[Experimental infection of periodic Brugia malayi in man].

We described the results of ten-year observations on the clinical manifestations, pathology, immunity to filariasis and aetiological biology of filariae in three volunteers (first author and his family members) who were inoculated experimentally with infective larvae of periodic Brugia malayi in 1981 and without use of any antifilariasis drugs. Microfilariae were first detected at 41 and 46 weeks after inoculation in two subjects and remained detectable in a small number until 8 and 8.5 years after infection. Eosinophilia occurred mainly before and at the initial stage of microfilaremia. The increase in the lymphocytes to some extent was observed at 2-156 weeks after infection. Biopsy at inoculation site 6 weeks after inoculation showed the lymph node with the infiltration of inflammatory cells, mainly eosinocytes, lymphocytes and monocytes. Lymphangiotasis and lymphostasis were observed in both limbs and pelvic regions by lymphangiogram taken 11 weeks after inoculation. Antibody against B. malayi first appeared at 2-5 weeks after infection and reached the highest at 12-56 weeks and thereafter declined gradually. Two subjects turned to be antibody free 10 years after infection. E-rosette forming lymphocytes became lower than normal at 11 weeks and recovered to normal within 10 years after infection.

A ten-year observation on experimental infection of periodic Brugia malayi in man.

This paper reports the results of 10 years of observations on the clinical manifestations, pathology and immunity to filariasis and aetiological biology of filariae in three volunteers (first author and his family members) who were inoculated experimentally with infective larvae of periodic Brugia malayi in 1981. The changes in clinical symptoms and signs were recorded systematically. Microfilariae were first detected at 41 and 46 weeks after inoculation in two subjects and remained detectable in small numbers until 8-8.5 years after infection. The microfilarial density fluctuated at 1-2 mf 120 microliters-1. Thereafter no microfilariae were detected in 12 blood sample examinations, suggesting that the adult reproductive period of periodic B. malayi could last up to 8-9 years in the human body. Eosinophilia occurred mainly before and at the initial stage of microfilaraemia. An increase in the lymphocytes was observed to some extent at 2-156 weeks after infection. Biopsy at the inoculation site 6 weeks after inoculation showed infiltration of the lymph node by inflammatory cells, mainly eosinocytes, lymphocytes and monocytes. Lymphangiectasis and lymphostasis were observed in both limbs and pelvic regions by lymphangiogram taken 11 weeks after inoculation. Antibodies against B. malayi first appeared at 2-5 weeks after infection, peaked at 12-56 weeks and thereafter declined gradually. Subjects A and C became antibody free but subject B remained positive to antibody against B. malayi 10 years after infection. E-rosette forming lymphocytes became lower than normal at 11 weeks and recovered to normal within 10 years after infection.

Laboratory studies of desiccation resistance in Mesocyclops (Copepoda: Cyclopoida).

The desiccation resistance of 4 species of Mesocyclops from varied geographical locations was tested against water content in sediment, temperature, and photoperiod. Trays containing sediment were inoculated with copepods and allowed to dry out for a period of 2 months and then reflooded. Both copepodids and adults of all species tested displayed desiccation resistance, with water content having greatest effect on survival.

Comparison of sampling efficacy of sweeping and dipping for Aedes aegypti larvae in tires.

A sweep net with a flexible plastic frame was compared to a dipper for sampling efficacy for Aedes aegypti larvae in different-sized tires. When known numbers of mosquito larvae were introduced into tires, from 2 to 6.8 times more larvae were recovered by sweeping than by dipping. Sediment in the tires significantly reduced the recovery of larvae by both methods. Sampling efficacy was affected by water level and tire size. In relation to dipping, sweeping showed less variation in percentage recovery, higher sensitivity for detecting larvae and had better correlations with known numbers of larvae in tires. We conclude that sweeping is superior to dipping for sampling mosquito larvae in tires.

Observations on experimental infection of periodic Brugia malayi in man.

Three volunteers were inoculated with different numbers of infective larvae of periodic Brugia malayi from an artificially infected Meriones unguiculatus. At different times after inoculation, the volunteers developed clinical manifestations such as chills, fever, cough, asthma, skin itching, edema, adenolymphangitis and eosinophilia. Microfilaremia was first detected at 41 and 46 weeks after inoculation in two subjects. At 11 weeks, the percentage of E-rosette forming lymphocytes in these subjects was below the normal level. Specific antibody was first detected in three volunteers at 2, 3 and 5 weeks after inoculation, respectively, and increased to various extent at 12-16 weeks, but decreased in varying degrees at 44-56 weeks. The results also showed that antibody titres fluctuated at different periods of infection.

Studies on the efficacy and persistence of the microbial agent bacillus sphaericus against larvae of culex pipiens pallens.

This paper evaluates the efficacy of the bacterial larvicide bacillus sphaericus strains BS-10 and C3-41, which are isolated in China, as well as BS2362 against larvae of Culex pipiens pallens in laboratory and under field conditions. The results indicate that C3-41 has the highest toxicity with LC50 at 0.0057 ppm and the bacterial formulations are more effective in light polluted water than in heavy polluted one, but the action of B. sphaericus could persist longer in more polluted water.