Considerations on the Life-history of Tapeworms of the Genus Moniezia

Extract

Lambs contract Moniezia infection either at or very soon after birth, since they have been observed to harbour adult worms at 2–3 months old and in one case, to pass proglottids at 4–6 weeks.

The intermediate host, if such exists, must be frequent on the pasture in early spring, otherwise lambs would not be found to harbour adult tapeworms so regularly or in such numbers when slaughtered in early summer. In the small intestine of a lamb from 3–4 months old slaughtered at Aberystwyth, there occurred 75 individuals.

The fact that lambs regularly harbour adult tapeworms before they are weaned suggests the possibility of their contracting the infection from the mother-ewes. No direct evidence in this direction has been obtained, however, and an attempt to produce a larval stage in the udder region of a ewe by feeding to it the eggs of a tapeworm proved abortive.

Hitherto, all attempts to produce the adult tapeworms directly by feeding the eggs to sheep have failed; there is, however, the remote possibility that the eggs require to undergo some kind of maturation process outside the body of the sheep before they will develop. The fact that several species of Moniezia occur in the domestic sheep would seem to require an intermediate stage, which would occur in a corresponding number of intermediate-host species.

The disease seems prevalent in flocks which are singularly free from ectoparasites.

The invertebrates which seem most likely to harbour an intermediate stage are coprophagous insects, etc. (beetles, flies, mites). Attempts to infect species of Aphodius have nevertheless proved fruitless.

Moisture favours the survival of the eggs of Moniezia: eggs kept in water for a period of several months seemed to remain perfectly viable. Nevertheless tapeworm is common among flocks on pastures about Rome which are characteristically dry.

A comprehensive series of experiments under conditions of the most complete control would almost certainly clear up the life-history; on economic grounds alone the problem is urgent.

The overwhelming majority of a quantity of worms collected from slaughter-houses in Aberystwyth, Aberdeen, Beauly (Inverness-shire) and Newcastle-on-Tyne proved to be of the species M. expansa. The only other species found were M. trigonophora and M. alba. The identification was based on anatomical characters and not on externals, which are useless.

The writer intends directing his attention to coprophagous mites as carriers, viz. Gamasus coleoptratorum, G. fimetorum, Macrocheles glaber.