D8371.PDF

Rev. sci. tech. Off. int. Epiz., 1988, 7 (4), 783-795.
Research on wildlife diseases:
is a reappraisal necessary?
W. PLOWRIGHT *
Summary: Past antipathy or apathy to research on wildlife infections and
diseases (they are not synonymous) has probably been based on the belief that
veterinary and paraveterinary workers are almost entirely concerned with diseases
transmissible to domestic animals and man. There is, however, great scientific
and practical potential in studying diseases of free-living animals per se as an
important branch of their ecology, essential to their sound conservation and
economic exploitation.
From the present base there are considerable difficulties in increasing the
veterinary contribution to research on wildlife: the recognition of disease is not
easy; notification may be delayed or is suppressed; some biologists, the lay press
and the public seem to find it easier to understand "pollution" than infectious
disease wild animals which are sick tend to die and to be removed very quickly.
Wildlife veterinarians act primarily as providers of an emergency service
but they could play a much more important part in wildlife programmes. They
require continuous access to animal populations to detect low levels of, or
inapparent but significant, infection. Additional, basic training in epidemiology,
ecology and conservation techniques is highly desirable for them and many
wildlife biologists would benefit from a better knowledge of infectious diseases.
The most important methods for monitoring microbial infections in wild
animals are discussed in relation to some past and present epizootics. The
Resolutions of the 56th General Session of the OIE are to be welcomed as a
step in the right direction.
KEYWORDS: Animal diseases - Animal production - Animal welfare Ecology - Epidemiology - Veterinary research - Wild animals.
INTRODUCTION
The theme of this issue of the O I E Scientific and Technical Review, " W i l d animal
diseases transmissible t o domestic a n i m a l s " is, in itself, a reflection of the
overwhelming need for a reappraisal of the attitudes a n d role in wildlife biology of
those with special knowledge of animal disease. T h e unfolding saga of the recent
seal mortality in Western E u r o p e , as judged largely by press a n d television reports,
on which most of us have perforce depended, shows how infrequently veterinarians
and their scientific co-workers are regarded as the experts by the media, the public
or those confronted more immediately by a spectacular epidemic decimating some
of our largest m a m m a l s .
* Whitehill Lodge, Reading Road, Goring, Reading RG8 OLL, England.
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It is an objective of this paper to examine some of the reasons for this state of
affairs and t o suggest ways in which veterinary a n d paraveterinary expertise can be
better equipped and applied to problems of disease in wildlife, whether transmissible
or non-transmissible. The examples quoted bear inevitably a personal bias; they reflect
an initial experience in Africa with major plagues transmissible to domestic species,
and recent data on spectacular lethal infections of wildlife.
At the opening of the Third International Wildlife Disease Conference in 1975,
the President, Milton Friend, referred to the difficulties of pursuing wildlife studies
in these words: "resistance or apathy towards controlling wildlife disease arises
because:
1. seldom is this action initiated primarily for the direct benefit of wildlife;
2. the action may be at the direct expense of wildlife;
3. there has been little to demonstrate that wildlife diseases can be controlled in
free-living populations;
4. the role of disease in the population dynamics of wildlife species has not been
adequately d o c u m e n t e d " (15).
Veterinary workers w h o have experience of investigating disease in wildlife or,
more particularly, inoffensive infections of wildlife which are more serious when
transmitted to m a n or his domestic animals, will recognise this "resistance or a p a t h y "
and the justice of these complaints.
In North America, for which Friend was speaking, the situation is more favourable
t h a n in E u r o p e . Wildlife research in the U S A began in the early 1900's at the Bureau
of Biological Survey, later to become the US Fish and Wildlife Service. The Wildlife
Disease Association (WDA), which published its first quarterly Bulletin in 1965, soon
to become the Journal of Wildlife Diseases, was "dedicated to the conservation of
wildlife through sharing the study and understanding of diseases of wild animals.
The object of the Association is to advance knowledge of the effect of infectious,
parasitic and physiologic diseases and other factors u p o n the health and survival of
free-living and captive wild animals, upon populations of wild animals and upon their
relationship to m a n " . In this statement there is a conspicuous omission of any direct
reference to diseases transmissible from wildlife to m a n or his domesticated animals
or vice versa, although this may be covered by the phrase "their relationship to m a n " .
The primary purpose of this article is to focus attention o n infections and diseases
of wildlife per se. Microbiologists, parasitologists, toxicologists, specialists on nutrition
and metabolic disease as well as general epidemiologists and others should all be
brought to recognise the practical necessity for independent study of wildlife pathology
in its broadest sense and a vigorous development of its scientific potential.
DIFFICULTIES IN T H E RECOGNITION OF INFECTIOUS DISEASES
IN WILDLIFE
It is indisputable that the level of disease and mortality in a free-living population
usually reaches severe or even catastrophic proportions before it is noticed and
recorded. The reasons for this are manifold. They include the relative isolation and
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inaccessibility of wildlife populations. For example, rabies was estimated to have killed
30,000 to 50,000 greater k u d u in the years 1977 to 1983, spreading out from the
O k a h a n d j a area of Namibia; furthermore, it was found to spread experimentally by
the oral route (20). Laws and Taylor (32) reported a n 8 5 % mortality amongst 2,500
crabeater seals (Lobodon carcinophagus) o n sea ice near the tip of the Antarctic
Peninsula between 4 September and 21 October 1955; the sledging party which
discovered them noted abortions and concluded the disease was probably due t o an
unidentified virus (31). There are press reports that 1,000 of the 6,000 hippopotamuses
in the Luangwa river valley in Z a m b i a died of a disease, never officially notified but
thought t o be anthrax, in an u n k n o w n period u p t o J a n u a r y 1988; the infection was
stated to have spread to elephant, buffalo, kudu, p u k u and Thornycroft's giraffe.
Surprisingly, a pack of "wild d o g s " , presumably the African hunting d o g (Lycaon
pictus), a species which is becoming rare and on the threatened list, was said to have
been reduced to a single adult survivor with pups (23).
A n o t h e r reason for the paucity of recorded outbreaks of infectious disease in
wildlife may be the failure to call in qualified investigators before or at the time of
epidemics. This omission is sometimes, unfortunately, attributable to a vested interest
in incriminating other more " p o p u l a r " causes, such as chemical pollution, along with
real difficulties in recognition of its infectious character and even a desire to conceal
the existence of transmissible disease, ostensibly in the interests of the animals
themselves.
As an example of the first two of these factors in operation, Smith (53) reported
the history of " W e s t e r n duck sickness" which caused tremendous mortality from
1910 onwards in waterfowl on lakes and mudflats of the western U S A . It was not
until 1930 that the original attribution to alkali poisoning from lakes with high salinity
(e.g. the Great Salt Lake) was shown to be mistaken and type C botulism confirmed
as the cause. Similarly, the death of 50,000 birds, including 8 0 % of the spoonbills,
occurred in 1973 in the C o t o D o ñ a n a Reserve at the m o u t h of the Rio Guadalquivir
in Spain; whilst attributed at first t o pesticide poisoning it was later shown to be due
to type C botulism (53, 54). A similar sequence of events was recorded in the Mersey
estuary (England) in A u t u m n 1979, where lead poisoning was at first invoked as the
cause of death in 2,400 water birds, whereas later bacteriological investigation showed
the probable involvement of type C botulism (55).
It is interesting to observe parallels with the recent seal morbillivirus epidemic
off Western E u r o p e a n coasts (40). Press reports have continued to emphasise a n
imputed association with pollutants, especially polychlorinated biphenyls ( P C B ' s ) ,
D D T , lindane and dioxin, etc. O n 27 September 1988, Nicholson-Lord reported in
The Times (London) that "scientists have argued that pollution cannot be ruled out
as an underlying cause of the epidemic. Although the trigger was the canine distemper
virus (CDV), toxins may have harmed the i m m u n e system" (36). This was after a
conference in L o n d o n on 11 August which decided that the primary cause " o n the
basis of epizootiological observations is generally believed t o be infectious" (41). A
later report of 27 deaths in a population of 220 grey seals in the Dee estuary (England)
between March and September 1988, postulated that this was possibly due to an
unidentified virus unrelated to CDV and "caused by mercury p o l l u t i o n " (37).
On the question of concealing disease in wildlife in the belief that this is in their
best interests, two examples will suffice. Long after a high incidence of bovine
tuberculosis in badger populations in parts of south-west England had been confirmed
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pathologically and bacteriologically as a source of infection for cattle, there were
strident objectors to the control measures, which involved the killing of infected
badgers. Some of them, lay-persons admittedly, strongly denied that tuberculosis did
in fact occur in badgers (62) and did everything within their power to conceal its
presence.
In East Africa, where there was a long history of wild ungulates serving as a
reservoir and means of dispersal of rinderpest virus (7, 45), there is little d o u b t that
a tendency grew u p o n the part of some authorities in the National P a r k s and game
reserves to minimise and delay reports of mortality in rinderpest-susceptible species
in the belief, not unfounded, that publicising the information would lead to unwanted
investigation of these species by the veterinary authorities and subsequent pressure
to control their movements and numbers by rather drastic measures. This tendency
for development of a conflict of interests between veterinarians and conservationists
was also commented on in a more general sense by Woodford (59). It later diminished
with the recognition of a c o m m o n interest in eradication of a lethal disease but it
has probably not disappeared.
In South Africa, a long-standing record of moderate attitudes on the part of the
veterinary authorities (56, 9, 11) has been, apparently, conducive to better
collaboration with those in National Parks, etc. (60) leading to some excellent examples
of the part which the investigation of disease or methods for its prevention in wildlife
can contribute to conservation (anthrax in wildebeest in the Etosha National P a r k ,
Namibia: 12, 5; development of anthrax immunisation from helicopters, of roan
antelope in the Kruger National P a r k , South Africa: 10).
Other important reasons for the failure to observe and report disease in wild
animals are the frequent lack of easily recognisable signs, the rapid deterioration of
animals which become sick and die and their early detection and removal by scavengers
leading to the "impression that wild game populations are not frequently decimated
by disease" (60). It is remarkable, for instance, that approximately 13,000 of 16,000
juvenile buffaloes in a total population of 61,000, died in the Serengeti National Park
of Tanzania in the years 1970-71 and 1971-72 without severe morbidity becoming
apparent on continuous close observation. This was in the absence of rinderpest, which
u p to 1963-65 had been a major external " r e g u l a t o r " of the buffalo population,
possibly since the great panzootic of the early 1890's (51). The removal of this regulator
was considered to be largely responsible for the rapid increase in the population or " e r u p t i o n " - which followed u p to the early 1970's (52); nevertheless catastrophic
or striking mortality in buffaloes had been observed very irregularly and usually in
localised form.
"Scavengers" in the sense employed by Young (60) include predators such as lion,
leopard, hyenas and jackals, as well as vultures, etc. and their ability to recognise
relatively minor incapacity in their prey is well known. In early attempts to immobilise
and fit identification collars on species such as hartebeest and wildebeest in Kenya,
it was found that a large proportion of the subjects " d i s a p p e a r e d " very quickly. It
was then discovered that the premature release of immobilised animals led to their
rapid recognition, probably from gait abnormalities, and a speedy despatch by the
ever-present hyenas. It is nevertheless debatable whether predation generally is selective
for unhealthy individuals (6) and May (34) remarked about this popular ecological
notion as follows: " I have yet to see the suggestion that microparasites are beneficial
in supplying weakened prey to sustain predator populations". The rapidity with which
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wildlife species die was supported by evidence from the Pretoria zoo; in spite of daily
inspections, 8 0 % of 280 m a m m a l s which died had shown no premonitory signs and
the figure could be higher in wild birds and reptiles (61).
T H E ROLE OF WILDLIFE VETERINARIANS
It has been evident for many years in Africa, with its great resources of wildlife,
that there was a need for veterinarians who concerned themselves entirely with their
diseases or infections. The first "wildlife veterinarian" to be appointed in Kenya under
the United Nations Development P r o g r a m m e (through the F A O ) arrived in 1967;
the account o n his activities (13) contains much that was relevant to defining the
functions of the office then and to-day.
Thus it was recognised that wildlife were among the most important national assets
and that their diseases needed to be studied in depth whether or n o t they were
transmitted to domestic animals. They also needed to be viewed consistently and
primarily in an ecological context; national parks and reserves were delineated and
protected (thus not a completely " n a t u r a l " environment) and monitoring the health
of wildlife populations was an important factor in the successful exploitation of the
resources. A team approach was necessary, so that consultation and cooperation with
biologists allowed the best use of restricted materials, obtained, for example, in the
course of culling operations. Again, inspection of wildlife products was necessary
if they were destined for h u m a n consumption - or, incidentally, to control movement
of agents of animal disease.
This broadly based and positive approach to the functions of wildlife veterinarians
may be compared with a recent statement of its objectives and scope from the
Veterinary Specialist G r o u p (VSG) of the S S C / I U C N (24). This affirmed that the
" s t u d y of disease conditions in wildlife is a relatively new discipline... still in the
descriptive s t a g e " , and concluded that the first important concern of members was
" t h e justification for veterinary intervention in cases of wildlife disease or i n j u r y " .
The statement recognised that "disease is part of the ecosystem and plays an important
part in natural selection" but that " t h e r e are examples where intervention is plainly
justified, as for instance in populations of seriously endangered s p e c i e s . . . " .
The subsequent references to parasitism, deficiency diseases and " z o o n o s e s " , the
effects of overcrowding and disease in species reintroduced to the wild are depressingly
those of a " s e r v i c e " profession, rather than one which actively participates, as of
right, in research on all aspects of the impact of wildlife disease in ecology and
conservation and contributes to its understanding. The second major concern of the
VSG is said t o be "immobilising and tranquillising of wild a n i m a l s " , undoubtedly
a very important technique, but hardly more t h a n that and certainly not elevating
the practitioners out of the service role.
It is in this context that the recent Resolutions from the 56th General Session of
the Office International des Epizooties (39) should be welcomed, as going some way
towards recognising the intrinsic economic and ecological importance of wildlife
diseases per se, promoting their study a n d accepting them as proper subjects for the
agenda of Conferences. W h a t will need to be determined next is the source of funds
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for these increased activities and the procuring of access to the required material,
when legislation or public pressures can n o longer demand t h e m on the grounds of
transmissibility of disease agents to m a n or domestic species.
Some of these functions deserve further comment if suitably trained individuals
are to be employed to m a x i m u m capacity. It is highly improbable that the basic
veterinary training in E u r o p e is adequate t o impart an ecologically balanced view
of wildlife disease and its probable influence on population dynamics and conservation
policies. Primary or secondary training in zoology or wildlife management would
surely improve the chances of successful collaboration of veterinarians within
multidisciplinary teams, including zoologists and ecologists. In the same way, an
understanding of the principles and techniques of epizootiological investigations should
be more widely appreciated by biologists and conservationists.
T H E NEED FOR CONTINUOUS OBSERVATION OF WILDLIFE
POPULATIONS
It is not usually possible to mount satisfactory disease investigations when mortality
has already become evident for all to see. Continuous disease monitoring is as
important in wildlife populations as it is in domesticated species or m a n . As Young
(61) warned, " t h e eradication of an infectious disease amongst free-living wild animals
is by no means an easy matter and its control can be badly hampered by a delayed
or wrong diagnosis". It would be wildly optimistic to hope that low levels of infectious
disease and mortality will be notified to veterinarians by wildlife biologists. Access
by wildlife veterinarians should, therefore, be continuous and there are numerous
examples of the ills that can occur, o n the one hand, if it is not provided or, on the
other, if the opportunity of access is not taken u p , due to lack of funds, motivation
and understanding.
A recent catastrophe was that which befell the sole, small but thriving population
of the black-footed ferret (Mustela nigripes) in W y o m i n g , U S A . This was reduced
from 128 in 1984 to 45 in August 1985 and 29 in September 1985; canine distemper
virus which caused the mortality was not confirmed in captured animals until late
October 1985, by which time a captive breeding p r o g r a m m e had been initiated and
very few animals survived in the wild (33, 47). In retrospect it was suggested that
an epizootic of sylvatic plague affecting prairie dogs (Cynomys spp.), the main prey
species for the ferret, had served to "distract wildlife managers and administrators
from what was likely a simultaneous canine distemper epizootic among the blackfooted ferrets and other susceptible carnivores, e.g. coyote (Canis latrans) and badgers
(Taxidea toxus)" (57).
The story of the black-footed ferrets now seems in all respects to be a
"precautionary t a l e " (33) of what was to happen to the seal populations of Western
E u r o p e from April 1988 (40); the detection of a morbillivirus in this case was not
reported until the end of August at a time when 12,000 harbour seals (Phoca vitulina)
had already died. It was, incidentally, reported that the strains of virus involved did
not present unusual difficulties in isolation, as they directly produced cytopathic effects
in the M D C K cell line (42) and in seal kidney cells (26). It is not, of course, the case
that the harbour seal is a threatened species, like the black-footed ferret; however,
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the possibility of spread to the Mediterranean m o n k seal (Monachus tropicalis) which
is endangered (58) and t o sea otters (38), presents a more serious threat.
METHODS FOR THE MONITORING OF INFECTIOUS DISEASES
IN WILDLIFE
A commonly effective way of monitoring infections in wildlife, indeed often the
only way, is by serological investigations. Thus, the occurrence of widespread
rinderpest virus infection in buffalo, wildebeest, etc. in the Serengeti region of
Tanzania and south Kenya was followed, from 1960-70, by surveys of rinderpest
neutralising antibody in collections of serum. Clinically recognisable disease and
mortality were not reported after 1961 (45, 46, 47) but seroconversions continued
to be frequent until at least 1963 and then virtually disappeared. The disease reappeared
in a highly lethal form in buffaloes in 1982 and whilst mortality declined or ceased
in subsequent years, infection was shown by serological means to persist in buffaloes
at least until 1984 in Kenya and to 1987 in the Serengeti National P a r k (2, 47).
Collections of sera for rinderpest surveys, for example, were used to show the
universal and usually inapparent infection of buffaloes by BHV-2 (bovine herpesvirus 2) (48) and the distribution of the alcelaphine herpesviruses (AHV-1 and AHV-2)
of malignant catarrhal fever in East Africa (50). A similar use was m a d e by Hedger
and co-workers of sera collected primarily for foot and m o u t h disease (FMD)
investigations to study infection by A H V - 1 , B H V - 1 , BHV-2 and BVDV (18, 19, 21).
Limitations on the value of serum are often imposed by inadequate representation
of an ecosystem with respect to species, numbers, age classes, spatial distribution
within the geographical region and sequential sampling within the study area (46).
The use that can be m a d e of a b u n d a n t materials derived from game control
(warthog: 8), harvesting or culling operations (hippopotamus: 29, 49; seals and whales:
30) or even epidemic disease (seals: 32, 27,28) to establish inter alia, good ageing criteria
as well as the presence and quantity of antibodies is still not adequately appreciated.
Many serum samples do not carry a sufficiently accurate estimate of the ages of the
donors t o give the m a x i m u m epidemiological information.
Once again, the published data from recent investigations of seal mortality (42)
do little to reassure about the size and diversity of origin of serum b a n k s , on which
many deductions about the novelty and source of the infection will depend. It is to
be hoped that there has not been a failure to take full advantage of periodic culling,
immobilisation (4) and economic harvesting of seals in areas of over-population to
make large, balanced and well-documented collections of serum samples over a period
of years. The incentive must surely have existed when the list of recognised microbial
pathogens in seals was already quite a long one, including caliciviruses (47), sealpox
(25), influenza viruses and mycoplasmas (16, 17, 22) and a herpesvirus (43).
A second basic method of monitoring disease in wildlife populations is, of course,
to collect, enumerate and identify their macroparasites and isolate, define and preserve
their microbial parasites. In some instances this has been done systematically and
the results have been of great practical and scientific interest. T h u s , it was shown
that the high but declining mortality in Australian rabbits which followed the
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introduction of m y x o m a virus was associated with a fall in the pathogenicity of virus
isolates and a n increased genetic resistance in the rabbits (14); the ecological impact
of these events on predators and other elements of the community structure were
outlined by Anderson and May (3). The investigation of F M D viruses (types SAT
1, 2 and 3) in the African buffalo, particularly by Hedger and co-workers, did much
to clarify the behaviour of these viruses in their original reservoir host and the real,
as opposed to the conceived, dangers of transmission to domestic stock. The
pathogenicity of these viruses to species such as kudu and impala, as opposed to their
relative innocuity in buffaloes, may well account for the epidemiology observed (47).
The results of detailed examination, by molecular virological techniques, of isolates
from wild animals have sometimes given valuable results, e.g. the F M D viruses
obtained from buffaloes in Kenya were distinguishable from viruses of the same type
circulating simultaneously in cattle, by T ribonuclease oligonucleotide mapping ( l ) .
In this issue Pastoret et al. (44) record the discovery of differences between serologically
related alphaherpesviruses infecting cattle, red deer, reindeer, Indian buffaloes and,
perhaps, other species. Influenza viruses (H7N7 and H4N5) isolated from seals off
the north-east coast of America are closely related to avian strains and the molecular
changes which may underly the change from avian to m a m m a l i a n hosts are of great
interest (22).
1
Although the information obtained from repeated isolations of viruses in the course
of an epidemic can be very useful on subsequent molecular studies, as in the
Pennsylvania avian influenza epizootic of 1983-84 (summary: 47), there is sometimes
little evidence of a coordinated or international approach to the wildlife infections
which may occur simultaneously over wide geographical areas. Thus, it is unfortunate
that no isolates were obtained from the severe rinderpest epizootic which occurred
in buffaloes in Tanzania in 1982 (47); hence any comparison, by partial genomic
sequencing for example, with any previous or later isolates of apparent reduced
pathogenicity will not be possible.
In general the results of serological surveys can only be interpreted with confidence
if the causal agents have been identified and studied for host-range, pathogenicity
and, increasingly, molecular characterisation.
As a final argument for the coordinated collection of viable microbiological disease
agents - and macroparasite specimens - from wildlife, we may note their potential
importance in reintroduction of captive-bred animals to a depleted natural
environment. Golden-lion tamarins (Leontopithecus
rosalia) bred in captivity were
reintroduced to a protected area in south-east Brazil and in the first two years 18 of 26
"acclimatised" animals died and 3 were missing (35). The majority of deaths occurred
shortly after release, due to a variety of causes of which " d i s e a s e " was said to be
the main factor; after conjecture about herd immunity in captivity and in the wild
it was suggested that " s o m e kind of immunological preparation, possibly including
vaccination against specific infections, may come to be a significant part of reintroduction p r o g r a m m e s " (35). It is impossible to see how the objective could be achieved,
in this or in any other case, without identification and culture of the " n a t u r a l "
pathogens and development of the associated serological techniques. Zoological
collections would provide a very unreliable guide to what m a y occur outside.
*
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LA RECHERCHE SUR LES MALADIES DE LA FAUNE SAUVAGE : UNE RÉÉVALUATION EST-ELLE NÉCESSAIRE? - W. Plowright.
Résumé : L'aversion ou l'indifférence passées pour la recherche sur les infections
et les maladies (deux mots qui ne sont pas synonymes) de la faune sauvage,
étaient sans doute dues à l'opinion que les spécialistes vétérinaires et paravétérinaires ont pour préoccupation quasi exclusive les maladies transmissibles
aux animaux domestiques et à l'homme. Or, ce sont de vastes perspectives
scientifiques et pratiques qui s'ouvrent si on étudie pour elles-mêmes les maladies
des animaux vivant en liberté, comme un élément important de leur écologie,
essentiel pour leur conservation et leur exploitation économique rationnelles.
A partir de la situation actuelle, l'accroissement de la contribution vétérinaire
à la recherche sur la faune sauvage se heurte à des difficultés considérables :
l'identification des maladies est malaisée ; leur déclaration peut être faite avec
retard, ou pas du tout ; la notion de pollution paraît plus facile à comprendre
que celle de maladie infectieuse pour certains biologistes, la grande presse et
l'opinion publique ; en général, lorsqu'ils sont malades, les animaux sauvages
meurent et leurs cadavres disparaissent très vite.
Les vétérinaires spécialistes de la faune sauvage peuvent jouer dans les
programmes relatifs à cette faune un rôle beaucoup plus important que celui
de simples fournisseurs d'un service d'urgence. Ils doivent avoir accès en
permanence aux populations animales, afin de dépister des infections évoluant
à bas bruit ou inapparentes, mais dont les conséquences peuvent être
considérables. Il est hautement souhaitable de leur donner une formation plus
poussée en épidémiologie, en écologie et en techniques de conservation de la
faune ; d'autre part, une meilleure connaissance des maladies infectieuses serait
profitable à de nombreux biologistes de la faune sauvage.
Les principales méthodes de surveillance des maladies infectieuses chez les
animaux sauvages sont discutées à la lumière de quelques épizooties passées
et présentes. Les Résolutions de la 56 Session Générale de VOIE doivent être
saluées comme un pas dans la bonne direction.
e
MOTS-CLÉS : Animaux sauvages - Bien-être animal - Ecologie Epidémiologie - Maladies animales - Production animale - Recherche
vétérinaire.
*
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INVESTIGACIONES SOBRE LAS ENFERMEDADES DE LA FAUNA SALVAJE: ¿ ES
NECESARIA UNA REEVALUACIÓN? - W. Plowright.
Resumen: La pasada aversión o la indiferencia por la investigación sobre las
infecciones y enfermedades (dos palabras que no son sinónimas) de la fauna
salvaje se debían sin duda a la opinión que los especialistas veterinarios y
paraveterinarios se ocupan cási exclusivamente de las enfermedades transmisibles
a los animales domésticos y al hombre. Ahora bien, son amplias perspectivas
científicas y prácticas las que se abren si se estudian las enfermedades de los
animales que viven en libertad, como un elemento importante de su ecología,
esencial para su conservación y su explotación económica racionales.
Partiendo de la situación actual, el aumento de la contribución veterinaria
a la investigación sobre la fauna salvaje choca con dificultades considerables:
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la identificación de las enfermedades es complicada; su notificación puede
hacerse con atraso o no hacerse; para algunos biólogos, la prensa y la opinión
pública, la noción de contaminación parece más fácil de comprender que la
de enfermedad infecciosa; por lo general, cuando están enfermos, los animales
salvajes mueren y sus cadáveres desaparecen muy rápidamente.
Los veterinarios especialistas en fauna salvaje pueden desempeñar en los
programas relativos a esta fauna, un papel mucho más importante que el de
simples prestatarios de un servicio de emergencia. Deben tener constante acceso
a las poblaciones animales para poder diagnosticar infecciones poco aparentes,
o inaparentes, pero cuyas consecuencias pueden ser considerables. Es altamente
aconsejable darles una formación más sólida en epidemiología, ecología y
técnicas de conservación de la fauna y, por otra parte, un mejor conocimiento
de las enfermedades infecciosas resultaría conveniente para numerosos biólogos
de la fauna salvaje.
Los principales métodos de vigilancia de las enfermedades infecciosas en
los animales salvajes se debaten a la luz de algunas epizootias pasadas y presentes.
Las Resoluciones de la 56 Sesión General de la OIE deben saludarse como
un paso en la buena dirección.
a
PALABRAS CLAVE: Animales salvajes - Bienestar animal - Ecología Enfermedades animales - Epidemiología - Investigación veterinaria - Producción
animal.
*
* *
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