A historical perspective on the immunodiagnosis of schistosomiasis in China

Abstract

The investigation and application of immunodiagnosis in schistomiasis have had a history of about 50 years so far in China. The author, in this paper, briefly review the progress of the technology involved here in the country, putting the stress on the latest issues during last decade. Also showed some limits in the use for control program of the disease through summary of some collaborative studies with the attempt in identifying guidelines for the implementation of serology in schistosomiasis immunodiagnosis. In addition, it was pointed out that a seroepidemiological approach in the identification of target individuals for treatment or re-treatment may be realistic and practical, which emphasized that the immunodiagnostic approach for public health use could ignore individual identification of the real infections. In this way, it became possible to bypass the complexity of interpreting the seroreactivity of an individual in assigning him/her with qualitative testing to the normal or infected person. Instead, one needs only to divide individuals in a community into ‘normal’ or ‘infected’ groups according to the titer distribution, which leads to identifying target groups for treatment.

Introduction

Since 1950s, parasitic diseases with emphasis on malaria, schistosomiasis, filariasis and leishmaniasis etc. have become one of highlights in national disease control endeavors in China and after decades of control efforts, outstanding progresses have been made with remarkable decline in morbidity and mortality of these diseases. Perhaps one of the biggest stories of our many proud accomplishments is the significant success in the control of schistosomiasis japonica in the country, which reveals that only an estimated 0.7 million individuals are still infected with the parasite currently while the figure was 10 million in the early 1950s. Since the availability of praziquantel, large-scale chemotherapy has been recognized to be a main approach for the control of this disease over the past two decades, which resulted in the reduction of both prevalence and intensity of this infection year after year. Because reinfection is very common, especially in endemic areas of schistosomiasis japonica like in China, the ‘test-treat’ approach is probably the most cost-effective strategy to meet the needs of identifying target individuals for repeated re-treatments. In this case, diagnosis at the levels of both individual and community is essential for the control program. Direct parasitological techniques, apart from being labour-intensive and time-consuming, have become relatively insensitive following widespread chemotherapy that results in generally lower worm burdens. For this reason, although definitive diagnosis of schistosomiasis japonica still relies on the demonstration of viable ova in feces or histological samples, the immunodiagnostic technology, owing to its rapid, affordable and easily acceptable (high compliance) advantages superior to parasitological techniques, has been, in reality, integrated into the control program in China as a way of improving the diagnostic record in identifying the target individuals for treatment since early 1980s when the safe and effective anti-schistosomiasis drug–praziquantel was introduced. This paper attempts, from viewpoint of historical perspective, to review briefly the progress of technology here in China, putting the stress on the latest issues during the last decade and to express the opinion of the authorship for the further endeavor in this field.