Historical data from a pilot study conducted in Guantang, Luyi in central China from 1971-1995, were extracted and digitised. We are going to summarise all data into four parts: study site, control and measurements, malaria data (including monthly numbers of reported cases, febrile cases, parasite carriage rates, the neonatal infection rate), and entomological data from Anopheles sinensis.
Guantang Township is located 10km south of Luyi County, 33°51´ north latitude and 115°21´ east longitude, within the river network region of Henan province, bordering Anhui Province in the east (Figure 3). There were 114 villages in the township with a population of about 40,000. In the early 1970s, about 4% of the cultivated land was planted with rice. Subsequently most arable land was replaced with dry land crops, such as cotton. Most of the houses were poorly ventilated bungalows with wood and mud structures. In summer and early autumn, residents generally had the habit of spending the evening outdoors or sleeping outside. These villages are crossed by more than 10 small but permanent rivers with considerable aquatic vegetation. In addition, there are over 200, mostly perennial, water bodies, of varying sizes, scattered within villages. The annual average temperature was 13.9-15°C, and the annual average precipitation was 731. 8mm. More than 63% of the precipitation is concentrated in June-September.
In 1970 a malaria outbreak in central China (including Henan province) drew the attention of multiple levels of the Chinese administration to the problem of malaria (Figure1) 7. A pilot study in Guantang was established in 1971 to study patterns of P. vivax transmission, and served as a demonstration project for large-scale comprehensive malaria control in central China. Investigations and research on the epidemiology and control of malaria were carried out until 1995 4.
Main control measures
From 1971 to 1995, the pilot site continually received special funds and implementation guidance from a professional malaria control team. Integrated control methods were implemented throughout the province. The standard control strategy was: 1) immediate treatment of diagnosed patients with 3 days chloroquine (day1: 600mg, day 2: 300mg and day 3: 300 mg) together with 5 or 8 days primaquine (150 mg for 5 days or 180 mg for 8 days) regimens or a 3-day-double-course therapy (chloroquine and primaquine base in divided doses); 2) in years with high incidence rates during the transmission season, mass prophylaxis with pyrimethamine was applied at the village level, while anti-malaria medication was applied in outbreak foci; 3) during the non-transmission seasons, patients with malaria infection history in the previous transmission season were treated to clear hypnozoites with different regimes at different time periods. Before mid-1970s, a regime of 8 days of primaquine (22.5mg per dose) and 2 days pyrimethamine (50mg per dose) was applied. After the mid-1970s, a regime of 3 days of chloroquine (day1: 600mg, day 2: 300mg and day 3: 300 mg) together with 5 or 8 days of primaquine (150 mg for 5 days or 180 mg for 8 days) was used. In the years with high incidence rates, a mass hypnozoite clearance program was implemented at village level; 4) Mass anti-mosquito campaigns were carried out annually. There was no unified anti-mosquito technique applied in the province4. Only community-based anti-mosquito campaigns were carried out, which was one of the country's biggest "four pests" - rats, flies, mosquitoes, and sparrows campaigns introduced by Mao Zedong aiming to eradicate the transmission of pestilence and diseases9. In a few places with appropriate budgets, such as Guangtang, larvicides, e.g. Hexachlorocyclohexane powder, were applied to water bodies to eliminate mosquito larval 4 10.
Malaria data collection
Malaria case reports: Confirmed malaria cases were reported at different levels of the surveillance system and hospitals. Due to institutional reforms, there is differing levels of available data over the period 1971-1995. Annual malaria case data of Guantang were available for each year from 1971 to 1995, while monthly data were only available from 1971-1984.
Febrile patients: Between 1979 and 1981, febrile patients with four classified groups, namely those presumptively diagnosed as malaria by symptoms, suspected malaria, unexplained fever or suspected cold, were verified by blood smears test, the gold standard for malaria cases11. Due to the typical fever pattern of P. vivax patient, a fever that recurs every second day 11, the fever pattern was used as one criteria for malaria vivax clinical diagnosis. The blood test results of four types of patients were counted and summarized.
Parasite rates of residents: Each year from 1971 to 1982 (except the year 1981) in the months of June and November, clustered sampling, such as school-, community-based sampling, accounting for 1 to 5% of whole township population, were carried out by blood smear test (finger-prick test) to check for malaria infection (Table 1). After 1983, this sampling investigation was discontinued due to low parasite rates and difficulty in collecting large amounts of blood samples.
Antibody survey: From 1978 to 1995 (with a few years omitted), the indirect fluorescent antibody (IFA) test12 was used to exam malaria antibody levels within randomly selected residents.
Malaria infection in neonates: From 1976 to 1981, infants born between November in previous year and October of the current year were required to undergo blood tests to identify any malaria infection if fever occurred during between beginning of the transmission season in June of the current year through to June next year (see Figure 4). Malaria infection rates for the year were calculated given the confirmed cases in this newborn infants’ cohort. Those who experienced symptoms during the transmission season from June to December were recorded as short-latency episodes, while those who experience symptoms from January the following year until the next transmission season were classified as long-latency episodes.
Entomological study of An. sinensis
Mosquitoes were trapped using a variety of methods, differing in trap location (indoor / outdoor), the host used as bait (human and/or cattle), time and duration (e.g. 2 hours after sunset / overnight (8pm-4am)). An. sinensis was the only malaria vector found in the pilot study area10. No other Anopheles mosquito species were detected.
Human and cattle outdoor trapping for 2 hours after sunset: For each year between 1971 and 1984, every 10 days during the transmission season from the beginning of June until the end of October, fixed-point outdoor mosquito landing collections were carried out in parallel on both human and cattle. The two mosquito traps were separated by 100 meters and mosquitoes were caught continuously for 2 hours after sunset.
Human indoor / outdoor overnight trapping: Once a month in the years 1976, 1977 and 1982, from June to September, indoor human mosquito landing collections were carried out from 8pm until 4 am and the number of mosquitoes was recorded. In addition, fixed-point outdoor human landing collections were conducted from 8pm until 4am every 10 days from June until the end of October in 1975 through to 1984.
Habitats of indoor resting mosquitoes: An. sinensis uses a wide range of resting places. Between 1971 and 1975, from May to October each year, female mosquitoes were caught by a person for 15 minutes inside various buildings, including bedrooms, cattle stalls, pig stalls, garages, other rooms, and brick kilns.
Blood-feeding behavior: In 1975 and 1978, newly blood-fed female mosquitos in different types of habitats in the wild were caught. Blood samples were tested by an electrophoresis antigen-antibody reaction to define blood-feeding hosts 13.
From June to September of 1975, female mosquitoes under the bridge Zhouqiao near Guantang village were captured to check blood-fed specimens. The stage of blood meal digestion within a mosquito was classified according to the Sella scale 4.
Vectorial capacity: Between 1975-1984, vectorial capacity (C) from June to September was estimated based on the Garrett-Jones’s original equation (1)14 by local malaria health workers:
Where m is the ratio of mosquitoes to humans; a: the rate at which mosquitoes bite humans (per day) biting rates ; n: the parasite's extrinsic incubation period (EIP, n days); and p is the mosquito survival through one day.