EFFECT OF IVERMECTIN ON FILARIAE OF MASTOMYS-NATALENSIS

The efficacy of ivermectin (Iv) was evaluated against four species of filariae, Litomosoides carinii, Acanthocheilonema viteae, Brugia pahangi and Brugia malayi in Mastomys natalensis. Animals with patent infections, induced with L3 larvae, by intravenous (iv) infusion of the respective microfilariae (Mf) (5×104 Mf per animal) or by intraperitoneal (ip) route (2×104 Mf per animal) were used in this study. A single dose of Iv (100 μg·kg-1) given subcutaneously (sc) to Mastomys infected with L. carinii or A. viteae resulted in the disappearance of microfilaremia within 2 h of treatment. Iv treatment of sc-infected animals with Brugia spp. had no immediate effect on the circulating Mf 60 days posttreatment. In contrast, such treatment of animals infected with Mf by intravenous infusion completely eliminated the larvae of all four species from the circulation. Iv treatment had no significant effect on the Mf of L. carinii, B. pahangi and B. malayi in animals infected by the ip route. However, the drug had dramatic effect in killing the Mf of A. viteae in the peritoneal cavity. Sera from Iv-treated normal or from L. carinii- or A. viteae-infected Mastomys were effective in clearing the circulating Mf of the species when administered to animals with the respective infections. Similar rapid clearance of Mf was seen when the sera were administered to animals infected iv with these larvae. Furthermore, adult females of L. carinii and A. viteae recovered from Mastomys on different days after Iv treatment released smaller numbers of Mf in vitro. Thus, Iv effect was most pronounced on the Mf of A. viteae and of L. carinii and less so on the Mf of Brugia. Iv kills the adults of A. viteae and to a lesser extent those of L. carinii and arrests the release of Mf from them. Iv had no effect on adults of Brugia parasites. © 1990 Springer-Verlag.