Biology of parasitic protozoa
IV. Apicomplexa I (SAR)
Andrea Bardůnek Valigurová
andreav@sci.muni.cz
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5 supergroups = megagroups
cortical alveolae
Tetrahymena (Ciliophora)
SAR (Harosa) - Alveolata
• SAR supergroup: Stramenopiles (heterokonts), Alveolata, and Rhizaria
• Alveolata: monophyletic group; 3 main subgroups: ciliates, dinoflagellates and
apicomplexans
• extremely diverse modes of nutrition, such as predation, photoautotroph and
intracellular parasitism
• cortical alveolae = system of flattened vesicles packed into a continuous layer
supporting the membrane, sometimes secondarily lost
• ciliary pit or micropore
• mitochondrial cristae tubular or ampulliform
Cortical alveolae
Ciliata Dinozoa Apicomplexa
Apicomplexa
• monophyletic taxon
• 1.2 -10 million apicomplexan species, only about 0.1% have been named and
described to date
• all parasitic = obligate parasites of vertebrates and invertebrates
• monoxenic or heteroxenous parasites
• at least 1 stage of the life cycle with flattened cortical alveoles and apical complex
• apical complex = 1 or more polar rings, conoid, rhoptries, micronemes,
subpellicular microtubules
• cell movement / locomotion by gliding, body flexion, longitudinal folds, and/or cilia
• complicated life cycle usually comprising sexual (gametogony) and asexual
(merogony also known as schizogony, sporogony) part
Apicomplexan life cycle
(general scheme)
Apicomplexan life cycle
(general scheme)
Environment
(exogenous part)
Intermediate host
Asexual reproduction
Reproduction in Apicomplexa
• Asexual reproduction of haploid stages via merogony, endodyogeny, endopolyogeny
and/or binary fission
❑ merogony (schizogony) = multiple fission in which nuclei and other organelles in
the meront (schizont) divide repeatedly and migrate to the cell periphery before
internal membranes develop around them to produce a large number of daughter
cells (merozoites) = budding takes place at the plasma membrane, nuclear
division occurs before daughter assembly
❑ endopolyogeny = internal budding resembling merogony, but budding takes
place internally within the cytoplasm, daughter assembly precedes nuclear
division
❑ endodyogeny = only 2 daughter cells (endozoites) are assembled within the
mother
❑ sporogony = asexual division, development of zygote (motile zygote = ookinete)
producing sporozoites within oocysts (usually inside sporocysts); reductive
division of the zygote forms haploid nuclei which (along with other organelles)
undergo multiple divisions to form a sporoblast; sporozoites arise by cytoplasmic
division of the sporoblast (sporulation)
https://doi.org/10.3389/fcimb.2020.00269
Sexual reproduction
Reproduction in Apicomplexa
• sexual reproduction (where known) by syngamy followed by immediate meiosis to
produce haploid progeny
❑ gametogony (gamogony) = transformation into a
gamonts that produce male and female gametes
▪ syzygy and gametocyst formation (gregarines)
▪ isogamy (similar gametes) x anisogamy (dissimilar
gametes, flagelatted microgametes in some taxa)
▪ syngamy (fusion of gametes)
Fertilisation in T. gondii
Oocyst = resistant stage of apicomplexans
Apicoplast
✓ relict, non-photosyntethic plastid
✓ secondary endosymbiotic chloroplast
limited by 4 membranes
✓ 35 kb long circular DNA strand that
codes for approximately 30 proteins
✓ heme and amino acid syntheses and
likely involved in lipid metabolism
✓ sensitive to herbicides
✓ promising drug target
Zoite organisation
• standard equipment of the eukaryotic
cell
• organelles characteristic of Apicomplexa:
apical complex and apicoplast
• conoid = hollow cone of spirally arranged fibers
located within the polar rings
• polar ring(s) = 1-2 electron dense structures
located just behind the zoite‘s apical tip and
directly under the plasma membrane
• micronemes = convoluted, elongate bodies in
zoite's anterior end whose contents are
released during host cell invasion, likely
involved in affecting plasma membrane fluidity
• rhoptries - elongated, club-shaped organelles
in apical region of zoite whose contents are
released during host cell invasion, likely
involved in forming the membranous
scaffolding supporting the zoite within the
parasitophorous vacuole (PV)
Tachyzoite of Toxoplasma gondii
Bradyzoite of T. gondii
Apical complex
• micropores = usually present
at some stage which are
morphologically similar to
clathrin-coated pits and are
involved in endocytosis
• subpellicular microtubules =
microtubules under the
pellicle running posteriorly
(parallel to the cell axis)
Apical complex
Invasion process in Toxoplasma gondii
Host cell invasion
Parasite's superficial antigen
▪ zoite attachment, orientation and adhesion by its apical end 
moving junction
▪ host cell penetration and formation of parasitophorous vacuole
▪ shedding of the zoite antigenic surface completion of PV and
modification of the parasite's niche
https://doi.org/10.1371/journal.ppat.0010017
Parasite niche in host cell or tissue
✓ intercellular
✓ extracellular
✓ epicellular
✓ intracellular epiplasmatic
✓ intracellular
Hypothesis on evolution of parasitism in Apicomplexa:
Myzocytotic predation  myzocytotic extracellular parasitism + origin
of epicellular parasitism (modification of attachment apparatus and
motility in trophozoite)  intracellular parasitism (lost of cell polarity
and motility in trophozoite)
Host-parasite interactions in Apicomplexa
Valigurová et al. 2015 in https://doi.org/10.1371/journal.pone.0125063
Phylogenetic distribution of
diverse organism-environment
interactions in Myzoza
https://doi.org/10.1016/j.pt.2020.06.002
Co-occurrence of predation and parasitism. Colpodellids (A) are
predators of algae and protists. They penetrate the cell surface to
access the cytosol of the predated cell. The mode of action is, in
principle, quite similar to that of early-branching apicomplexan
parasites such as gregarines (B) living in the gut of various animals.
Apicomplexa
Multiprotein phylogeny of Apicomplexa and related taxa
➢ apicomplexans are
polyphyletic
➢ similar morphological features
appeared convergently at
least 3x
➢ gregarines and eugregarines
are monophyletic
➢ Eleutheroschizon is related to
Eucoccidia and Rhytidocystis
has emerged as the basal
group of Coccidiomorpha (the
most medically important
representatives)
➢ plastids are common in basal
Apicomplexa; in eugregarines
they are abnormally reduced
or absent
https://doi.org/10.7554/eLife.49662
Apicomplexa
Aconoidasida••• …………………….next lecture
• apical complex lacking conoid in asexual motile stages; some diploid motile
zygotes (ookinetes), with conoid; macrogametes and microgametes forming
independently; heteroxenous
• Haemospororida••••
• Piroplasmorida••••
Conoidasida•••………………………this lecture
• Gregarinasina••••
• Cryptosporidium••••
• Coccidia••••
• Adeleorina•••••
• Eimeriorina•••••
Apicomplexa
Conoidasida•••
• complete apical complex, including a conoid in all or most asexual motile stages
Gregarinasina••••
• mature gamonts usually develop extracellularly; syzygy of gamonts generally
occurring with production of gametocyst; similar numbers of macrogametes and
microgametes maturing from paired gamonts in syzygy within the gametocyst
• syngamy of mature gametes leading to gametocyst that contains few to many oocysts
Cryptosporidium••••
• endogenous stages with attachment “feeder” organelle; microgametes non ciliated;
oocysts without sporocysts, with 4 naked sporozoites
• extracytoplasmic localisation in host cell (based on Adl et al. 2012) vs. epicellular
(Valigurová et al. 2008, 2015)
Coccidia••••
• mature gametes develop intracellularly; microgamont typically produces numerous
microgametes
• syzygy absent; zygote rarely motile; sporocysts usually form within oocysts
Apicomplexa
Gregarinasina
• gregarines are highly diverse - intestine and
body cavities of invertebrates (arthropods,
annelids, molluscs, …) and hemichordates
• considered the most ancestral Apicomplexa
• trophozoites mucron or epimerite
• large and motile trophozoites and gamonts
(usually extracellular)
• syzygy - pairing of 2 gamonts before
gametocyst formation
• syngamy of gametes within the gametocyst
 zygotes  gametocyst containing few to
many oocysts with sporozoites
▪ Archigregarinorida
▪ Eugregarinorida
▪ Neogregarinorida
Archigregarinorida
• marine invertebrates (annelids, ascidians, hemichordates, sipunculids)
• ancestral to the other gregarines and probably all Apicomplexa
• epicellular development at brush border of enterocytes
• apical complex preserved at trophozoite/gamont stage
• aseptate trophozoite, merogony
• bending, rolling motility
Selenidium pendula from polychaete
https://doi.org/10.1016/j.protis.2016.06.001
Host-parasite interactions in archigregarines
Schematic view of anterior region of
Selenidium trophozoite
Apical pole of Selenidium pendula
• myzocytosis via mucron - conoid, rhoptries + subpellicular microtubules = plesiomorphic
features present in trophozoite/gamonts stage („hypersporozoite“)
Host-parasite interactions in archigregarines
S. hollandei
Eugregarinorida
• arthropods (mostly insects), polychaetes
• epicellular at brush border of enterocytes
• aseptate or septate trophozoites (epimerite,
protomerite, deutomerite)
• apical complex present only in sporozoites
• merogony absent
• gliding motility, metaboly
Gregarina polymorpha
Life cycle of G. cuneata
in mealworm larvae
https://doi.org/10.1371/journal.pone.0042606
https://doi.org/10.1016/j.ijpara.2009.04.009
Host-parasite interactions in eugregarines: simple epimerite
Cephaloidophora communis from crustacean Gregarina garnhami from locust
Actinocephalus dujardini
from centipede
Beloides tenius from skin beetle Ancyrophora stelliformis
from ground beetle
Host-parasite interactions in eugregarines:
complicated epimerite
Host-parasite interactions in eugregarines:
modified protomerite
Urospora travisiae from polychaete
Bothriopsides histrio from diving beetle
Neogregarinorida
• neogregarines derived from eugregarines, merogony (secondarily obtained)
• parasitising insects and are usually found in the fat body, haemolymph, hypodermis,
intestine or Malpighian tubules
• intracellular, epicellular development
• apical complex present in later stages
• trophozoite with epimerite or mucron
• usually pathogenic for their hosts, even fatal
https://doi.org/10.3390/microorganisms9071430; https://doi.org/10.1016/j.ejop.2006.07.007
Mattesia dispora in fat body of larval Mediterranean flour moth
Apicomplexa
Cryptosporidium spp.
• single genus Cryptosporidium, currently
more than 30 species
• cosmopolitan, mainly intestinal or gastric
• monoxenous
• epicellular niche - parasite attached to
the host cell by a feeder organelle
• small oocysts (4,8-5,6 x 4,2-4,8 μm) with
4 naked sporozoites (no sporocysts)
• autoinfective stages - type I merozoites
capable of forming new type I meronts
and thin-walled oocysts that may liberate
sporozoites to initiate new infections
https://doi.org/10.1016/j.ijpara.2007.11.003
https://doi.org/10.1016/j.ijpara.2007.11.003
Formation of epicellular niche in cryptosporidia
https://doi.org/10.3390/microorganisms9122434
Schematic diagram of host-parasite interactions in cryptosporidia. 3 colours are used to distinguish between
the parasite (in green), the host cell including its parts modified due to parasitisation (in grey), and the contact zone
between the host and the parasite (in white with black dots) where the interactions of the two organisms become
more intimate. (A) Invading zoite (either sporozoite or merozoite). (B) An early trophozoite partially enveloped by
an incomplete parasitophorous sac (PS). (C) Young trophozoite almost completely enveloped by a PS. Note the
tunnel connection between the interior of the anterior vacuole and the host cell cytoplasm that developed as the
result of the Y-shaped membrane junction. (D) Almost mature trophozoite. Note the folding of the anterior vacuolar
membrane during its transformation into the feeder organelle (FO). (E) Mature stage with a prominent filamentous
projection at the base of the PS and with a fully developed FO, the lamellae of FO formed from the anterior vacuole
membrane.
av - anterior vacuole, db - dense band, dl - dense line separating the feeder organelle from the filamentous
projection of the PS, if - incomplete fusion of PS, mv - host microvilli, po - pore on the PS, tu - tunnel connection
Life cycle of cryptosporidia
https://www.youtube.com/watch?v=ee159M3wxA8 https://www.youtube.com/watch?v=pCTwMCwxudU
Extracellular stages in the life cycle of cryptosporidia ???
https://doi.org/10.1016/j.pt.2008.08.002
https://doi.org/10.1016/j.watres.2016.09.013
https://doi.org/10.1016/j.ijpara.2013.07.005
Zoonotic potential of cryptosporidia
https://doi.org/10.1016/j.ijpara.2013.07.005
https://doi.org/10.3390/microorganisms9122434
Cryptosporidum parvum
• intestinal pathogen of mammalian hosts
Pathological changes in rodents with intestinal cryptosporidiosis
Healthy jejunum
Jejunum with C. parvum, absorptive cells
exhibiting protuberances
Ileum (BALB/c) with C. parvum, villous atrophy
• epithelial cells lining intestinal
tract, does not invade deeper
layers of the intestinal mucosa
• major pathological changes:
villous atrophy, shortening of
microvilli and sloughing of
enterocytes
Pathological changes in rodents with intestinal cryptosporidiosis
Colon – mucus production (BALB/c mouse)Goblet cells with mucus (BALB/c mouse)
• cryptosporidia on the surface of the intestinal mucosa
• villous atrophy of the small intestine, inflammatory infiltrate in the lamina propria
Cryptosporidium muris https://doi.org/10.1017/S0031182013001637
sporozoite
trophozoites
10 µm
oocyst
type II merogony
type I merozoites I
type II merozoitesmacrogamontsmicrogamonts
zygote
excystation
type I merogony
host cell
invasion
• epithelial cells within crypts of the gastric
glands (glandular part of the gastric mucosa)
• prepatent period in BALB/c mice 7-10 days,
in Mastomys natalensis 14-21 days
• later this isolate has been identified as a
new species and named C. proliferans
merogony
Life cycle of C. muris in rodent host
type II
merogony
6 µm
type I
merogony
Life cycle of C. muris in rodent host
6 µm
microgamontmacrogamont
fertilisation
Life cycle of C. muris in rodent host
thick-walled
oocyst
zygotes developing oocysts
thin-walled
oocyst
Pathological changes in rodents with gastric cryptosporidiosis
healthy gastric epithelium
crypt of gastric gland
glandular part
of gastric mucosa
parasitised gastric
epithelium
glandular part of gastric mucosa
crypt of gastric gland
✓ obvious dilatation of gastric glands
✓ epithelial hyperplasia and mucosal hypertrophy without inflammatory exudate
Pathological changes in rodents with gastric cryptosporidiosis
Cryptosporidum fragile
• luminal surface of gastric epithelium and the crypts
of gastric glands
• from naturally infected black-spined toads
Duttaphrynus melanostictus obtained via import of
pet animals from the Malay Peninsula in 2006
• infection spontaneously disappeared 24–51 days
after arrival
https://folia.paru.cas.cz/artkey/fol-200802-0001_new_species_of_cryptosporidium_tyzzer_1907_apicomplexa_from_amphibian_host_morphology_biology_and_phyloge.php
healthy gastric epithelium parasitised gastric epithelium
Pathological changes in toads with gastric cryptosporidiosis
• animal and human diseases
• significance: cattle++++, sheep++, goat++, poultry++, reptiles++, human+, horse+, pig+,
dog+, cat+
• no effective chemotherapy
• emerging infectious diseases, zoonotic character, primary symptoms are acute,
watery, and diarrhoea without blood
• other symptoms may include anorexia, nausea, vomiting and abdominal cramping/pain,
weight loss, electrolyte imbalance
• self-limiting in immunocompetent people – parasite life-cycle ends when host immune
response eliminates the reproductive cycle
• in immunosuppressed patients (diarrhoea can reach 10–15 times per day), such as
those with AIDS or those undergoing immunosuppressive therapy, the parasite
overwhelms its host due to recycling of type I meronts and infection may lead to
dehydration and even death - opportune parasites
• extra-gastrointestinal sites include lung, liver and gall bladder, where it causes
respiratory cryptosporidiosis, hepatitis, and cholecystitis, respectively
Cryptosporidiosis
Clinical signs of human cryptosporidiosis
Diagnosis of cryptosporidiosis
✓ flotation methods
✓ stained smears
✓ immunoassays
✓ molecular methods – multipathogen
molecular panels, molecular typing
Water-borne cryptosporidiosis in Milwaukee (1993)
The largest waterborne disease outbreak in
documented US history (infection caused by C. hominis).
It is suspected that The Howard Avenue Water
Purification Plant was contaminated due to an ineffective
filtration process.
This abnormal condition lasted from March 23 through
April 8, after which, the plant was shut down. Over the
span of approximately two weeks, 403,000 of an
estimated 1.61 million residents in the Milwaukee area
(of which 880,000 were served by the malfunctioning
treatment plant) became ill with the stomach cramps,
fever, diarrhoea and dehydration caused by the
pathogen. Over 100 deaths were attributed to this
outbreak, mostly among the elderly and
immunocompromised people, such as AIDS patients.
The total cost of the outbreak, in productivity loss and
medical expenses, was $96 million
Cryptosporidium starring in the movie THIRST (1998)
The town of San Paulo is suffering from a heatwave.
Engineer Bob Miller turns up at work to learn that the
new water filtration plant he has been building has
been cancelled and that he is now unemployed. At the
same time, Bob’s wife Susan has to deal with a series
of mystery deaths at the hospital where she works as a
nurse. Bob realizes that the cause might be the water
supply. Dr Lawrence Carver confirms that the water is
infected with a deadly bacteria Cryptosporidium.
They discover that the Cryptosporidium is throughout
the town’s drinking water. The only choice is to turn the
water plant off and for everybody to drink only bottled
or boiled water. As the death toll grows, they realize
that they are dealing with a mutated form of the
bacteria that is resistant to boiling. Meanwhile, the
state governor’s office makes the decision to put a
military quarantine around the town...... .
Water-borne cryptosporidiosis in Ostersund (2010)
https://doi.org/10.3201/eid2004.121415
Water-borne cryptosporidiosis
Blastogregarinea
Siedleckia nematoides
• only two genera (Chattonaria, Siedleckia) known from polychaeta
• blastogregarines possess both gregarine and coccidian features
• permanent multinuclearity and gametogenesis (merogamont)
• epicellular development - brush border of enterocytes
• myzocytosis via mucron (conoid, rhoptries) + subpellicular microtubules =
plesiomorphic features („hypersporozoite“)
• wavy and bending motility
https://doi.org/10.1016/j.protis.2018.04.006
Cell organisation in blastogregarines
♂♀
https://doi.org/10.1016/j.protis.2018.04.006
Protococcidiorida
• incertae sedis Apicomplexa reported from polychaetes
• life cycle of protococcidia not completely understood
• epicellular within parasitophorous sac at the brush border of host enterocytes
• apical complex detected only at sporozoite stage
• trophozoites and gamonts appear nonmotile
Eleutheroschizon duboscqi
Epicellular niche
of Eleutheroschizon duboscqi
young trophozoite microgamont macrogamont
F-actin
Agamococcidiorida
• agamococcidia
• incertae sedis Apicomplexa
• intracellular in polychaete enterocytes
• apical complex not seen in trophozoites
• trophozoites appear nonmotile
• merogony and gametogony not observed
• life cycle not known
Rhytidocystis pertsovi
https://doi.org/10.1038/s41598-020-72287-x
Apicomplexa
Coccidia
• important parasites of humans and animals
• monoxenous or heteroxenous
• all endogenous stages are intracellular, no mucron or epimerite
• merogony, gamogony, and sporogony normally present
• mostly without syzygy - macrogamonts and microgamonts develop independently
• microgametocytes usually produce many microgametes (with 1 – 3 flagella)
• normally is zygote non-motile
• sporozoites in oocyst
• most coccidia develop resistant oocysts are passed in the faeces
▪ Adeleorina
▪ Eimeriorina
Apicomplexa
Adeleorina
• monoxenous in arthropods (often referred to as adelines) x heteroxenous cycling
between blood-feeding invertebrates (definitive hosts) and various vertebrates
(intermediate hosts), usually referred to as haemogregarines
• usually complex life cycle – 1 or more merogonies  gametogony  sporogony
• meronts often of morphologically distinct types: 1) meront producing large merozoites
that initiate another round of merogony, 2) meront producing smaller merozoites that
represent the gamonts progenitors
• microgamonts produce 1-4 microgametes that associate with macrogamete in
syzygy
• endodyogony absent, sporozoites in sporocysts and/or oocysts
Apicomplexa
Monoxenous adelines
• e.g. Adelina and Adelea from insects, Klossia from kidney of molluscs, Klossiella
from kidney of vertebrates, ...
sporogony oocyst syzygy
merogony
Adelina tribolli Adelina melolonthae
Apicomplexa
Polysporocystic oocysts
from kidney of Triodopsis
hopetonensis
Klossia helicina
Klossia razorbacki
Monoxenous adelines
Klossiella equi
K. equi multifocally expanding tubular epithelial
cells (schizont - arrow; sporocysts - arrowheads)
Sporocysts found on centrifugal flotation of horse
urine
Apicomplexa
Heteroxenous haemogregarines
• Hepatozoidae, Haemogregarinidae and Dactylosomatidae comprising several
genera, including pathogens of vertebrates:
▪ Hepatozoon from carnivores and reptiles
▪ Haemogregarina from fish and turtles
▪ Dactylosoma from fish or amphibian (possibly also reptiles)
• in all of them, invertebrate plays role of the definitive host with gamogony in its
digestive tract, and parasite transmission occurs in 2 modes:
1) inoculation - infectious sporozoites enter the vertebrate host during blood
feeding of vector (Haemogregarina, Dactylosoma)
2) ingestion of infected definitive (invertebrate) host by vertebrate host – may
involve a paratenic host when the next definitive host is infected
exclusively via blood feeding (Hepatozoon, Haemolivia, Karyolyssus)
Apicomplexa
genus Hepatozoon
• more than 300 species
• sporogony in invertebrate host  oocysts
with large number of sporocysts with
sporozoites
• sporozoites in liver of the vertebrate host
(asexual reproduction)  merozoites
• merozoites in bloodstream  gametocytes
= conspicuous organisms in erythrocytes /
lymphocytes
• sexual reproduction in haemocoel of
invertebrate host
• hepatozoonosis – when animal eats the
invertebrate host (e.g. tick, disease is not
spread by tick bites!), infection may cause
polyostotic aggressive lesions
Hepatozoon americarum
Skeletal muscle containing a developing
meront, mucopolysaccharide layers produced
by host cell protect the developing organisms
from the dog’s immune system
Pyogranuloma in skeletal muscle of a
infected dog, zoites displace the nucleus in
several of the inflammatory cells
Oocysts in hemocoel of Amblyomma
maculatum tick, each oocyst with
hundreds of small round sporocysts
containing 10-6 sporozoites.
Pelvic limb of infected dog showing
smooth periosteal proliferation on
the cranial aspect of the femur.
Moderate to severe illness: fever, lethargy,  appetite, weight loss, muscle
pain/weakness, reluctance to move, discharge from the eyes/nose, enlarged
lymph nodes. Periods of illness and apparent resolution; without treatment
 damage to the blood vessels and kidneys often with death within 1 year.
Hepatozoon canis
Meront in splenic tissue of a dog demonstrating
the typical “wheel spoke” pattern
Gamonts in neutrophils on a blood smear
• most dogs infected show no or only mild signs of illness:
fever, weight loss, lethargy, anaemia, enlarged spleen
• in some dogs with high parasite numbers, the disease can
become more severe and may be potentially life-threatening
• immunosuppression or concurrent disease is an important factor
in expression of illness in H. canis (but not in H. americanum)
Hepatozoon ayorgbor
• African Python regius
• merogony in liver and spleen,
gametocytes in erythrocytes
• transmitted by Culex quinquefasciatus
• rodents as a reservoir
https://www.parazitologie.cz/protozoologie/Personal%20homepages/Votypka/Hepatozoon%20ayrbor.pdf
Apicomplexa
genus Haemogregarina
• infected leech feeding on a reptile or amphibian injects sporozoites into the bloodstream
where they enter erythrocytes  trophozoites
• erythrocytes with trophozoites lodge in the capillaries of the bone marrow 
macromeronts  merozoites infect new erythrocytes  micro-/macrogametocytes
• fusions of gametes  oocyst in the gut of leech where they hatch and sporozoites
migrate through the intestinal wall into the circulatory system, sporozoites ending up in
the proboscis are injected into the next host
Haemogregarina bigemina
https://doi.org/10.1016/j.ijpara.2012.11.012; https://doi.org/10.1016/j.ijppaw.2019.01.006
• ectoparasitic gnathiid isopods likely
serve as vectors
Haemogregarina stepanowi
https://doi.org/10.1017/S0031182013001820
• turtle Emys orbicularis (not only)
• trasmitted by leeches
genus Dactylosma
• amphibians, fish
• transmitted by leeches and possibly mosquitos
Blood smear from Pelophylax frog
with merogony (primary meront)
Blood smear from Pelophylax frog with gamont
Apicomplexa
Eimeriorina
• homoxenous or heteroxenous life cycles
• syzygy is absent - macrogametes and microgametes develop independently
• anisogamous microgamonts produce a large number of flagellated microgametes
• zygote is nonmotile, sporozoites enclosed in a sporocyst
https://www.youtube.com/watch?v=euHBghFhJRc
Sporulation in coccidia
Excystation of coccidian oocyst
Factors affecting the significance of individual coccidian species
Factors affecting the host
✓ "technology" of animal breeding
✓ host immunity (age category)
✓ nutrition, other diseases
Factors of individual species of coccidia
✓ pre-patent period
✓ patent period
✓ number of merogonies
✓ size of developmental stages
✓ sporulation time
✓ extraintestinal development
Chicken coccidiosis (vaccination available)
https://www.youtube.com/watch?v=NFh2aPmuYQE
https://www.youtube.com/watch?v=u1iIZQrB_B4
https://www.youtube.com/watch?v=HnVCmZUoork
Taxonomy of coccidia
Sporocysts: 2
Sporozoites: 8
Eimeriorina
Eimeriidae - monoxenous Sarcocystidae - heteroxenous
Eimeria (4-2)
Isospora (2-4)
Caryospora (1-8)
Tyzzeria (0-8)
Wenyonella (4-4)…
x
Morphology of coccidian oocyst
Oocyst of Eimeria
Oocyst of Isospora
Oocyst of Caryospora
Coccidia in poultry
9(7) Eimeria species - „pathogenicity top-ten“
1. Eimeria necatrix - small intestine
2. Eimeria tenella - ceca
3. Eimeria maxima - small intestine
4. Eimeria brunetti - small intestine, ceca, rectum
5. Eimeria mitis - small intestine, ceca, rectum
6. Eimeria acervulina (E.mivati ??) - duodenum
7. Eimeria praecox (E. hagani ??) - duodenum
632
Localisation of developmental cycle and pathological
changes in the intestine
E. tenella E. necatrix E. acervulina E. maxima
Clinical signs of poultry coccidiosis
Pathology of poultry coccidiosis
Coccidia in rabbits
11 Eimeria species - „pathogenicity top-ten“
1. Eimeria intestinalis - jejunum, cecum, colon
2. Eimeria flavescens - jejunum, cecum, colon
3. Eimeria stiedai - liver
4. Eimeria magna - jejunum, cecum, colon
5. Eimeria irresidua - jejunum, ileum
6. Eimeria media - jejunum, ileum
7. Eimeria piriformis - jejunum, ileum
8. Eimeria vejdovski - jejunum, ileum
9. Eimeria coecicola - cecum
10. Eimeria exigua - ileum
11. Eimeria perforans - duodenum
Coccidia in rabbits
Coccidia in pigs
7 Eimeria species - „pathogenicity top-ten“
1. Eimeria scabra - small intestine
2. Eimeria polita - small intestine
3. Eimeria debliecki - small intestine
4. Eimeria spinosa - small intestine
5. Eimeria neodebliecki - small intestine
6. Eimeria porci - ?
7. Eimeria suis - ?
Cystoisospora suis
• non-haemorrhagic transient diarrhoea, resulting in poor weight gain
• it appears that primary immune responses against C. suis cannot readily be mounted by
neonates, contributing to parasite establishment and rapid, while in older pigs, age-related
resistance prevents disease development (morbidity ++++, mortality +)
C. suis in pigletsoocysts
Cystoisospora suis
Cystoisospora suis
https://doi.org/10.3389/fvets.2015.00068
Coccidia in ruminants
Cattle - 12 Eimeria species
Eimeria zuernii - pathogenic
Eimeria bovis - pathogenic
Both species responsible for severe clinical disease characterised by
haemorrhagic diarrhoea with sometimes fatal outcome.
Eimeria alabamensis - also can cause clinical disease
Prevalence of Eimeria infection in cattle is generally high and can reach 100% in
calves.
Eimeria ellipsoidalis - bloody diarrhoea in calves and young cattle on pasture,
„red dysentery of cattle„, "neurological coccidiosis"
Pathological changes in the small and large intestine - hyperaemia,
haemorrhages, pseudomembranes.
Coccidia in ruminants
Sheep - 11 Eimeria species
Eimeria bakuensis - pathogenic
Eimeria ovinoidalis (E. ninakohlyakimovae) - middle pathogenicity
Eimeria crandalis - pathogenic
Eimeria ashata - pathogenic
Goat -13 Eimeria species
• similar morphology of oocysts to sheep, different species
Eimeria ninakohlyakimovae - slightly pathogenic, high prevalence
Eimeria arloingi - most pathogenic
Eimeria arloingi
gamonts
macromeronts
Coccidia in carnivores
Dog - 3 (5) Isospora species
Isospora canis
Isospora ohioensis
Isospora burrowsi
• cause of diarrhoea in young animals
• dormozoites (hypnozoites) in rodents
• Neospora / Hammondia
Cat - 3 (5) Isospora species
Isospora cati
Isospora rivolta
• cause of diarrhoea in young animals
• dormozoites (hypnozoites) in rodents
• Toxoplasma / Hammondia
genus Caryospora
• mostly monoxenous
• oocyst with 1 sporocyst with 8 sporozoites inside
• parasites in snakes a raptors
• about 70 described species
Caryospora bigenetica
C. simplex
• facultatively heteroxenous
• primary and secondary hosts
• caryocyst (dormant stage) in secondary host
• dermal coccidiosis in secondary host
• potentially zoonotic
Life cycle of Caryospora bigenetica
A) First type of final host (rattlesnake)
1) The sporulated oocyst contains a single
sporocyst with 8) sporozoites. 2–4) After oral
infection with oocysts 2 generations of meronts
are formed inside the intestinal epithelium. 5-6)
Male and female gamonts are formed and later
gametes occur. The male gamont (G) forms
numerous gametes. 7-8) After fertilisation a
thick-walled oocyst is formed inside the host cell
and becomes free within the faeces. While
sporulating on the ground a single sporocyst
with 8 sporozoites is formed inside each oocyst.
B) Second type of final host (mice, cotton
rats, dogs)
2.1–2.4) Repetition of the merogonic and
gamogonic development (described in 1–8). The
sporulation of oocysts may occur in skin regions
(2.4). 2.5) Sporozoites that were set free from
their sporocysts while still inside the skin of their
hosts enter...
Caryospora simplex
Caryospora bigenetica
genus Lankesterella
• parasites of amphibia reptiles, birds; transmission by a leeches
• heteroxenous with entire replicative process occurring in vertebrate host
(connective tissue, visceral organs - liver, spleen, intestine, lung, kidney)
• absence of environmentally resistant oocysts
• thin-walled oocysts harbour variable numbers (usually more than 32) of naked
sporozoites (no sporocysts) which after exiting the oocyst in situ enter blood cells
and become dormant until they are ingested by leech vectors during a blood meal
Blood smear from Pelophylax frog with Lankesterella sporozoites
Thank you for your attention ☺
Lectures
✓ Introduction: BPP 2022 I
✓ Euglenozoa (Excavata): BPP 2022 II
✓ Fornicata / Preaxostyla / Parabasala (Excavata): BPP 2022 III
✓ Apicomplexa I (SAR): BPP 2022 IV
 Apicomplexa II (SAR): BPP 2022 V
• Amoebae (Excavata, Amoebozoa): BPP 2022 VI
• Ciliophora, Opalinata (SAR): BPP 2022 VII
• Pneumocystis (Opisthokonta, Fungi): BPP 2022 VIII
• Microsporidia (Opisthokonta, Fungi): BPP 2022 IX
• Myxozoa (Opisthokonta, Animalia): BPP 2022 X