The fate of the filaria Monanema martini in two rodent hosts: recovery rate, migration, and localization.

In Meriones unguiculatus, the recovery rate of 80 inoculated larvae was low (about 20%) and irregular. In the natural host Lemniscomys striatus, the recovery rate was about 50% with inoculated doses of 30, 80 or 400 L3, but slightly higher for 400 L3. This rate was constant from day 2 to month 8 post infection (p.i.). When 7-9 reinoculations were performed in one year, the recovery rate of the late inoculation was of only 14%. After subcutaneous inoculations, larvae penetrated into the peripheric lymphatic vessels from hour 6 p.i. and migrated to the lumbar and mesenteric lymph nodes; this first migratory phase was achieved 5 days p.i. Later, the larvae migrated into the digestive tract lymphatic system. Filarial localization did not depend upon the L3 dose: half were found in the caecum and anterior colon (3 cm) wall, and half were distributed in the posterior colon, mesentery and small intestine. A small number (3-5%) of the filariae were found in the pulmonary blood vessels, as a result of accidental migration by the thoracic canal. A similar phenomenon is known in the lymphatic filariae Brugia spp. in rodents and Conispiculum flavescens in a lizard. Several arguments suggest that the genus Monanema is fundamentally lymphatic. Migrations and life of filariae in the lymphatic system seems to be more usual than it is generally admitted. In onchocerciasis, this may at least partially explain the lymphopathology of the inguinal region.