Effect of reduction of habitat
Diseases are another problem, especially in the Kruger National Park in South Africa. Since in 1995, a first fatal case of tuberculosis occurred among lions, extensive studies have been conducted in the park. According to the report, the infection rate of animals in the southern sector of the park by the deadly bacteria was more than 90%. The infection came from the buffalo hunted by lions, in contact with domestic cattle, have introduced the disease into the park and infected lions. About 70% of cattle suffering from pulmonary tuberculosis (phthisis), while among the lions, the disease occurs mainly in the digestive system. The animals become weaker, lose weight much and die within a few years. Besides tuberculosis, there is a second very common disease. Approximately 60-70% of the Kruger Park lions are infected with feline immunodeficiency virus, which "paralyze" the immune system of the animal and opens the way for tuberculosis. Exterminators against both viruses, there is no vaccination.

In 1994, one third of the lions of the Serengeti National Park have died after contracting the disease Carré against which they are very vulnerable.

Currently, lion populations are highly concentrated as contained in parks or reserves, other areas become unfit to survive by becoming farmland. The loss of genetic diversity leads to the appearance of disease as has been observed in the Hluhluwe-Umfolozi Game Reserve in South Africa, where lions present 120 in the 2000s down from 1960 three lions of years. But some biologists estimate that 500 to 1000 adult individuals genetic diversity necessary for a population of them to be considered viable, that is to say having the minimum of genetic diversity necessary to survie Few of these people fit this criterion. In 2007, these lion populations are not yet considered at-risk populations, although no study on this issue is undertaken. Unlike other species, no large-scale preventive transfer is made to reduce the risk of loss of genetic inheritance. However, to solve specific problems of the reserve of Hluhluwe-Umfolozi, artificial insemination attempts were made to avoid difficulties with social integration problems associated with introductions