A. Subphylum Sporozoa
1. Class Telosporea
a. Subclass Coccidia (e.g., Isospora)
(1) Order Eucoccidia
(a) Suborder Eimeriina
(b) Suborder Hemosporina (e.g., Plasmodium)
b. Subclass Gregarina
2. Class Toxoplasma (e.g., Sarcocystis, Toxoplasma)
3. Class
Haplosporea
General characteristics
1. They
are obligate intracellular parasite of blood and tissue cells of vertebrate and
invertebrates.
2. The
life cycle is characterized by alternation of generation or development, occur
in the same host or they need another host.
3. The
schizogony stage, which is the asexual cycle of development usually occur in
the epithelial cells of the intestinal mucosa. The end product is the
schizonts.
4. The
sporogony or the sexual cycle of development usually occurs within the
intestinal lumen of the invertebrate host. The end product is the spores.
5. The
intermediate host is the one in which the schizogony stage of the parasite
takes place.
6. The
definite host is the one wherein sporogony occur.
Stages of development
1. Trophozoite
– feeding or growing stage in the asexual cycle of the sporozoa, it lives
within the tissue cell.
2. Schizont
– the sporozoan body during schizogony which includes the period of initial
growth (early schizont or pre–segmenters) to the complete splitting up of the
nucleus with merozoite production.
3. Merozoite
– late segment, end product of schizogony of malarial parasites in human RBC;
pathogenic stage; motile and escape from the infected cell; some will infect
other tissue cell, again going to the trophozoite stage, the rest will be
differentiated into male and female forms (gametocytes).
4. Gametocyte
– immature sexual form
5. Microgametocyte
– the male gametocyte that will produce a group of microgametes.
6. Microgametocyte
– the female gametocyte that will produce a macrogamete; mature only to be fit
for fertilization
7. Gametes
– mature sexual forms.
8. Microgametes
– the male sex cell in sporozoa
9. Macrogametes
– the female sex cell in sporozoa
10. Zygote
– union of micro and macrogametes; a fertilized ovum before cell division
11. Oocyst
– an encysted zygote
12. Sporoblast
– one of a number of bodies in many sporozoa into which zygote divided and from
which sporozoites are formed.
13. Sporocyst
– as used in Coccidia, the separated membrane that surrounds a sporoblast and
subsequently the group of sporozoites formed from this sporoblast.
14. Sporozoite
– the end product of sexual multiplication of malarial parasite in the
mosquito.
CLASS TELOSPOREA
*********** THE PLASMODIUM SPECIES ***********
Characteristics in general
1. Obligate
intracellular parasite of blood and tissues.
2. Alternation
of generation (sexual and asexual development)
3. Alternation
of host
4. Sexual
cycle takes place within the definite host or mosquito vector (female Anopheles
flavirostris)
5. Asexual
phase takes place within the intermediate host (man).
6. Pigment
producing during erythrocytic stage.
7. Four
species are known to affect humans:
a. Plasmodium
vivax – benign tertian malaria
b. Plasmodium
ovale – benign ovale tertian malaria
c. Plasmodium
malariae – benign quartan malaria
d. Plasmodium
falciparum – malignant tertian or subtertian or Estivo – autumnal malaria
|
SPECIE
IDENTIFICATION OF MALARIAL PARASITE |
|||
|
P.
vivax |
P.
ovale |
P.
malariae |
P.
falciparum |
|
Schuffner’s
dot |
James’
dot |
Ziemann’s
dot |
Maurer’s
dot |
 |
 |
 |
 |
(Use the Mnemonic: V/S-Victoria Secret, O/J-OJ Simpson, M/Z-Malik Zayn, F/M-FM Radio)
****** PLASMODIUM VIVAX ******
Morphology:
Early trophozoite or ring : relatively
large; usually one prominent chromatin
dot,
sometimes 2; often 2 rings, sometimes more in
one
cell.
Large trophozoite : large, markedly amoeboid; abundant
chromatin;
Prominent
vacuole; pigment is fine.
Young schizonts or
pre–segmenters : large; somewhat amoeboid; dividing
chromatin masses numerous, pigment
in fine rodlets
Mature schizonts or : schizonts & merozoites large; pigment coalescent
Segmenters
Number of merozoites : 12
– 24, usually 12 – 18
Microgametocytes : smaller and less numerous than
macrogametocytes;
spherical; compact; no
vacuole;
undivided chromatin; diffuse coarse
pigment;
cytoplasm stains light blue
Macrogametocytes : spherical; compact, larger than microgametocyte,
smaller
nucleus; same pigment; cytoplasm stains
darker
blue
Alteration in infected
red cell : enlarged and decolorized; Schuffner’s
dots
usually
seen.
Length of asexual phase : 48
hours
Minimal prepatent period : 8
days
Usual incubation period : 8
– 31 days
Interval between parasite
patency and gametocyte
appearance : 3 – 5 days
Development period in
mosquito : 10 days at 28 – 30oC
****** PLASMODIUM OVALE ******
Morphology:
Early trophozoite or ring : one
chromatin dot; double infection uncommon
Large trophozoite : small;
compact, not amoeboid, vacuole
inconspicuous,
pigment coarse
Young schizont or
pre–segmenter : medium size; compact, few chromatin masses,
coarse
pigment
Mature schizone or
segmenter : merozoites larger than in P.
malariae;
irregular
rosette
Microgametocyte : similar to P. vivax
Macrogametocyte : similar to P. vivax
Pigment except in mature
schizonts : similar to but somewhat coarser than
P.vivax;
sometimes
clumped or in lateral bands
Alterations in the infected enlarged; decolorized;
prominent Schuffner’s
RBC : dots appear early; infected cells
maybe oval–
shaped
with finfrainted ends.
Length of asexual phase : 49
– 50 hours
Minimal prepatent : 9 days
period
Usual incubation period : 11
– 16 days
Interval between parasite
patency and gametocyte
appearance : 5 – 6 days; appearance irregular and
numbers
are
few
Developmental period
in mosquito : 16 days at 25oC
14
days at 27oC
****** PLASMODIUM MALARIAE ******
Morphology:
Early trophozoite or ring : one
chromatin dot; double cell infection
uncommon
Large trophozoite : smaller than vivax; compact, often
band
Shaped;
not amoeboid; vacuole inconspicuous
Coarse
pigment
Young schizont or
pre–segmenter : small; compact; few chromatin masses;
coarse
pigment
Mature schizont or
segmenter : schizonts smaller but merozoites
larger
Number of merozoites : 6
– 12, usually 8
Microgametocyte : similar to P. vivax but smaller and
less numerous
Macrogametocyte : similar to P. vivax but smaller and
less numerous
Pigment except in mature
schizonts : seen in young rings; granules rather than rods;
tendency
toward peripheral scatter (rosette)
Alterations in the infected
RBC : cell may seem smaller, fine stippling
(Ziemann’s
dot),
occasionally seen
Length of asexual phase : 72
hours
Minimal prepatent : 14 days
period
Usual incubation period : 28
– 37 days
Interval between parasite
patency and gametocyte
appearance : 10 – 14 days
Developmental period
in mosquito : 30 – 35 days at 20oC
25
– 28 days at 22oC
****** PLASMODIUM FALCIPARUM ******
Morphology:
Early trophozoite or ring : small,
delicate, sometimes 2 chromatin dots
multiple
red cell infection,
Large trophozoite : medium size; usually compact, rarely
amoeboid;
Vacuole
inconspicuous; rare in peripheral blood
After
half grown; granular pigment
Young schizont or
pre–segmenter : small, compact; numerous
chromatin masses;
single
pigment mass; rare in peripheral blood
Mature schizont or
segmenter : smaller merozoites; single pigment
mass
Number of merozoites : 8
– 26 usually 8 – 18
Microgametocyte : crescents, usually sausage–shaped;
diffuse
Chromatin;
large grains of scattered pigments;
Large
nucleus; cytoplasm stains dark blue
Macrogametocyte : crescents, often longer and more
slender; central
chromatin;
more compact pigments; compact
nucleus;
cytoplasm stains dark blue
Pigment except in mature
schizonts : granular pigment; early tendency to
coalesce;
typical
single solid mass in mature trophozoite;
coarse
scattered “rice grains” in crescents
Alterations in the infected
RBC : normal size but may have
“brassy”appearance.
Maurer’s
dots or clefts common.
Length of asexual phase : 36
– 48 hours
Minimal prepatent : 5 days
period
Usual incubation period : 7
– 27 days
Interval between parasite
patency and gametocyte
appearance : 8 – 11 days
Developmental period
in mosquito : 22 – 23 days at 20oC
10
– 12 days at 27oC
Blackwater fever – acute
hemolytic syndrome resulting from intravascular hemolysis characterized by
hemoglobinuria, fever, nausea and vomiting, jaundices, oliguria and anuria. It
is associated with falciparum malaria.
****** ISOSPORA BELLI / ISOSPORA HOMINIS ******
Disease: Human coccidiosis
Morphology:
Since they are
morphologically the same, they are taken together
1. Belli
– passed out in the stool as immature or unsegmented (thicker wall)
2. Hominis
– passed out in the stool as mature form
Immature oocyst:
20–33u x 10–19u
It is
elongatedly ovoidal in shape with one end
narrower
than the other. This contains the
micropyla.
It has a thin, inner membranous layer
and an
outer, thick impermeable layer. It usually
contains
a spherical mass of granules, may have
sporoblast.
Mature oocyst: 29 x 14u
Contains
2 sporocyst, each containing 4 sporozoite
Habitat
Small intestine of man (lower portion
of ilium and cecum). It is believed that the schizogony occurs within
epithelial cells of the intestinal mucosa while gametocyte formation,
maturation of the sex takes place within the intestinal lumen.
Life cycle
****** EIMERIA SP. ******
– Characterized by an oocyst
having 4 sporocysts and each has 2 sporozoites.
– The sizes vary depending on the
species.
– The shape is usually ovoidal,
spherical or ellipsoidal
– They are coprozoites or
spurious parasite of man, they are just an accidental host; has been diagnosed
in human stool by the ingestion of non–viable cyst from the sardines and fishes
which are their natural host.
–
It should not be confused with
Isospora
CLASS TOXOPLASMA
****** TOXOPLASMA GONDI ******
Disease: Toxoplasmosis
Morphology:
–
it has a delicate ovoidal,
pyriform or crescentric body measuring 4–6u with one or both extremities
pointed or rounded. The nucleus is located at one end and the paranuclear body
on the other end.
–
masses of these parasites are
observed in mononuclear and endothelial cells and might easily be mistaken for
leishmanias without careful study.
Mode of
transmission:
Ingestion of
undercook meat, fecal contamination, accidental infection, nasal route,
transplacental transmission.
Cats are
important in this disease because they are the vectors; they are asymptomatic
and have the capacity to give the highly infectious oocyst.
Life cycle
Three types of
Toxoplasmosis
1. Congenital
– infection through the fetus occur on the 1st 4 months of pregnancy
but not later than because of antibody production.
Tetrad of
signs or Sabin–Feldman syndrome:
a. Internal
hydrocephalus and microcephalus
b. Chorioretinitis
c. Convulsion
and psychomotor disturbances
d. Intra–cerebral calcification
2. Acquired
– post–natal; majority of the cases are inapparent or subclinical; some cases
are grouped into:
a. With
fever, lymphadenitis resembling glandular fever or infectious mononucleosis
b. Without
fever, with enlargement of lymph glands without other signs and symptoms
c. Typhus–like
syndrome
d. Cerebro–spinal
form
e. Increase
protein and increase mononuclear cells.
3. Opportunistic
– in decrease immunity especially those taking immunosuppressive drugs.
Diagnosis:
Ventricular aspirate, from biopsy of
lymph node, liver or spleen, or as necropsy and intraperitoneal inoculation
into mice; demonstration of specific antibodies using the CFT combined with
Sabin Feldman dye test
****** SARCOCYSTIS LINDEMANNI *******
Disease: Focal myositic with eosinophilia
Morphology:
1. Consist
of a cylindrical, elongated or fusiform body, hyaline in appearance with more
or less pointed ends, lying lengthwise in the affected muscle fibers. It is
enclosed in a membrane and contains myriads of round and crescent – shaped
spores, “Miescher’s tubes.”
2. The
outer membrane may show radial striation and from it, fine prolongations
extend, dividing the tube into separate compartments, of which the outer
contain round cells, while the inner compartment, there are more or less banana–shaped
trophozoites or “Rainey’s corpuscles” or “spores.”
Habitat
Muscles of human larynx, esophagus,
diaphragm, chest and abdomen, heart muscle and muscles of extremities
Diagnosis
Demonstration of Miescher tubes in the
affected muscles during autopsy.
(+) Sabin – Feldman dye Test
UNCLASSIFIED AS SPOROZOA OR FUNGUS
****** PNEUMOCYSTIS CARINI ******
Disease: Interstitial plasmacellular pneumonia
pneumocystosis
Morphology:
Small, round cyst containing 8
uninucleated bodies, trophozoites which could be crescent, sickle or pear–shaped
with amoeboid movement.
Pneumocystis jirovecii (previously classified as Pneumocystis carinii) was previously classified as a protozoa. Currently, it is considered a fungus based on nucleic acid and biochemical analysis.
The Pneumocystis trophic forms, however, do not proceed to show either pseudohyphal or true hyphal growth morphologies. Hence, Pneumocystis cannot be viewed as a dimorphic fungus in the classical sense. Although the typical Pneumocystis cyst forms that are observed on silver staining are structurally reminiscent of yeast forms present in other fungal infections, during active infection, the overwhelming majority (>90%) of Pneumocystis organisms present in the lung are of the trophic form morphology.
In further contrast to other ascomycetous fungi, and
despite extensive and ongoing efforts, Pneumocystis remains nonculturable in
defined media. Although this may in part be nutritional, efforts to supplement
defined media with lung extracts and with varying oxygen tensions and pH have
been disappointingly unsuccessful.
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