Neuropathogenic properties of Argas (Persicargas) walkerae larval homogenates.

Several tick species have been demonstrated, described, or suspected to cause paralysis in their host during the repletion process, presumably by impairing neurotransmission. The resulting polyneuropathy gradually spreads to the upper limbs causing incoordination and ends in respiratory failure. This form of paralysis is commonly confused with Guillain-Barrè syndrome, botulism and myasthenia gravis and although the clinical symptoms of these diseases are similar, it is not clear whether the pathogenesis is also the same. During this study we investigated the mechanism of paralysis by the tick Argas (Persicargas) walkerae by determining the effect of larval homogenates on both potassium-stimulated (calcium-dependent) and veratridine-stimulated (external calcium-independent) release of [3H]glycine from crude rat brain synaptosomes. The results indicated that larval homogenates inhibited both processes. These findings are reconcilable with the results obtained for two other paralysis-causing tick species, Ixodes holocyclus and Dermacentor andersoni, which were indicated to cause paralysis by decreasing the synthesis or release of acetylcholine at the neuromuscular junction.