| Moniezia expansa | |
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| Species: | M. expansa |
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| Moniezia expansa Rudolphi, 1810 | |
Moniezia expansa is commonly known assheep tapeworm ordouble-pored ruminant tapeworm. It is a largetapeworm inhabiting thesmall intestines ofruminants such assheep,goats andcattle. It has been reported fromPeru thatpigs are also infected.[1] There is an unusual report of human infection in an Egyptian.[2] It is characterized by unarmedscolex (i.e., hooks androstellum are absent), presence of two sets ofreproductive systems in eachproglottid, and each proglottid being very short but very broad.
M. expansa has a typicalcestode body, consisting of the anterior scolex, followed by the neck and a highly extended body proper, thestrobilus. 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 norostellum 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, beingmonecious, contains both male and femalereproductive 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. Thetestes are numerous.
The completelife cycle requires two hosts,ruminants asdefinitive hosts, andoribatid mites asintermediate hosts.[4][5] Eggs are passed out from theintestine of the ruminant host along thegravid proglottids in thefeces into the soil. The eggs are eaten by soilmites. Eggs must reach the gut of mite hosts within 1 day of release otherwise they aredesiccated. However, chances of development is very good as soil mites can be so numerous on apasture that even if only 3% are infected (with 4-13cysticercoids each), a grazing ruminant may ingest over 2,000 cysticercoids perkilogram of grass. Once inside the intestine of mites, the eggs hatch and the oncospheres penetrate into thehaemocoel 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 thesmall intestine within 5–6 weeks.
M. expansa infections are generally harmless andasymptomatic, even when the tapeworms are present in large numbers in younglambs. However heavy infection may cause intestinal obstruction,diarrhea and weight loss.[6]
Diagnosis is done by analysisstool sample in which eggs can be detected, or often observation of the gravid proglottids in feces andanus.[3]Niclosamide is most often used.Praziquantel (while not approved for use in ruminants in the US) is also 99–100% effective whilealbendazole is 19-75% effective;[7] and praziquantel +levamisole combination is very effective in reducing worm burden and improvement of weight.[8]