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Reverse migration is one of the main flows of rural-urban linkages. This flow is formed by some pushing forces in cities, such as high living costs and air pollution, as well as some pulling factors in rural areas, such as low living costs, pleasant weather, and the opportunity to spend leisure time. It also has various effects on both the origin and the destination of the migration. The purpose of this paper is to analyze the status of reverse migration in terms of both spatial and temporal dimensions. This research is applied research and in terms of the method is exploratory, descriptive and analytical. The data used in this research has been obtained from the Statistical Centre of Iran and has been analyzed during two 5-year periods: 2006-2011 and 2011-2016. Data analysis was performed using spatial statistics techniques in the Arc Map software environment. Research findings at the national level show a relative decrease in reverse migration over five years from 2011 to 2016. At the provincial level, 28 provinces of Iran have experienced negative growth and a relative decrease in reverse migration, and only 3 provinces have experienced positive growth. Findings from spatial analysis at the county level of Iran also show the spatial concentration of a large number of reverse migrations around the two metropolises of Tehran and Mashhad. Also, high values of the ratio of reverse migration to the total number of immigrants are concentrated in the central and northern regions of Iran. [ABSTRACT FROM AUTHOR]

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Background: Dictyocaulus Viviparus nematode is the cause of severe bronchitis in dairy animals which lead to significant economic losses in the industry of this type of livestock. The present study aimed to determine the incidence of D. viviparous, a highly endemic parasite in cattle and water buffaloes in Guilan province, Iran. Materials & Methods: Stool samples from 212 cows and 189 buffaloes were tested using the Baermann technique. After slaughtering the animals, the lungs of all cows and buffaloes were isolated, sampled and carefully studied to determine D. viviparus in the lungs. Results: In general, there was a significant difference in the prevalence of D. viviparus in the fecal samples of cows (22.64%) and buffaloes (26.32%). Macroscopic study revealed symptoms of severe pneumonia, nodular lesions, and hyperemia in lung tissues of 5 cows and 5 buffaloes. Microscopic (histopathological) studies showed lymphocytic bronchiolitis and multifocal eosinophilic with wide interalveolar walls in lungs infected with D. viviparus. Conclusion: The prevalence of this parasite among cattle and buffaloes were 22.64% and 26.32%, respectively; but the difference between these two animal species was not significant. Overall, the prevalence of D. viviparus was higher among young animals in both species. [ABSTRACT FROM AUTHOR]