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tanzania study tour; Serengeti lions location
The Serengeti National Park is located in Tanzania, in East Africa. Most people going on a study safari will either drive or fly from Arusha, Tanzania.
Within the Serengeti National Park, the serengeti lions research center ("LRC") scientists study 15 lion prides and other nomadic lions located in the South-Eastern portion of the Park in addition to studying the prides living in the Ngorongoro Crater.
serengeti lions virus study;
Distemper Virus Killing Lions, UT Researcher Says in Nature
Tanzania study tour
KNOXVILLE, Tenn. -- A virus normally found mostly in dog-like animals has killed a third of the lions in Africa's Serengeti National Park, a University of Tennessee scientist reports in the current issue of Nature.
tanzania study touri; Dr. Linda Munson,
a pathologist in UT's College of Veterinary Medicine,
said a 1994 outbreak of a type of canine distemper virus,
or CDV, has killed more than 1,000 lions in the Serengeti
and Masa Mara areas of East Africa since 1993.
tanzania study touri; CDV is thought to
have caused several fatal epidemics in foxes, wild dogs
and other animals in Africa and elsewhere, but the outbreak
identified by Munson's research team is the first known
to be fatal to lions.
The source of the epidemic was probably the domestic dogs belonging to villagers living near the park, Munson said. An outbreak of distemper among these dogs, most of which are not vaccinated, preceded the lion epidemic, she said.
tanzania study tour; The virus may have been spread to the lion population by hyenas, which live among both domesticated dogs and lions, she said.
''CDV is a canine virus that for years has sometimes affected raccoons, ferrets, and just a few cases in cats,'' Munson said. ''But something happened about 1991 and it started affecting big cats in zoos, and then we had the big epidemic in 1994, and it's also affecting hyenas now.''
serengeti lions tanzania study tour
Munson, whose work is primarily funded by a faculty research grant from UT, says she does not know why the virus suddenly extended its range of hosts and became fatal to lions. She is part of an international research team tracking the virus globally to see if it has affected other species of carnivores.
African government officials have implemented a program to vaccinate domestic dogs near the Serengeti, Munson said. The epidemic seems to have subsided and the death rate of serengeti lions has returned to normal, but future outbreaks are a threat to endangered species, she said.
''The CDV epidemic clearly emphasizes the need for continued monitoring for infectious diseases in valuable wildlife resources and for initiating vaccination programs for domestic animals in contact with wildlife,'' Munson said
tanzania study tour; Danger to serengeti lions
Burgeoning human population growth around the Western edges of the park poses a great threat to big cats and other predators that roam the Serengeti plains. Many of the villagers living outside the park own dogs, and these dogs oftentimes are not vaccinated against such common diseases as rabies or CDV. When these dogs intermingle with Serengeti predators at kill or scavenge sites, viruses such as CDV that can be spread through mucus secretions have a means by which to jump from domestic to wild animal populations. In the case of the CDV outbreak of big cats in the Serengeti in 1994, it is thought that hyenas intermixing with domestic dogs at one of these sites contracted the virus and then spread it to other predators at different kill sites throughout the park. How the fatal virus was able to make the leap from afflicting domestic dogs to threatening to wipe out a sizable lion population was a question scientists did not have any answer to. And if the virus could do so much damage this time around, what, if anything, could be done to protect the lion population from future outbreaks?
tanzania study tour; Description
serengeti lions
The Serengeti game reserve in Tanzania, Africa is one of the largest wildlife areas left in the world and is known in part for its well-documented and studied lion prides. Here, thousands of antelope, wildebeests, and other herbivores carry on a daily life and death struggle with the hyenas, jackals, cheetahs, and lions that inhabit the reserve. The income derived from the thousands of tourists that annually visit the park is a key source of revenue for the Tanzanian government.
Several years ago, a mysterious virus appeared among the thriving serengeti lions population in 1994 and proceeded to wipe out a third of the population before the eyes of baffled scientists worldwide. It was only after the virus had run its course several months later that the culprit was found: Canine Distemper Virus (CDV). Previously thought to only afflict dogs and a small number of other mammals on a limited scale, its discovery lead scientists to wonder how this potent virus had jumped species with such lethal results.
The Serengeti National Park is a 15,000 square kilometer ecosystem and a place where natural preservation and economic development are on equal footing. In 1994, there were an estimated 3,000 serengeti lions , the largest population of big cats in the world.
Between January and March of that year,
11 lion carcasses were found - representing a dramatic
increase in mortality from previous years and indicating
to observers that there was a serious epidemic stalking
the serengeti lions. Tourists, many flying in hot-air
balloons over the park to get a better view of the wildlife,
were the first to notice that the serengeti lions were
dying. One of the first lions suspected of suffering from
CDV-like symptoms was observed on February 3, 1994 and
was identified because of the uncontrollable twitching
and convulsions that wracked its body. After watching
many of the serengeti lions dying or after examination
of their corpses, no one scientist knew why the outbreak
had been so sudden or severe or if in fact it was CDV
that was killing the cats. At least 40 serengeti lions
had died since the outbreak started in February and some
of the largest and best-studied prides had been wiped
out.
Tanzania study tour
In fact, by early that year, approximately a third of a well- known serengeti lions population study group of 250 was culled by the virus. There was nothing experts could do to stop the current outbreak of the virus except to let it run its natural course. The only vaccine they had was of a weakened live virus and they didn't want to use it because of the small chance of infecting healthy serengeti lions (Morrell 1994, 1664). Fortunately, the virus did not kill all those lions that were infected so that the survivors will have immunity against future outbreaks.
As investigators suspected and later confirmed through extensive scientific analysis, the animals of the Serengeti were dying of a canine distemper virus (CDV) that belonged to a morbillivirus family or a virus very similar to it. CDV is a viral disease that causes severe neurological symptoms and usually death (Leary 1994, 13). Serengeti lions that were severely affected almost inevitably died. CDV kills by attacking the respiratory, gastrointestinal, immune, and central nervous systems of its victims.
tanzania study tour; It affected the lions' brains and caused facial twitching, flailing paws, and convulsions. Other symptoms included: lions looking off color with dull coats to complete paralysis. The virus struck down lions of all ages throughout a 1,000 kilometer area within a few weeks of the initial outbreak.
Some mammals have their own version of the canine distemper virus such as seals, dogs, black-footed ferrets, and livestock (Miller 1994, 5). The virus strikes humans in the form of measles. CDV can be so pervasive that it nearly wiped out the black-footed ferret population in the Western U.S. in the 1980s. The virus had occurred in lions and leopards in American zoos in earlier years but never was such a large-scale epidemic among big cats observed previously in the wild.
The disease is spread through fine droplets of an animal's breath and is as easily transmitted as a cold. For instance - a hyena or jackal scrapping with domestic dogs over a carcass could have picked up the infection and passed it along to the lions in the park in the same way (drooling, snapping, or biting) (The Economist 1994, 76). It is thought that hyenas were the most likely vectors of the virus because they travel great distances and intermingle with both lions and domestic dogs at separate kill and scavenge sites within and without the park. Nomadic lions (not attached to any pride) could also have contributed to CDV dissemination.
The high densities of these susceptible carnivores at kill sites could have provided an ideal environment for CDV amplification and transmission.
tanzania study tour; Even though several suspected vectors were identified, no one knew why there was a sudden outbreak within the serengeti lions in 1994 because canines and felines had lived together for many years without the virus jumping species with such virulity. It has been known throughout the scientific community that CDV has infected hyenas in the park since the 1960s and both hyenas and lions have shared the same food supplies since then.
If that were true, why then was there a major lion epidemic of CDV in 1994 and not earlier? One of the theories put forward by scientists was that CDV may have always been present in big cats but that it had recently mutated to become more virulent (New Scientist 1994, 8).
As scientists later discovered, the CDV had mutated due to an influx of CDV-infected dogs in the villages surrounding the park allowing for the easy exchange of microbes between species as domesticated dogs and wild animals intermingled.
To find out if the virus was a mutant virus, tissue samples of 23 dead serengeti lions, 11 sick lions, and 72 apparently healthy lions were taken and sent to several labs in the U.S. It was hoped that through extensive scientific analysis it could be determined whether the affliction was a new strain of CDV and how it had jumped species from dogs to cats after historically not doing so.
After many months of study and through the use of new genetic analysis techniques, scientists were able to confirm that the Serengeti organism was a new variant, or biotype, that was genetically different from normal CDV (Morrell 1996, 596).
The new biotype was identified in several different ways. The new ionsstrain infected lions' hippocampus whereas other strains primarily cause an inflation of the brain stem in dogs. It also affected dogs' bronchial tubes but in cats, it attacked alveoli, the air sacs in the lungs (Morrell 1996, 597). A virus that has expanded and affected new tissue areas previously not shown to be afflicted is a sure sign of an emerging biotype. Besides the symptoms that characterize CDV such as grand mal seizures and recurrent twitching, scientists were able to diagnose that the lions that had died in 1994 as also suffering from encephalitis and pneumonia. These two diseases were usually not found in dogs suffering from a normal CDV strain.
tanzania study tour; Scientists have been able to trace environmental changes that apparently prompted the mutation: growing human settlements along the Serengeti National Park's western border, with large populations of CDV-infected domestic dogs. "Human activity was the underlying cause of the epidemic." (Schwartz 1996, 4) The Serengeti is surrounded by a human and dog population that is growing at four percent a year and the people in the area own roughly 30,000 dogs. People are moving to these areas to look for work and the opportunity to make a living. Poor soil conditions and job scarcity are often the reasons people leave the surrounding areas to crowd around the national parks.
Vaccination of the dogs in these villages against CDV is rare although some dogs in the surrounding villages had been vaccinated against distemper and rabies. Between 1993 and 1994 a CDV epidemic swept through villages to the west of the Serengeti killing thousands of dogs. Tissue samples of lions taken between 1990 and October 1993 showed no evidence of CDV. Of samples taken in 1994, 63 apparently healthy serengeti lions and 8 of the 11 sick lions showed evidence of infection.
Burgeoning human populations and their diseased animals put new and unexpected pressures on wilderness areas - pressures that make it more likely that dangerous microbes will move between species in the future (Schwartz 1996, 1). An exchange of diseases between species often encourages and promotes successful mutations. Unfortunately, there are too many dogs to inoculate against these diseases and prevent their mutation. The dogs have an extremely high birthrate and a high population turnover so there are lots of susceptible CDV host-animals. This kind of environment provides an ideal condition for maintaining an epidemic.
tanzania study tour; Morbilliviruses have
made incredible gains in these kinds of environments and
have evolved considerably to increase their host range.
In fact, new morbilliviruses have recently been identified
in seals, dolphins, and horses and it is thought that
genetic changes may make such expansion possible. The
human population growth combined with a pool of CDV-susceptible
dogs probably lead to the new strain of the virus that
afflicted the seremgeto lions.
Scientists were and still are alarmed about this latest outbreak because the virus could come back at any time because of the close proximity of so many non-vaccinated dogs. With the number of dogs increasing yearly, there is a more likely chance of contact between domestic dogs and wildlife in the future and thus a chance of that another outbreak could occur.
To help prevent this reoccurrence, veterinarians from the Institute of Zoology in London and the Tanzanian Parks Service are vaccinating dogs to try and get rid of some of the reservoir where the disease could remain.
Currently, Project Life Lion, a group local veterinary services and wildlife authorities is traveling from village to village vaccinating dogs in hopes of creating a cordon sanitaire around the western villages (Miller 1995, 10). Supported mainly through private donations, the vaccination program for dogs uses First World money to protect an ecosystem of global importance.
This programme will benefit the serengeti lions and the other cats. In 1995, forays into local villages helped vaccinate 80 percent of the dogs in the places they visited. It is not certain, however, how many dogs have to be vaccinated before the chain of transmission is broken.
The veterinarians have funding until 1999 and hope that three years of intensive vaccination will eliminate the disease. They are also vaccinating for rabies to stop the outbreak of that disease. Yearly vaccination in the cattle of the villages since the 1950s to stop the spread of rinderpest (a morbillivirus that fatally afflicts cattle) has proved successful. It is hoped that the same kind of yearly vaccination program would work as well for the dogs.
Scientists believe that the reason the outbreak was so severe in 1994 was because the lions were immunologically naive to CDV. It is ironic that rinderpest in cattle has been controlled, however, since lions may have gained immunity to CDV by eating wildebeest or cattle infected with rinderpest (a cousin of CDV).
There are some studies that have shown that carnivores can be protected from CDV by exposure to rinderpest (The Economist 1994, 76). Hence, its eradication through widespread vaccination of cattle within the past twenty years may have left lions more vulnerable to a virulent CDV strain this time around.
Previous samples taken from 77 lions tested between 1984 and 1989 showed exposure to a virus suggesting that a similar but less lethal epidemic occurred about a decade ago. Lions vulnerability in the park may also be caused by the lions higher population density (3,000 individuals in 1994, an all-time high) or their resistance to disease might have been reduced by other infections or drought.
The large lion numbers possibly made it easier for the disease to pass from animal to animal because there was more frequent contact.
By the time the outbreak was over several months later, approximately 1,000 lions died of CDV and all sixteen prides within the park were affected. It was hard for scientists to get an exact figure because the park is so large and the serengeti lions prides are generally spread out. Combined with the fact that scavengers can reduce a carcass to nothing overnight, it was difficult to calculate how many serengeti lions actually died.
tanzania study tour; Because of this new potent CDV strain, prospects for endangered populations where it occurs may quickly take a turn for the worse. CDV impact on other carnivore species is unknown. Less dense populations of cheetahs, serengeti lions, or wild dogs are a clear cause for concern if exposed to a virulent pathogen such as the new CDV biotype. There was fear among Tanzanians and scientists that the CDV strain would spread to the lions of the Ngorongoro Crater, an inbred and isolated population of 80 individuals located just outside of the Serengeti.
Their genetic homogeneity could have caused them to succumb easily to the disease (Miller 1994, 5) Fortunately, the biotype didn't spread into their areas and the lions remained unaffected. Besides afflicting lions, the new pathogen also killed a large number of hyenas, leopards, and bat-eared foxes. After infecting the Serengeti, the CDV spread northwards from Tanzania to the Maasai Mara Game Reserve in Kenya.
For now, the threat to the serengeti lions is past. No new cases of CDV have been reported within the last year. Survivors have developed an immunity and the lion population has already recovered a quarter of its losses. By August of 1994, 85 percent of the Serengeti lion population were found to have anti-CDV antibodies (Roelke-Parker et al. 1996, 441). A number that bodes well for lions facing possible future outbreaks.
However tragic it may seem to human observers, the epidemic has simply returned the population to its previous level since 3,000 animals was an all- time high (Morrell 1994, 1404). The surviving lions from the latest outbreak could teach scientists about genetic factors that made them immune to the virulent pathogen.
The serengeti lions study shows the reproductive cycle begins when a female enters a period of sexual receptivity called "estrus". Males periodically sniff female reproductive organs for signs of oncoming estrus and if these signs are detected, they will follow a female until she is ready to mate. Females may signal their interest in mating with elaborate tail movements and by "walking sinuously past" a male and assuming a mating position. During mating males often bite the female at the nape of her neck and the act often ends with the female snarling with bared teeth at the male.
Females remain in estrus for approximately 4 days and mating occurs several times an hour throughout the entire period. Males actively guard estrous females from their companions, and fights can occur if other males get too close. If females fail to conceive they will re-enter estrus approximately two weeks later and the cycle begins anew.
During November to mid-march the serengeti lions mating is high.
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