EMERGING
INFECTIOUS DISEASES
Lecture 12
Morbillivirus
Infections in Aquatic Mammals
50 New Viruses in Past Decades
Include:
§ Ebola ivory coast
§ Andes virus
§ Hepatitis G
§ Fakeeh
§ Pirital
§ Oscar virus
§ Hendra virus
§ Black lagoon virus
§ Nipah
§ Whitewater arroyo
Three Distinct New Viruses for the Disease
and Death of Seals and Dolphins
Morbilliviruses
§
In Family
•
Paramyxoviridae
•
Serologically related,
single-stranded RNA viruses
§
Until 1988
•
Canine distemper virus
(CDV)
•
Measles virus (MV)
•
Rinderpest virus (RPV)
•
Peste des petites
ruminants virus (PPRV)
Percentage Amino Acid Identity in Various
Morbillivirus Proteins.
*nc sequence not completed
yet.
Nucleotide Sequence and Antigenicity
§
DMV and PMV most closely
related to RPV and PPRV
§
DMV and PMV are strains
of same viral species
§
PDV and Baikal seal
morbillivirus closely related to CDV
Five Pinniped/ Cetacean Epizootics
§ 1988, U.S.A. East Coast Hundreds of bottlenose dolphin
§ 1988, NW Europe 20,000 harbor seals
Several
hundred gray seals
§
1987-8
Lake Baikal, Thousands of Baikal seals
Siberia
§ 1987-8 Mediterranean sea Thousands of striped dolphins
§ 1993-4, Gulf of Mexico Scores
of bottlenose dolphins
Confirmed Morbillivirus Infections
§
Atlantic coast
bottlenosed dolphin epizootic
1987-88
§
Northwestern Europe:
harbor seals, harbor porpoises
1988
§
Western Mediterranean:
striped dolphins
1988
§
Gulf of Mexico;
Bottlenose dolphins
1993-1994
§
Eastern pacific common
dolphins
1998
Epizootic of European Harbor Seal
Morbillivirus (1988)
§
Contact with arctic seal
species most likely source (harp seals migrating south)(PDV-1)
§
Lake Baikal Siberian
seals acquired canine
distemper virus (PDV-2) from land animals
1990 Mediterranean Dolphin Epizootic
§
Striped dolphins
§
500 deaths - strandings
off Spain
§
Pneumonia and
encephalitis
§
Morbillivirus antigen
found
§
PDV (or closely related
virus) was causal
§
First report of
Morbillivirus in dolphins
§
Domingo et al, Nature,
1990
Gross Pathology: Cetaceans
§
1990-1992 Mediterranean
striped dolphin epizootic
•
Exudative bronchial
pneumonia
•
Ulcerative
Stomatitis
•
Enlarged pulmonary lymph
nodes
•
Cerebral cortical
hemorrhagic necrosis
§
1987-1988 Bottlenose
dolphin epizootic
•
Pneumonia
•
Skin and buccal mucosal
ulceration
•
Septicemia, pleural
serosanguinous fluid
•
Pulmonary, myocardial,
hepatic, pancreatic fibrosis
DMV Clinical Signs: Dolphins
§
Skin lesions
§
Buccal mucosal erosions
§
Increased epizoa on skin
and teeth
§
Tachycardia
§
Abnormal respiratory
rate
§
Muscular tremors
§
Impaired swimming
1995 Mediterranean Blue Whale Stranding
§
4 whales stranded (Sept.
29 - Nov. 27)
§
Mottled skin, one had
fever, increased RBC
§
All had increased lead,
mercury, and cadmium levels
§
Probably morbillivirus
infection
Other Documented Cases: 91'-95'
§
Long island harbour
seals
§
NW Europe harbour
porpoises
§
Western Atlantic harp
seal and pilot whales
MV Seropositivity also in:
§ Polar bear
§ Manatee
§ False killer whale
§ Pigmy sperm whale
§ Spotted dolphin
§ Minke whale
§ Walrus
§ Crabeater seal
§ Fin whale
§ Hooded seal
§ Leopard seal
§ Ringed seal
§ Others
Gross Pathology: Pinnipeds
§
Pneumonia in 75% of
harbor seals
§
Pulmonary abscesses
§
Hydrothorax and
hemothorax
§
Heavy lungworm
infections
§
Lymphadenopathy
PMV Clinical Signs: Harbor Seals
§
Fever, weight loss,
lethargy
§
Oculonasal discharge
(serous or mucopurulent)
§
Dyspnea
§
Diarrhea
§
Abortion
§
Loss of buoyancy control
(subcutaneous emphysema)
§
40-80% mortality
Clinical Pathology: Morbillivirus Infection
§
Grey seals: increased
plasma thymulin
§
Striped dolphins, harbor
seals: Leucopenia, hemoconcentration
Carcass Examination
§
Microscopic evidence of
nuclear and cytoplasmic acidophilic inclusion bodies in diverse cells
(e.g., CNS, lymphoid, epithelial)
Development of Monoclonal Antibodies for
Differential Diagnosis of Morbilliviruses
in Marine Mammals
Diagnosis in Live Animals
§
Cytologic and
immunofluorescence examination of conjunctival or nasal smears for inclusion
bodies or morbillivirus antigen
§
Stage of infection,
titer of antibody
Distribution and frequency
of DMV-antigen in organs of 57 Striped dolphins (Stenella coeruleoalba)
*Positive
cases/total number of dolphins investigated for this tissue or organ
Sample Questions:
1). The dolphin
morbillivirus has been shown to possess structural similarity to all but which
one of the following?
a.
Measles virus
b.
Feline leukemia virus
c.
Phocine morbillivirus
2). Observations of
afflicted animals in the Mediterranean striped dolphin and/or Atlantic
bottlenose dolphin epizootics have included all but which of the following?
a.
Exudative bronchial pneumonia
b.
Septicemia
c.
Ocular opacity
3). Morbillivirus - positive
(DMV or PMV) serology has been observed in all but which of the following
species?
a.
Sea otters
b.
Atlantic bottlenose dolphins
c.
Pilot whales and manatees
4) Please indicate which of
the following comments is not correct.
a.
PMV is known to infect dolphins
b.
The lungs and bronchial system are primary targets of MV in marine mammals
c.
MV frequently attacks the brain of marine mammals