When looking at table 1, it is possible to see that Africa, South America and South Asia all have fairly similar environments; they all have a large difference in temperature, have varying relief and rainfall. They are all tropical countries with the same climate (although in varying proportions) and they have all had an epidemic of leprosy. Is this due to their similar physical environments? (See figures 3 and 4).
As shown by figures 3 and 4, the different climates of the three countries do not match the differing leprosy rates. In Africa (point 1) it is possible to see that it has a tropical wet climate yet has a differing leprosy rate from 0 to above 5 in that small region alone. At point two in South Asia, it is possible to see that the climate is again tropical wet and the leprosy rate is 0. If this is compared to point 3 in South America, the climate is also tropical wet but the leprosy rate is very high (above five in every 10,000 of the population). From this it is possible to deduct that it is not specifically the physical environment which affects the spread of leprosy.
Sudan is a country in Africa. It has a population of 28,311,000 and its gross national product is US$420 which makes it one of the poorest places in the world. Leprosy is endemic in several places in Sudan.
Figure 5, Map of Sudan
One of the states in Sudan is the Gedarif State. The climate of the state is semiarid. The villages of Um Salala (population 1200) and Koka (population 1100) are home to two tribes; the Masalit and the Hawsa tribes. The two villages are within four miles of each other. The Masalit are laborers and subsistence farmers whereas the inhabitants of Koka village are farmers, fisherman and traders. Malaria, visceral leishmaniasis and leprosy are the most prevalent infections in Um Salala. In Koka, malaria and visceral leishmaniasis are much less common than in Um Salala. The total number of leprosy cases in December 1995 in Um Salala was 22, and in Koka it was 4. How can the leprosy numbers be so different when the physical environment is the same if the spread of leprosy is really dependant on the physical environment?
The Hawsa have a better standard of living and a higher level of nutrition than the Masalit. The Masalit live in grass huts under conditions of poor hygiene. As this is the only difference between the two villages, this suggests that it is not the physical environment which affects the spread of leprosy as both villages have the same climate and terrain but possibly is the standard of living and education on the prevention of disease which affect the spread.
Five countries with the highest leprosy rates are all found in South Asia, South America and Africa. Over 83% of all leprosy cases are registered in these countries.
Table 2, Physical environment of chosen countries
Table 2 shows that these countries all have varying terrains, most have plains but also have mountains, highlands, deserts and plateaus. They all have a very similar climate with a fairly high annual rainfall. All these countries have a tropical climate. As all of them have very similar physical environments this could show that it does have an effect on the spread of leprosy. However when looking at map C it is possible to see that Nepal, Madagascar, India and Myanmar are all very poor countries with a GNP of less than US$500.
The Gross National Product (GNP) is the total output of goods and services in an economy. It is used to rank countries as rich, poor, developed or developing. The basis of the indicator is the amount of services which people use; the more they use, the better off they are.
Figure 7 shows that Brazil is the only country out of the five most leprosy stricken countries in the world to have a GNP of US$1,800 – 4,100. This could be because although the poor are very poor and living in favelas, the rich are very rich and this increases the countries GNP. 46m out of 170m people in Brazil live on less than one dollar a day. Some areas are occasionally hit by drought and Rich European Nationals and Japanese move there which also increases Brazil’s GNP.
Figure 6 implies that leprosy is related to standard of living. If leprosy is related to standard of living then this could mean that leprosy declines with rising living standards and this probably relates to lots of different factors such as overcrowding, hygiene, nutrition, lack of an education and cleanliness.
Leprosy has been a particularly interesting disease to cover in this context as the transmission of it not only relates to the physical environment but on other factors as well. Obviously the presence of the leprosy bacillus in the environment is essential for infection, but other factors such as environmental factors like overcrowding due to inadequate housing which leads to more frequent contact with the source of infection which may further the spread of leprosy.
The physical environment does not play a big role in the spread of leprosy. When looking at Map A at Africa, it is possible to see that the leprosy rate changes from 0 to above 5000 in an area with the same physical environment; this is supported by the leprosy rates of the Hawsa and Masalit tribes who also have differing leprosy rates in the same environment.
The spread of leprosy however, maybe indirectly related to the physical environment, for example, in Northern India the terrain is mountainous so there maybe clusters of leprosy sufferers where medical workers cannot reach. Another way leprosy could be seen to be indirectly related to the physical environment is by GNP. If the climate is hot, there is little rainfall or if terrain is mountainous then GNP will be low. GNP is low because it is hard to grow crops, places are very inaccessible or natural hazards like drought will occur. In turn, a low GNP means lack of an education on how to prevent disease, not being able to afford vaccinations (leprosy is cured by a drug called ‘di – amino di – phenyl’), or shortage of proper housing, adequate food and drink to have a nutritious diet. This means that countries with a low GNP and a particular physical environment are much more prone to leprosy than those without. This particular environment is hot, humid and with difficult terrain. This is shown by the Africa, South Asia and South America case studies. The case study of the two tribes in Sudan and their differing leprosy rates show that leprosy is controlled by methods of simple hygiene or normal methods of cleanliness. This means that it is more GNP then the physical environment which affects leprosy spread. Countries like the USA, UK and Italy have no leprosy cases and they have some of the highest GNPs in the world. South Africa is the richest country in Africa and it is one of the few countries in Africa which have little or no leprosy.
The fact that leprosy used to be common worldwide but is now just centered in the tropics where poor living standards exist suggests that it is a disease of filth and low living standards and that with economic development, the availability of soap and water and the elimination of overcrowding, leprosy would disappear. The exact mode of transmission has been unknown for 130 years and is still unknown. This is because leprosy is the most complex of all the human bacterial diseases.
Taken from ‘Time - intergrative Geographic Information Systems’ written by T Ott and F Swiaczny