Epidemiology and control of ascariasis in Korea

Prevention and Control Strategies for Parasitic Infections in the Korea Centers for Disease Control and Prevention

Korea is successfully controlled intestinal parasitic infections owing to economic development and high health consciousness. The Division of Vectors and Parasitic Diseases (formerly the Division of Malaria and Parasitology) is in the Center for Laboratory Control of Infectious Diseases of the Korea Centers for Disease Control and Prevention. It has been the governmental agency responsible for controlling and leading scientific research on parasitic diseases. The Division of Vectors and Parasitic Diseases has conducted and funded basic research and disseminated the research results to various medical fields, ultimately promoting public health in Korea. Among the noteworthy achievements of this division are the national surveillance of healthcare-associated parasitic infections, prevention and control for parasitic infections, and the elimination of lymphatic filariasis from Korea. On a broader scale, the division's research programs and academic supports were influential in preventing and treating infectious parasitic diseases through public policies and laws. In this review, we summarize the past and present role of the Division of Vectors and Parasitic Diseases in preventing and treating infectious parasitic diseases in Korea.

Survey on Intestinal Helminthic Infection Status of Students in Two Counties, Hadong-gun and Goseong-gun, Korea

This study was conducted to investigate the prevalence of intestinal parasites among students from Goseong-gun, Gangwon-do and Hadong-gun, Gyeongsangnam-do as typical low and high endemic counties. From May to July 2017, a total of 2,033 fecal samples were collected at 27 elementary, 10 junior high, and 8 high schools from 2 counties and examined by the Kato-Katz technique for egg-positive surveys (Collection rate: 37.02% [2,033/5,492]). Of the participants examined, 13 (0.64%) were found to harbor eggs of 3 parasitic species, Trichuris trichiura, Clonorchis sinensis and Metagonimus yokogawai. Based on the regional distribution, the egg-positive rate in Goseong-gun was 0% (0/550) and that in Hadong-gun was 0.88% (13/1,483). The positive rates for C. sinensis, M. yokogawai, and T. trichiura in Hadong-gun were 0.20% (3/1,483), 0.61% (9/1,483), and 0.07% (1/1,483), respectively. The present survey showed that the prevalence of parasitic infection among students is currently very low even in remote, previously endemic areas, and the present status of parasitic diseases can be summarized as some transmission of fish/food-borne trematodes. Thus, it is necessary to carefully, continuously monitor the trematode infection status, particularly of C. sinensis and M. yokogawai.

Ascaris egg profiles in human faeces: biological and epidemiological implications

Since 2 morphological forms (fertilized and unfertilized) of egg can be produced by Ascaris, infected humans can release in their faeces fertilized eggs only (FEO), unfertilized eggs only (UEO) or both fertilized and unfertilized eggs (FUE) (designated herein as the 3 different egg profiles). Epidemiologically, fertilized eggs are of significance as they enable effective transmission of the parasite. This study, for the first time, characterizes the Ascaris egg profiles in human faeces in an endemic region of China, explores possible host- and parasite-factors related to these profiles, and discusses the biological and epidemiological implications of the findings. The 3 egg profiles were recorded throughout the study period of 2 years, and the overall percentages of people with FEO, FUE and UEO profiles were approximately 41-47%, 32-42% and 17-21%, respectively. The overall number of unfertilized eggs for the entire population accounted for approximately 6-9% of all eggs excreted. The different Ascaris egg profiles showed no correlation to host gender, but they did relate to age and worm burden of the host and to the sex ratio and developmental status of the parasite. While an annual universal anthelmintic treatment resulted in some fluctuation in the values of individual egg profiles, the general features of these profiles remained similar throughout the study period. The findings of this study should have significant implications for understanding transmission patterns of Ascaris and for the implementation of control measures against ascariasis in endemic regions.

Drug-based helminth control in Western Pacific countries: a general perspective

Helminthiases still have a relevant detrimental role in the health of large groups of human population. Where poor hygiene and lack of access to education, health services and essential care characterize living conditions, parasitic infections dramatically affect essential aspects of individual life, such as nutrition, cognitive performance, susceptibility to infections and micronutrient deficiency. Severe illness is associated with schistosomiasis, lymphatic filariasis and food-borne trematode infections. Drugs are the cornerstone of control strategies for such infections, the World Health Organization (WHO) list of essential drugs contains several highly efficacious anthelmintics which are all safe, single-dose and cheap. If given regularly to infected communities, these drugs effectively control the morbidity related to the major endemic helminth infections. New strategies for mass drug administration to human populations have been tested, and several endemic Western Pacific countries have achieved excellent results in reducing morbidity in spite of continuous transmission. In this region, experience over the last decades proves the feasibility of helminth control, but also shows the need for long-term commitment and continuous support.

The global burden of intestinal nematode infections — Fifty years on

Fifty years after Stoll published his 'This Wormy World' article, the global prevalence of infections with intestinal nematodes remains virtually unchanged. The main species involved are Ascaris lumbricoides, Trichuris trichiura and hookworms, and there are now approximately one billion infections with each of these, worldwide. Given these large numbers, Man-Suen Chan here focuses on attempting to quantify the disease burden caused by these infections, using a recently formulated method of calculating disability-adjusted life years (DALYs). Using a mathematical model, it is estimated that approximately 70% of this burden can be prevented in high-prevalence communities by treating schoolchildren alone. Programmes targeted at schoolchildren have been shown to be extremely cost-effective, and hence this provides a realistic approach for combating these infections in the future.