 1997;
(2):18-21. |
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