Type E Botulism in Michigan - Michigan Sea Grant

Type E Botulism in Michigan: A
Historical Review
Thomas Cooley
Wildlife Disease Laboratory

In the Beginning
• The first waterfowl dieoff
attributed to
botulism in Michigan
occurred in 1941, being
diagnosed in wild ducks
in the Lake Erie marshes
near Monroe. The toxin
was identified as Type C.
• Approximately 1000
ducks and shorebirds
died.

In the Beginning (cont.)
• Scattered reports of dead gulls and 1 loon
occurred in counties on Lake Michigan, Lake
Huron, and Lake Superior between 1959 and
1962.
• No birds were examined,
so no cause of death
was determined.

1963
• The first waterfowl die-off attributed to Type
E botulism toxin occurred in 1963.
• Prior to this die-off Type E botulism was not
known to exist in wild birds in North America.
• The 1963 die-off extended from the Indiana
border to Leelanau County, nearly the entire
Lake Michigan shoreline of the Lower
Peninsula.
• The estimated mortality was 7720 birds (3300
loons, 4290 gulls, and 130 miscellaneous
birds).

1963 (cont.)
• The die-off occurred between August and
December.
– Gulls in early August in Van Buren County.
– Loons in mid-November in Berrien County.
– Loons and Gulls in early December in Van Buren
County.
• The greatest mortality occurred in late
November/early December.

Type E Botulism in Michigan, 1963

1964
• The 1964 die-off occurred along the northern
end of Lake Michigan from St. Ignace to
Wisconsin.
• The estimated mortality was 4920 birds (3570
loons, 820 gulls, 200 grebes, 240 ducks, and 30
miscellaneous birds).
• The die-off occurred between August and
October.
– Gulls in early August in Delta County (Upper
Peninsula), and Benzie, Oceana, and north and
south Manitou Islands (Lower Peninsula).

1964 (cont.)
– Loons in early September in Delta County.
– Loons in late September/early October in Delta,
Schoolcraft, and Mackinac Counties.
– Loons in early October in Leelanau County and on
Beaver Island (Charlevoix County).
• Compared to 1963 there were considerably
fewer gulls but more grebes and ducks. Total
loon numbers were comparable.

1964 (cont.)
• Mortality was the
heaviest in the north
end of Lake Michigan
and peaked among
loons in early
October.
• Several waves of loon
carcasses were found
over a 3 month
period.
Bollinger

Type E Botulism in Michigan, 1964

1965
• No estimates were determined in the 1965
die-off.
• The mortality of loons was probably less than
in 1963 and 1964.
• Mortality was confined largely to the northern
end of Lake Michigan and primarily involved
loons and grebes. Dead gulls were more widely
distributed.

• Heavy losses also
occurred among gulls
on Saginaw Bay in
Lake Huron.
1965 (cont.)

Type E Botulism in Michigan, 1965

1966
• The 1966 die-off consisted of scattered losses
of gulls along much of Lake Michigan with
additional mortality consisting of minor loon
losses and significant grebe losses.
• Mortality was along the Upper Peninsula
shoreline.
• The die-off occurred in October.
• Considerable mortality of gulls and some
water birds in Saginaw Bay in Lake Huron.

Type E Botulism in Michigan, 1966

1976
• The 1976 die-off extended from the Indiana
border to Muskegon.
• The estimated mortality was 600-1000 birds.
• The die-off occurred in October and
November.
• November 8, 1976 - A flight from the Indiana-
Michigan border to Muskegon (145 km) found
592 dead loons, 6 moribund loons, and 6 dead
gulls.

1976 (cont.)
• Between October 26 and November 19, 1976,
342 avian carcasses were collected and
examined. The species examined were 330
common loons, 1 red-throated loon, 6 gulls, 1
old squaw (long-tailed duck), 2 grebes (1
eared grebe and 1 unidentified), 1 redhead,
and 1 white-winged scoter.

Type E Botulism in Michigan, 1976

1981
• The 1981 die-off occurred along the southern
and eastern end of Lake Superior at Whitefish
Point in Chippewa County.
• 13 birds were examined and Type E botulism
was confirmed.

Type E Botulism in Michigan, 1981

1983
• The 1983 die-off occurred along the northern
end of Lake Michigan in Delta and Schoolcraft
Counties in the Upper Peninsula.
• The estimated mortality was 592 common
loons.
Timmermans

1983
• It was suspected that the loons dying during
this outbreak were from large rafts of birds
reported by the Michigan Department of
Natural Resources to be offshore and to the
southeast of the Garden Peninsula.

Type E Botulism in Michigan, 1983

Source of the Clostridium
botulinum Type E Organism
• Spores of C. botulinum type E are widely
distributed in bottom sediments and in the
alimentary tracts of fish from the Great Lakes.
Because of this it is apparent that a potential
exists for development of toxin.
• The organism is found in the bottom sediments
of the Pacific and Atlantic Oceans.
• Serious effects are derived from the
consumption of the toxin that is produced as
the bacteria grows.

Source of the Clostridium
botulinum Type E Organism (cont.)
• Possibly the carcasses of dead fish provide a
good medium for growth and toxin production.

Consumption of the Bacteria
• Type E botulism affects primarily inhabitants
of the open lake and bare beaches, namely
gulls, loons, grebes, and mergansers. All of
which are fish eaters.
• Fish remains have
consistently been
found in dead birds
(80-100% of the
affected birds
examined).

Gulls
• The gulls that died during the 1963 through
1966 die-offs likely were infected by
consuming dead fish, particularly alewives,
which accumulated in considerable quantities
in the water and on the beach.
• The alewife had become the predominant fish
in Lake Michigan. The alewife, an invader from
the Atlantic Ocean was estimated to
constitute 95%, by weight, of the fish in Lake
Michigan.

Gulls (cont.)
• The first record of
alewives in Lake Michigan
was in 1949 and they
were considered rare
until the mid 1950’s.
• The unusual
characteristic of this fish
species was they died en
mass annually.

Loons, Grebes, and Mergansers
• The means by which they ingest the bacteria
and toxin was in question since they do not
eat dead fish. They may mistake fish carcasses
in the water for live fish
or fish eaten by the
species may have
become moribund from
the botulism toxin.
Wills

Food Habit Studies for the 1963
• In Gulls:
and 1964 Die-offs
– 28 birds studied
– Alewives and yellow perch
composed 82% of the food
items present.
• In Loons:
– 149 birds studied
– Alewives and smelt composed 85% of the food
items present.
Record-Eagle

Clinical Signs of Type E Botulism
• Botulism toxins exert their primary action on
nerve endings and prevent the transmission of
nerve impulses to the muscles (flaccid
paralysis).
• Loss of muscle (motor) control of the wings,
legs, neck, and then the remainder of the
body.
• Wings hanging at their sides.
• Head erect in some birds, others are too weak
to hold head erect.

Clinical Signs of Type E Botulism
(cont.)
• Eyes are closed, the
nictating membrane
becomes paralyzed.
• Labored breathing and
eventual respiratory
failure.
• Retention of
consciousness.
• Legs are extended to
the rear.
Bourque

Pathology
• No lesions observed except wet frothy lungs
which suggests drowning.
• Birds are generally in good to excellent
physical condition.
• No evidence of significant toxicological levels –
either metals or pesticides.

Seasonality/Carcass-Maggot Cycle
• Gull die-offs in July and August
• Loons, grebes, and merganser die-offs in late
September and October.
• Loon and Gull die-offs in late November/early
December.
• Type E botulism generally occurs in cool fall
weather when fly infestation of carcasses is
less likely.

Seasonality/Carcass-Maggot Cycle
(cont.)
• Healthy loons usually raft offshore in the fall
and are not likely to be exposed to carcasses
along the shore or to consume maggots or
other invertebrates associated with carcasses.
• Most loons died on the open lake and drifted
some distance in the wind and water currents
before washing up on shore.
• Gulls died in the water as well as on the
beach.

Significant Findings from the Dieoffs
• “The most significant finding to date is the
presence of the toxin of Type E Clostridium
botulinum, causative agent of botulism, in the
blood of dead loons and gulls.”
• “A most significant finding was the occurrence
of toxin of C. botulinum type E in the tissues
of a majority of the birds.”

Significant Findings from the Dieoffs
(cont.)
• “I wonder if there is a significance in the fact or only
coincidental, that the problem of Type E botulism in
the region has become apparent only since the
advent of high populations of alewife in the upper
Great Lakes.”
• “While the vulnerability of gulls, loons, and other
water birds to the toxin has not yet been fully
demonstrated, we believe that accumulated
evidence points strongly to botulism caused by the
toxin of C. botulinum type E as the cause for recent
Lake Michigan bird mortalities.”

Significant Findings from the Dieoffs
(cont.)
• “Evidence suggests that botulism Type E in
gulls and loons is acquired through ingestion of
fish containing the toxin.”
• “The sporadic reports of epizootics of Type E
botulism suggests that factors determining
toxin production or its availability to birds
vary from year to year.”

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