3491
Only 45 million cattle , of 172 million present in sub-Saharan Africa , are kept in tsetse-infested areas but are often forced into fragile ecosystems like highlands or the semiarid Sahel zone , which increases overgrazing and overuse of land for food production .
 location: sub-Saharan Africa; location: Sahel
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 location: sub-Saharan Africa; location: Sahel