No abstract

Dermatitis caused by penetrating bird schistosome cercariae is an emerging global public health problem. Infections may be prevented by the use of topical formulations that inhibit cercarial skin penetration. We evaluated nine water resistant formulations by exposing treated arms of volunteers to Trichobilharzia szidati cercariae. Six formulations protected from cercarial invasion. However, after immersion of the treated skin in water (2 x 20 min), only two formulations offered full protection: (1) Safe Sea, a cream protecting against jelly fish, (2) niclosamide in water resistant sun protecting cream formulations at concentrations as low as 0.05%. In an in vitro system Safe Sea and a 0.1% niclosamide formulation caused a high damage rate in T. szidati (92% and 99% after 5 min; only niclosamide with lethal effect) but not in Schistosoma mansoni (1% and 72%; both formulations with lethal effect). However, a 1% niclosamide formulation damaged S. mansoni sufficiently (100% after 5 min) and might offer full penetration protection.

In five patients with unilateral wasting of the hand muscles as a result of cervical rib and band, F waves were recorded from the hypothenar muscles following stimulation of the ulnar nerve at the wrist. Twelve healthy control subjects were also examined. F-wave latency was consistently increased in the affected hands of the patients, compared with results from the unaffected and control hands. This increase persisted after removal of the cervical band in four patients and was thought to be mainly due to degeneration of fast-conducting fibers. In the fifth patient, F-wave latency decreased after operation, suggesting recovery of a local conduction block in the proximal part of the nerve.

Cercariae of Diplostomum spathaceum penetrate the skin of fish, and then migrate along blood vessels and tissues towards the head and the eye-lens. We studied their orientation behaviour in tail fins of guppies and in chemical concentration gradients within agar-filled choice chambers. In fins, they entered veins and orientated cranially, independent of the blood flow and living cells. In choice chambers, they were attracted by a small molecular fraction of fish serum, D-glucose (at 1, 10, and 1000 mM), D-mannose, D-maltotriose and Cl-ions, whereas D-glucosamine repelled them (even at 1 . 0 nM). Amino acids were not attractive, but arginine in tetrapeptides attracted at concentrations as low as 1 mM and melatonin at 0 . 4-4 . 3 pM. We suggest a preliminary model for the behaviour of diplostomula in fish fins and attracting (+) or repelling (x) host cues: (1) migration towards deeper skin layers and avoidance of skin surface, cues: Cl-ions (+ and x), glucose (+), glucosamine (x), light radiation (x); (2) orientation in cranial direction, cue: Cl-ions (+) ; (3) localization of blood vessels, cues : glucose (+), arginine-residues (+); (4) localization of the retina, cue: melatonin (+). A comparison with the navigation mechanisms of tissue-migrating schistosomules and hookworm larvae reveals an enormous diversity of strategies.

The visual and somatosensory evoked potentials were delayed in two cases of the adult form of metachromatic leukodystrophy. Brainstem auditory evoked potentials were normal. The conduction velocity along peripheral nerves was 50% slowed in one case and near normal in the other. The findings are compatible with demyelination in the central and peripheral nervous systems. The diagnosis of metachromatic leukodystrophy should be considered in cases of early dementia, with or without psychosis or other neurologic deficits, in which evoked potentials are delayed and peripheral nerve conduction is slowed.