Sarcocystis is a genus of protozoan parasites that infect the muscles of intermediate hosts such as mammals and birds. It was first discovered in 1843. The parasites have an indirect life cycle involving a transport host and a definitive carnivore host. In the carnivore, the parasites mature and release oocysts that infect transport hosts when consumed. In muscles of transport hosts, sarcocysts form that can infect carnivores, completing the cycle. Most infections are asymptomatic, but some species can cause illness in horses and humans who act as accidental intermediate hosts. No effective treatments exist beyond preventative hygiene measures.

1. Sarcocystis
 Sarcocystis
is
a
genus
of
protozoa.
 Species in this genus are
parasites, the majority infecting
mammals, and some infecting
reptiles and birds.
 It was first found in a mouse by
Miescher in 1843.
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2. Scientific Classification
Kingdom
Chromalveolata
Phylum
Apicomplexa
Class
Conoidasida
Order
Eucoccidiorida
Family
Sarcocystidae
Genus
Sarcocystis

3. Geographical Distribution
 These are parasites which live in a number of
hosts; therefore their distribution is wide, varied
and infect animals worldwide.
 Most prominent cases are observed in:
North America
 South Africa
 Australia
 Canada


4. Major Species


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It has more than 130 recognized species so
far.
Some of them that are quite important are;
Sarcocystis cruzi( Ducks, cattle & birds)
Sarcocystis rileyi( Sheep, Pigs, & waterfowl)
Sarcocystis neurona(Equines)
Sarcocystis fusiformis(Humans)
The most common species is Sarcocystis
rileyi, which causes the disease known as
"rice breast disease" in waterfowl

5. Hosts

It’s hosts are;

Ducks
Sheep
 Cattle
 Pigs
 Rats
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 Raccoons
Horse
 Water fowls
 Humans
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6. Transmission in
Host
 The mode of transmission from animal to
animal is incompletely understood.
 For many years it was believed
Sarcocystis was transmitted by ingestion of
flesh containing sarcocysts.
 Now another indirect method of infection has
been proven whereby carnivores and
omnivores pass an infective stage of the
parasite in their feces.
 An animal is infected by ingesting material
contaminated by the infected feces.

8. Life cycle of
Sarcocystis

10. Life Cycle
 The Sarcocystis sp. parasites have an indirect life
cycle that requires a paratentic or transport
host animal (a bird), in which they live for a time
before they are transported to a definitive host
animal (a carnivore), in which they reach
maturity.
 Birds ingest the eggs or oocysts of the mature
parasite in food or water that is contaminated by
carnivore feces, which contain the oocysts.
 The oocysts develop in the intestine of the bird
into an intermediate form, the sporozoites, that
enter the bird’s bloodstream and infect specific

12.  Multiplication of these cells gives rise to a
second intermediate form, merozoites, that are
carried by the blood to the voluntary muscles,
where elongated cysts or macrocysts are
eventually produced.
 The life cycle is completed when a carnivore
ingests the infected muscle tissue of a bird and
the parasite reaches maturity and releases
oocysts in the intestines of the carnivore.
 The carnivore is infected only in its intestine.
Macrocysts do not develop in the carnivore, and
the Sarcocystis sp. parasite rarely causes the
carnivore illness or other forms of disease.

13.  For some species, humans are the definitive
host i.e. the host in which sexual reproduction
is completed.
 In this case there is intestinal sarcocystosis.
Humans may also act as accidental deadend intermediate hosts for several other
species and in these cases there is muscular
sarcocystosis.
 In horses infected with Sarcocystis neurona,
the sporozoites enter the endothelial
cells and replicate asexually, developing into
tachyzoites, which then migrate to the
animal's central nervous system

14. Signs & Symptoms
 Sarcocystis is a nonfatal, usually asymptomatic
infection.
 There are no recognizable signs of the infection in
most living animals.
 In heavy infections,
Lameness
 Weakness
 paralysis
 Muscle pain

Mild fever
Painful muscular swelling

15. Diagnosis
 Diagnosis is usually made by finding the
striated muscle after the animal's death.
 Further diagnostic methods include;
Complement-fixation
 Dermal sensitivity tests
 Frozen muscle tissue
 Muscle biopsy

cysts in

16. Treatment
 No effective treatment is known. Since the disease
can be transmitted by the ingestion of feces
containing sporocysts.
 Good sanitation and hygiene are important in
preventing the disease.
Cotrimoxazole
 Primaquine
 Both these drugs are appears to be a
logical -but unproven-choice till present….
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