Monanema martini in its murid hosts: microfiladermia related to infective larvae and adult filariae.

The microfiladermia of Monanema martini was studied in two natural murid hosts, Lemniscomys striatus and Arvicanthis niloticus, with 137 and 39 rodents respectively inoculated once, twice or several times. Microfilarial densities (mf/mm2) were measured at the ear pinna every three months. Almost all the rodents developed a microfiladermia. When L. striatus rodents were inoculated once with 30, 80, or 400 infective larvae, microfiladermia increased (peaks of 108, 148, 174 mf/mm2 respectively, at six to nine months p.i.); this fits with the fact that, in this filaria-host pair, the number of adult filariae is proportional to the number of inoculated larvae, and remains at a constant level for more than eight months. Nevertheless microfiladermia was limited, especially during the peak, showing the complexity of its regulatory mechanisms. Several low doses over one year, resulting in 145 L3, increased the microfiladermia at the same level than one dose of 400 larvae; the recovery rate of the larvae was reduced but the total number of filariae recovered was increased. A. niloticus, from which the filarial strain originates, showed a much lower microfiladermia than L. striatus (7 mf/mm2 with 80 larvae, at six months p.i.). This was due to a smaller recovery rate of the infective larvae in this host and, overall, to a reduced fertility of the female worms and a shorter lifetime of adult filariae. However, repeated inoculations increased the microfiladermia (32 mf/mm2), due to the constant presence of small numbers of young filariae producing microfilariae. It is to be noted that the two biological systems presented by M. martini in L. striatus and A. niloticus correspond to the two types of ocular pathology described in a recent opthalmological study, chorioretinal atrophy and keratitis respectively.