A protozoan parasite of avian
erythrocytes transmitted by the
'blackfly' Simulium spp.
Infection causes the disease
parasites were first seen by
Danilewsky in 1884 in blood from an
There are over 100 species in this genus.
There are over 100 species in this
genus, but the 3 most important species
that’ve infected the most common
domestic birds are;
Leucocytozoon simondi(ducks and
In Thailand, India, Taiwan, Japan, Burma, Sri
Lanka, the Philippines, Singapore, Malaysia,
Indonesia, China, and Korea, USA, Canada
and Africa most cases have been reported.
outbreaks of leucocytozoonosis have
been reported in chickens, turkeys,
waterfowl and wild birds worldwide.
Hosts & Vectors
Similar waterfowl and Chickens
Black Fly(Simulium spp)
Leucocytozoon use Black flies (Simulium
species) as their intermediate host and
Birds as their definitive host.
Over 100 species of birds have been recorded
as hosts to these parasites.
Leucocytozoon does not threaten human
populations in terms of potential infection,
infected poultry is not pathogenic in humans.
Still, the parasite's economic impact could hurt
poultry farmers' revenue as mortality rates are
extremely high, especially among young birds
Transmission in Host
Leucocytozoon's involves an
intermediate host (the blackfly) which
carries the parasite from one avian host
When the blackfly vector bites a bird,
perhaps around the unfeathered eye
area, sporozoites are released in the
vector's saliva and into the bird's
It completes it’s life cycle in Two
different hosts i;e Intermediate
host(black fly) and Definitive host(birds)
In Black fly, it enters in it’s body when
the fly feeds on the bird already been
infected by the parasite.
After penetrating in the fly it’s
gametophytes get mature and
reproduce in Midgut.
In the insect vector these elongated
gametocytes become either a female
(macro)gametocyte with a red-staining
Male (micro)gametocyte with a palestaining diffuse nucleus, which come
together to form an ookinete.
This ookinete invades an intestinal cell
of the fly vector, where it matures into an
This oocyst produces sporozoites which
migrate to the salivary glands of the
blackfly, thus reinitiating the cycle.
In Birds, sporozoites invade the liver cells
and develop into small schizonts, which in
turn produce merozoites.
Schizonts release merozoites or secondary
schizonts in the endothelial cells of the blood
vessels and in essentially any of the viscera.
The merozoites either enter red blood cells or
In the red blood cells, merozoites develop into
In the macrophage, merozoites develop into
megaloschizonts, which then divide into primary
Five days post infection:
Many schizonts develop in hepatocytes
Seven days post infection:
Megaloschizonts begin to appear in spleen
Also appear in Lymph and other tissues
Gametocytes accumulate in liver
12+ days post infection
Hemorrhagic scars from rupturing
Area of Infection
Leucocytozoon’s infect the
A diagnosis can be made by
The demonstration of gametocytes in blood
Histopathological examination of the liver,
spleen and brain can show developing
Necropsy may reveal an enlarged spleen and
Since the majority of birds are sub clinically
infected with Leucocytozoon, other causes of
death must be ruled out even with the presence of
Leucocytozoon gametocytes in peripheral blood
The majority of birds affected with
leucocytozoonosis exhibit no clinical
Visibly affected show mild to severe
signs of anorexia, luekocytosis,
weakness, anemia, emaciation, and
have difficult breathing.
Young birds manifest in appetence,
weakness, dyspnea, and sometimes
death within 24hrs.
in adults appear less abruptly and
consist of listlessness and a low
The mortality in adult birds occurs as a
result of debilitation and increased
susceptibility to secondary infection.
Granulomatous and lymphocytic lesions are
seen in the lungs, heart, brain and
peripheral nerves. Large gametocytes can
block capillaries of the lungs.
Treatment and Control
Treatment usually is not effective,
control of the Leucocytozoon in
domestic avian species has, until
recently, been limited to control of the
Preventive medication using
Pyrimethamine(1 ppm) and
Sulfadimethoxine(10 ppm) combined in
the feed controls it.
controls invertebrate vectors are helpful.
have been used i;e parasitemia is
reduced, but the infection is not cleared.
Vaccines based on TRANSGENIC plants.
a protozoan parasite of
peripheral blood neutrophils.
It’s genus Apicomplexan protozoa which
incorporates over 300 species obligate
intra erythrocytic parasites.
Infection caused by hepatozoon is called
A Hepatozoon parasite was initially
reported from a cat in India in 1908.
widely distributed in the world
mainly found in;
North and South America.
Hosts and Vectors
other domestic animals
Hepatozoon has more than 300 species but
the most imp. Of them which cause infection
Hepatozoon canis.(dogs, jackals and all
And very recently discovered
Hepatozoon sipedon.(infect Snakes and
Transmission in Host
Transmission of the infection occurs via
ingestion of infected ticks.
Dogs are infected by ingesting infected
ticks during grooming behavior or eating
prey that has attached ticks.
It’s not transmitted by Tick biting.
In Snakes, it is transmitted through
infected mosquitoes that are ingested
by some frogs that later on, eaten by the
snake transmitting it.
Mosquitoes get infected by feeding on
Members of the genus Hepatozoon possess
particularly complex life cycles which vary
considerably among species.
Sexual reproduction and sporogenic
development occur in haemocoel of the
It also has two hosts;
Vertebrate host, consumes the infected
The sporozoites then migrate to the liver of
the vertebrate, where they undergo multiple
fission (asexual reproduction) to produce
Merozoites are released into the bloodstream
where they form gametocytes.
Gamonts are large, conspicuous organisms
which occupy significant portion of
the erythrocyte, and are easily visible on
simple blood films.
The invertebrate vector feeds on the blood
of the infected vertebrate
The gamonts are taken up into the gut once
more, where they undergo gametogenesis
and the cycle begins once more.
In case of snakes, they do not typically
feed on mosquitoes, a third, intermediate
host is required, in this case a frog.
The frog ingests the infected mosquito, and
the snake acquires the infection by feeding
on the now infected frog.
Another mosquito can then feed on the
snake, thus continuing the life cycle.
Is based on,
Biopsy of skeletal muscles
Clinical Signs & Symptoms
or persistent fever
Weakness muscle atrophy
Stiff gait and hind limb paralysis.
Pus-filled eye discharge.
Treatment & Control
The current therapy for hepatozoonosis
Pyrimethamine (TCP) drugs for two
weeks to destroy the parasites.
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