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Korean J Parasitol > Volume 6(1):1968 > Article

Original Article
Korean J Parasitol. 1968 Jun;6(1):1-10. English.
Published online Mar 20, 1994.  http://dx.doi.org/10.3347/kjp.1968.6.1.1
Copyright © 1968 by The Korean Society for Parasitology
Studies on filariasis in Korea - On the morphology and development of larvae of Brugia malayi in Aedes togoi-
Hee-Kwan Kim and Byong-Seol Seo
Department of Parasitology and Institute of Endemic Diseases, College of Medicine, Seoul National University, Seoul, Korea.

Since Senoo and Lincicome (1951) first have brought up for attention to the existence of malayan filariasis in Korea, several reports on the epidemiological investigations of the disease had already been made by many workers. However it is little known what kind of mosquitoes are involved as the major vectors in main endemic areas. In Cheju-Do, known as one of main endemic areas in Korea, Aedes togoi is most likely suspected as an important vector because of their abundant collections and vigorous biting attack to human.

As a part of studies on filariasis in Korea, an essential preliminary is to determiine whether this mosquito, Aedes togoi collected in the above areas is receptive to the microfilariae of B. malayi. Therefore, the present paper is concerned chiefly with the development of B. malayi in A. togoi. It is also hoped that the studies on the larval morphology in the mosquito host and the structure of microfilariae will provide the base line data required for later investigation of the different vector hosts.

The studies were summarized as follows:

1) The measurements of the fixed points in percentage of the body length of microfilariae from the Giemsa stained thick films were made, and they showed that cephalic space was 8%,cephalic space length to width, 1.3:1, nerve ring, 21.2%, excretory pore, 30.8%, excretory cell, 36.5%, R1 cell, 66. 5%, anus 80.4% and body length 202µ (l81-228µ) maximun width 7.6µ.

2) A study on the development of microfilaria malayi in the mosquito, Aedes togoi was carried out at room temperature (24-30℃). Mosquitoes used in this experiment were reared from larvae collected from the tide water rock pool in the coastal areas of Cheju-Do and they were fed with a blood meal of carrier donors whose microfilaria densities were in the range from 0.5 to 0.7 per cmm of blood.

3) All of the microfilariae ingested by mosquito exsheathed in stomach, penetrated into the body cavity and then migrated into the thoracic muscles of the mosquitoes within 10 hours, after two moults in the mosquito host, the length of the developing 3rd stage larvae reached in size of 1.3~1.7 mm × 23~32 µ with anal ratio, 2.6 to 3.6. The first appearance of 3rd stage larvae in the mosquito host in this experiment was in 8th day after infection. The larvae were observed in the various cavities of mosquito, such as head, thoracic cavity, abdomen, halters, eye and legs. During the larval development in larval development in the host, the shortening of body length was first observed and then elnongation was followed until becoming 3rd stage larvae.

4) Aedes togoi was proved to be the most suitable host for this species of microfilaria malayi in the above endemic areas.


Fig. 1
Microfilaria malayi in thick film, dehemoglobinized, fixed in absolute methanol and stained in Giemsa. (camera lucida drawing) (CS, cephalic space; NR, nerver ring; EP, excretory pore; Ri, cell A, anal pore)

Fig. 2
Head and tail part of microfilaria malayi in thick film (camera lucida drawing).

Fig. 3
The general appearance and attitude of microfilarias from thick blood smear, showing no kinking and no shrinkage (camera lucida drawing).

Fig. 4
Cross sections of the third larva of B. malayi in proboscis(camera lucida drawing.) A and B; at level of muscular esophagus and D; at nerve ring E; at glandular esophagus

F; genital primordium and glandular esophagus

G; at level of mid-intestine

H; just behind the anus

Plate. I
Fig. 1. The general appearance of microfilaria malayi in thick blood smear

Fig. 2. Anterior portion of microfilaria showing the nerve ring and excretory pore.

Fig. 3. Posterior portion of microfilaria showing the tail with terminal nuclei and anal pore.

Fig. 4~7. Photographs showing the sections of larvae of B. malayi in the thorax of Aedes togoi.

Fig. 4. Third stage larva in the thoracic cavity.

Fig. 5. 34 hours in the thoracic muscles of mosquito.

Fig. 6. 34 hours lateral view of the tail showing R2-R4 Cells incorporated into the rectum.

Fig. 7. 34 hours lateral view of the tail showing typical shape of tip of the tail and the appearance of R2-R4 Cells and anal pore.

Plate. II
Fig. 1. Section of the head and thorax of the mosquito with mature larvae in eye (three cross sections are seen).

Fig. 2. Section of the eye of the mosquito with mature larvae (two cross section are seen).

Fig. 3 & 6. Section of labium of the mosquito with mature larvae (2 or 3 cross scetion are seen).

Fig. 4. Showing mature larvae emerging from the tip of labellum.

Fig. 5. Section of proboscis of the mosquito with mature larvae.

Plate. III
Fig. 1. Head part of 3rd stage larva. 10.7 days after infection in glycerine medium (oil immersion).

Fig. 2. Portion of the mid-intestine of the same larva (oil immersion).

Fig. 3. Portion of the tail, showing anal pore and rectum (oil immersion).

Fig. 4~10. All the figures are photographs taken from parts of Aedes togoi infected with third stage larvae showing the cross sections of the larvae in the labium or in the various parts of the body cavity.

Fig. 4 and 8. at level of muscular esophagus.

Fig. 5. at nerve ring.

Fig. 6. at genital primordium and glandular esophagus.

Fig. 7. behind the anus.

Fig. 9. at glandular esophagus.

Fig. 10. at level of mid-intestine.


Table 1
Measurements of Microfilaria malayi (µ) and measurements of the fixed points in percentage of the body length (From Giemsa stained thick blood film)

Table 2
Average Measurements (µ) of the microfilariae of B. malayi

Table 3
Average Measurements in microns of the Larvae of B. malayi collected from experimentally infected Aedes togoi

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