Elisabeth called me with worrisome news: "The chief has a small cough, and four others." She'd just returned from Kwitonda Group, a family of 19 mountain gorillas. My brain didn't want to accept the information. If Kwitonda and his group had come down with respiratory disease, it would bring the total to four groups in four months (in Rwanda). Yikes.
Kwitonda's home range overlaps with two of the other three groups, Hirwa and Group 13, so it made sense that the disease had spread again, either gorilla to gorilla or people visiting gorillas to gorillas. Those people, by the way, include all of us who visit the park — vets, trackers, guides, researchers and tourists.
Eilsabeth added, "It's not bad. All the gorillas are moving, eating, and the babies are playing."
Kwitonda Group's Ndimubanzi
After I hung up the phone, the long list of unanswered questions about the origin and spread of respiratory disease in mountain gorillas ran through my head. We've also recently discussed these same questions here in Rwanda with park (ORTPN) and researcher (Karisoke) staff in various meetings.
Are we reintroducing these viruses each year, or are they just moving around? (All evidence suggests that viruses cause the disease, but we cannot entirely rule out bacteria.)
How did they get into the gorillas — was it someone visiting from another country or living locally? Was it a one-hour visit (i.e., a tourist or park guide or vet) or a long close-up encounter (i.e., a researcher or park tracker)?
Have the weather patterns been different, with cooler drier nights that favor the spread of most respiratory viruses? Could one infection have spread from the Susa gorillas, which live on Karisimbe volcano, all the way over to the Hiwra, Group 13 and Kwitonda gorillas, which live on Sabinyo?
And how would it have spread — via gorilla movements (there are wild gorillas in the region) or people? Or, is it being reintroduced in each place as the result of a bad "flu" or "grippe" season that is spreading among the local community?
Kwitonda Group's Umoja
In the last instance, the source of the infection would be people living close to the park, but where did those people get the disease? They could have picked up the infection from a visiting tourist, but most people who come to see the gorillas stay in the region for only a day or two. These folks are not likely to be spreading the disease.
Respiratory disease and pneumonia among the poor and malnourished are well-documented problems in developing countries. Are they the source of the illness in the gorillas, given that park staff live in the local community? This question feels as if it's been burning a hole in my head these days. We need to better understand the health of the people around the park, both for their sake and the gorillas'.
Kwitonda Group's Karibu
The other confusing thing about respiratory disease in habituated mountain gorillas (there have been cases in Uganda, too, so it's not just Rwanda) is that there are some differences when compared to habituated chimpanzees.
Outbreaks of illness with runny noses, coughs, fever, secondary pneumonia and deaths have been recently documented in chimps. Chimps get sicker and die more quickly than mountain gorillas, which means there are a lot more samples to analyze.
It's hard to make conclusions from lots of gorillas that are sick but recovering, and hard to say we should be intervening more often to get samples when the mortality of respiratory disease is low, and, equally important, is not new. This may be a bad year, but the historical record shows gorillas have had similar outbreaks for two decades.
Ururabo's baby has recovered from a severe bout
with respiratory illness.
For example, it's difficult to make any sort of definitive diagnosis or to isolate a virus from nose and throat swabs taken from one or two individual mountain gorillas. Though we have samples from Ururabo and her infant in Susa Group, and from Muninya in Hirwa Group, and we're trying to identify the source of the illness, we don't have any clear answers yet.
Similarly, a single blood sample from a sick gorilla — or human — may show a high antibody level, or titer, to a particular virus, such as influenza, but that result proves only that the individual has been exposed recently. We need a second blood sample two to three weeks later to document active infection. These sampling challenges are the reason we’re pursuing noninvasive sampling methods, such as the saliva study.
Urungwuko's baby rides on her back during a bout with respiratory illness.
There are also other differences between chimpanzee and mountain gorilla respiratory disease. The outcome differs as I've mentioned: more chimps sicken and die of secondary bacterial infection than gorillas.
Among the four groups recently affected, all of the individuals in each group showed signs of illness. That's a total of 80 mountain gorillas affected! Fortunately, only two required treatment, and they lived.
The origin of the infection also seems to be a bit different. When the really bad outbreaks of respiratory disease occurred in chimps, it was before visitation rules were in place. Now that chimp researchers and tourists maintain a greater distance from the chimps and are more aware of their personal hygiene, the number of respiratory disease outbreaks has gone down.
Susa Group's Ururabo and her infant
In Rwanda and Uganda, the situation is different. Gorilla researchers and the field vets follow a self-imposed quarantine as needed (we wait at least two weeks after travel on buses or airplanes to make sure we haven't come down with a respiratory illness). We follow the same distance and personal health and hygiene rules established for all park visitors, including tourists.
Is it that, on the whole, we're not following these rules well enough? Or is the disease simply better established among the gorillas and circulating now no matter what we do? Or, again, is there more of it in the local community?
The other factor is, of course, the Democratic Republic of Congo, where no rules are being followed whatsoever when it comes to visiting mountain gorillas and there are many people living illegally inside the park.
Getting back to my phone conversation with Elisabeth, I knew Kwitonda and his group had suffered through a severe outbreak of respiratory illness just last year in April (2007), so my next thought was that maybe this one wouldn't be so bad. The group should have some immunity to the infectious organism, most likely a virus, if it's the same or related to the one that affected them last year.
I remember because a tiny baby, the 3-month-old infant of Mugeni, had died suddenly. The mother had shown only mild signs and her baby none, until it died — presumably of an overwhelming viral respiratory infection. The incident cemented in my mind the importance of preventing these outbreaks to begin with if we can, because once they hit, there’s nothing we can do for the very youngest of the group. The babies and infants are, of course, the future of the population.
Okapi, one of the juveniles in Kwitonda Group, is eating fine despite a mild cough.
I heard a cough even before we reached the group — just one. As usual, the sound, a loud short burst of expelled air, took me by surprise. It came from somewhere down and to the right of where we'd been climbing. The tracker, Jerome, and I scoured the trees to find the source. We could see branches moving in the distance.
Then I saw a young gorilla, probably Ndimubanzi (nee mu ban zee) crossing a stream. Seconds later, we reached the group resting at the base of a clump of trees. One of the females, Mbimbilibili (mim bili bili), coughed softly three times. I craned my neck to see her face. She gazed back at me bright-eyed with no nasal discharge, a good sign. One of her offspring, Chiri, picked her nose but then tumbled around in play. Ndimubanzi appeared minutes later in a closer tree and coughed twice, confirming our earlier guess.
Mugeni , one of the adult females in Kwitonda Group, showed no
signs of illness during the 2008 respiratory outbreak.
On my way out of the forest, I called Elisabeth on the cell phone and suggested that I become the vet assigned to the Kwitonda Group respiratory illness — in case it turned out to be a severe one. That way, she and Jean Felix could continue to check other groups as needed. As an extra precaution, I also asked that the park service assign the same guide to visit the group, and that no trackers move from one group to the other.
The vets have limited their movements during these illnesses, but we haven't asked the park staff to do the same. Though these may sound like obvious and easy preventive measures, tracking and visiting the gorillas on a daily basis involves a complex set of logistics. As I've stressed during our meetings, the key is that no one sick goes to work. Unless you're coughing or sneezing, you're not likely to spread a disease. So while we can, and have, limited where staff go, it's how we're feeling each day that matters.
Mugeni's infant played and played, showing no signs of
illness during this year's (2008) outbreak of respiratory disease in Kwitonda Group.
On my next several visits, the Kwitonda gorillas were feeding high up in the Drombere trees, eating flowers. I'd hear a cough and then wait and wait until I could see exactly who produced it. The trackers did a terrific job keeping notes, too. Their understanding of this disease and why we worry about it has increased greatly.
The outbreak was indeed very mild, though it steadily spread through the group with one or two new individuals affected each day. Mugeni, who has a new infant, coughed only a few times on one day. Thankfully, her new baby never showed signs of any illness. He played and played.
Silverback Kwitonda, on the day after he fought with one of his group's blackbacks.
The silverback, Kwitonda, was the only gorilla to cough for more than two days in a row. He ate well and moved about normally, until we found him one morning unwilling to get up from his nest. When he finally sat up, I could see he had a swollen lip and bruised forehead. I felt relieved that all he'd had was a fight with one of the young males in the group.
In fact, on that day and the next, Kwitonda's cough was the least of his worries. Had the situation been different and we hadn't just been through such severe outbreaks in two other groups, I'm not sure we would have placed much significance on this mild Kwitonda Group cough. As they say, context is everything.
[Rwanda, 2008. Pictures: Dr. Lucy Spelman/MGVP]
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