This worm (Fig. 1.1), 7cm in length, was passed by a 14 month old child. The family had recently returned to Tasmania after a 12 month stay in Darwin. The father stated that they had gone to Darwin to renovate an old, heavily rat infested house and that they had lived in the house during the renovation activities.
The child was generally unwell and irritable and presented with signs and symptoms of a mild upper R.T.I. The child had not suffered from any episodes of diarrhoea. The worm was clearly segmented to the naked eye and under the low power of the microscope, was noted to have an anterior end with rows of recurved hooklets (Fig. 1.2).
The worm is Moniliformis moniliformis, an acanthocephalan (thorny/spiny-headed) worm. These are normal intestinal parasites of rats. They show superficial segmentation (ie external but not internal segmentation as in tapeworms) and have a characteristic proboscis with many rows of recurved hooklets at the anterior end. They have a life cycle involving an insect intermediate host (eg cockroaches and beetles). The rats become infected on ingestion of the insect. Humans in rat infested environments can become infected if they ingest an infected insect.
Due to the presence of the hooks on the proboscis by which the worms attach to the gut wall, infection can result in ulceration and inflammation of the gut. With heavy worm loads, this can result in abdominal pain, diarrhoea and other more generalised clinical features such as exhaustion, somnolence, tinnitus, irritability, cough and retarded growth in children ( Belding,1965; Beaver et al, 1984).
Infections have been recorded sporadically from many parts of the world including Australia (Prociv et al, 1990; Bettiol and Goldsmid, 2000).
Most published reports suggest infection with a small number of worms, but some cases are on record with large worm loads as discussed by Goldsmid et al (1973).
Infections are usually diagnosed when a worm is passed in the faeces of the patient, but sometimes characteristic eggs 80 -100 x 40 - 50 mu in size (Fig.1.3) may be detected on stool examination. It is worth noting that in countries where rodents may comprise part of the local diet, transit eggs may be passed and these spurious infections need to be differentiated from a true infection by examination of repeat stool specimens (Prior and Goldsmid, 1974).
Fig. 1.3 - Egg of Moniliformis moniliformis
Beaver,P.C., Jung, R.C., Cupp, E.W. (1984). Clinical Parasitology. 9th Edition. Lea and Febiger. Philadelphia.
Belding, D.L. (1965). Textbook of Parasitology. 3rd edit. Appleton-Century- Crofts. N.Y.
Bettiol, S. and Goldsmid, J.M. (2000) A case of possible Moniliformis moniliformis infection in Tasmania. J. Trav. Med. 7: 336-337.