Download Emerging Diseases in Manatees and Dolphins

Emerging Diseases in Manatees
and Dolphins: From Tumors to
Toxins
Gregory D. Bossart, V.M.D., Ph.D.
Center for Coastal Research
Marine Mammal Research and Conservation
Program
Harbor Branch Oceanographic Institution
Ft. Pierce, Florida
Emerging Diseases in Manatees and Dolphins: From Tumors to Toxins
In the past two decades, 30 diseases all new to medicine have emerged. During the
same period, older diseases such as malaria, cholera and tuberculosis have made a
global resurgence. The magnitude of infectious disease resurgence has not been
observed in developed countries since the 1850s. Similar trends are being
documented in marine ecosystems and, in particular, are impacting marine
mammals. Emerging and resurging diseases of marine mammals may have
epizootic potential, zoonotic implications and a complex pathogenesis involving
other co-factors such as immunologic dysfunction. This presentation will discuss
emerging diseases in dolphins and manatees particularly relating to neoplasia and
biotoxins.
Note: Written permission from the author is necessary prior to the outside use of the
images from this presentation.
1
‘Environmental distress syndrome’…
‘Environmental distress syndrome’…
The cause of the emerging disease phenomena is likely multifactorial and may
reflect an ‘environmental distress syndrome’ whereby ecologic and climatic
changes associated with human activities are encouraging the selection of new and
opportunistic pathogens.
Diseases of emerging interest in marine mammals include infectious (viral,
bacterial, fungal, protozoal), neoplastic, environmental, anthropogenic and
idiopathic. Selected diseases or disease agents of cetaceans and sirenians include
various papillomaviruses, dolphin poxvirus, and other viral infections; lobomycosis;
neoplasia; harmful algal bloom
biointoxications;; manatee “cold stress syndrome”
syndrome”; and the idiopathic
cardiomyopathy of pygmy and dwarf sperm whales.
whales
Advanced diagnostic technologies have greatly enhanced the ability to identify
disease etiologies. Marine mammal veterinarians play a critical role in identifying
diseases occurring in marine mammals and the impact these diseases have on
individuals, populations and the ecosystem as a whole.
Reference:
Bossart GD. Marine mammals as sentinel species for oceans and human health.
Oceanography 19(2): 44-47, 2006.
2
Stranding data………
Source of data for documenting emerging disease in marine mammals
Historically, much of the pathologic data on marine mammal disease came from
marine mammal strandings, which is still a valuable source. However, the quantity
and quality of the data collected from strandings may vary considerably which may
preclude detailed in-depth studies.
3
Health assessment data…
Source of data for documenting emerging disease in marine mammals (cont’d):
More in-depth pathologic and epidemiologic data now originate from dedicated
marine mammal population health assessment programs which use marine mammal
species as sentinels for oceans and even human health. Such sentinels are used to
gain early warnings about current or potential negative trends and impacts. In turn,
such indicators and warnings permit us to better characterize and potentially
manage negative impacts on human and animal health associated with our oceans.
Marine mammals are probably one of the best sentinel organisms in aquatic and
coastal environments because many species have long life spans, feed at a high
trophic level, and have extensive fat stores that can serve as depots for
anthropogenic toxins. Additionally, marine mammals are conspicuous and
charismatic megafauna that elicit strong human emotions and are thus more likely
to be observed. As such, health maladies that impact these species may make
humans more likely to pay attention to deteriorating ocean health issues.
These slides are from health assessment studies done on the Atlantic bottlenose
dolphin (Tursiops truncatus) in the U.S and the Antillean manatee (Trichechus
manatus manatus) in Mexico.
Reference:
Bossart GD, Goldstein JD, Murdoch EM, Fair PA, and McCulloch, S. Health
assessment of bottlenose dolphins in the Indian River Lagoon, Florida and
Charleston, South Carolina. Harbor Branch Oceanographic Technical Report No.
4
Papillomaviruses….
• Genital: sperm whale, dusky dolphin,
Burmeister’s porpoise, bottlenose dolphin
• Gastric: beluga whale
• Cutaneous: harbor porpoise, killer whale,
Florida manatee
• Oral: bottlenose dolphin?
A. Characteristics of papillomaviruses
ƒOncogenic, forming papillomas that may spontaneously regress, persist and in
some instances undergo malignant transformation
ƒNonenveloped DNA viruses that are typically species-specific
ƒTransmission: Direct contact
ƒImmune compromise may play a role in tumor formation in some species
B. Tissues and cetacean/sirenian species that papillomaviruses have been reported
in are listed on the slide
References:
Bossart GD, Cray C, Solorzano JL, Decker SJ, Cornell LH and Altman NH.
Cutaneous papovaviral-like papillomatosis in a killer whale (Orcinus orca).
Marine Mammal Science 12:274-281, 1996.
Bossart GD, Decker SJ and Ewing RY. Cytopathology of cutaneous viral
papillomatosis in the killer whale (Orcinus orca). In: Pfeiffer C (ed.), Molecular
and Cell Biology of Marine Mammals, Krieger Publishing Co., Melbourne, FL, pp.
213-224, 2002.
Bossart GD, Ewing R, Lowe M, Sweat M, Decker S, Walsh C, Ghim S and Jenson
5
Papillomaviruses…
• Clinical signs
– Plaques
– Warts
– Papillomas→
Carcinoma
– Variable size
A. Morphology of gross lesion types associated with papillomavirus infection in
marine mammals
•
Killer whale (Orcinus orca) (top right photo)- large elevated fissured cutaneous
plaque behind pectoral fin
•
Atlantic bottlenose dolphin (Tursiops truncatus) (lower right photo)- verrucoid
lesion of the tongue. Also, sessile orogenital papillomas were first reported in
this species in 2005.
•
Florida manatee (Trichechus manatus latirostris) (lower left photo)- slightly
raised nodular cutaneous lesion first reported in 2002 in this endangered species
Reference:
Bossart GD, Ghim S, Rehtanz M, Goldstein J, Varela R, Ewing R, Fair P, Lenzi R,
Joseph B, Hicks C, Schneider L, McKinnie CJ, Reif JS, Sanchez R, Lopez A,
Novoa S, Bernal J, Goretti M, Rodriguez M, Defran RH, and Jenson A. B.
Orogenital neoplasia in Atlantic bottlenose dolphins (Tursiops truncatus).
Aquatic Mammals 31(4): 473-480, 2005.
Also, see previous slide.
6
Manatee PV…
Verruciform or filiform lesions…
A. Florida manatee cutaneous viral papillomas occur in 2 phenotypic forms:
•Verruciform/filiform-occur on contact surfaces of face (nasal, lips, oral disc) (see
photos on this slide)
•Maculopapular lesions-occur along dorsal and lateral trunk (next slide)
7
Second phenotype-sessile
maculopapular lesions often
in a linear pattern suggesting
traumatic self inoculation …
A. Florida manatee cutaneous viral papillomas occur in 2 phenotypic forms:
The photos on this slide are typical of the maculopapular lesion often found in a
linear pattern suggesting traumatic self inoculation. These lesions are clinically
persistent and do not typically regress. The presence of this type of lesion is
associated with immune suppression.
8
Verruciform
Sessile
A. Histologic differences between cutaneous papilloma forms in manatees
•
Verruciform form (left photos)- note the lesion is composed of focally-extensive
hyperplasic and occasionally dysplastic keratinocytes raised above the surface
of the skin. Thick dermal papillae containing capillaries separate the rete ridges.
Moderate numbers of keratinocytes of the stratum spinosum and stratum
granulosum have vacuolated cytoplasm and pleomorphic round vesicular nuclei
that are centrally or eccentrically located. These cells have features similar to
koilocytes described in other species that are exhibiting the cytopathic effects of
papillomavirus infection (lower left photo). Inclusion bodies are not observed.
In some instances, degenerate and nondegenerate neutrophils infiltrate the
stratum corneum and occasionally are associated with keratinocyte necrosis and
superficial colonies of a heterogeneous gram-negative bacterial population.
•
Maculopapular form (right photos)-note the lesion is characterized by focal
sessile plaques composed of hyperplastic keratinocytes with broad rete ridge
formation. Fine dermal papillae containing capillaries separate the broad rete
ridges. Koilocytes are minimal in number.
9
Ultrastructural findings…
A. Transmission electron microscopy of manatee papillomas
By transmission electron microscopy, cytoplasmic vacuolation and karyomegaly
with peripherally redistributed chromatin are present. The nucleoplasm of
sparse numbers of keratinocytes contain viral plaques consisting of round to
hexagonal 45-50 nm virus particles, ultrastructurally identical with those of
papillomaviruses (PV) (left photo- low power electron photomicrograph
showing keratinocyte nucleus with viral plaques; right photo- higher power
electron photomicrograph of left photo showing PV virions).
10
Immunohistochemical findings…
A. Immunohistochemistry (IHC) of manatee tumors
Utilizing a polyclonal antibody produced against bovine papillomavirus type 1
(BPV-1), PV structural antigens are present within the nuclei of koilocytes and
within other keratinocytes of the stratum granulosum. PV antigens are
particularly diffuse (see photo) in almost all differentiating keratinocytes of the
maculopapular types indicating a large viral load.
(Note: Bovine papillomavirus type 1 is the prototype PV and has at least 40 distinct
linear epitopes that are conserved to various degrees among the mammalian and
avian PVs. This immunohistochemical technique is routinely used to screen
animal tissues for evidence of productive PV infections.)
11
TmPV-1 summary ….
1) A transmissible (direct contact if viral load is high), oncogenic and
probably latent viral infection that involves activation by specific co-factors
(immunosuppression, etc.).
2) Two distinct phenotypic, persistent or site-variable regressive/recurrent
lesions (common fibropapilloma and lesions similar to those of other species
with immunosuppression which can progress to cancer).
3) ELISA Test- seroepidemiologic evidence of TmPV-1 infection suggests that
infection is limited to a small group of manatees at the present time
4) Most focal hyperplastic epidermal lesions (i.e. papillomas, etc.) commonly
seen in captive and free-ranging manatees are likely not caused by TmPV-1.
A. Manatee papillomavirus is now designated as TmPV-1
Our present knowledge of this emerging disease is summarized in this slide.
References:
Bossart GD, Ewing R, Lowe M, Sweat M, Decker S, Walsh C, Ghim S and Jenson
AB. Viral papillomatosis in Florida manatees (Trichechus manatus latirostris).
Experimental and Molecular Pathology 72:37-48, 2002.
Rector A, Bossart GD, Ghim SJ, Sundberg JP, Jenson AB, and Van Ranst M.
Characterization of a novel close-to-root papillomavirus from a Florida manatee
by using multiply primed rolling-circle amplification: Trichechus manatus
latirostris papillomavirus type 1. J. Virol. 78: 12698-12702, 2004.
12
Orogenital tumors in bottlenose
dolphins…
A. Newly reported orogenital tumors in captive an free-ranging Atlantic bottlenose
dolphins
In 1987, a comprehensive review reported only 41 confirmed tumors in cetaceans.
The majority of tumors represented benign mesenchymal and epithelial
neoplasms; the organ systems most commonly involved were the
gastrointestinal tract, skin, and internal female reproductive tract. Since 1987,
reports of neoplasia, particularly malignant neoplasia, have increased in some
marine mammal species. This pattern of increasing occurrence may represent an
emerging disease phenomenon or be the result of increased surveillance by
veterinarians, pathologists and others who deal with marine mammal strandings,
free-ranging animal health assessment studies and captive animal health care.
We are now observing lingual papillomas and squamous cell carcinomas and genital
papillomas in Atlantic bottlenose dolphins. Tumors are found in both freeranging and captive animals. Some dolphins have multiple tumors of mixed
histologic type, consisting of papillomas and squamous cell carcinomas,
suggesting malignant transformation of the benign papillomatous lesions.
Pathologic evidence suggests that these tumors may be of infectious etiology,
possibly transmitted by the orogenital route.
Reference:
Bossart GD, Ghim S, Rehtanz M, Goldstein J, Varela R, Ewing R, Fair P, Lenzi R,
Joseph B, Hicks C, Schneider L, McKinnie CJ, Reif JS, Sanchez R, Lopez A,
13
Oral sessile papillomas…
A. Gross appearance of dolphin orogenital tumors
Grossly, orogenital lesions are composed of two distinct types. Type 1 anteriodorsal
tongue and genital lesions are focal to multifocal, irregular to circular, raised,
soft, light pink to white, and sessile, ranging from 0.5-2 cm in diameter as seen
in this slide. The surface of these lesions may be fissured or velvety and nonulcerative. Type 2 lesions are found on the surface or beneath the tongue and are
focal to multifocal, raised, firm, pink, sometimes ulcerated and coalescing
nodules with irregular and thickened erythematous borders measuring from 3-7
cm in diameter. Some dolphins have multiple lingual lesions involving both
Type 1 and Type 2 forms.
While presently the role of herpesvirus in lesion pathogenesis is unknown, it is
interesting to note that some of the orogenital lesions have gross and histologic
features similar to oral hairy leukoplakia in humans (as seen in this slide). Hairy
leukoplakia is associated with Epstein Barr virus (EBV) infection, a human
gamma herpesvirus, which is virtually restricted to immunosuppressed patients
particularly those with human immunodeficiency virus infection. In humans,
dual infection with EBV and human papillomavirus may play a role in oral and
nasopharyngeal carcinogenesis. However, the specific contribution of EBV to
oral and nasopharyngeal squamous cell carcinoma remains controversial due to
conflicting data on the varied presence of EBV within the lesion.
14
Histopathology...
A. Microscopic appearance of oral tumors in dolphins
Microscopically, Type 1 orogenital lesions as seen in this slide are diagnosed as
sessile papillomas characterized by focal sessile plaques composed of uniformly
proliferating keratinocytes and occasionally dysplastic keratinocytes with
elongation of submucosal papillae. Rarely, keratinocytes contain vacuolated
cytoplasm and pleomorphic, round, vesicular nuclei that are centrally or
eccentrically located. These cells have features similar to koilocytes described
in other species that are exhibiting the cytopathic effects of papillomavirus
infection. Inclusion bodies are not observed.
15
Genital sessile papillomas…
A. Gross appearance of genital tumors in dolphins
The gross appearance of the genital mucosal lesion is similar to the oral lesions. The
lesion in this slide is a Type 1 genital tumor.
16
A. Gross appearance of genital tumors in dolphins
This slide is of a Type 1 sessile papilloma on the penis of a bottlenose dolphin.
17
Histopathology…
A. Microscopic appearance of the genital tumors in dolphins
This slide is a low power photomicrograph of the center of a Type
Type 1 genital lesion.
The lesion is composed of proliferating keratinocytes with microscopic
microscopic
similarities to the Type 1 oral lesions.
18
Transmission electron microscopy…
A. Transmission electron microscopy of the orogenital tumors in dolphins
Transmission electron microscopy reveals that the nucleoplasm and cytoplasm of
moderate numbers of epithelial cells of the sessile oral and genital papillomas
contain encapsidated intranuclear particles and enveloped cytoplasmic virions
consisting of capsids and enveoles, measuring approximately 120-160 nm in
diameter. Bar = 500 nm.
19
A. Transmission electron microscopy of the orogenital tumors in dolphins
Transmission electron micrograph of a keratinocyte from a genital sessile papilloma
from a dolphin, which demonstrates enveloped virions within the cytoplasm
(large arrow). A virion (small arrow) obtains an outer envelope in passage
through the nuclear membrane (arrowhead). Bar = 500 nm.
20
Immunohistochemistry…
Bovine Herpesvirus (BHV-1) IHC
A. Immunohistochemistry (IHC) of dolphin orogenital tumors
This slide demonstrates positive IHC using a primary antibody to bovine
herpesvirus type 1 in a dolphin genital papilloma.
21
Viral isolation and
sequencing…
1) Specimens of this lesion and of several additional
dolphin lesions were used to extract the whole DNA.
Isolated viral DNA was amplified using the isothermal
multiply primed rolling-circle-amplification technique.
2) The search for a restriction enzyme cutting the
amplified DNA once revealed the presence of viral
DNA of the typical PV-specific size of around 8kb.
The whole viral DNA was subsequently cloned
into a sequencing vector.
3) A new PV was discovered and named TtPV-2. All
putative genes of the virus were identified and submitted
to the GenBank. The first PV isolated from a genital lesion of
a bottlenose dolphin – TtPV-1 – was derived from a captive
animal living in a Europe.
A. Molecular virology
A new dolphin papillomavirus has been isolated, cloned and sequenced from a
small number of dolphin genital tumors.
Reference:
Rehtanz M, Ghim S-J, Rector A., Van Ranst M, Fair P, Bossart GD and Jenson A.B.
Isolation and characterization of the first American bottlenose dolphin
papillomavirus: Tursiops truncatus papillomavirus type 2. Journal of General
Virology 87: 3559-3565, 2006.
22
Herpesvirus-associated
genital lesions ...
PCR with DNA-extractions from genital lesions using degenerate
herpesvirus primer pairs recognizing the DNA polymerase gene...
demonstrating a dolphin herpesvirus DNA polymerase gene part.
A. Molecular virology (cont’d)
Molecular data provides evidence that all of the genital sessile papillomas of
dolphins studied to date are associated with a similar herpesvirus infection.
PCRs with DNA-extractions from genital lesions were utilized to investigate the
presence of viral DNA using degenerate herpesvirus primer pairs that recognize
the DNA polymerase gene of several human as well as animal herpesviruses
known to date. This method demonstrated the presence of a dolphin herpesvirus
in all biopsies. A close sequence investigation lead to the conclusion that the
virus isolated from dolphins belongs to the family of gammaherpesviruses. The
role of herpesvirus in lesion pathogenesis is presently unknown.
23
Malignant transformation…
A. Transformation of benign tumors
Type 2 lesions are found on the surface or beneath the tongue and are focal to
multifocal, raised, firm, pink, sometimes ulcerated and coalescing nodules with
irregular and thickened erythematous borders measuring from 3-7 cm in diameter
(top right photo). Occasionally, dolphins have multiple lingual lesions involving
both Type 1 and Type 2 forms.
Microscopically, Type 2 tongue lesions are distinctly different and are
diagnosed as squamous cell carcinomas. The mucosa and submucosa of
these lesions contain a poorly circumscribed invasive malignant neoplasm
characterized by nests and cords of atypical squamous cells. Squamous
cells have prominent intercellular bridges, scant eosinophilic to lightly
basophilic cytoplasm, pleomorphic round vesicular nuclei, prominent
basophilic to magenta nucleoli and abundant, often bizarre, mitoses (left and
lower right photos). Additionally, occasional nests of cells display central
accumulations of compact, partially keratinized cells or keratin pearl
formation. Some dolphins have multiple lingual lesions consisting of both
Type 1 and Type 2 lesions, and are diagnosed with distinct sessile
papillomas and squamous cell carcinomas, respectively.
At necropsy, dolphins with oral squamous cell carcinoma can have
widespread metastatic squamous cell carcinoma with metastases in the
lung, liver kidneys, pulmonary-associated lymph nodes, pleura, diaphragm,
pre-scapular lymph nodes, and mediastinal lymph nodes.
24
Orogenital tumors….
ƒ First report of oral papillomas in free-ranging bottlenose dolphins.
ƒ First report of genital papillomas in free-ranging bottlenose
dolphins from Atlantic coastal waters.
ƒ Tumors may represent one or more progressive emerging diseases.
ƒ Preliminary evidence also suggests that these tumors may be
infectious (herpesvirus and/or PV) , most likely having an
orogenital route of transmission.
ƒ Combined infections (i.e. PV and herpesvirus) possible.
ƒ Progression to cancer, exacerbation by pregnancy and other
breeding implications…
ƒ Development of a seroepidemiological screening system and the
corresponding vaccine
ƒ Cases are increasing in some free-ranging Florida dolphin
populations (0%-2003; 11%-2004; 47%-2005; 23% 2006).
A. Orogenital tumors in dolphins- Summary
In summary, the occurrence of a cluster of orogenital neoplasms among captive and
free-ranging dolphins suggests that an emerging disease, presumably of infectious
etiology, may be present. Further research to define the extent of the condition,
isolate and characterize the causal agent(s) and search for factors that may be
responsible for the recent apparent increase in incidence of these tumors is needed.
25
Immunoblastic malignant lymphoma…
„Species
(bottlenose dolphins and spotted dolphins)
„Florida Atlantic and Gulf Coasts
„Free-ranging and captive animals
„Aggressive with widespread metastases
„Cluster pattern of disease/infectious etiology?
A. Malignant lymphoma in dolphins
A polymorphic immunoblastic malignant lymphoma is described in a cluster of
captive and free-ranging dolphins. This is a highly aggressive neoplasm that
appears to be rapidly fatal and may be associated with a retroviral infection.
A. Reference:
Bossart GD, Ewing R, Herron AJ, Cray C, Decker S,
Alexander J and Altman NH. Immunoblastic
malignant lymphoma in dolphins: ultrastructural and
immunohistochemical features. J Vet Diag Invest
9:454-458, 1997.
26
Harmful algal blooms…
...and the waters that were in the river were turned to blood. And the fish
that were in the river died; and the river stank and the Egyptians could
not drink of the water of the river... Exodus 7: 20-21
Harmful Algal Blooms (HABS) and Their Toxins
HABs and the potent biotoxins they elaborate are incriminated in mass mortalities
of dolphins, sea lions, and manatees. The range of biotoxins produced by HABs is
extensive and associated with many human HAB illnesses. HAB biotoxins include:
brevetoxins, the cause of neurotoxic shellfish poisoning (NSP); saxitoxins, the
cause of paralytic shellfish poisoning (PSP); okadaic acid, the cause of diarrhetic
shellfish poisoning (DSP); azaspiracid, the cause of azaspiracid shellfish poisoning
(ASP); and numerous others. The HAB problem is significant, growing worldwide,
and poses a major threat to human and ecosystem health. Marine mammals appear
to be good sentinels for the ecosystem and public health effects of HABs. For
example, the inhalational route of brevetoxin exposure appears to be unique in
manatees, but it is shared with humans.
References:
Bossart GD. Marine mammals as sentinel species for oceans and human health.
Oceanography 19(2): 44-47, 2006.
Van Dolah FM, Douchette GJ, Gulland F, Rowles T, and Bossart G. Impacts of
algal toxins on marine mammals. In: Vos JG, Bossart GD, Fournier M and O'Shea T
(eds.), Toxicology of Marine Mammals, Taylor & Francis, London, pp. 247-270,
2003.
27
A. Geographic distribution of HABs in the United States
28
Florida
red tide…..
A. Satellite view of a Florida red tide bloom
The red tide bloom in the photo is represented as intense red-yellow zones primarily
along the southwest coast of Florida.
29
A. Other marine species impacted by brevetoxicosis
Red tide blooms are often associated with large fish die-offs as well as sea turtle and
marine bird mortalities.
Reference:
Kreuder C, Mazet J, Bossart GD, Carpenter T, Holyoak M, Elie, M and Wright S.
Clinicopathologic features of suspected brevetoxicosis in double-crested cormorants
(Phalacrocorax auritus) along the Florida gulf coast. J Zoo Wildlife Med 33: 8-15,
2002.
30
The Florida manatee….
ƒOrder-Sirenia (4 existing species) Trichechus
manatus latirostris
ƒAll listed as vulnerable to extinction by IUCN
-the World Conservation Union
ƒ2006 Mortality-416 manatees died; the deadliest year on record
ƒOver a five-year period, a total of 2098 manatees have died, and about 23%
of these deaths were caused by watercraft collisions.
A. Brevetoxicosis and Florida manatees
Brevetoxins have neurotoxic and hemolytic properties and are produced by the
dinoflagellate (Karenia brevis) found in Florida red tide blooms. Florida manatees
seem particularly prone to the chronic effects of inhalational and ingestional
brevetoxicosis, with the primary pathologic lesions consisting of a catarrhal rhinitis,
multiorgan congestion and hemorrhage and less commonly hemosiderosis and
nonsuppurative meningitis. However, the precise pathogenic mechanism of this
intoxication in manatees is unknown and the exclusionary diagnosis of
brevetoxicosis is based the absence of preexisting disease, the typical, but
nonspecific pathologic lesions and a temporal correlation of high levels of
brevetoxins in tissues by an ELISA technique and presence of red tide.
References:
Bossart GD, Meisner R, Rommel SA, Lightsey JA, Varela RA, and Defran RH.
Pathologic findings in Florida manatees (Trichechus manatus latirostris). Aquatic
Mammals 30 (3): 434-440, 2004.
Bossart GD, Meisner R, Rommel SA, Ghim S and Jenson AB. Pathological features
of the Florida manatee cold stress syndrome. Aquatic Mammals 29 (1): 9-17, 2003.
Bossart GD, Baden DG, Ewing RY, Roberts B and
Wright SD. Brevetoxicosis in manatees
31
Brevetoxicosis (NSP)…
Neurotoxic properties:
Brevetoxins (9 or more; PbTx) produced by dinoflagellate Karenia brevis
-Excitatory lipophilic polyether neurotoxin
-Binds Na+ gated channels in brain, heart, muscle
Hemolytic properties:
-Hemorrhage and anemia
Immunosuppressive properties:
A.The pathologic properties of brevetoxins
Some of the known pathogenic mechanisms of brevetoxins are listed in this slide.
32
Manatee Brevetoxicosis
Manatee
Brevetoxicosis…
160
140
N u m b e r of D e ath s
120
100
80
60
40
20
ƒ17 % of annual manatee mortality
attributed to brevetoxicosis
0
1982 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
Year of Occurrence
A. Annual occurrence of Florida manatee brevetoxicosis
The annual occurrence data for Florida manatee brevetoxicosis is indicated in this
slide.
33
Histopathologic diagnoses…1996
epizootic
Catarrhal rhinitis
Pulmonary hemorrhage
and edema
Hemosiderosis (hepatic,
lymphoid, CNS)
Nonsuppurative meningitis
Cerebral hemorrhage
100%
95%
78%
55%
45%
A. Pathologic lesions of manatee inhalational brevetoxicosis
The lesions above are typically associated with mortality-associated inhalational
brevetoxicosis in Florida manatees. Data suggest that ingestional and combined
inhalational/ingestional toxicosis also occur in this species.
34
A. Microscopic lesions of inhalational brevetoxicosis in manatees-catarrhal rhinitis
These low power photomicrographs are from a manatee that had inhalational
brevetoxicosis and demonstrate a severe diffuse catarrhal rhinitis. The submucosa
is infiltrated by many lymphocytes and plasma cells with congestion and
hemorrhage often with a catarrhal exudate. Occasionally, intramucosal vesicles
containing proteinaceous fluid (upper right photo) are present.
35
A. Microscopic lesions of inhalational brevetoxicosis in manatees-pulmonary
hemorrhage, edema and congestion
These low power photomicrographs are from a manatee that had inhalational
brevetoxicosis and demonstrate pulmonary hemorrhage, edema and congestion.
36
A. Microscopic lesions of inhalational brevetoxicosis in manatees- hepatic and CNS
hemosiderosis
These low power photomicrographs are from a manatee that had inhalational
brevetoxicosis and demonstrate hepatic and CNS hemosiderosis. Hemosiderin
deposits are brown and granular found in siderophages within the liver and brain
(perivascular sites).
37
The problems…
1) Chronic environmental PbTx
exposure is common--- threshold
and baseline levels are undetermined.
2) Once a toxin burden is established, toxin pharmacokinetics,
residence time and pathogenesis are unknown.
3) PbTx types and concentrations that can
functionally compromise and adversely affect a manatee are unknown.
A. Some brevetoxicosis diagnostic problems in manatees and dolphins
Diagnostic issues with brevetoxicosis in manatees and dolphins are discussed in this
slide. To help with this problem, we developed an immunohistochemical technique
that detects the presence, abundance and distribution of brevetoxins (PbTx) in
tissues.
38
Immunohistochemistry…
A. Immunohistochemical (IHC) technique for manatee brevetoxicosis
This slide is a high power IHC photomicrograph of a lymph node of a manatee with
brevetoxicosis. Lymphocytes and macrophages are intensely brevetoxin positive
(i.e., brown granular staining). The inset photo is a negative control manatee lymph
node.
References:
Bossart GD, Baden DG, Ewing RY, Roberts B and
Wright SD. Brevetoxicosis in manatees
(Trichechus manatus latirostris) from the 1996
epizootic: gross, histologic and immunohistochemical
features. Toxicologic Path 26:276-282, 1998.
Bossart GD, Baden DG, Ewing RY and Wright SD.
Manatees and brevetoxicosis. In: Pfeiffer C (ed.),
Molecular and Cell Biology of Marine Mammals,
Krieger Publishing Co., Melbourne, FL, pp. 205-212,
2002.
39
Bottlenose dolphins…
• Similar pathogenesis?
Florida Panhandle UME-2004
A. Immunohistochemical (IHC) technique for brevetoxicosis in Atlantic bottlenose
dolphins (Tursiops truncatus)
This slide is a low power IHC photomicrograph of a lymph node of a dolphin with
suspected brevetoxicosis (right photo). Scattered lymphocytes and macrophages are
intensely brevetoxin positive (i.e., brown granular staining). The left photo is a
negative control dolphin lymph node.
40
Brevetoxin
vectors…
10,000
1000
1,000
100
Brevetoxin
concentration
(ng ml -1 or ng g -1)
K. brevis density (cells per ml)
BrevetoxinConcentrations inSeagrass
DuringMass-mortalityEvents
100
10
10
1
*
1
6 Jun
9 May
23 May
25 Apr
11 Apr
28 Mar
21 Mar
26 Feb
13 Mar
0.1
Sampling date in 2002
A. Brevetoxin vectors
Important new data indicate that brevetoxin vectors such as seagrasses and fish can
result in delayed or remote manatee and dolphin exposure causing intoxication in
the absence of toxin-producing dinoflagelates. Thus, unexpected toxin vectors may
account for mortality long after or remote from a dinoflagellate bloom.
References:
Flewelling LJ, Naar JP, Abbott JP, Baden DG, Barros
NB, Bossart GD, Bottein MD, Hammond DG, Haubold
EM, Heil, CA, Henry MS, Jacocks HM, Leighfield TA,
Pierce RH, Pitchford TD, Rommel SA, Scott PS,
Steidinger KA, Truby EW VanDolah, FM and
Landsberg, JH. Red tides and marine mammal
mortalities. Nature 435: 755-756, 2005.
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Immune suppression…
1) Inhalation exposure, low/high exposure to brevetoxin 3 in rats produced :
ƒ small numbers of splenic and peribronchiolar lymphoid tissue macrophages
stained IHC positive for brevetoxin (Benson et al., 2004)
ƒ humoral-mediated immunity was suppressed in brevetoxin-exposed rats as
indicated by a >70% reduction in splenic plaque-forming cells in brevetoxinexposed animals compared to controls.
2) Manatees with inhalational brevetoxicosis:
ƒ decreased lymphocyte proliferation (Walsh et al., 2005)
Results suggest that the immune system is a target of toxicity following
brevetoxin inhalation……
A. Brevetoxicosis and immune suppression
This concept is discussed in this slide.
Reference:
Benson JM, Hahn FF, March TH, McDonald JD, Sopori ML, Seagrave JC, Gomez,
A, Bourdelais AJ, Naar J, Zaias J, Bossart GD, and Baden DG. Inhalation toxicity of
PbTx 3 in rats exposed for five days. Journal Toxicol Environ Health 67(18): 14431456, 2004
42
Public health significance…
•
Acute gastrointestinal toxicity
(neurotoxic shellfish poisoning)
•
Significant acute respiratory
change in asthmatics exposed to
brevetoxin aerosols
•
Increased incidence of other
pulmonary disease due to
aerosolized brevetoxins on an
emergency basis
•
Potential effects of chronic
exposure on immunity
A. Public health significance of red tides exposure
The public health issues of brevetoxicosis are discussed in this slide.
Reference:
Backer LC, Fleming LE, Rowan A, Cheng Y, Bensen J, Pierce RH, Zaias J, Bean J,
Bossart GD, Johnson D, Quimbo R and Baden DG. Recreational exposure to
aerosolized brevetoxins during Florida red tide events. Harmful Algae 2: 19-28,
2003.
43
Florida’s
2000 pound canary…
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ƒ
ƒ
ƒ
ƒ
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Intoxication route-ingestion and/or inhalation in manatees and humans
Among mammals, the inhalational route of brevetoxicosis appears to be unique in
manatees and humans.
New vector mechanisms (i.e., intoxication in the absence of toxin producing
dinoflagellates). Human poisoning via contaminated fish…
Ingestion (NSP)- acute neurotoxic properties -excitatory lipophilic polyether
neurotoxin that binds Na+ gated channels in brain, heart, muscle.
Inhalation- increased incidence of acute or chronic human respiratory disease with
increased red tides
Other insidious effects on manatees and humans...immune suppression with
secondary opportunistic disease, toxic shock due release of inflammatory
mediators???
A. The manatee may be a good sentinel species for brevetoxicosis…
44
Intoxication… dependent on exposure
route/time, toxin type and toxin dose …
• Transmission- inhalation and/or ingestion
• Acute Intoxication- Neurotoxic properties
-Excitatory lipophilic polyether neurotoxin
-Binds Na+ gated channels in brain, heart, muscle
• Chronic Intoxication
-Hemolytic properties- Hemorrhage and anemia
-Immunologic- catastrophic cascade release of
inflammatory mediators and immune suppression
A. Possible pathogenic mechanisms of brevetoxicosis
The pathogenesis of manatee brevetoxicosis is suspected to involve direct inhalation
of toxins and/or ingestion of toxins in food sources. The pathogenesis of dolphin
brevetoxicosis is likely by ingestion of toxins in food sources, only. Diagnosis of
brevetoxicosis in manatees and dolphins is typically by exclusion and may be based
on pathologic findings and postmortem demonstration of the toxins in fluids and
tissues. The pathologic findings of inhalational brevetoxicosis in manatees are
catarrhal rhinitis, pulmonary hemorrhage and edema, multiorgan hemosiderosis and
nonsuppurative leptomeningitis. Immunohistochemical staining is used to determine
the presence, abundance and distribution of brevetoxins in tissues.
The present data suggest that manatee and dolphin mortality resulting from
brevetoxicosis may not necessarily be acute but occur after chronic inhalation
and/or ingestion and involve the release of inflammatory mediators that result in
fatal toxic shock. The inhalational route of brevetoxin exposure appears to be
unique in marine mammals but shared with humans. Increases in human pulmonary
emergency room diagnoses are temporally related to ‘red tide’ occurrences, which
may be increasing in frequency along Florida coastlines.
45
Diagnosis by exclusion and with caution…
The precise pathogenic mechanism(s) of brevetoxicosis in marine
mammals is unknown. The exclusionary diagnosis of brevetoxicosis
could be based on:
1) the absence of preexisting disease and significant histologic lesions or the
presence of the typical, but nonspecific lesions, observed in manatees…
2) immunohistochemical findings…
3) the temporal correlation of high levels of brevetoxins in tissues (by
ELISA, etc.) and presence of red tide…
4) other? (e.g., comparative concurrent mortality/health assessment studies,
etc.)
A. Diagnosis of brevetoxicosis
Criteria for suspected brevetoxicosis are based on
the temporal correlation of a bloom of red tide
(Karenia brevis), high tissue levels of brevetoxins
determined by an ELISA technique, and presence
of characteristic gross and microscopic nasal
and/or pulmonary lesion , and absence of
traumatic injury or other indications of pre-existing
disease conditions.
Reference:
Bossart GD, Meisner R, Rommel SA, Lightsey JA,
Varela RA, and Defran RH. Pathologic
findings in Florida manatees (Trichechus manatus
latirostris). Aquatic Mammals 30 (3):
46
The End………..
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