[Investigation on anopheline species in Chayu County, Linzhi Prefecture of Tibet Autonomous Region].

OBJECTIVE: To investigate Anopheline species in Chayu County of Linzhi Prefecture, Tibet. METHODS: Four natural villages in Chayu County were selected in this study in 2010. The methods of overnight/semi-overnight trapping indoor and outdoor human-bait, and overnight trapping with light traps were used, and all the Anopheline mosquitoes were confirmed by morphological characteristics. RESULTS: Totally 2 991 Anopheline mosquitoes were captured, with 76.36% (2 284/2 291) of An. peditaeniatus, 22.30% (667/2 291) of An. maculates group. The average densities of An. peditaeniatus by semi-overnight trapping were 56.2/per person indoor and 4/per person outdoor respectively, and the average densities of An. maculatus group by semi-overnight trapping were 17.8/per person indoor and 17.9/per person outdoor respectively. The man-biting rates of An. peditaeniatus by overnight trapping were 28.1/per person indoor and 2/per person outdoor respectively, and were both 8.9/per person to An. maculatus group. CONCLUSION: An. peditaeniatus and An. maculatus group are the possible transmission vectors of malaria in Chayu County.

[Application of Susceptible-Infected-Recovered model in dealing with an outbreak of acute hemorrhagic conjunctivitis on one school campus].

To simulate intervention measures in controlling an outbreak of acute hemorrhagic conjunctivitis on one school campus by using the Susceptible-Infected-Recovered (SIR) model, to provide evidence for preparedness and response to the epidemic. Classical SIR model was used to model the epidemic. Malthusian exponential decline method was employed to estimate the infective coefficient ß for interventions. The initial value of parameters was determined based on empirical data. The modeling was implemented using Matlab 7.1 software. Without interventions, the outbreak was expected to experience three phrases: (1) early stage (the first 5 days) in which the epidemic developed slowly and could be intervened easily; (2) rapid growing stage (6 - 15 days) in which the number of infected cases increased quickly and the epidemic could not be well controlled; and (3) medium and late stage (16 days and later) in which more than 90% of the susceptible persons were infected but the intervention measures failed to prevent the epidemic. With the implementation of interventions, the epidemic was predicted to be controlled in the early stage, under the SIR model. The simulation based on the SIR model kept an acceptable consistency with the actual development of epidemic after the implementation of intervention measures. The SIR model seemed effective in modeling interventions to the epidemic of acute hemorrhagic conjunctivitis in the schools.

[An epidemiological analysis on malaria in Linzhi district of Tibet in 1986-2004].

OBJECTIVE: To investigate the epidemiological characters of malaria in Linzhi district of Tibet. METHODS: A retrospective analysis on the epidemiology of malaria was carried out using the data on malaria situation in Linzhi district of Tibet in 1986-2004, referring to the distribution of season, population and region. RESULTS: The accumulative number of malaria cases in the period of 1986-2004 was 2459. The annual incidence of malaria in the district was reduced from 2.44 per ten thousand in 1986 to 1.03 per ten thousand in 2004, declined by 57.8% in 17 years. 99.3% of the cases were reported from Motuo County which was a typical high endemic area of malaria. The peak of prevalence occurred in June-October and 66.7% of the total cases were in the age group of 15-59 years old. 81.0% of the cases were farmers and 90.0% were Menba nationality. CONCLUSION: Motuo County has been the major area of malaria endemic in Linzhi district of Tibet. Most malaria cases in other counties are imported from Motuo.