Moniezia expansa

Moniezia expansa is commonly known as sheep tapeworm or double-pored ruminant tapeworm. It is a large tapeworm inhabiting the small intestines of ruminants such as sheep, goats and cattle. It has been reported from Peru that pigs are also infected.[1] There is an unusual report of human infection in an Egyptian.[2] It is characterized by unarmed scolex (i.e., hooks and rostellum are absent), presence of two sets of reproductive systems in each proglottid, and each proglottid being very short but very broad.

Moniezia expansa
Scientific classification
Kingdom:
Animalia
Phylum:
Platyhelminthes
Class:
Cestoda
Order:
Cyclophyllidea
Family:
Anoplocephalidae
Genus:
Moniezia
Species:
M. expansa
Binomial name
Moniezia expansa
Rudolphi, 1810

Structure

M. expansa has a typical cestode body, consisting of the anterior scolex, followed by the neck and a highly extended body proper, the strobilus. It is an extremely long tapeworm, and can reach an enormous length up to 6–10 m. The scolex bears four large suckers, which are the holdfast organs to the host. There are no rostellum and rostellar hooks, and the suckers are devoid of spines.[3] The boundary between the proglottids are studded with a row of interproglottid glands, which are yet undefined in terms of function. The tapeworm, being monecious, contains both male and female reproductive organs in an individual. Thus each proglottid is a complete reproductive unit. Moreover, one defining feature of the genus is that there are two sets of reproductive organs situated at lateral sides with the associated cirrus pouches and genital pores in each proglottid. The testes are numerous.

Life cycle

The complete life cycle requires two hosts, ruminants as definitive hosts, and oribatid mites as intermediate hosts.[4][5] Eggs are passed out from the intestine of the ruminant host along the gravid proglottids in the feces into the soil. The eggs are eaten by soil mites. Eggs must reach the gut of mite hosts within 1 day of release otherwise they are desiccated. However, chances of development is very good as soil mites can be so numerous on a pasture that even if only 3% are infected (with 4-13 cysticercoids each), a grazing ruminant may ingest over 2,000 cysticercoids per kilogram of grass. Once inside the intestine of mites, the eggs hatch and the oncospheres penetrate into the haemocoel and develops to the cysticercoid stage. This stage may take up to 4 months. When the infected mite is eaten by the grazing ruminants, mature cysticercoids are digested out of the mite, and develop into mature tapeworms in the small intestine within 5–6 weeks.

Pathogenicity

M. expansa infections are generally harmless and asymptomatic, even when the tapeworms are present in large numbers in young lambs. However heavy infection may cause intestinal obstruction, diarrhea and weight loss.[6]

Diagnosis and treatment

Diagnosis is done by analysis stool sample in which eggs can be detected, or often observation of the gravid proglottids in feces and anus.[3] Niclosamide is most often used. Praziquantel (while not approved for use in ruminants in the US) is also 99–100% effective while albendazole is 19-75% effective;[7] and praziquantel + levamisole combination is very effective in reducing worm burden and improvement of weight.[8]

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References
  1. Gómez-Puerta, Luis Antonio; Lopez-Urbina, Maria Teresa; González, Armando E. (2008). "Occurrence of Moniezia expansa (Rud, 1810) Blanchard, 1891 (Cestoda: Anoplocephalidae) in domestic pig (Sus scrofa domestica Linnaeus, 1758) in Perú". Veterinary Parasitology. 158 (4): 380–1. doi:10.1016/j.vetpar.2008.08.019. PMID 19028016.
  2. el-Shazly AM, Morsy TA, Dawoud HA (2004). "Human Monieziasis expansa: the first Egyptian parastic zoonosis". J Egypt Soc Parasitol. 34 (2): 380–381. PMID 15287174.
  3. Mehlhorn H (2008). Encyclopedia of parasitology, Volume 1 (3rd edn). Springer. ISBN 978-3-540-48994-8
  4. Sinitsin DF (1931). "A glimpse into the life history of the tapeworm of sheep, Moniezia expansa". Journal of Parasitology. 17 (4): 223–227. doi:10.2307/3271458. JSTOR 3271458.
  5. Denegri, G; Bernadina, W; Perez-Serrano, J; Rodriguez-Caabeiro, F (1998). "Anoplocephalid cestodes of veterinary and medical significance: a review". Folia Parasitologica. 45 (1): 1–8. PMID 9516990.
  6. Elliott, D.C. (1986). "Tapeworm (Moniezia expansa) and its effect on sheep production: the evidence reviewed". New Zealand Veterinary Journal. 34 (5): 61–5. doi:10.1080/00480169.1986.35289. PMID 16031272.
  7. Bauer, C (1990). "Comparative efficacy of praziquantel, albendazole, febantel and oxfendazole against Moniezia expansa". The Veterinary Record. 127 (14): 353–4. PMID 2260242.
  8. Southworth, J.; Harvey, C.; Larson, S. (1996). "Use of praziquantel for the control of Moniezia expansa in lambs". New Zealand Veterinary Journal. 44 (3): 112–5. doi:10.1080/00480169.1996.35947. PMID 16031907.
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