사상충자충의 생태에 관한 연구

Abstract

Introduction

Though the filariasis is one of the main mosquito-borne endemic disease in Korea,

the vector species of mosquitoes has not yet been clearly differentiated. The

present study is designed to supplement the knowledge of the behavior or bionomics

of microfilariae of Brugia malayi(B. malay) and Dirofilaria immitis (D.immitis) in

the host animals and in the possible vector mosquitoes caught in the endemic areas

and, in addition, several bionomical studies of these microfilariae were carried

out in vitro or in vivo.

The methods and materials used and the results in this study are summarized.

Materials and Methods

1. Mosquito collection: The investigators collected mosqutoes from cow stables or

indoors in endemic areas of human filariasis inculding Cheju-Do and Yongju, and an

area of dog filariasis, Chinju.

The mosquitoes caught were brought to the laboratory, identified and dissected

under the microscope to examine the filarial larvae in them.

2. Mosquito rearing: The larvae of mosquitoes were collected from the field and

brought to the laboratory to be reared at room temperature(26°±2℃).

After emergence, the female adult mosquitoes were fed on a dog infected with

D.immitis, and the development of the microfilariae in the mosquitoes was observed

day by day.

3. Viability of the infective larvae in the environmental media: The infective

larvae escaped from the proboscis of the infected mosquitoes were placed into

saline, distilled water, well water and serum or a blood cell suspension of human

and dog blood in saline solution, and the motility and morphological change were

observed.

4. Life span of the microfilariae: Blood infected with D.immitis was transfused

to non-infected healthy dog. The number of microfilariae in 0.02ml. of blood of the

dog transfused with infective blood was examined at intervals of 4-7 days after the

transfusion until the disappearance of all microfilariae from the blood.

5. Periodicity of microfilariae in the peripheral blood: Peripheral blood was

taken every three hours from the infected human and dog, and the number of

microfilariae in 0.02ml. of blood was checked.

6. Provocation test of microfilariae in the peripheral blood: Diethylcarbamazine

citrate (Supatonin, Tanabe) 3mg/kg, was given one time only to the filariasis and

elephantiasis cases. The microfilariae was checked before and 20 minutes after the

drug administration.

7. Phototaxis of the microfilarise: The blood which contained the microfilaria of

D.immitis was introduced into a slender glass tube, 2.5mm in diameter on the

surface of which 5cm. of black enamel alternated with 5cm. of unenameled area.

Both ends of the tube were sealed with vaseline. The tubes were placed in a water

bath of 10℃ and 36℃, and exposed to direct sun-light for the study of the

behavior of the microfilariae.

Results

The mosquitoes collected from the endemic areas of filariasis were as follows:

Anopheles sinensis, A.sineroides, Culex pipiens, C.tritaeniorhynchus, C.sinenis,

C.orientalis, C.hayashii, C.vagans, Aedes vexans, Ae.koreicus, Ae.albopictus,

Ae.togoi, Ae.japonicus, Ae.esoensis and other unclassified Aedes sp.

Anopheles sinensis and Culex pipiens in inland and Aedes togoi and Aedes

albopictus in Cheju-Do (island) were predominant.

No larvae of filaria species could be found from the dissected mosquitoes which

were caught at the endemic area. It was observed that the microfilaria of D.immitis

fed by mosquitoes (Aedes Koreicus, Aedes albopictus) developed to infective stage

within 2-3 weeks. The infective larvae which emerged from the proboscis of the

mosquitoes into the water were observed to be able to survive for an hour.

The microfilariae placed into the slender tube in the water bath under the

exposure of sunlight showed that the microfilariae were gathered in large number at

the enameled dark portion but there were no sign of temperature influence on

travelling of the microfilaria at temperature difference between 10° and 36℃.

The nocturnal periodicity of microfilariae of both B.malayi and D.immitis in the

hosts was observed and showed peaks at the period of 23-24 o'clock for B.malayi and

at 00-01 o'clock in d.immitis.

The microfilariae in the viscera of the host showed no significant changes

following the administration of Diethylcarbamazine citrate.

The microfilariae introduced by blood transfusion into the non-infected healthy

host were able to survive up to 105 days.

Discussion

Since Senoo (1951) and others have reported that the species of human filaria in

Korea was B.malayi, many workers have reported several endemic areas of B.malyai in

Korea. Although no vector mosquitoes of the filariasis have as yet been

differentiated in this study, Anopheles sinensis, Culex pipiens, Aedes togoi and

Aedes albopictus have been suspected as vectors by some previous workers.

Fourteen specles of mosqultoes including Anopheles, Culex and Aedes were

collected during the mosquito season in the endemic areas such as Yongju, Chinju

and Cheju-Do. The predominant species were Anopheles sinensis and Culex pipiens in

the inland but Aedes togoi were in the island of Cheju-Do.

The development of the microfilariae of D.immitis in the mosquitoes was observed

and Aedes Koreicus appeared to be the possible vector mosquitoes of D.immitis.

Though the nocturnal periodicity of both B.malayi and D.immitis was confirmed by

many workers, the peak density of the microfilariemia in the present study was

between 23-24 o'clock in B.malayi

Although Katamine (1952) observed the increased microfilariae of Wuchereria

bancrofli in peripheral blood after the administration of Deithylcarbamazine, the

result of the present provocation test showed no difference in the number of

microfilariemia before and after the administration of the same drug. This suggests

that there might be some complex biological difference between these two filaria

species.

The microfilaria of D.immitis showed negative phototaxis in the present study.

This fact may supplement that of the nocturnal periodicity of microfilaria.

High fever and other side actions were observed after the administration of

diethylcarbamazine in filasiasis but these side reactions were decreased after

repeated administration of the drug.

The side reactions appeared to be caused by a pyrogenic substance coming from

dead microfilariae of D.immitis which were transfused into non-infected healthy dog

which was able to survive up to 105 days, although Wong (1964) observed that the

microfilariae introduced in a non-infected healthy dog were found in the peripheral

blood until 11-43 days after the transfusion of the infected blood.

About two third of the larvae disappeared within 34 days after the transfusion.

this indicates that life-span of larvae is not long and it causes a constant

microfilariemia in the peripheral blood of the host.

To consider the possibility of escape of larvae from the proboscis into the

environmental media, the fate of the filarial larvae was studied. They survived

5-24 hours in saline, serum of blood cell solution and were destroyed within one

hour in well or tapwater. The natives believed that filaria could be infected

orally (by drinking well water) but this is not believable from the evidence above.

Summary

The present study supplements the knowledge of bionomics of microfilariae and

infective filarial larvae of the Brugia malayi and Dirofilaria immitis. The results

are summarized as follows:

(1) Fourteen species of mosquitoes were collected in the endemic areas of

filariasis, including Yongju, Chinju, and Cheju-Do.

(2) Culex pipiens and Anopheles sinensis were predominant in inland Korea, and

Aedes togoi and Aedes albopictus in Cheju-Do(island).

(3) Microfilaria immeitis developed to infective stage in Culex pipiens from 16

days, in Aedes albopictus from 13 days and in Aedes koreicus from 14 days.

The rate of development of microfilariae to the infective stage in the mosquitoes

was 68.5 per cent in Culex pipens, 20.3 per cent in Aedes albopicuts and 45.0

percent in Aedes Koreicus.

(4) The infective larvae which escaped from the proboscis of the mosquitoes

survived one hour in water and 40 hours in human and dog serum.

(5) The transfused microfilaria immitis survived as long as as 105 days in

healthy dog vessels.

(6) The peak density of microfilariae in the peripheral blood of the host

appeared at 23-24 o'clock in B.malayi and at 00-01 o'clock in D.immitis.

(7) Microfilaria immitis showed negative heliotropism.

(8) Diethylcarbamazine citrate administration appeared to cause no definite

effect on microfilaria in ;the peripheral blood of the malayian filariasis cases.

(9) side action including high fever after Diethylcarbamazine citrate treatment

appeared to be due to production of the pyrogenic substance from dead microfilaria

which had been destroyed by the drug.