Studies on age groups within activity cycles, age composition and survivorship in natural populations of Mansonia in Kampung Pantai, Bengkoka Peninsula of Sabah state have been described. Early activity of 3-5 parous Ma. bonneae during the first hour after sunset was noted. Age composition of Ma. bonneae at forest shade, indoor and outdoor of house, comparative buffalo vs human bait outdoor in Kampung Pantai showed all round high parous rates ranging from 66.7 to 75.4%. Population 3-parous and older ranged from 18.8 to 26.7%. Nine of the 14 infective Ma. bonneae were 3-parous and this segment of the population was engaged in active transmission. High parous rates were observed in Ma. dives and Ma. uniformis taken in small numbers. Parous rates of Ma. bonneae taken in Kampung Delima and Kampung Taradas were also high. Estimates of daily survivorship of Ma. bonneae and Ma. dives determined by two methods were very high.
This paper reports the experimental transmission of a bird parasite into jirds. Infective larvae of Cardiofilaria nilesi obtained from laboratory colonized Coquillettidia crassipes mosquitoes which had fed on an infected chicken were inoculated subcutaneously into jirds. The number of larvae per jird varied from 10 to 228. Microfilaraemia appeared 22 to 89 days after inoculation of the infective larvae. Experiments were carried out with 24 jirds through six generations extending over a period of 22 months and 17 produced patent infections. At present 8 infected jirds are being maintained in the laboratory; their patent periods ranging from 6 to 13 months. However, the longest patent period observed was about thirteen months. The percentage of adults recovered in autopsied jirds ranged from 0 to 40 with an average of 16. The chicken showed a microfilarial periodicity with the peak microfilarial density around 2200 hours. However, in jirds there was a change in sub-periodicity. This model in the jird may be very useful for the screening of filaricides and in immunological work.
Surveillance methods for Coquillettidia crassipes were studied in an open housing estate near Kuala Lumpur using three types of traps Trinidad 10 trap, modified Lard can trap and IMR trap, each baited with chicken or pigeon. All traps attracted Cq. crassipes. There was no significant difference in the catches in the three traps. There was also no significant difference between chicken and pigeon as bait. Catches at heights of 1.5, 3, 4.5 and 6 m did not show any significant difference in density. Cq. crassipes was active at night with an early peak during the first hour of the night and a minor peak between 0100 and 0200 hours. The activity of the parous and nulliparous sections of the population was similar, except that a higher proportion of the parous females was active during the second peak compared with the nulliparous females. The parous rate was 22.3%, and the probability of survival through one day for two gonotrophic cycles was 0.711 and 0.650. The infection rate for Cardiofilaria was 29 out of 1052 (2.76%) and the infective rate (L3 larvae) was 13 out of 1052 (1.24%). 48.3% of the infected Cq. crassipes had a worm burden of more than ten larvae. One of the chickens in the traps was positive for microfilariae of Cardiofilaria four weeks after exposure as bait. Laboratory bred Cq. crassipes fed on this chicken produced infective larvae in ten days, and these were inoculated into clean chickens and pigeons. Microfilariae appeared in the chickens but not in pigeons. The adult worms recovered await identification.
Using seven methods of surveillance, 58 species of mosquitoes from nine genera were in Pantai and the two neighbouring villages during two visits in 1982. Ma. bonneae was the most prevalent species attracted to man. In the forest shade Ma. bonneae and Ma. dives showed activity throughout the 24 hours with peak biting during 1900-2100 hours. An. balabacensis exhibited peak activity shortly after midnight. Inside and outside house, Ma. bonneae showed similar activity except that it ceased during the day. Mansonia was only mildly zoophilic. CDC light traps gave poor yields of mosquitoes. Pyrethrum spray catch inside houses early morning did not include any Mansonia. Outdoor day resting catch included Ma. bonneae fed on man. Transmission of Brugia, probably human filariasis, by Ma. bonneae occurred in Pantai and in the two neighbouring villages. One infection in Ma. dives was found in Pantai. The monthly infective biting rate and monthly transmission potential for Ma. bonneae were estimated at the forest shade and outside the house in Pantai.
Field observations were made on Coquillettidia crassipes during a study of Mansonia in a swamp forest ecotype in Tanjong Karang. There was an increase in abundance in July consistent with the increase in abundance of Mansonia and an increase in rainfall. The biting cycle showed a dramatic early peak during the period 1900-2000 hours. The probability of daily survival through one day for the first three gonotrophic cycles was 0.770, 0.722 and 0.759. Two of the 54 Cq. crassipes dissected were infective, with two and 25 L3 larvae of Brugia. Both subperiodic B. malayi and B. pahangi developed into L3 larvae in laboratory bred Cq. crassipes. The index of experimental infection was higher for B. pahangi. Mansonia bonneae and Ma. uniformis showed higher indices of experimental infection than Cq. crassipes for subperiodic B. malayi. It is concluded that in an endemic area with a high density of Cq. crassipes it could act as a secondary vector of Brugian filariasis.
Methods are described for the laboratory colonization of Mansonia uniformis, Ma. indiana and Ma. bonneae in Malaysia. Gravid females oviposited in 500 ml beakers with a layer of water covered with small leaves of Salvinia. Newly hatched larvae were set up in a basal medium of guinea pig dung and water or liver powder, yeast powder and water. Larvae attached to aquatic plants or 'Keaykolour' ruffia snow white paper. The cultures with paper gave better yields than those with plants. Production of Ma. uniformis was higher than the other two species. Twelve generations of Ma. uniformis and 11 generations of Ma. indiana and Ma. bonneae were monitored in the laboratory.