From Plasmodium vivax outbreak to elimination: lessons learnt from a retrospective analysis of data from Guantang

Abstract

Background: Malaria was once a serious public health problem in China with Plasmodium vivax the major species responsible for more than 90% of local transmission. Following significant integrated malaria control and elimination programs, malaria burden declined, and by 2017 China recorded no indigenous cases. To understand the historical malaria transmission patterns and epidemic characteristics in China and insights useful to guide P. vivax malaria control and elimination elsewhere, a retrospective study was carried out. Materials and Methods: Historical data from a pilot study conducted in Guantang, Luyi in central China from 1971-1995, were digitised. The data included monthly numbers of reported cases, febrile cases, parasite carriage rates, the neonatal infection rate, and entomological data from Anopheles sinensis. Results: Following 25 years of continuous integrated malaria control activities, malaria incidence in Guantang decreased from 4,333 cases per 10,000 in 1970 before integrated implementation to 0.23 cases per 10,000 in 1991, and no cases in 1992-1995. Some fluctuations in incidence were observed between 1977 and 1981. During the period parasite rates, antibody levels and the neonatal infection rate also decreased. The pattern of seasonality confirmed that P. vivax in Henan Province was primarily of long incubation type (temperate) during non-transmission period. The findings retrospectively provide a scientific basis for the implementation of mass campaigns of liver stage hypnozoite clearance. Entomological studies indicated that An. sinensis was the only vector, and it preferred bovine to human hosts, predominantly biting and resting outdoors. Mosquito densities declined between 1971 and 1984.Conclusion: The integrated malaria control approach in Guantang effectively controlled malaria and achieved elimination. Analysis of the effectiveness of the program can provide guidance to other regions or countries with similar ecological settings aiming to move from malaria control to elimination. There is a potential challenge in the maintenance of non-transmission status owing to imported cases and the long dormancy of liver stage hypnozoites.

Pipiserpin, a Culex factor Xa inhibitor, affects female reproductive capacity and serves as a potential target for mosquito control

“…Other malaria vectors, such as An. sinensis , are preferentially zoophilic, 50 with an averaged preference ratio of 1:11.93 between humans and cattle 51 . Our results showed that Pipiserpin may be used to vaccinate animals to generate antisera, which would then be ingested when mosquitoes feed on these animals.…”