Prediction of malaria cases in the southeastern Iran using climatic variables:An 18-year SARIMA time series analysis

Objective:To predict future trends in the incidence of malaria cases in the southeast of Iran as the most important area of malaria using Seasonal Autoregressive Integrated Moving Average(SARIMA)model,and to check the effect of meteorological variables on the disease incidence.Methods:SARIMA method was applied to fit a model on malaria incidence from April 2001 to March 2018 in Sistan and Baluchistan province in southeastern Iran.Climatic variables such as temperature,rainfall,rainy days,humidity,sunny hours and wind speed were also included in the multivariable model as covariates.Then,the best fitted model was adopted to predict the number of malaria cases for the next 12 months.Results:The best-fitted univariate model for the prediction of malaria in the southeast of Iran was SARIMA(1,0,0)(1,1,1)12[Akaike Information Criterion(AIC)=307.4,validation root mean square error(RMSE)=0.43].The occurrence of malaria in a given month was mostly related to the number of cases occurring in the previous 1(p=1)and 12(P=1)months.The inverse number of rainy days with 8-month lag(β=0.3292)and temperature with 3-month lag(β=-0.0026)were the best predictors that could improve the predictive performance of the univariate model.Finally,SARIMA(1,0,0)(1,1,1)12 including mean temperature with a 3-month lag(validation RMSE=0.414)was selected as the final multivariable model.Conclusions:The number of malaria cases in a given month can be predicted by the number of cases in the prior 1 and 12 months.The number of rainy days with an 8-month lag and temperature with a 3-month lag can improve the predictive power of the model.

Preparation and evaluation of a glycerol-preserved direct agglutination antigen for long-term preservation:a comparative study of the detection of anti-Leishmania infantum antibodies in human and dog

Objective:To prepare and evaluate a glycerol-preserved antigen from an Iranian strain of Leishmania infantum(L infantum) for use in glycerol-preserved direct agglutination tests (GP-DAT) as an alternative to freeze dried direct agglutination teals(FD-DAT) that use freezedried antigen.Methods:Glycerol-preserved DAT antigen was prepared and stored at different temperatures.We tested antigen stored at 4℃,22-37℃and 50℃over a period of 365 days. Seven hundred twenty-nine serum samples were collected from different geographical zones of Iran from 2007-2009,and 80 of these samples were pooled to produce sera.Each pooled serum contained 10 sera.All positive and negative pooled sera were separately tested for anti-L. infantum antibodies with GP-DAT,FD-DAT and formaldehyde-fixed direct agglutination test (FF-DAT) antigens;tests were performed on both human and dog sera over a period of 12 months. Results:There was strong agreement between the results obtained using GP-DAT and FDDAT antigens stored at 22-37℃for 12 months for both human(100%) and dog(100%) pooled sera.The direct agglutination test results were highly reproducible(weighted kappa:GP=0.833, FD=0.979 and FF=0.917).Conclusions:Because GP-DAT antigen is highly stable over a range of temperatures and is easy to transport in the field,this type of antigen may be particularly useful in areas with endemic visceral leishmaniasis.