Objective: To evaluate malaria situation by indirect fluorescent antibody test (IFAT) in 12 villages of six counties along Yellow River and Huihe River in Anhui, Henan and Hubei Provinces.
Methods: Cross sectional seroepidemiologic survey was conducted through IFAT in Anopheles sinensis area and A. anthropophagus plus A. sinensis area respectively in 2006 and 2007. The blood-filter papers collected from residents were tested by IFAT to calculate malaria antibody positive rate (APR) and positive GMRT in different age groups. The predictive infection probability was evaluated by reversible catalytic model based on antibody positive rate in the group of less than 20 year-old and compared to the annual parasite incidence.
Results: In 2006 and 2007, the average antibody positive rate in the investigated villages was 6.1% and 12.0% respectively. In An. sinensis areas, the APR in 2007 (12.0%) was significantly higher than that in 2006 (4.1%) (chi2 = 69.9, P < 0.01) while in An. anthropophagus plus An. sinensis areas there was no significant difference in 2006 (10.3%) and 2007 (12.1%) (chi2 = 0.17, P > 0.05). The average positive GMRT of the 12 villages was 26.2 in 2007, slightly higher than that in 2006. In both An. sinensis area and An. anthropophagus plus An. sinensis area, the predictive infection probabilities were higher than the annual parasite incidence with an average 117.3 and 17.20 times higher than the latter respectively. 87.8% of the antibody positive cases were asymptomatic, indicating that there were potential infection sources with symptomatic parasitaemia in the areas.
Conclusion: Malaria is still prevalent in areas along Yellow River and Huihe River and the actual number of malaria cases are underestimated by the case report system. Malaria reemergence may occur in An. sinensis area but relatively stable in An. anthropophagus plus An. sinensis area.