D9027.PDF

Rev. sci. tech. Off. int. Epiz., 1996, 15 (1), 55-71
Husbandry practices employed by private
aviculturists, bird markets and zoo
collections, which may be conducive to
fostering infectious diseases
P.L. W O L F F *
Summary: Zoos, quarantine stations, and bird markets, dealers and breeders
are in the business of propagating or moving birds. Facilities often house and
transport birds which have unknown histories of exposure to disease. As few
tests are available for disease screening and monitoring in exotic avian
species, familiarization with significant avian pathogens will enable the
manager and veterinarian to recognize and prevent a disease outbreak.
Implementing aviary management practices which minimize the spread of
pathogens, in conjunction with quarantine and the proper handling of birds
during shipment, can greatly reduce the threat of disease.
The author reviews the husbandry practices (caging, nutrition, transport,
quarantine) which can reduce the incidence and spread of infectious disease.
Significant avian pathogens (bacteria, viruses, parasites) are listed together
with their host range and modes of transmission.
KEYWORDS: Avian diseases — Aviary management - Birds — Disease
control — Quarantine.
INTRODUCTION
Each bird carries its own resident population of bacteria, viruses and parasites. If
stress is minimal, host and parasites may co-exist with little risk of disease. Factors
which disrupt the homeostatic balance, however, can often precipitate a disease
process.
The captive environment is full of stress. Captured wild birds are often subjected
to minimal care conditions during transport. Birds of various species and from
numerous locations may be housed together during shipment, exposing each other to
novel diseases. In quarantine stations, bird markets and dealer facilities, birds are
frequently subjected to crowded conditions, unnatural social situations, unfamiliar
diets, and handling for marking, sexing, testing and treatment. On reaching a zoo or
breeding facility, the bird is again exposed to a novel environment and food, further
handling, and a new social group. In view of these extreme changes, it is amazing that
the majority of birds survive. There are many factors within this process where the
* Veterinary Services Director, Walt Disney World Co., The Wild Animal Kingdom, P.O. Box 10,000,
Lake Buena Vista, FL 32830-1000, United States of America.
56
veterinarian and aviary manager can reduce or eliminate stress and the possibility of
illness or death due to disease. Pre-shipment, transport, quarantine, caging, diets,
aviary environment, pest control and disease surveillance are all areas which should
be reviewed.
For domestic fowl and waterfowl, there is a relatively broad understanding of the
transmission, pathophysiology, diagnosis, treatment and prevention of disease-causing
organisms. For the majority of avian taxa, however, knowledge of disease processes
is limited. The avian veterinarian and manager should recognize the major avian
pathogens. Even a superficial familiarity with disease processes, in conjunction with
proper husbandry, can have a major impact on preventing a disease outbreak.
H O U S I N G : C A G E A N D AVIARY D E S I G N
Design of the aviary is probably the most important factor in limiting and
controlling disease in avian species. Floor substrate, cage materials, air flow,
temperature, humidity, cage location, and feeding and watering systems should all be
reviewed and designed to minimize disease risks. Cages should be suspended over
cement floors, with perches which can be easily removed for cleaning. To minimize
faecal contamination, food and water containers should not be placed beneath perches
and roosts. Potential pests should be identified, and measures should be taken to
exclude these from the aviary; where necessary, a rigorous pest control programme
should be implemented. Unfortunately, all too frequently, cage and aviary design
decisions are based on personal preference, aesthetics, visitor and staff comforts, or
cost. Often, designs are modified only after a significant disease problem has occurred.
Aviaries in zoological gardens are designed to be aesthetically appealing to the
visitor and to house a wide variety of avian species. Many zoological facilities
therefore lack the flexibility to consider disease prevention as a major criterion in
designing spaces for avian collections. Large multi-species exhibits often contain
natural substrate, heavy vegetation and cage furniture (e.g. branches, logs and stumps).
Also, food is usually supplied in large communal pans, and the water source is often
a naturalistic, ground-level pool. In outdoor aviaries, it is difficult to isolate the birds
from feral species. Despite the visual appeal of these exhibits, such design may
increase the likelihood of disease transmission. Exhibition environments of this type
are difficult to clean and are impossible to sanitize without complete disassembly. The
design of aviaries in non-display avian facilities (i.e. those managed by private
breeders) is usually more flexible and is subject to fewer restrictions; features which
promote disease control can thus be included during construction.
Warm temperatures, and available food, water and hiding places, provide the ideal
environment for rodents, insects and other pests. Bacteria such as
Mycobacterium
avium have contaminated soils in aviaries, resulting in widespread infection and
necessitating the depopulation of the majority of the avian collection (5). Outdoor
aviaries have reported outbreaks of mosquito-transmitted avian malaria (Plasmodium
spp.) in penguins (16), eastern equine encephalitis in whooping cranes (Grus
americana) (19), cerebrospinal nematodosis (Baylisascaris procyonis) in a mixed
group of macaws (2), and repeated epizootics of avian botulism in ducks housed in an
area used as a nesting colony by free-ranging, black-crowned night herons (Nycticorax
nycticorax) (9).
57
All managers of aviaries should be made aware of the potential avenues for disease
transmission. Aviary design should be reviewed with veterinarians or animal managers
who are familiar with disease aetiology, transmission and prevention.
NUTRITION, A N D M A N A G E M E N T OF F O O D A N D WATER
Dietary composition and the storage, preparation and presentation of food are
important factors in the management of disease. Currently, scientifically-formulated
diets based on known nutritional requirements are available for few bird taxa (8).
Many diets for birds are still based on the 'smorgasbord' philosophy, i.e. the
assumption that, when presented with a wide variety of food items, the bird will
choose a nutritionally-balanced diet. A lack of basic knowledge concerning the
nutritional composition of the natural diet of the bird leads to another erroneous
assumption: that the specific food items available in the captive setting (i.e. seeds and
fruits) are identical to what is eaten in the wild. Unfortunately, nutritional deficiencies
are not uncommon in avian species and can predispose birds to infectious disease.
Vitamin A deficiency in psittacines has been associated with concurrent bacterial
infections (24). All bird diets should be reviewed and analyzed for nutritional content.
Diet formulation should be based on scientific knowledge, and feed items should be
selected by the avian manager, not the bird.
Feed which is improperly stored or handled acts as an important source of bacterial
and mycotic pathogens. Both fresh and dry food items should be properly stored to
protect them from mould, pests and bacteria. Klebsiella, Salmonella, Leptospira and
Listeria have all been associated with rodent contamination of fresh vegetables and
fruits (11). Frozen products (e.g. fish and meat) must be stored at the appropriate
temperature, and should be refrigerated while thawing to decrease bacterial
contamination (4).
The quantity of food offered to each bird should be only slightly more than the bird
is likely to consume; this will minimize spillage and waste. All dishes and remaining
food should be removed at the end of the day to prevent overnight access by pests and
birds. Sliced produce kept at room temperature for 24-48 h enabled culturing of large
numbers of Gram-negative organisms, including Enterobacter spp., Pseudomonas spp.
and Escherichia coli (21). Access to food should be limited, if possible, to the cage
occupant. Opportunistic pests (e.g. rats and mice) are known to carry bacteria such as
Salmonella (13) and E. coli (11), and can spread disease by contaminating food or
water. Ants, cockroaches and crickets are considered food sources by many birds, and
can serve as intermediate hosts for internal parasites such as Geopetitia (22),
Dispharynx (13, 51) and Sarcocystis (13). In outdoor aviaries, it is almost impossible
to screen out pests. In one zoo, submersible diets were developed for captive
waterfowl to protect the food from avian and mammalian pests, and thus prevent
disease transmission from this source (17).
Water can also act as a significant source of potential pathogens. Cultures from
water containers, faucets and hoses have yielded Pseudomonas spp., E. coli and other
Enterobacteriaceae species (11).
58
TRANSPORTATION
Collections of birds are rarely static. Bird markets exist to move animals in and out,
and breeder facilities produce their major income by selling the young from breeding
pairs. Zoos trade or sell birds to establish their collections, or to maximize the genetic
potential of certain pairings and thus protect a threatened species.
Transport of the bird from the source of capture or from its home aviary is often
the first point at which disease exposure occurs. International guidelines for transport
cages exist for airlines which ship birds (36). These regulations are intended to ensure
that the bird has adequate space, ventilation, food and water during shipment. These
guidelines do not cover ground transport, however, or the thousands of birds which are
shipped illegally each year.
The majority of birds which undergo shipment are not adequately isolated from
other birds, thus allowing for potential disease transfer. Shipping is also a stressor for
the bird. Even clinically-normal birds can experience shifts in intestinal flora during
environmental or physiological stress, allowing normally non-pathogenic organisms to
act as disease agents. Chickens (Gallus domesticus) stressed by heat and by water
deprivation were found to increase shedding of Salmonella Typhimurium (58).
Reviews of disease outbreaks from quarantine stations indicate that many birds are
diseased prior to shipment, acquire infections during transport, or have increased
susceptibility to disease following shipment (34, 52, 60).
Before shipping, a number of measures should be taken to decrease the stress of
transport and the potential exposure of birds to pathogenic organisms. Only healthy
birds should be shipped. Wild-caught birds, or birds of unknown history and disease
status, should undergo pre-shipment quarantine and disease screening. Shipping
containers should conform with regulations (36) where necessary, and should always
be properly designed to meet the physiological and social needs of the birds. If
possible, individual shipments of birds should be isolated from other lots of birds
during transport. Unfortunately, such isolation may be impractical for all but the most
valuable species. The United States Department of Agriculture (USDA) furnishes
designs for disposable isolation units for shipment. These units are impervious to
moisture and contain filtered air vents to minimize the risk of airborne pathogens
contacting the bird (28).
QUARANTINE
Quarantine may be the single most important aviary management process in
preventing a potential disease outbreak. The term 'quarantine' originates from the
Italian, quaranti giorni (lit. 'forty days'), the length of the isolation period instigated
in 14th century Europe to prevent travelers from introducing bubonic plague through
the ports of Venice (10). The U S D A quarantine period required for any avian species
entering the United States of America (USA), for commercial, zoo or research
purposes, is thirty days. During quarantine, birds are screened for forms of Newcastle
disease and avian influenza which may be lethal to poultry (52). Chlortetracycline
treatment for Chlamydia is technically required but is not enforced in practice (12).
Numerous viruses (including forms which are not lethal to poultry) - for example,
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paramyxovirus, influenza type A viruses, psittacine herpesvirus (Pacheco's disease
virus), reoviruses and poxvirus - have also been isolated from psittacines in quarantine
stations in the U S A and Great Britain ( 1 , 52). Thus, to prevent introduction of disease
into a zoo or breeding facility, it is recommended that birds released from governmentmandated quarantine stations undergo a second quarantine period before entering a
bird collection.
Groups of birds should be quarantined as a unit. The quarantine period begins when
the last group of birds has entered the quarantine room (i.e. 'all-in/all-out' system).
This prevents birds at the end of their quarantine period from being exposed to disease
by birds entering later, and allows for the quarantine rooms to be thoroughly
disinfected between batches of birds. Most veterinarians dealing with birds
recommend a forty-five day quarantine period. This is often unpopular with aviary
managers in zoos and breeding facilities, who are anxious to get birds into the
collection as soon as possible. Quarantine in bird markets is almost certainly non­
existent, and thus markets are potential sources of disease.
The incubation period for many avian diseases is unknown or is dependent on
numerous factors (25, 29, 45). A forty-five day quarantine period covers the minimum
natural incubation period of Chlamydia in Psittaciformes (forty-two days) (27). In
turkeys (Meleagris),
however, clinical signs of chlamydiosis following natural
infection may occur at any time between two and eight weeks after exposure,
depending on age, dose, and the virulence of the strain (31).
The introduction of disease into populations of both captive and free-ranging avian
species is well documented (15). This has often been caused by a lack of quarantine,
or quarantine protocols which failed to detect a specific disease entity. When
developing a quarantine protocol, it is important to be aware of the potential disease
agents to which the avian species may be susceptible, and the mode of transmission
(Tables I, II and III). Appropriate quarantine periods and methods for disease screening
should be adapted and updated as the characteristics of avian diseases are further
defined, and as new or improved diagnostic tests are developed.
DISEASE SURVEILLANCE
Quarantine is designed to allow time for the clinical signs of any disease process
which is present to become manifest. However, the incubation periods of many current
and emerging avian diseases are unknown or are longer than any practical quarantine
period. The avian practitioner must therefore develop a comprehensive disease
surveillance protocol for use before, during and after the quarantine period. A
comprehensive surveillance programme should include the following elements (42):
a) species-specific protocols for quarantine
b) development of serum banks for retrospective testing
c) identification of laboratories to test for specific diseases
d) defined species standards for interpretation of test results
e) centralization and communication of results.
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TABLE I
Bacteria and fungi commonly associated with disease in avian species, together with
the reported host range and predominant mode of transmission
Host range
Transmission
All species susceptible
Phasianidae (b)
Ingestion
Aerogenic
Egg transmission
All species susceptible
Birds without caeca (b)
Chicken (Gallus domesticus)
S. Pullorum and S. Gallinarum
Free-ranging passerines and aquatic species
in the USA (55) - S. Typhimurium
Faecal shedding - ingestion
Contaminated feed/water
Aerogenic
Subclinical carriers
Vermin vectors
Egg transmission
Many species susceptible
Weaver finch (Parmoptila spp.)
Wax bill (Estrilda spp.)
Ostrich (Struthio camelus)
Faecal shedding
Pseudomonas,
Aeromonas
Many species susceptible
Anseriformes (free-ranging) (b)
Sphenisciformes (zoo collections)
Proliferates in water
Ingestion
Egg transmission
Klebsiella
Many species susceptible
Weaver finch spp. (b)
Environmental contaminant horizontal transmission
Yersinia (a)
Many species susceptible
(Y. pseudotuberculosis thought to be
indigenous in Northern and Central Europe)
Turaco spp., Eubucco spp.
Ramphastidae (b) canary (Serinus
canaria)
(46)
Faecal shedding
Carrier state in free-ranging birds and
rodents
Opportunistic - outbreaks related to
secondary stressor
Many species susceptible
Psittaciformes
Meleagris spp.
Fringillidae spp.
(Alcaligenes) Common in aquatic
habitats, faecal shedding, egg
transmission
(Bordetella) Faecal and respiratory
tract shedding, egg transmission
Many species susceptible
Higher rate of recovery from
scavengers/omnivorous species than from
graniverous species (53)
Faecal shedding
Ingestion
Spirochaetaceae
Anseriformes, Galliformes, Columbiformes
House sparrow (Passer domesticus)
European starling (Sturnus vulgaris)
African grey parrot (Psittacus erithacus)
Corvus spp.
Biting arthropod vectors - ticks,
contaminated inoculation needles (3)
Pasteurella
Many species susceptible
Known to cause disease in Phasianiformes,
Columbiformes, Anseriformes, Galliformes,
Psittaciformes and Passeriformes
Contact with infected secretions aerosols
Chronic carriers
Avian/mammalian vermin
Biting arthropods
Bites from carnivores
Organism
Bacteria
Escherichia
Salmonella
(a)
(c)
( c )
Citrobacter
(b)
(b)
Alcaligenes,
Bordetella
(b)
(b)
(b)
Campylobacter
(a)
61
TABLE I (contd)
Host range
Transmission
Actinobacillus
Known to cause disease in Psittaciformes,
Anseriformes, Columbiformes and
Fringillidae spp.
Probably horizontal
Egg transmission (chickens and
geese)
Haemophilus
Gallus domesticus - H. paragallinarum
Disease known in Columbiformes,
Anseriformes, Psittaciformes, Galliformes,
Passeriformes and Gruiformes
Aerosols - respiratory secretions
Carrier birds
Staphylococcus
All species susceptible
Horizontal, wound entry
Egg transmission
Streptococcus,
Enterococcus
All species susceptible
Faecal shedding, aerogenic (57)
Egg transmission
Mycobacterium
avium
All species susceptible
Captive Phasianidae, Coturnix spp.,
Gruidae and certain raptors (50)
Free-ranging species associated with urban
areas (50)
Direct contact, ingestion of infected
prey item, aerogenic
Avian vermin
Egg transmission
Probably all species susceptible (6)
Galliformes - Meleagris sp. (b) (6)
Anseriformes (b)
Ingestion
Reservoirs - pigs, raw fish and
rodents
Many species susceptible
Canary
Ubiquitous
Faecal shedding, aerogenic
Susceptibility varies with Clostridium sp.
Phasianifonnes
- C. perfringens
(C. welchii) types, A, B, C and D
Anseriformes (b) - C. botulinum
Vulture species quite resistant (26)
Ubiquitous - ingestion, wound
contamination
Decrease in gastrointestinal motility
Many species susceptible
Domestic turkeys (USA), domestic ducks
and geese (Central Europe), rock dove
(Passer domesticus) in urban centres
world-wide (38)
Faecal shedding - ingestion,
aerogenic
Vertical
Subclinical carriers
All species susceptible
Juvenile or neonatal birds, and birds
treated with antibiotics
Ubiquitous
Normal inhabitant of gastrointestinal
tract
Many species susceptible
Gaviidae, Sphenisciformes, Galliformes,
Anseriformes, Falconiformes,
Psittaciformes (37)
Ubiquitous organism
Aerogenic
Wound contamination
Egg transmission
Organism
Bacteria (contd)
(c)
(a)
(b)
Erysipelothrix
Listeria
(a)
(b)
Clostridium spp.
(b)
Chlamydia
(a)
Fungi
Candida
(b)
Aspergillus
(b)
a)
b)
c)
USA:
zoonotic potential (14, 47, 48)
particularly susceptible or common hosts
host-adapted strain
United States of America
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TABLE II
Viruses commonly associated with disease in avian species, together with the reported
host range and predominant mode of transmission
Transmission
Virus/disease
Host range
Avipoxvirus
Many species susceptible
Canaries , Anatidae
in zoos (USA),
free-ranging raptors (USA) (32)
Direct - wound entry
Aerogenic, biting arthropods
Carrier state
Infectious laryngotracheitis
Some Galliformes, canary (Serinus
canaria) (25)
Aerogenic - respiratory
shedding
Carrier state
Amazon tracheitis
Amazon parrots (Amazona spp.), some
Galliformes (25)
Aerogenic - respiratory
shedding
Duck plague/
duck virus enteritis
Anatidae (susceptibility varies between
species)
Direct contact - water-borne
Carrier state
Pacheco's disease
virus
Psittaciformes
Ingestion, aerogenic
Carrier state
Budgerigar
herpesvirus
Budgerigar (Melopsittacus
Inclusion body
hepatitis of pigeons
Columbiformes
Budgerigar, cockatiel (Nymphiscus
hollandiscus)
Ingestion
Falcon herpesvirus
Falconidae in the northern hemisphere
Ingestion - speculation (59)
Owl herpesvirus
Strigiformes
Species with yellow-orange irises
Ingestion - speculation (59)
(b)
(b)
Herpesviridae
a-Herpesviridae
^-Herpesviridae
undulatus)
(b)
Vertical transmission
(25)
Eagle herpesvirus
Eagles
Ingestion - speculation (59)
Inclusion body
disease of cranes
Gruidae, variable species susceptibility
Described only in captive species
Direct contact, ingestion
Carrier state
Inclusion body
hepatitis of storks
Black stork (Ciconia nigra)
White stork (C. ciconia)
Unknown (25)
Marek's disease
virus
Galliformes
Aerogenic - feather dander
Carrier state
Gouldian finch
herpesvirus
Gouldian finch (Chloebia
- rare in other taxa
gouldiae)
Horizontal - aerogenic
Papovaviridae
Papillomavirus
Fringillidae, Psittaciformes
Unknown
Polyomavirus/budgerigar
fledgling disease
Fringillidae, Psittaciformes,
Galliformes, Passeriformes
Aerogenic - feather dander
Ingestion
Vertical transmission
Carrier state
Psittaciformes
Aerogenic - feather dander
Ingestion
Vertical transmission
Subclinical infection
Circoviridae
Psittacine beak
and feather disease
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TABLE II (contd)
Virus/disease
Host range
Adenoviridae
Aviadenovirus
Transmission
(b)
Parvoyiridae
Goose parvovirus infection/
Derzy's disease
Galliformes
Anseriformes, Psittaciformes,
Columbiformes, Falconiformes (25)
Horizontal - faecal shedding
Aerogenic
Vertical transmission
Carrier state
Muscovy duck (Cairina
geese
Horizontal - faecal shedding
Aerogenic
Vertical transmission
Carrier state
moschata),
Reoviridae
Avian orthoreovirus
Psittaciformes, Columbiformes
Anseriformes, Fringillidae
Orbivirus
Budgerigar, cockatiel
Rotavirus
Galliformes, Columbiformes,
Horizontal - faecal shedding
Aerogenic
Vertical transmission
Biting arthropods
Horizontal - faecal shedding
Anseriformes, love birds
(Agaponis spp.)
Arboviruses
Eastern and western equine
encephalomyelitis virus
(a)
Paramyxoviridae
PMV-1 (Newcastle d i s e a s e )
(a)
Phasianidae (b)
Many species of birds may
be subclinical reservoirs (35)
Biting arthropods, mosquitoes
Horizontal - feather picking in
turkeys
Many species susceptible
Resistance varies, aquatic birds
more resistant than flocking birds (1)
Horizontal - faecal shedding
Aerogenic
Egg/vertical transmission
Carrier state
Horizontal - faecal shedding
Aerogenic
PMV-1 (pigeon)
Columbiformes
Cracidae, Pavonidae, Phasianidae,
other species
PMV-2
Passeriformes, Psittaciformes
Horizontal - faecal shedding
Aerogenic
Psittaciformes (b)
Horizontal - faecal shedding
Aerogenic
PMV-3
(b)
Meleagris spp., Passerifonnes
PMV-5
Budgerigar, rainbow lory
Horizontal - faecal shedding
Aerogenic
(Trichoglossus ornatus) (b)
Orthomyxovirus
Avian influenza virus/fowl
plague
( a )
Retroviridae
Avian sarcoma and leukosis
virus
Picorniviridae
Viral enteritis in cockatoos
Many species susceptible
Anseriformes (b) Passerifonnes,
Psittaciformes, Galliformes,
Charadiformes
Horizontal - faecal shedding
Aerogenic
Carrier state
Galliformes - Gallus spp. (b)
Horizontal - faecal/oral shedding
Vertical transmission
Cockatoos (Eolophus
Cacatua galerita)
Horizontal - faecal shedding
a) zoonotic potential (14, 47, 48)
b) particularly susceptible or common hosts'
roseicapillus,
PMV: (avian) paramyxovirus
USA: United States of America
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TABLE III
Parasites commonly associated with disease in avian species, together with the reported
host range and predominant mode of transmission
Host range
Transmission
Many species susceptible, highly hostspecific
Faecal shedding - horizontal
transmission
Sarcocystis spp.
Reported in over sixty species (33)
Birds can act as intermediate host
for some species of sarcocystis
and as definitive hosts for others
(44)
Atoxoplasma spp.
Psittaciformes, Passeriformes
Faecal shedding - horizontal
transmission
Many species susceptible
Psittaciformes, Anseriformes, Galliformes,
Passeriformes
Faecal shedding, aerogenic horizontal transmission
Many species susceptible - serve as
intermediate hosts
Faecal shedding from definitive
host (Felidae) - horizontal
transmission
Ingestion of infected birds by
some birds of prey
Parasite
Protozoa
Coccidia
Eimeria spp.,
Isospora spp.
Cryptosporidium s p p .
Toxoplasma gondii
(a)
Flagellates
Psittaciformes , cockatiel (Nymphisus
hollandiscus), budgerigar (Melopsittacus
undulatus) ^
Faecal shedding - horizontal
transmission
Budgerigars, cockatiels
asymptomatic carriers (30)
Trichomonas gattinae
Many species susceptible
Psittaciformes, Galliformes,
Columbiformes, Falconiformes
Oral secretions - horizontal
spread
Columbiformes are subclinical
carriers (39)
Hexamita
Psittaciformes, Galliformes,
Columbiformes
Faecal shedding - horizontal
transmission
Histomonas
Galliformes - occasionally seen in nongallinaceous species
Histomonads found in the
nematode Heterakis gallinarium
Haemoproteus spp.
Many species susceptible if vector is
present
Anseriformes, Passeriformes,
Falconiformes
Vector species - biting flies of
the family Hippoboscidae
(louse fly) and Culicoides midges
Leukocytozoon spp.
Infestation reported in over 100 species
(20)
Anseriformes , Falconiformes ,
Galliformes
Vector species - ornithophilic
biting flies of the family
Simuliidae and Culicoides midges
(54)
Many species affected
Vector species - mosquitoes of
the genera Culex, Aedes and
Anopheles
Many species affected
Numerous arthropod vectors
Giardia
(a)
w
Haemosporidia
w
w
Plasmodium spp.
(b)
Haemoflagellates
Trypanosoma spp.
65
TABLE III (contd)
Host range
Transmission
Ascaridia spp.
Many species susceptible
Faecal shedding - eggs very
resistant to environment
Heterakis spp.
Galliformes, Anseriformes
Faecal shedding - horizontal
spread ingestion of earthworms
Capillaria spp.
Many species susceptible
Faecal shedding
Earthworms may serve as
intermediate host
Syngamus trachea
Passeriformes, Galliformes, Anseriformes ground-feeding species or species which
ingest intermediate host
Faecal shedding
Earthworms are primary
intermediate host, but also other
invertebrates
Ground-feeding birds or species which
ingest intermediate host
Ingestion of intermediate host pill bug (Armadillidium vulgare)
and sow bug (Porcellio scaber)
Many species susceptible
Biting Diptera
Acanthocephalans
Birds which ingest intermediate host
Require one or more intermediate
host - avian species
intermediate/definitive host
Cestodes
Birds which ingest intermediate host
Most commonly seen in ground or aquatic
species
Birds which ingest intermediate host
Common in aquatic species
Intermediate hosts - insects,
crustaceans, earthworms
Many species affected
Direct contact, entire life cycle
on the host
Highly host-specific
Many species affected
Direct contact - can remain in
abandoned nests for new host
(56)
Many species but primarily in the
subtropical Americas
Flea burrows mouth part into
slrin to feed
Dermanyssus spp.,
Ornithonyssus spp.
Many species affected
(Dermanyssus spp.) Only adults
on host at night to feed, survives
months without host
(Ornithonyssus spp.) All life
stages on host, only ten days
without host
Knemidokoptes spp.,
Psittaciformes, budgerigars
Passeriformes
Parasite
Nematodes
Spiruroidea
Dispharynx
nasuta
Filarioidea filarioids/microfilaria
Trematodes
External parasites
Lice
Mallophaga spp.
Fleas
( a )
Stickfast flea
(Echidnophaga
gallinacea)
Mites
First phase of life cycle must
include a mollusc, many species
also require second intermediate
host
( a )
Flies
Hippoboscidae
(louse fly)
( a )
Many species affected
a) zoonotic potential (14, 47, 48)
b) particularly susceptible or common hosts
w
Direct contact, high incidence
among in-bred birds (30)
Direct contact
66
For effective implementation of a disease surveillance programme, the following
criteria are important:
a) screening of individuals or flocks for potential disease-causing organisms prior
to introduction into an existing facility
b) accurate diagnosis of the cause of a disease outbreak
c) effective means to control the disease and prevent future outbreaks.
The domestic poultry industry has developed numerous screening and diagnostic
tests for diseases caused by bacteria, fungi and viruses. Many of these tests can be
directly adapted for disease screening in exotic birds. Infections caused by Borrelia
anserina (3), Chlamydia spp. (31), Aspergillus spp. (7), adenovirus (40) and eastern
equine encephalomyelitis virus (35) can all be diagnosed using serological tests
originally developed for use in poultry (25, 26). As the science of non-domestic avian
medicine continues to evolve, tests for diseases specific to exotic avian species are
being produced. Blood tests are now available for the psittacine Polyomavirus which
causes budgerigar fledgling disease type 1 (BFDV-1), and for the circovirus which
causes psittacine beak and feather disease (18).
For many avian diseases, definitive diagnosis can only be achieved through culture
of the specific organism, virus isolation or identification of characteristic lesions on
histopathology. When die-offs occur, it is critical that a thorough necropsy is
performed and tissues sampled appropriately for definitive diagnosis. Species- or
taxon-specific necropsy protocols have been developed for bird populations managed
through regional species conservation programmes (41, 43).
Prevention of disease through vaccination is possible for a number of common avian
viruses. Effective vaccines are available (25) against diseases caused by herpesviruses
(e.g. Pacheco's disease [23], infectious laryngeal tracheitis, duck virus enteritis),
eastern and western encephalomyelitis virus, poxvirus (23) and Polyomavirus (49).
Avian medicine has greatly benefited from the development of new anaesthetic
agents, diagnostic equipment and disease detection methods with high sensitivity and
specificity, and safe and effective vaccines. In all but the smallest birds, diagnostic
screening for bacterial, fungal, parasitic and viral diseases is possible. Thus, with the
development of a strict quarantine protocol, and routine and thorough disease
surveillance, as well as the development and implementation of correct husbandry
practices, the avian practitioner and manager should be able to greatly decrease the
probability of a devastating disease outbreak.
*
* *
LES PRATIQUES POUVANT FAVORISER LA PROPAGATION DE MALADIES
INFECTIEUSES DANS LES ÉLEVAGES AVIAIRES PRIVÉS, LES MARCHÉS
D'OISEAUX ET LES PARCS ZOOLOGIQUES. - P.L. Wolff.
Résumé : Les activités des parcs zoologiques, des stations de quarantaine, des
marchés d'oiseaux, des vendeurs et des éleveurs impliquent la reproduction ou
le déplacement d'oiseaux. Les installations et les moyens de transport dans ce
domaine d'activité sont destinés à des oiseaux dont on ignore généralement
l'exposition antérieure à des agents pathogènes. Il existe peu de tests pour le
67
diagnostic et la surveillance des maladies des oiseaux exotiques ; les
gestionnaires d'établissement et les vétérinaires doivent donc connaître les
principaux agents pathogènes s'ils veulent détecter et contrôler l'apparition de
maladies. Il est possible d'en réduire les risques en instituant des pratiques de
gestion adaptées aux oiseaux qui permettent de minimiser la propagation
d'agents pathogènes, conjointement à des mesures de quarantaine et à une
manipulation correcte des oiseaux pendant les transports.
L'auteur passe en revue les pratiques d'élevage (mise en cage, nutrition,
transport, quarantaine) qui réduisent l'incidence et la propagation des
maladies infectieuses. Il dresse un inventaire des principaux
agents
pathogènes aviaires (bactéries, virus, parasites) ainsi que de leurs hôtes et de
leurs modes de transmission respectifs.
MOTS-CLÉS : Contrôle des maladies - Gestion des élevages aviaires Maladies aviaires - Oiseaux - Quarantaine.
PRÁCTICAS DE CRÍA EMPLEADAS POR AVICULTORES PRIVADOS,
MERCADOS AVIARES Y ZOOLÓGICOS, QUE PUEDEN PROPICIAR LA
APARICIÓN DE ENFERMEDADES INFECCIOSAS. - P.L. Wolff.
Resumen: Los parques zoológicos, las instalaciones de cuarentena, los
mercados avícolas, los intermediarios y los criadores son otras tantas
instancias que intervienen en el negocio y traslado de aves. Sus instalaciones
suelen albergar y trasladar a animales cuyo historial de exposición a
enfermedades se ignora por completo. Dadas las pocas pruebas disponibles
para la detección y monitoreo de enfermedades en aves exóticas, sólo el
conocimiento de los patógenos aviares más importantes permitirá al que cuida
a los animales y al veterinario reconocer y prevenir la aparición de brotes
infecciosos. La aplicación de prácticas de manejo aviar que minimicen la
propagación de agentes patógenos, junto con la cuarentena y el cuidado
adecuado de las aves durante el transporte, pueden reducir en gran medida el
peligro de enfermedad.
El autor efectúa un repaso de las prácticas de manejo (enjaulamiento,
alimentación, transporte, cuarentena) capaces de reducir la incidencia y
propagación de enfermedades infecciosas. Enumera asimismo los patógenos
aviares (bacterias, virus y parásitos) más importantes, la gama de sus
huéspedes y sus modos de transmisión.
PALABRAS CLAVE: Aves - Control de enfermedades - Cuarentena Enfermedades aviares - Manejo avícola.
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