Brugia malayi: serum dependent cell-mediated reactions to microfilariae.

Sheathed and exsheathed microfilariae of Brugia malayi are killed by normal rat cells in the presence of immune serum in vitro. Immune serum heated at 56 degrees C for 1 hour lost this activity which was largely restored by the addition of fresh normal rat serum. EDTA but not EGTA abolished this activity indicating the operation of complement by alternate pathway. Fresh normal rat serum alone promoted cellular adherence without exerting cytotoxicity to the microfilariae. The activity in the immune serum could be removed with Staphylococcus aureus cells containing Protein A or anti-IgG antiserum. The activity could also be absorbed to and eluted from Protein A--sepharose CL-4B suggesting the involvement of IgG. Neutrophils and macrophages participate in the antibody dependent cell-mediated cytotoxicity phenomenon. Eosinophils while adhering to the microfilariae exert cytotoxicity only to the exsheathed parasites.

Susceptibility of Aedes aegypti to infections with Dirofilaria immitis and Dirofilaria repens.

Eight stocks of Aedes aegypti-4 geographic stocks and 4 selected stocks-were tested for their susceptibility to infection with Dirofilaria immitis and D. repens. Four of the stocks were found to be susceptible and the other 4 were refractory of infection with D. immitis. All the stocks of Ae. aegypti that were susceptible to D. immitis were also susceptible to D. repens but the stocks that were refractory to D. immitis were all partially susceptible to D. repens.

Studies on Malayan filariasis in Bengkulu (Sumatera), Indonesia with special reference to vector confirmation.

In an endemic focus of Brugia malayi in Bengkulu, Indonesia the microfilariae rate was 25%. The microfilariae showed nocturnal periodicity. Domestic cats in the same area were found to harbour B. pahangi, with a microfilariae rate of 23%. In the study area, the most prevalent man-biting Mansonia mosquitoes were Mn.bonneae (41%), followed by Mn.annulata (27%), Mn.uniformis (25%) and Mn.dives (7%). More Mansonia mosquitoes were collected outdoors than indoors between 1800-2200 hours. Natural infections with infective larvae of Brugia spp. were found in Mn.bonneae, Mn.dives, Mn.uniformis, Mn.annulata, and An.nigerrimus. Experimental infection studies revealed that Mn.annulata, Mn.bonneae, Mn.uniformis, An.nigerrimus and An.peditaeniatus permit the development of infective larvae. Under experimental condition, the vectorial competence is high in Mn.bonneae, intermediate in Mn.uniformis and low in An.hyrcanus group. It is concluded that the principal vectors of periodic B.malayi in the study area in Bengkulu are four Mansonia species (Mn.annulata, Mn.bonneae, Mn.uniformis and Mn.dives), and that the potential vectors include two Anopheles species (An.nigerrimus and An.peditaeniatus). This is the first record of Mn.bonneae being a vector of periodic B.malayi in Indonesia.