R. R. Suswillo

The resistance to re-infection of cats repeatedly inoculated with infective larvae of Brugia pahangi

Seven microfilaraemic and five amicrofilaraemic cats which had been repeatedly infected with Brugia pahangi were challenged along with normal cats 28, 14 and 1 day before autopsy. The lymphatics of the amicrofilaraemic cats contained no female adult worms originating from the repeat infections and only two adult males (both from the same cat). Only 5.2% of the worms in the control cats were recovered from the amicrofilaraemic cats. Most of the challenge worms were killed in the first 24 h. The microfilaraemic cats all contained fertile adult male and female worms derived from the repeated infection but in such low numbers as to indicate considerable resistance to infection. Compared to their controls 26.4% of the challenge worms were recovered. Analysis of the life-cycle stages recovered showed that in both groups there was attrition of all stages and that although a number of worms reached L5 these were all killed later in the amicrofilaraemic cats.

The anthelmintic effects of flubendazole on Brugia pahangi.

The anthelmintic effects of flubendazole (methyl [5-(4-fluorobenzoyl)-1-H-benzimidazol-2-yl] carbamate) (Janssen Pharmaceutica) were evaluated in jirds (Meriones unguiculatus) and cats (Felis cattus) infected with Brugia pahangi. Flubendazole was macrofilaricidal at 5 x 2.5 mg/kg and 1 x 25 mg/kg in jirds and 1 x 100 mg/kg in cats when administered by subcutaneous injection. It also killed developing larvae in jirds. It was not microfilaricidal.

Expression of cross-reactive surface antigens by microfilariae and adult worms of Brugia pahangi during infections in cats

Microfilariae of Brugia pahangi were labelled with 125-Iodine using the reagent IODOGEN. Electron microscope autoradiographs of sections of iodinated microfilariae showed that the label was strictly confined to their sheath. Adult worms were also iodinated by the same procedure. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of detergent extracts of radio-labelled parasites revealed components of molecular weights 113, 81-71, 46 and 33 kDa in microfilariae, and of molecular weights 29, 20 and 16 kDa in adult worms. All but the 33 kDa component of microfilariae were immunoprecipitable with sera of infected cats and therefore antigenic. Antibodies to the 81-71 kDa and the 46 kDa microfilarial antigens were detected by immunoprecipitation before patency. Similarly, the 29 kDa antigen of adult worms was immunoprecipitable before the fourth moult. Therefore, during infection in cats, these antigens cross-react with epitopes present on earlier developmental stages.

STUDIES WITH BRUGIA PAHANGI 17. THE ANTHELMINTIC EFFECTS OF DIETHYLCARBAMAZINE

Diethylcarbamazine (DEC) was active in vitro against infective larvae and microfilariae of Brugia pahangi but only at high concentrations. When fed to mosquitoes which were infected with B. pahangi it had little or no activity. In jirds it was inactive against B. pahangi microfilariae and adults when administered at 300 mg/kg for 5 days either by the intraperitoneal or oral route. In cats given 25 or 50 mg DEC/kg intraperitoneally on 3 or 5 occasions it was not microfilaricidal, but most of the adult worms died within 30 days of the end of treatment. Although most microfilariae disappeared from the blood of cats immediately (i.e., within an hour) after treatment, they reappeared within a few hours in the same numbers. Microfilarial levels were reduced after treatment but there was no precipitate decline as occurs in human B. malayi patients.

Parasitological observations on Meriones unguiculatus singly or multiply infected with Brugia pahangi

When jirds were infected with a single inoculum of 25-50 infective larvae of Brugia pahangi an overall mean recovery of adult worms of 44.5% (n = 41) was obtained. There was no difference in recoveries between male and female jirds. If jirds were repeatedly inoculated with larvae into the peritoneal cavity yields were only slightly reduced. Yields were 30.5% for 5 infections (n = 10), 26.7% for 10 infections (n = 8), 34.4% for 15 infections (n = 10) and 28.5% for 20 infections (n = 7). Twice as many worms were recovered from intraperitoneally inoculated jirds than from subcutaneously inoculated jirds.

Studies on Brugia pahangi . 13. The anthelmintic effect of compounds F151 (Friedheim), HOE 33258 (Hoechst) and their reaction product

F151 was a potent filaricide against adult Brugia pahangi in cats and jirds. HOE 33258 did not kill adult worms in cats but had a marginal effect on adult worms in the peritoneal cavity of jirds. It was not immediately microfilaricidal in cats but the microfilarial counts of treated cats fell within a few weeks of treatment. The reaction product, or mixture, of these two compounds (V5851 = E) was strongly macrofilaricidal in cats and jirds.

The infectivity of microfilariae of Brugia pahangi of different ages to Aedes aegypti.

By transferring microfilariae of Brugia pahangi which had been born over a 24-hour period in the peritoneal cavities of jirds (Meriones unguiculatus) to the blood circulation of other jirds, infections of known age were tested for their ability to develop into third-stage larvae (L3) in mosquitoes Aedes aegypti. Microfilariae less than three days old were not able to develop to L3. Microfilariae which had been in circulation for three days to six months were capable of developing if ingested.

Survival of Loa loa following transplantation from drills (Mandrillus leucophaeus) into jirds (Meriones unguiculatus): parasitology and pathology

Two drills infected with Loa loa maintained a microfilaraemia for four and a half years ranging from less than 1 mf/100 microliters to 1150 mf/100 microliters. No significant tissue reactions to the adult worms were seen at autopsy. Adult worms were transplanted into the peritoneal cavities of naive jirds when a persistent microfilaraemia first developed by 17 days. Retransplantation of adult worms into naive jirds produced a microfilaraemia and microfilariae in the peritoneal cavities of three out of five animals. These three animals were all negative for circulating parasites by eight and a half months. The tissue reactions to the worms in the jirds are described, including a granulomatous response surrounding adults and a myositis involving microfilariae.

Hybridization between Brugia patei, B. pahangi and sub-periodic B. malayi.

Virgin females of Brugia malayi, B. pahangi and B. patei were mated with males of species other than their own to determine whether they would hybridize. Microfilariae were produced in all but one cross (that between B. pahangi males and B. malayi females). Hybrid infective larvae, produced in mosquitoes and inoculated intraperitoneally into jirds, grew to adults but these were unable to produce microfilariae because hybrid males did not produce spermatozoa. Hybrid females were fertile and produced microfilariae when crossed with males of their parental species.

Experimental Brugia pahangi and B. malayi infections of callitrichid primates.

The callitrichid primates, Callithrix jacchus jacchus (the marmoset) and Saguinus labiatus (the tamarin) were inoculated with infective larvae of Brugia malayi and B. pahangi. Microfilaraemia at low levels developed in 3 out of 4 C.j. jacchus infected with B. malayi and living or dead adult worms found in all 4. Only one of 4 C.j. jacchus became microfilaraemic (mf + ve) when given B. pahangi and adults were found in two. Of 4 S. labiatus given B. pahangi one became very lightly mf + ve and adults were found in 3. It is concluded that these animals are not suitable hosts for chemotherapeutic experiments.