Analysis of temporal trends of human brucellosis between 2013 and 2018 in Yazd Province, Iran to predict future trends in incidence: A time-series study using ARIMA model

Objective:To determine the temporal patterns of cumulative incidence of brucellosis using autoregressive integrated moving average models.Methods:This cross-sectional study employed yearly and monthly data of 1117 laboratory-confirmed human brucellosis cases from January 2013 to December 2018 using the Yazd brucellosis national surveillance system.The monthly incidences constructed a timeseries model.The trend of cumulative incidence was perceived by tracing a line plot,which displayed a seasonal trend with periodicity.Thus,the ARIMA models were selected.Thereafter,Akaike information criteria(AIC)and Bayesian information criterion(BIC)values among different models indicated a preferable model from models which were expanded by diverse lags[(3,0,3),(2,0,3),(3,0,2),(4,0,3)and(3,0,4)].Then,the achieved ARIMA model was applied to the forecasting cumulative incidence of monthly brucellosis incidences.All analyses were performed using Stata,version 11.2.Results:For the ARIMA(3,0,4)model,MAPE value was 56.20%with standard error 0.009–0.016,and white noise diagnostic check(Q=19.79,P=0.975)for the residuals of the selected model showed that the data were completely modelled.The monthly incidences that were fitted by the ARIMA(3,0,4)model,with AIC(25.7)and BIC(43.35)with a similar pattern of actual cases from 2013 to 2018 and forecasting incidences from January 2019 to December 2019 were,respectively,0.50,0.44,0.45,0.49,0.55,0.58,0.56,0.51,0.46,0.44,0.45 and 0.49 per 100000 people.Conclusions:In summary,the study showed that the ARIMA(3,0,4)model can be applied to forecast human brucellosis patterns in Yazd province,supplementing present surveillance systems,and may be better for health policy-makers and planners.

Phenology and population dynamics of sand flies in a new focus of visceral leishmaniasis in Eastern Azarbaijan Province,North western of Iran

Objective:To investigate species composition,density,accumulated degree-day and diversity of sand flies during April to October 2010 in Azarshahr district,a new focus of visceral leishmaniasis in north western Iran.Methods:Sand flies were collected using sticky traps biweekly and were stored in 96%ethanol.All specimens were mounted in Puri’s medium for species identification using valid keys of sandflies.The density was calculated by the formula: number of specimens/m of sticky traps and number of specimens/ number of traps.Degree-day was calculated as follows:(Maximum temperature + Minimum temperature)/2—Minimum threshold.Diversity indices of the collected sand flies within different villages were estimated by the Shannon- weaver formula(H’=sum form(i=1) to s Pi log_e Pi ).Results:Totally 5 557 specimens comprising 16 Species(14 Phlebotomus,and 2 Sergentomyia) were indentified.The activity of the species extended from April to October.Common sand-flies in resting places were Phlebotomus papatasi, Phlebotomus sergenti and Phlebotomus mongolensis.The monthly average density was 37.6.41.1, 40.23,30.38 and 30.67 for Almalodash,Jaragil,Segaiesh,Amirdizaj and Germezgol villages, respectively.Accumulated degree-day from early January to late May was approximately 289 degree days.The minimum threshold temperature for calculating of accumulated degree-day was 17.32℃.According on the Shannon-weaver(H’),diversity of sand flies within area study were estimated as 0.917,1.867,1.339,1.673,and 1.562 in Almalodash,Jaragil,Segaiesh,Amirdizaj and Germezgol villages,respectively.Conclusions:This study is the first detailed research in terms of species composition,density,accumulated degree-day and diversity of sand flies in an endemic focus of visceral leishamaniasis in Azarshahr district.The population dynamics of sand flies in Azarshahr district were greatly affected by climatic factors.According to this study the highest activity of the collected sand fly species occurs at the teritary week of August.It could help health authorities to predicate period of maximum risk of visceral leishamaniasis transmission and implement control program.