retention of erythrocyte integrity. Emboli of necrotic
hepatocytes and cell debris evident in hepatic vessels
(Figure 5)
Figure 4: Liver histopathology revealing pan-necrosis with fragmentation of hepatocellular cords due to cell dissociation and only sinusoidal
lining still intact.
Figure 5: Liver histopathology with emboli of necrotic hepatocytes in
vessels (arrows).
Water samples collected were initially examined
directly under the microscope revealing large
conglomerates of round to oval shaped, variably sized
algae resembling cyanobacteria (Figure 6).
Figure 6: Direct microscopic examination of water revealed sheets of
round to oval cyanobacterial bodies.
This water sample was the submitted for algal
analysis. Algae were identified as exclusively
Microcystis aeruginosa and an extremely high algal
count of > 1 000 000 cells/ml was documented.
Microcystis aeruginosa is a common unicellular,
planktonic freshwater cyanobacterium which are
regularly found at the surface of water bodies in
spring and summer. The existence of intracellular
structures, the gas vesicles, provides cells with
buoyancy. These hollow, gas-filled structures can keep
Microcystis cells close to the surface of water body,
where there is optimal light and oxygen for growth.
Cyanobacteria may adopt different strategies to
reduce the possibility of being consumed by their
upper trophic level of food web, such as morphology
and intracellular toxins. Cyanobacteria are capable
of producing 3 different structural groups namely
cyclic peptides (microcystins, nodularins) which target
hepatic function; alkaloids (anatoxins, saxitoxins) that
target the nervous system and lipopolysaccharides
which are potential irritants.
This toxin production creates health risks for
populations (animal and human) living and harvesting
in contaminated areas where these cyanobacteria
bloom. Blooms occur when nutrient levels spike in
aquatic environments or nutrient levels are selective
toward microcystin producing cyanobacteria.
The microcystins are produced by the genera
Microcystis, Anabaena and Oscillatoria and are protein
phosphatase inhibitors and potent hepatotoxins.
Toxicity of microcystis in mammals is characterized
by fulminant intrahepatic hemorrhage followed
by hypovolaemic shock, secondary to massive
hepatocellular necrosis and collapse of hepatic
parenchyma and death. Under these circumstances
Microcystis aeruginosa (most commonly) or Anabaena
and Oscillatoria (less frequently) are among the most
ecologically damaging species due to their toxicity to
aquatic and terrestrial organisms.
The nature of this pathology in conjunction with
the clinical history and photographic evidence, algal
identification and Microcystis aeruginosa counts would
strongly support a diagnosis of microcystis poisoning.
2016
SEPTEMBER
23