Kruger’s Lion Unaffected By Bovine TB

By Lauren Smit

Concern has been rising for some time over the prevalence and impact of bovine tuberculosis (BTb) on Kruger’s buffalo and more recently, lion populations. Yet, recent research findings fly in the face of speculation that BTb is ravishing the park’s iconic lion. In fact, in this world-renowned protected area, the population have been stable for roughly 30 years.

Thought to have been introduced into the park via co-grazing between cattle and buffalo in the far south near Crocodile River during the 1960’s, BTb wasn’t actually detected in lion until the 1990’s.
This chronic disease has been travelling north ever since its introduction to the park and has been found in a range of species, including; lion, leopard, cheetah, kudu and baboon, although buffalo are the primary host. SANParks’ disease ecologist Danny Govender said that buffalo play the primary roll in disease transmission. 

Lion mainly come into contact with BTb via the kills they make, and the disease has been known to manifest itself not only in the lungs but also in the gastro-intestinal system. Eerosol, gastro-intestinal and bites and scratches are all viable routes for BTb infection.

“In their lifetime, they’re not just infected once-off. They get multiple infections and also have different forms of infection. Even though they are feeding on a buffalo carcass, they are not just ingesting, they are breathing in,” said Govender.

In 2005 and 2006, SANParks large mammal ecologist, Dr Sam Ferreira and Tshwane University of Technology’s Prof Paul Funston used call-up stations (speakers which project the sound of a buffalo calf in distress for kilometres around) to estimate lion numbers, sex and age structure. Using this data, they evaluated the impacts of BTb on lion densities across the park and their respective survival rates.
Their findings completely contradicted pre-study estimates and have flown in the face of speculation that BTb is ravishing the lion population.

“There were only two locations where lion estimates were done before, one was in the central region of the park and the other at Lower Sabie,” said  Ferreira.

“when we compiled all the data, we could actually illustrate that they have been stable for roughly 30 years.

“Its very hard for us to find any evidence that BTb is having an effect on them.”

Their results indicate that BTb was having no observed effect on the age at which females have their first cubs, the interval between births or on the litter size. These findings raised the question of why chronic introduced disease such as BTb can be present in the Kruger’ Lion and buffalo and yet not be devastating to either population.

As fate would have it, it has slow disease dynamics ( far slower than its host dynamics) meaning that by the time an infected animal has died, that individual has already performed its key role (such as breeding) in the herd or pride. So, while researchers are seeing impacts the individual level, Kruger’s lion and buffalo populations are apparently not being affected.

The robust lion population has been stable at around 1700 individuals for the past 30 years. This has helped minimise the effects of BTb. Small or already weakened groups would have fared much worse. An abundance of prey biomass and good environmental conditions have also cushioned the impact of the disease in the park’s southern lion prides.

However, if a drought or combination of other disease such as canine distemper or feline immune-deficiency virus (FIV) are added to the mix, a different reaction and more substantial impact might be observed.

In 2009 and 2010. SANParks started an extensive lion-capture and –collaring programme to monitor individuals and their life history.

At the conclusion of the study, these findings will reveal intimate statistics of about 30 prides in Kruger and any possible impact that diseases like BTb might have on them as time and environmental conditions progress.