Gorilla

Posted on behalf of Ian Redmond.

The risk of droplet infection with new viruses is of global concern with the spread of H1N1 swine ‘flu virus, so soon after the H5N1 bird ‘flu.  Measures already in place to minimise the risk of such transmission to habituated apes include refusing a visit to anyone showing symptoms, the ‘no closer than 7m rule’ and preventing tourists from leaving any foreign objects, litter or bodily fluids (unless buried deep) in the park.

Some sites have gone further and request that tourists wear surgical masks for the time spent near the apes.  We do not know the mortality rate that such viruses might cause if they were to spread through a gorilla group, and whilst any such loss would be a blow to a small population, it is likely that most infected animals would recover and there-after be immune to that strain of ‘flu. 

The ‘worst nightmare’ scenario for all involved with the Mountain Gorillas is the possibility of an Ebola outbreak in the Virungas or Bwindi; we know from Western Lowland Gorillas that Ebola kills ninety something per cent of those infected – approximately one third of the western gorilla population has been killed by Ebola in the past decade or so.  

The promising tourism site at Lossi in Congo Brazzaville suffered in this way when the habituated animals died of Ebola, and the evidence suggests that there is a front of outbreaks, moving northwards towards the region with the largest concentration of western gorillas (see animation by Peter Walsh, and YoG interview to follow). Ebola has not yet been reported in eastern gorilla populations, but during the Great Ape Health workshop in Uganda, August 21-23, I learned that there was a close call recently with the closely related Marburg virus.
 
A Dutch tourist fell ill a few days after returning from a holiday in Uganda last year, and sadly died. Tests in the Netherlands revealed that she had contracted Marburg, and when her itinerary was examined, virologists concluded that she had most likely picked up the virus whilst visiting the Python Cave in the Maramagambo Forest. 

This is a fantastic place for any naturalist – a collapsed lava tube with a roost of Rousette’s Tongue-clicking Fruit Bats and pythons that coil around the rocks on the cave wall to snatch bats out of the air as they pass. I have taken tours there myself, and then – just as this lady did – gone on to visit the gorillas in Bwindi.  The difference is that this poor unfortunate woman was unknowingly incubating Marburg haemorrhagic fever when she reportedly came within 5m of the gorillas (http://www.cdc.gov/eid/content/15/8/1171.htm).  

Neither Marburg nor Ebola can survive long out of the body, and fortunately, neither the gorillas nor any of the 130 or so people she came into contact with were infected. But this tragic case should act as a warning, and simple measures such as introducing disinfected boot dips and asking tour companies that plan to visit the caves, to do so after seeing the gorillas would further minimise the risk.

Cheers, Ian

Read Ian’s previous post here!