A light microscopy study of the migration of Naegleria fowleri from the nasal submucosa to the central nervous system during the early stage of primary amebic meningoencephalitis in mice.

The migratory pathway of Naegleria fowleri from the nasal submucosa to the central nervous system (CNS) during the early stage of primary amebic meningoencephalitis (PAM) was investigated in mice. Twenty-one-day-old CD-1 mice were inoculated by intranasal instillation of 1 x 10(6) amebas. Animals were divided into 3 groups of 5 and, after being anesthetized, were killed at intervals of 24, 32, and 48 hr postinoculation by transcardial perfusion with formaldehyde, acetic acid, and methanol. The heads were decalcified, divided in the midsagittal plane, and the area of the cribriform plate removed and embedded in paraffin. Serial sections were cut at 8 microm and stained with a combination of celestin blue, Harris' hematoxylin, and acid fuchsin for light microscopy. Focal inflammation and amebas were observed in the submucosal nerve plexus, olfactory nerves penetrating the cribriform plate, and the olfactory bulb of the brain as early as 24 hr postinoculation. The time periods selected assured that the disease process would not obliterate soft tissue structures. Earlier studies used moribund mice in which the inflammation and the number of amebas were overwhelming. The present study provides convincing evidence that amebas gain initial access to the CNS through olfactory nerves within the cribriform plate during the early stages of PAM.

Localization and migration route of Cephalopina titillator (Diptera: Oestridae) larvae in the head of infested camels (Camelus dromedarius).

The localization and migration routes of Cephalopina titillator larvae were studied in the heads of 45 naturally infested camels. Larvae were located in the pharyngeal cavity (95.6%), the labyrinth of the ethmoid bone (71.1%), the turbinates (28.9%) and the lower nasal meatus (6.7%). Out of 261 first-instar larvae, 73.7% were found in the labyrinth of the ethmoid bone and 26.3% in the turbinates, while 88.9% of second-instar larvae were observed in the pharyngeal cavity and 11.1% in the labyrinth of the ethmoid bone. Most third-instar larvae (91.9%) were found in the pharyngeal cavity, with a few larvae in the labyrinth of the ethmoid bone (6.5%) and lower nasal meatus (1.6%). The first moult occurred in the labyrinth of the ethmoid bone. The second moult was observed in both the labyrinth of ethmoid bone and the pharyngeal cavity. The migration route of these larvae in the infested head was discussed.