Practical Manual - Malareo

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<strong>Practical</strong> 7 Mapping Malaria Outline Introduction Managing Disease Data Incidence vs Prevalence Thematic Mapping of Prevalence Interpolation of Prevalence Introduction Malaria is a vector borne disease, and is one of the largest killers in Africa. It is carried by the anopheles mosquito which is mobile. While their lifespan is limited and their flight ranges limited the sheer number of mosquitoes make a significant impact. While mosquitoes feed primarily on nectar, they require the iron and protein from blood in order to procreate. The Female transmits the malaria virus when she inserts her proboscis through the skin and injects an anti-coagulant into the victim to allow her to suck blood from the bite site. In order to target and combat Malaria, one needs to identify where the disease is located. The distribution of Malaria changes with time, primarily due to the presence or absence of mosquitoes. Hence in winter (Drier months) there is less malaria due to fewer mosquitoes. Therefore to adequately map the disease an understanding of the presence of the vector is required. The most common means of identifying where the highest prevalence of malaria is located is obtained from medical records where cases of malaria are treated. This can locate where the case was contracted, giving a general area where the disease is commonly found GIS is a useful means of mapping the presence and absence of a disease. The study of diseases is known as epidemiology. There are numerous methods of determining risk and distribution of disease You will look at a number of statistically based methods to show where malaria is located. John Snow is widely regarded as the father of Epidemiology, when he used the presence of cholera cases to pinpoint the source of the infection in London, tying it to dirty water from a pump. In essence you will be undertaking a similar exercise. QGIS for Malaria Page 56
In this practical you will undertake a number of mapping techniques to show the distribution of Malaria in KwaZulu-Natal Similar to what John Snow did in London. The principles learnt will apply in any environment or country. Managing Disease Data Before working with spatial and attribute data it is essential to understand where the dat comes from and what each attribute refers to. The main data you will be using is the malaria_case- Health_facility.shp file. This file list the number of malaria cases that could be traced back to a location after treatment in a health facility. A patient arrives at king Edward Hospital in Durban with malaria. If the individual has not travelled outside of their normal residential area the case can be attributed to a source within close proximity to his / her residence. How these sources are determined is usually linked to the size of the major settlements within each administrative area or the spatial closeness of settlements In the case of the data you will be using the nearest points to reported occurrences. These are places or settlements. The data contains numerous columns Oid_1 = Object ID (Auto Number for a spatial point) NOTIAREA = Notification area (The area which patient stated as their area of residence.) NOTIDISTMA = Notified Magisterial District SUMOF99_ to 08_ = The total sum of cases in each year falling within the NOTIAREA CORR_LOC_N = Corrected location LATITUDE = latitude of the place of residence LONGITUDE = longitude of the place of residence CODE = Code corresponding to the malaria area MAL_AREA = The name of the Malaria area POP01 = Population in 2001 HOMESTEADS = The number of homesteads in the Malaria area POP05 = the population extracted from the Census data in 2005. Data was extracted based on the location of the residence point falling within a Census area. QGIS for Malaria Page 57
Page 1 and 2:
Introduction to Geographic Informat
Page 3 and 4:
occurrences you can gain a better u
Page 5 and 6: Once in the folder, using your mous
Page 7 and 8: Map Legend You now have 2 layers lo
Page 9 and 10: Select the Identify features tool a
Page 11 and 12: 30% release it and click on Apply a
Page 13 and 14: It is important to note that althou
Page 15 and 16: Open your Identify features and exa
Page 17 and 18: Acquiring Spatial Data There are nu
Page 19 and 20: This adds the shapefile to the lege
Page 21 and 22: You will be creating a layer using
Page 23 and 24: This opens a co-ordinate reference
Page 25 and 26: Next you will create a line layer (
Page 27 and 28: Continue digitising the other roads
Page 29 and 30: If you are interested in seeing the
Page 31 and 32: PROJECT COORDINATE REFERENCE SYSTEM
Page 33 and 34: Task 1: Changing the Default CRS in
Page 35 and 36: Practical 5 Tabular Data Queries Ou
Page 37 and 38: ecords. Switching and clearing yo
Page 39 and 40: Practical 6 Spatial Analysis Outlin
Page 41 and 42: Task 1: Open a new QGIS project. A
Page 43 and 44: In order to make measurements in un
Page 45 and 46: Now to measure along the length of
Page 47 and 48: Buffer and Dissolve Buffer: Often i
Page 49 and 50: Open the Attribute Table for the Pr
Page 51 and 52: The result window shows the number
Page 53 and 54: Task 5: Slope Analysis Open a new
Page 55: Active Layers in the TOC Mathematic
Page 59 and 60: 1999 (which was year 1 of the 10 ye
Page 61 and 62: updated with percentages of prevale
Page 63 and 64: Click on Set to current extent Leav
Page 65 and 66: Practical 8 Summary Practical Outli
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Practical Manual - Malareo

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