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.
parasitology-helminth-nematoda ; Ascaris lumbricoides ; ascariasis ; epidemiology-reinfection ; pyrantel pamoate

The present authors investigated intestinal parasitic infections among North Korean residents and refugees in China in 2003. The Kato-Katz method was applied to 236 residents and soldiers in a town on the North Korea-China border and to 46 people at a refugee camp in China. Only eggs of Ascaris and Trichuris were detected, with egg positive rates of 41.1% and 37.6%, respectively. The total egg positive rate was 55.0% and most of those who were egg positive were only lightly infected. Women of 61.2% and men of 53.1% were egg positive. The refugees from rural areas showed higher egg positive rates than those from urban areas. The present investigation confirmed high prevalence of soil-transmitted intestinal helminths in rural borderline areas of North Korea.
Trichuris/*growth & development ; Trichuriasis/*epidemiology ; Male ; Korea/epidemiology ; Intestinal Diseases, Parasitic/*epidemiology/parasitology ; Humans ; Female ; Child ; Ascaris/*growth & development ; Ascariasis/*epidemiology ; Animals ; Adult ; Adolescent

A total of 2,026 leprosy patients of the National Sorokdo Hospital was examined their intestinal parasites by cellophane thick smear method in January 1983. The egg positive cases of Taenia spp. were treated with bithionol and the segments of Taenia were collected for species identification. The results were as follows: Total egg positive rate of any kind helminth was 78.2 percent and cumulative total was 85.2 percent. The egg positive rate for each helminth was as follow; Taenia spp. 3.4 percent, Ascaris lumbricoides 4.5 percent, Trichuris trichiura 72.l percent, Clonorchis sinensis 2.8 percent and other 0.05 percent. A total of 66 Taenia egg positive cases was treated; out of them proglottids of Taenia were collected from 26 cases. All of the collected worms were identified as T. saginata. The results revealed significantly high egg positive rate of T. trichiura. However, A. lumbricoides was found to be controlled considerably by repeated chemotherapy during past 3 years. If chemotherapeutic agent is replaced with oxantel-pyrantel tablet, better result is expected. No clue was found for prevalence of T. solium from both human and the pig in the island.
parasitology-helmith-nematoda-trematoda-cestoda ; trichuriasis ; Trichuris trichiura ; Taenia spp. ; Ascaris lumbricoides ; Clonorchis sinensis ; taeniasis ; ascariasis ; clonorchiasis ; Taenia saginata ; epidemiology

OBJECTIVEOur objective was to systematically evaluate chemotherapy-based control of ascariasis and hookworm infection and make predictions of the effectiveness of repeated mass treatment at different levels of coverage in highly endemic areas of China.

METHODSField surveys were carried out to acquire the ascariasis and hookworm prevalence and intensity (mean worm burden) at baseline, one month and one year later. We calculated model parameters based on the survey data, then incorporated them into a quantitative framework to predict the prevalence and intensity one year later. Sensitivity analyses were performed to assess the influence of the chemotherapy measures on prevalence and intensity, and model simulations were performed to evaluate the feasibility of achieving the proposed transmission control criteria under different chemotherapy measures.

RESULTSThe predicted prevalence and intensity one year from baseline were within the 95% confidence interval of actual values. As treatment frequency or coverage increased, the prevalence and intensity decreased. Model simulations show that many rounds of treatment are needed to maintain the prevalence at a low level in highly endemic areas of China.

CONCLUSIONWe should select different combinations of treatment frequency, coverage and drug efficacy according to available resources and practical attainable conditions. Mathematical modeling could be used to help optimize the chemotherapeutic scheme aiming at specific parasitic species and areas, and to direct the establishment of soil-transmitted helminthiasis control criteria in China.

Anthelmintics ; therapeutic use ; Ascariasis ; drug therapy ; epidemiology ; prevention & control ; China ; epidemiology ; Computer Simulation ; Endemic Diseases ; prevention & control ; Hookworm Infections ; drug therapy ; epidemiology ; prevention & control ; Humans ; Models, Biological ; Prevalence ; Reproducibility of Results ; Time Factors