Gorilla Health Threat:
Infectious Diseases

Due to the genetic similarity between humans and gorillas, gorillas are susceptible to many of the same infectious diseases that affect people. In the last 100 or so years, the gorillas have been exposed to an ever-growing number of humans with whom they share their forest homes. The parks where the mountain and Grauer’s gorillas live are surrounded by the densest human populations in continental Africa. While gorilla ecotourism ultimately helps conserve gorillas by providing the critical funding needed to protect and manage the national parks, it brings thousands of people from the local communities and from around the world into contact with mountain gorillas.

Through ranger-based monitoring and the veterinary team’s routine health checks, gorillas showing signs of respiratory disease—runny nose, coughing, lethargy—are flagged for more intensive observation. As in humans, typical respiratory illnesses usually start as a viral infection, which cannot be specifically treated with antimicrobial medicines. Most gorillas with viral respiratory disease recover on their own, but others deteriorate and develop secondary bacterial infections, causing even more severe respiratory disease, like bronchopneumonia, which can be fatal. Fortunately, bacterial infections can be treated if caught early enough.

When it becomes apparent that a gorilla has a severe respiratory infection and is not improving, the Gorilla Doctors will stage a medical intervention to dart the individual with antibiotics. Usually, a single darted injection of a powerful antibiotic such as ceftriaxone is enough to help most gorillas recover, but sometimes a second dose is required a few days after the first darting. In dire cases, the gorilla may be darted with an anesthetic drug so that the Gorilla Doctors can conduct a thorough physical examination, administer intravenous fluids and antimicrobials, and obtain diagnostic samples. During such interventions, samples are taken so that the exact cause of the disease can be identified. Knowing the precise cause of the infection helps inform the Gorilla Doctors’ medical decisions when dealing with future disease outbreaks. Samples are stored in a biobank for evaluation by researchers studying gorilla health issues.

Dr. Eddy prepares to dart a sick mountain gorilla in Virunga National Park with antibiotics.

Watch a video of the Gorilla Doctors darting a sick gorilla with antibiotics: Research* has shown that mountain gorillas can die as a result of contracting infections that originated in people. Second only to trauma (e.g. fatal injuries caused by fights, accidents or snares), infectious disease is the leading cause of death in mountain gorillas, accounting for more than 20% of mortality. The most common infectious disease in mountain gorillas is respiratory disease, which can range from a mild cold to severe pneumonia, in individuals or in whole groups.*Emerging Infectious Diseases 2011, 17(4): 711-713

Gorilla Health Threat:

Rope and wire snares set by poachers in the national parks pose a great threat to the gorillas. In general, poachers set snares to catch antelope and other forest animals in order to feed their families. The land surrounding mountain gorilla habitat is some of the most densely populated in Africa, and most of the population is extremely poor. The pressure for food is enormous and some people turn to poaching to survive.

Unfortunately, gorillas, especially infants and juveniles, sometimes get caught in these snares. Gorillas may lose limbs or digits to snares, or die as a result of infection or strangulation.

A rope snare wrapped tightly around juvenile gorilla Buchura’s hand, causing swelling and damage to the tissue.

When a gorilla is reported with a snare, the Gorilla Doctors make plans to intervene as soon as possible. An intervention team comprised of several veterinarians, national park staff members, and trackers and porters hike to find the ensnared gorilla and make an evaluation of the situation. In order for the team to safely approach the animal and treat its wound, the gorilla must be darted with an anesthetic drug. The Gorilla Doctors carefully prepare the amount of anesthesia needed to anesthetize the gorilla based on its estimated weight. The gorilla is darted with the drug using a compressed-CO2 dart projector.

Chemically immobilizing an ensnared gorilla can be complicated. If the affected gorilla is young and being carried by its mother, the mother must also be darted because she will not willingly give her up baby otherwise. The mother and baby must be darted simultaneously with two different dart guns, so it is challenging to find an opportunity to safely dart both. Whether darting one or two animals, it is necessary for the veterinarian doing the darting to hide behind two trackers so that the gorillas do not see the dart gun. The gorillas recognize guns and quickly flee if they spot one.

All veterinary care for wild human-habituated gorillas is delivered in the forest; gorillas are not removed from the wild, even temporarily, in order to facilitate treatment.

Watch a video of the Gorilla Doctors rescuing a baby gorilla from a snare: Once an animal is successfully darted, the veterinary team quickly moves in to remove the snare and treat the wounds. If the snare is tight around the gorilla’s limb the veterinarians may give the animal a steroid injection to prevent the toxins that have built up in the limb from making the gorilla sick when the snare is removed and circulation is restored. Wounds from the snare are cleaned and stitched if necessary, and the gorilla is given an antibiotic injection to help with the healing.

Gorilla Health Threat:
Human-Gorilla Conflict

Because the national parks where gorillas live directly border human settlements, interactions between gorillas and people are unavoidable. Gorillas sometimes leave the parks to raid crops and people sometimes enter the parks illegally to obtain resources such as firewood. The conflict between farmers and gorillas over crop-raiding, and the conflict between people illegally seeking park resources and the park authorities and conservationists, has resulted in gorilla deaths. Several of the gorillas Dian Fossey studied were killed, including her favorite gorilla, Digit. Fossey suspected the gorillas were killed by poachers as revenge for her attempts to stop their activities in the national park, but this has never been proven.

In June and July of 2007, seven mountain gorillas were killed in Virunga National Park in DRC. Evidence suggests the gorillas were executed because of park rangers’ efforts to stop illegal logging and charcoal production in the park. The Gorilla Doctors performed necropsies on the gorillas and worked with Virunga National Park rangers to save two female infants that were orphaned by the attacks, Ndakasi and Ndeze. Ndakasi was rescued in June by Virunga National Park Gorilla Caretaker Andre Bauma, who brought the orphan to the Gorilla Doctors for treatment. In July, five members of the Rugendo family were killed, including the silverback Senkwekwe and female Safari, the parents of Ndeze. Ndeze was saved by the blackback Mukunda, who carried her to safety. Because Ndeze needed milk to survive, the Gorilla Doctors darted Mukunda with anesthesia so they could take Ndeze and put her into Andre’s care with Ndakasi.

Grauer’s gorilla silverback Chimanuka crosses a road that cuts through Kahuzi Biega National Park, DRC.

Watch the video of Mukunda’s intervention in July 2010: Mukunda, now a lone silverback, has had frequent run-ins with people. Mukunda has attacked several people—always men wearing uniforms—in both DRC and Rwanda. In two other instances, he walked many miles outside of the forest and boldly entered villages with hundreds of people. Despite the chaos that erupted around him, Mukunda stayed in each location for days, eating crops and even visited the food market. In both cases, the Gorilla Doctors, with the help of Virunga National Park rangers, darted Mukunda with anesthesia and transported him back to the national park. In May 2011 Mukunda again traveled far outside of the park, but this time he turned around and walked back to the forest on his own when he saw the Gorilla Doctors approaching him. Happily, since the last incident, Mukunda has stayed well inside of the park and out of trouble.

Gorilla Health Threat:
Gorilla-Inflicted Trauma

Physical injury or trauma is the leading cause of death in mountain gorillas. Trauma can be human-induced (such as injuries caused by snares), the result of accidents, or caused by other gorillas. When taking over a group or acquiring new females, silverbacks sometimes commit infanticide on the other male’s infants, so that their mothers will start reproductively cycling again, enabling the new males to father their own offspring with the females. Silverbacks and blackbacks, with their long, sharp canine teeth, can inflict serious injuries when fighting with each other for dominance. Occasionally, adult females and youngsters get caught in the middle of fights and are injured.

While infanticide and fighting are natural occurrences in the gorilla population, the Gorilla Doctors will sometimes intervene to save individuals suffering from life-threatening injuries. Geneticists believe that because the mountain gorilla population is so small and genetic diversity is vital to the species’ survival, that individual gorillas contributing to the gene pool warrant life-saving veterinary care. The conservation personnel including the veterinarian team never step in to stop infanticide or violence as it is happening, since it is a natural behavior. However, the team may choose to intervene if the veterinarians and host government feel it is in the best interest of the population and/or the individual and the gorilla appears to have a chance at recovery with medical help.

For example, the Gorilla Doctors intervene in the case of badly injured breeding-age females. Unlike males, which may never succeed in leading their own family, almost all healthy adult females will have the opportunity to produce additional offspring. For this reason, the veterinary team performed multiple interventions on the adult female Samehe from Nkuringo group in Uganda’s Bwindi Impenetrable National Park recently, who suffered a serious head wound. Sadly, she succumbed to an infection. The Gorilla Doctors have also intervened in several instances when youngsters were injured.

Mountain gorilla silverback Getty, injured during an interaction with Susa group in Volcanoes National Park, Rwanda.

The decision to intervene when a silverback is injured is more difficult. Silverbacks fight to maintain dominance in a group or to take over the position of another silverback. Biologically, it is healthy for different silverbacks to introduce new genetics into a gorilla group, but the babies of the usurped silverback may be killed when a new male takes over. Thus far, the Gorilla Doctors have not performed any full interventions (meaning the gorilla is anesthetized so that veterinarians can provide hands-on care) on badly injured silverbacks. However, the veterinary team has darted wounded silverbacks with antibiotics and anti-inflammatory drugs to prevent infection and aid the healing process.

Our veterinary team continues to examine and debate the complicated issue of intervening to save gorillas suffering from wounds inflicted by other gorillas. We look forward to the day when the mountain gorilla population is large enough that there is no longer the need to intervene.