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Korean J Parasitol > Volume 15(1):1977 > Article

Original Article
Korean J Parasitol. 1977 Jun;15(1):17-29. English.
Published online Mar 20, 1994.  http://dx.doi.org/10.3347/kjp.1977.15.1.17
Copyright © 1977 by The Korean Society for Parasitology
Study on the quantitative evaluation of reinfection of Ascaris lumbricoides
Seung Yull Cho
Department of Parasitology and Institute of Endemic Diseases, College of Medicine, Seoul National University, Korea.
Abstract

The present study was undertaken to determine whether an analysis of the collected worms after chemotherapy with pyrantel pamoate could be used as a method measuring the amount of reinfection of Ascaris lumbricoides in a given population.

A total of 398 cases from two villages and one primary school were treated with pyrantel pamoate with dose of 10 mg/kg of body weight. The whole two-day stool specimens after treatment were examined. Out of 279 followed cases, 110 cases (39.4%) were found infected with A. lumbricoides. A total of 527 worms were collected, they were in the range of 1.2 to 32.5 cm in length and 0.0004 to 7.424 gm in weight. The measurements were made on the specimens fixed with 10% formalin.

The relationship between the number of worms per positive case(X) and the total weight of worms(Y) showed the positive linear regression; this was expressed by the equation, Y= 2.012X + 1.135 (Sy=4.84, r=0.92). From the above results, it seems that worms of small size may not be considered as a product of crowding effect in heavy infections.

The relation between the weight(Y) and length(X) of collected A. lumbricoides was expressed as an equation, Log(e)Y=3.032 log(e)X-8.2903(S.E. of reg. coeff.= 0.040, r=0.957). In the intestinal phase of development, the first increase of the length of the worm, up to 10-12 cm was observed and this followed by the well marked increase of weight from 13 cm upto 32.5 cm in the sexually maturing phase.

A total of 285 schoolchildren were treated by pyrantel pamoate, 10 mg/kg of body weight three times each in two months interval. After the second and third treatment, thirteen and fifty-four worms were collected respectively. They were measured in length and weight and were all in the range of 1.2 to 13.2 cm in length and 0.0006 to 0.436 gm in weight except 3 fully matured adults.

It is assumed that these young worms, defined as those less than 0.5 gm in weight and less than 13 cm in length should be regarded as those having reinfected during the previous two months period.

From this observation, it was possible to calculate the reinfected number of young worms. Therefore, it is suggested that the average number of Ascaris per month per person means the reinfection amount in a certain period of time in an endemic area of A. lumbricoides. In other words, reinfection amount may be expressed by the calculated figure of young worms reinfected in a certain period of time in a population.

Figures


Fig. 1
Relationships between the size(=number) of infection of A. lumbiricoides and total (A) and mean weight (B) of worms. One dot represents one infected case.


Fig. 2
The relationship between the length and the weight of Ascaris lumbricoides collected from three communites.


Fig. 3
Relationships of weight and length of 13 A. lumbiricoides collected two months after the first mass treatment in schoolchildren in Ejungbu City, on Septmber 17, 1976. These worms were considered to be infected from mid-June to mid-August, 1976, except 3 worms.


Fig. 4
Relationships of weight and length of 54 A. lumbiricoides collected on the third mass treatment in schoolchildren in Ejungbu City, on November 18, 1976. These worms were considered to be infected during the period from mid-August to mid-October. 12 sex-undetermined worms were excluded from dotting.

Tables


Table 1
Successive number of Ascaris lumbricoides expelled after chemotherapy with pyrantel pamoate by day in 20 children


Table 2
Status of Ascaris lumbricoides infection in three surveyed population revealed by worm collection after chemotherapy with pyrantel pamoate


Table 3
Ranges of variation in length (cm) of A. lumbiricoides analysed by the weight, expelled after chemotherapy and fixed in 10% formalin


Table 4
Ranges of variation in length (cm) of A. lumbiricoides analysed by the length, expelled after chemotherapy and fixed in 10% formalin


Table 5
An analysis of mass treatment results

No. treated : 285 throughout 3 treatments

No. observed : 193 in the 1st treatment, 173 in the 2nd treatment, 185 in the 3rd treatment



Table 6
Status of reinfection of A. lumbiricoides in three surveyed population measured by this method

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