| ObjectiveThe Democratic Republic of S?o Tomé and Principe(hereinafter referred to as "S?o Tome and Principe")was an area with low malaria incidence.From 2014 to 2019,the national malaria incidence rate was around 1%,and it did not continue to decline.According to the data of malaria cases from 2014 to 2019,the characteristics of the malaria epidemic need to be sorted out,and the malaria foci should be identified.Considering China’s experience on malaria control and prevention and the real malaria epidemic in S?o Tomé and Principe,we speculated that the main reason for the above situation was the existence of malaria residual foci.Since the source of infection had not been eliminated in these districts,residual active foci remained.Malaria incidence in these residual active foci was high and increased the risk of malaria transmission to other surrounding villages,thus leading from time to time to malaria outbreaks.The Centro National de Endemias(CNE)of S?o Tomé and Principe have drawn from China’s experience in the control and prevention of malaria to strengthen its malaria control and prevention measures to eliminate residual foci and thus speed up the progress of malaria control and prevention in S?o Tomé and Principe.Methods1.The national malaria case data of Sao Tome and Principe from 2014 to 2019 were selected from the malaria case database of the CNE as the research objects,including counties,villages,the time of onset(week),and the number of cases per week.From the three levels of "country-region-village"and the two dimensions of "time-space",the epidemiological characteristics of malaria were analyzed by the incidence of malaria,the number of new malaria cases per week,and the cumulative number of malaria cases per week at different times and in different regions.Malaria foci were found out by methods of spatial autocorrelation analysis and retrospective spatiotemporal scanning.2.Three monthly rounds of AP-MDA were implemented from July to October 2019 in Liberdade village,a residual malaria focus area selected as a study site(zone A).Budo Budo village(zone B)was selected as a control site.Meanwhile,villages within 1.5 km of the study site(zone C)and areas outside the 1.5 km(zone D)were also monitored and followed up.Parasite prevalence,malaria incidence,and the proportion of cases of Plasmodium falciparum malaria of each zone pre-and post-AP-MDA were compared.Results1.At the national level,the statistical results of the incidence of malaria from 2014 to 2019 showed that the incidence of malaria of each year was not all equal(P<0.05),indicating that the malaria prevalence in Sao Tome and Tome was different between different years,which reflected the heterogeneity of the malaria epidemic in the temporal distribution of the year.In the same year,during a period of 52 weeks,the number of new weekly malaria cases had a peak,and there was a trough before and after the peak;the cumulative number of malaria cases per week had a rapid growth period and two slow growth periods,which is characterized by "three-stage stepped growth".The country is in a state of low malaria prevalence from 1-13 weeks(January to March)and 28-52 weeks(July to December)every year,and high malaria prevalence in 14-27 weeks(April to June).2.At the regional level,the statistical results of malaria incidence in 6 counties and 1 autonomous region in Sao Tome and Principe from 2014 to 2019 showed that there were differences in the incidence of malaria in the same year and in different regions(P<0.05).The incidence of malaria in the same area and in different years was also different(P<0.05).The above showed that the malaria epidemic was heterogeneous in time distribution and regional distribution.According to the number of new malaria cases per week and the cumulative number of malaria cases per week,malaria epidemics in various regions had their own characteristics.The low prevalence status of malaria in Agua Grande was between the first to the 15th week(January-early April)and the 29th to the 52nd week(mid-July to December)and the high prevalence status of malaria was In the 16th-28th week(mid-April-early July).The low prevalence status of malaria in Cantagalo was the first week to the 12th week(January to mid-March)and the 28th week to the 52nd week(Mid July to December)and the high malaria prevalence status of each year.It was in the 13th-27th week(late March to early July).The low malaria prevalence status in Caue was in the first week-16th week(January-mid-April)and 27th week-52nd week(early JulyDecember)and the high malaria prevalence status was in each year.Week 17Week 26(late April-late June).The low prevalence status of malaria in Lemba was in the first week to the 18th week(January to late April)and the 28th week to the 33rd week(early July to mid-August)and the high malaria prevalence status was in each year.Week 19-Week 26(Early May-Late June)or Week 47-Week 52(Late November-Late December).The low prevalence status of malaria in Lobata was in the first week-the 14th week(Januaryearly April)and the 30th week-the 52nd week(mid-July-December)and the high malaria prevalence status of each year was In the 15th-29th week(midApril-early July).The low prevalence status of malaria in Me-Zochi was between the first week to the 15th week(January to early April)and the 29th week to the 52nd week(mid-July to December)and the high malaria prevalence status of each year was in the 16th-28th week(mid-April-early July).The Principe had a very low prevalence of malaria from 2014 to 2017.The number of malaria cases increased rapidly in 2018 and 2019.The high prevalence of malaria is from the 22nd to the 26th week of each year,and the low prevalence of malaria is in the first week-the 21st week and the 27th-the 52nd week of each year.3.At the village level,518 villages were sorted out in Sao Tome and Principe.The number of villages with malaria cases in each year from 2014 to 2019 was different.Among them,in 2015,there were only 162 cases,accounting for 31.27%;in 2018,it reached 224 cases,accounting for 43.24%.There were more villages with malaria cases in 2019 than in 2014,2015,and 2016.The number of villages with malaria cases in 2019 is higher than that in 2014,2015,and 2016.Compared with 2014,2015,and 2016,there is a significant difference(P<0.05),indicating that at the village level,the proportion of malaria cases in S?o Tomé and Príncipe Popularity shows a trend of expanding year by year.Compared with the proportion of villages with malaria cases in 2014,2015,and 2016,showed a significant difference(P<0.05)in 2019,indicating that at the village level,the malaria prevalence showed a trend of increasing year by year.At the village level,the distribution of malaria epidemics has the following characteristics:Malaria endemic villages are mostly distributed in areas close to the coastline,relatively flat terrain,and concentrated population;Malaria endemic villages are mainly located on S?o Tomé Island;Malaria endemic villages with a high incidence of malaria are concentrated in Agua Grande County in the northeast of Sao Tome Island.The statistical results showed that the incidence of malaria in malaria endemic villages was negatively correlated with altitude.Spatial autocorrelation analysis and retrospective spatio-temporal scanning methods were used,and four types of malaria aggregation areas were found,and a total of 27 malaria endemic villages were found.Combining the conditions for determining the source village,the malaria foci were found in the aggregation area.4.After three monthly rounds of AP-MDA,the prevalence of P.falciparum in zone A,as a residual malaria focus,decreased from 28.29‰ to 0,and the gametocyte prevalence of P.falciparum malaria was reduced from 4.99‰to 0.It shows that the artemisinin-piperaquine tablets have the same effect on the asexual and gametophytes of Plasmodium falciparum,which shows that AP-MDA has high efficiency and quick effect in killing Plasmodium in the population.5.From the 29th to the 50th week of 2019(From July 13,2019 to December 14,2019),the number of new malaria cases per week in District A was 0.It shows that three rounds of AP-MDA successfully eliminated the malaria parasites in the population of the focal village during the period.6.From the 29th week of 2019 to the 28th week of 2020(July 13,2019 to July 12,2020),The weekly number of new malaria cases in District A,District B and District C was lower than the data during the same period in the previous years.The number of new malaria cases per week in District D,Agua Grande and whole country was lower than the data during the same period in last year.Compared with the same period of the previous year,the incidence of diseases in district A has decreased(P<0.05),as well as in district B(P<0.05),in district C(P<0.05),in district D(P<0.05),in Agua Grande(P<0.05)and in the whole country(P<0.05).The decrease in the incidence of malaria year-on-year was as follows:District A(93.16%)>District C(85.68%)>District B(85.00%)>Agua Grande(68.33%)>the whole country(49.31%))>D district(32.55%).This showed that under the combined effect of the natural climate,regional environment and the existing malaria prevention and control measures in Sao Tome and Principe,compared with situation of the spread of malaria in districts B,C,D,and Agua Grande,three rounds of AP-MDA enabled the malaria transmission in district A to be better controlled.7.From the 29th week of 2019 to the 28th week of 2020,the proportions of the cumulative number of malaria cases in Area A,Area B,Area C,and Agua Grande all decreased year-on-year.There is a significant difference compared with the same period of the year(P<0.05),and the proportion of the year-on-year decline from large to small is Area A(84.75%)>Area C(71.59%)>Area B(69.89%)>Agua Grande(37.57%).The proportion of cumulative malaria cases in area D increased year-on-year,and there was a significant difference(P<0.05).Both the incidence of malaria and the proportion of the cumulative number of malaria cases in Area C have fallen second only to Area A.The decline in the prevalence of malaria in Area A has resulted in a simultaneous decrease in the prevalence of malaria in Area C.It shows that the three rounds of AP-MDA have greatly reduced the malaria prevalence in Area A,and at the same time have some deterrent effect on the malaria prevalence within 1.5 kilometers of its surrounding area.ConclusionsThe malaria epidemic fluctuates cyclically in S?o Tomé and Principe,and malaria residual foci were scattered in the whole country.Three monthly rounds of AP-MDA rapidly and effectively controlled malaria transmission in Liberdade village.They simultaneously reduced malaria incidence in a specific geographical space and within a limited time interval. |
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