Could lionnoisy have CDV?
A sick lion
A.
IDENTIFICATION
1. The Issue
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?
2. Description
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 lion 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 lions living within the Serengeti, 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 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 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
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 lions had
died
since the outbreak started in February and some of the largest
and
best-studied prides had been wiped out.
In fact, by early that year, approximately
a third of a well-
known lion 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 a healthy
lion
(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). Lions that were severely affected
almost
inevitably died. CDV kills by attacking the
respiratory,
gastrointestinal, immune, and central nervous systems of its
victims. 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.
Even though several suspected vectors were
identified, no one
knew why there was a sudden outbreak within the big cats of
the
Serengeti 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 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 lion strain 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.
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 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. 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 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. 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 lion 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 lions actually died. 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,
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.
3. Related Cases
APPLE Case
NEMATODE Case
BALLAST Case
TIGER Case
Key Words
(1):
Domain
= AFRICA
(2): Bio
geography
= DRY
(3): Environmental
Problem = INFESTation
4. Draft Author: Geoff
Galster (May, 1996)
B. LEGAL Clusters
5. Discourse and STATUS:
Agreement and In Progress
Although Tanzania has done little to
capitalize on its
natural resources, increased tourist activities could help
support
its conservation efforts. So far, Tanzanian authorities
have
limited tourist accessibility to the Serengeti for fear of too
much
destruction and tourist-driven development and degradation of
the
area. But if the Tanzanian government would allow more
tourist-
driven activities near the park, they could use the generated
revenue to potentially build housing elsewhere and relocate many
of
the villagers presently living on the park's western fringes.
(Or
they could institute a thorough dog vaccination campaign)
By
moving these people and their dogs, the risk of future CDV
outbreaks in the park becomes less-likely to occur.
6. Forum and Scope:
TANZANIA and UNILATeral
If the Tanzanian government had the money
and the
infrastructure in place, it could pass legislation making it
mandatory for all dogs in the Serengeti area to be vaccinated
for
CDV, rabies, and other highly-infectious diseases. Some sort
of
dog registration and vaccination could be required.
Presently, the
task of inoculating these village dogs has been taken over by
veterinarian groups based outside of Tanzania and funded
mostly
through private sources.
7. Number of Parties
Affected: 1
Tanzania's Serengeti National Park was the
most severely
affected area during the 1994 CDV outbreak. As noted
previously,
however, the virus did spread into neighboring Kenya and the
animals of the Maasai Masa Game Reserve. Overcrowding
and
encroachment on park areas is an increasingly-serious problem
faced
by many governments around the world. Trying to balance the
needs
of the country's populace with the needs of the country's
natural
resources is a difficult task. As long as you have
human
populations living in close proximity to wild animals, the
possibility for outbreaks like the one in 1994 in the Serengeti
are
inevitable.
8. Legal Standing:
NGO
Project Life Lion, run by veterinarians
based in the U.S. and
Britain, along with Tanzanian Park authorities, is doing all
that
it can to prevent future outbreaks by vaccinating as many dogs
as
possible before their money runs out.
C. GEOGRAPHIC
Clusters
9. Geography
a. Continental Domain:
AFRICA [AFRIC]
b. Geographic Site:
Eastern Africa
c. Geographic
Impact: TANZANIA
10. SUB-STATE: NO
11. Habitat Type:
TROPICAL [TROP]
D. TRADE Clusters
12. Type of Measure: Regulatory
Standard
The threat posed by new roads, hotels,
restaurants etc. is
really not comparable to what might happen if a more virulent
CDV
outbreak occurs among the lions in the near future. If a
high-
profile species like the lion is reduced to a few prides or
eliminated altogether from the park by a new outbreak, then
Tanzania is likely to have very little tourism at all and the
harm
inflicted by potential tourists is a moot point.
13. Impact Direct of Indirect:
INDirect
14. Relation of Measure to
Impact
a. Directly Related to
Product: NO
b. Indirectly Related to
Product: NO
c. Not Related to
Product:
NO
d. Related to
Process:
YES Species Loss Land
The only trade that would affected by the
loss of big game in
the Serengeti to a viral outbreak would be the tourist trade.
This
would directly impact the Tanzanian government's revenue flow
and
indirectly affect its populace and the wild animals
populations
still remaining. No mention of the zoo trade in animals of
the
Serengeti was indicated in any of the articles researched for
this
piece. It is not known whether the zoo trade negatively
impacts
these species or the loss of these species hurts the zoo
trade.
15. Product Type: TOURism
I don't think wild animals are products
although they can and
are marketed to foreign populations.
16. Economic Data
17. Degree of Competitive
Impact
Growing human population on the park's
western edges will have
a HIGH and severe impact on the wildlife within the park as long
as
domestic and wild animals intermix and as long as the domestic
dog
population remains infected with CDV or other diseases. Until
the
pathogen is completely eliminated in the domestic dog
population,
disaster for the Serengeti lions and other predators could
happen
any time. If the outbreak was serious, however, tourists
might
have stopped coming to visit and Kenya would have lost a source
of
income for its economy.
18. Industry Sector:
Tourism [TOUR]
19. Exporter and Importer: MANY
and Tanzania
E. ENVIRONMENT
Clusters
20. Environmental Problem Type:
Species Loss Land
21. Name, Type, and Diversity
of Species
Name:
Lion
Type:
Mammal-feline
Diversity:
See below
Only several thousand animals thought to be in existence
throughout
Africa. The Serengeti population, now a little more than
2,000
animals, represents the largest population of big cats
anywhere in
the world.
IUCN
Status:
VULNERABLE
22. Impact and Effect: HIGH and
SCALE
23. Urgency and Lifetime: HIGH
and 10-20 years
It has been found that morbilliviruses can genetically alter
to
infect a variety of hosts very quickly. Even though the lions
of
the Serengeti are immune to this last strain of CDV, no one can
say
for sure that if and when the next time a CDV strain jumps
species,
it won't be more devastating. Male lions usually live 10 to
15
years while the life expectancy of female lions is a little
more
than 20.
24. Substitutes: Habitat
Protection
F. OTHER Factors
25. Culture:
YES
Dogs are very revered by the Tanzanian
tribesmen for many
reasons including their ability to help with the hunt.
Vaccinations are not common and population grows incessantly
because there is no spaying or neutering of the animals.
26. Human
Rights: NO
27. Trans-Boundary
Issue: YES
It was in 1994 when the virus spread from
Tanzania to Kenya
and could be in the future because of the close proximity of
the
countries and the large game migrations.
28. Relevant Literature
The Economist 13 (August 1994): 76.
Leary, Warren. "A Mysterious Disease Strikes Serengeti Lions."
The
New York Times, 7 June 1994, sec. C p. 13:3.
Miller, Susan Katz. "Lions Die of Sneering Sickness." New
Scientist
4 (June 1994): 5.
Miller, Susan Katz. "Jabs for Dogs may save Serengeti Lions."
New
Scientist 2 (September 1995): 10.
Morrell, Virginia. "Mysterious Ailment Strikes Serengeti
Lions."
Science 3 (June 1994): 1404.
Morrell, Virginia. "Serengeti's Big Cats Going to the Dogs."
Science 17 (June 1994): 1664 - 1665.
Morrell, Virginia. "New Virus Variant Killed Serengeti Cats."
Science 2 (February 1996): 596 - 598.
New Scientist 11 (June 1994): 8.
Roelke-Parker, Melody E. et al. "A Canine Distemper Virus
Epidemic
in Serengeti Lions." Nature 1 (February 1996): 441- 444.
Schwartz, John. "Lions' Death Sent Scientists Tracking Virus
on
Serengeti." The Washington Post, 1 February 1996, sec. 1A. P.
4.
