Biology of parasitic protozoa
V. Apicomplexa II (SAR)
Andrea Bardůnek Valigurová
andreav@sci.muni.cz
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5 supergroups = megagroups
Apicomplexa
Apicomplexa
Aconoidasida••• …………………..this 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••• …………………………previous/ this lecture
• complete apical complex, including a conoid in all or most asexual motile stages
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••••
• oocysts and meronts with attachment “feeder” organelle; microgametes non ciliated;
oocysts without sporocysts, with 4 naked sporozoites
• extracytoplasmic localisation in host cell
Coccidia••••
• mature gametes develop intracellularly; microgamont typically produces numerous
microgametes
• syzygy absent; zygote rarely motile; sporocysts usually form within oocysts
Apicomplexa
Aconoidasida•••
• apical complex lacking conoid in asexual motile stages; some diploid motile
zygotes (ookinetes); macrogametes and microgametes forming independently;
heteroxenous
Haemospororida••••
• zygote motile as ookinete with conoid; ciliated microgametes produced by
merogony; oocyst formed in which sporozoites develop
• Haemoproteus, Leucocytozoon, Mesnilium, Plasmodium
Piroplasmorida••••
• piriform, round, rod-shaped or amoeboid; conoid and cilia absent in all stages;
polar ring present; without oocyst
• Babesia, Theileria
Apicomplexan life cycle
(general scheme)
Apicomplexan life cycle
(general scheme)
Environment
(exogenous part)
Intermediate host
Apicomplexa
Sarcocystidae
Sarcocystinae
• obligatory heteroxenous
Sarcocystis, Frenkelia
• Isospora-like oocysts
• fully sporulated oocysts in the fresh faeces/in situ
Toxoplasminae
• facultatively heteroxenous
Toxoplasma, Neospora, Besnoitia, Hammondia
• Isospora-like oocysts
• unsporulated in the fresh faeces
Sarcocystis
Toxoplasma
Toxoplasma,
Apicomplexa
Sarcocystidae
Sarcocystinae
Sarcocystis
Frenkelia
Toxoplasminae
Toxoplasma
Neospora
Besnoitia
Hammondia
genus Sarcocystis
• about 200 recognised species in this genus
• cyst-forming coccidia
• obligatory heteroxenous
• host specific or infect closely related host species
• IH: vertebrates
• DH: carnivorous and omnivorous vertebrates
• prey-predator relation of definitive and intermediate hosts
• extraintestinal merogony: in endothelial cells, RES cells or hepatocytes
• muscle tissue cysts - sarcocysts, zoites in sarcocysts - cystozoites
• Isospora-like oocysts, sporulation in situ
• terminology Sarcocystis bovicanis / Sarcocystis cruzi
Life cycle of Sarcocystis cruzi
Sarcocystis developmental stages
Sarcocystis stages in intermediate hosts (AF)
and definitive hosts (G-I). All micrographs
show S. cruzi, except E, which is an image of S.
hominis. A) Artery with a first-generation
multinucleate meront (arrow) in an endothelial
cell. B) Kidney glomerulus with immature
(arrowhead) and mature (arrow) secondgeneration
schizonts. C) Blood smear with a
merozoite in a mononuclear cell. D) Heart with
an immature sarcocyst containing globular
metrocytes. E) Skeletal muscle with a cross
section of a mature sarcocyst with a thick
striated wall surrounded by a mononuclear cell
infiltrate. F) Skeletal muscle with longitudinal
and cross sections of sarcocysts. The was no
inflammatory response. HE. G) Lamina propria
of small intestine with a macrogametocyte
(arrow). H) Small intestine with sporulated
sporocysts (arrow). Whipf’s polychrome stain. I)
Two sporocysts in a faecal float.
Sarcocystis
developmental stages
Sarcocysts of Sarcocystis cafferi from African buffalo. A-C) Unstained macrocysts (arrows). Sarcocysts are covered with
connective tissue in A. D-E) Sarcocysts in section stained with Toluidine blue. Note thin sarcocyst wall (opposing arrowheads) with
a pale staining outer zone with metrocytes (me), and intensely stained bradyzoites (br). F-G) Section of sarcocyst. HE. Note septa
(se) separating groups of bradyzoites (br), and pale staining metrocytes (me). Arrows point to longitudinally cut bradyzoites. H)
SEM of sectioned part of a sarcocyst revealing the cyst wall (cw), bradyzoites (br) and metrocytes (me) arranged in sacks enclosed
by thick septa (se).
H
https://doi.org/10.1645/13-467.1
Microcyst in myocardium of red deer
myositis
Microcysts of S. hominis nestled in beef tongue.
hepatitis
Pathology of sarcocystosis
in intermediate hosts
• equine protozoal myeloencephalitis
(EPM) of horses in America
• DH: opossum (Didelphis virginiana, D.
albiventris)
• relatively small sporocysts (10×8 μm)
• IH: horse (aberrant host, “dead-end„)
• sarcocysts (asexual stages, about 700
μm) in horse nervous tissue
• in any part of the central nervous
system CNS (brain, spinal cord)
• clinical signs of EPM, dependent on
the area of the CNS parasitised,
include ataxia, hypoalgesia, complete
sensory loss, facial nerve paralysis,
depression
• gradual progression of clinical signs
Sarcocystis neurona
A) Cross section of spinal cord of horse with focal
areas of discoloration (arrows) indicative of necrosis.
Unstained.
B) Section of spinal cord of a horse with severe EPM.
Necrosis, and a heavily infected neuron (arrows), all
dots (arrows) are merozoites. HE.
C) Higher magnification of a dendrite with numerous
merozoites (arrows). One extracellular merozoite
(arrowhead) and a young schizont (double arrowhead).
D) Section of brain of an experimentally-infected
mouse stained with anti-S. neurona antibodies. Note
numerous merozoites (arrows).
E) Immature meronts in cell culture: meront with
multilobed nucleus (arrow) and a meront with
differentiating merozoites (arrowheads). Giemsa.
F) Meronts with merozoites. Giemsa.
G) Mature sarcocysts with hairlike villar protrusions
(double arrowheads) on the sarcocyst wall. HE.
H) Mature live sarcocyst with numerous septa (arrows)
and hairlike protrusions on the sarcocyst wall (double
arrowheads). Unstained.
I) An oocyst with two sporocysts each with bananashaped
sporozoites. Unstained.
Sarcocystis neurona developmental stages and lesions
Merogony in Sarcocystis neurona
https://doi.org/10.1016/j.vetpar.2015.01.026
Asynchronous merogony in neural cell in the brain
of a raccoon naturally infected with S. neurona
Gliding merozoites, fluorescence
Sarcocystis and meat hygiene
Macroscopic meat changes
S. miescheriana (suicanis)
• wild boars
Sarcocystis rileyi
• new parasite in Europe
• wild duck
• water fowls "rice breast disease„
• Orava in Slovakia (January 8, 2011)
S. gigantea
• ovine oesophagus
Both species use humans as
definitive hosts and are
responsible for intestinal
sarcocystosis in the human host.
Humans may also become deadend
hosts for non-human
Sarcocystis spp. after the
accidental ingestion of oocysts.
Life cycle Sarcocystis hominis and S. suihominis
https://doi.org/10.1016/j.rvsc.2021.02.008
Human muscle sarcocystosis
https://doi.org/10.1371/journal.pntd.0002876
Human sarcocystosis
DOI: 10.1055/s-0034-1370004
https://doi.org/10.1371/journal.pone.0187984
Human sarcocystosis
https://doi.org/10.1128/CMR.00113-14
Humans as aberrant intermediate hosts for Sarcocystis spp.
Humans as definitive (final) hosts for Sarcocystis spp.
Toxoplasma gondii
• DH: Felidae
• IH: birds and mammals (warm-blooded
vertebrates)
• 3 types of infectious stages:
tachyzoites - tachos = rapid,
endodyogeny
bradyzoites - brady = slow, endopolygeny
sporozoites in fully sporulated oocyst
• bradyzoites  tachyzoites - immunologically
mediated (IFN-γ)
• in vitro cultivation
• toxoplasmosis = zoonosis
• nearly one-third of humans has been exposed
• abortions in animals (small ruminants,
antelopes, marine mammals, …)
https://doi.org/10.1080/08830180213279
Developmental stages of Toxoplasma gondii
tachyzoites
Subcellular organisation of Toxoplasma gondii
https://doi.org/10.1186/s13071-020-04445-z
Tachyzoite
Macrogamete Microgamete
Subcellular organisation of Toxoplasma gondii
https://doi.org/10.1186/s13071-020-04445-z
Tachyzoite (a), bradyzoite (b), and sporozoite (c)
Endodyogeny in Toxoplasma gondii (in vitro)
Endodyogeny in Toxoplasma gondii
a-b) The first to divide is the Golgi complex and the apicoplast.
c) Nucleus assumes a horse-shoe shape. Two new apical
complexes start to form.
d) Inner pellicle grows and embraces the structures of the
daughter cells, including nucleus.
e) The last to be separated between the daughter cells is the
mitochondrion. Apical complex of mother cell is still maintained.
f) Two daughter cells emerge, and the outer membrane of the
mother cell is incorporated. Apical complex of the mother cell
disappears.
g) Two daughter cells remain linked to the residual body where
acidocalcisomes (green) start to accumulate.
h) Process is repeated until a parasite rosette is formed (i)https://doi.org/10.1186/s13071-020-04445-z
Life cycle of Toxoplasma gondii
https://www.youtube.com/watch?v=wML68MA--Kw
https://www.youtube.com/watch?v=YGTe6Kk9w8E
https://doi.org/10.1186/s13071-020-04445-z
a) Feline definitive host (cat).
b) Unsporulated oocysts in cat faeces.
c) Food contaminated with sporulated oocysts.
d) Oocysts may be ingested by intermediate hosts via water
or raw vegetables.
e) Intermediate hosts (e.g. cattle, sheep, poultry and swine).
f) Ingestion of tissue cysts in uncooked meat.
g) Intermediate hosts (humans).
h) Tachyzoites transmitted through the placenta to the foetus.
i) Transmission by blood transfusion and organ transplant (j)
https://www.youtube.com/watch?v=Z-fF-QRxOE0&t=6s
History of Toxoplasma gondii
Charles Nicolle
(1866-1936)
Ctenodactylus gundi Rothmann, 1776 Alfonso Splendore
(1871-1953)
Biological and epidemiological characteristics
of the main Toxoplasma genotypes
Human toxoplasmosis
✓ most common parasitic infections of man
✓ worldwide from Alaska to Australia
✓ nearly 1/3 of humanity has been exposed
✓ in most adults it does not cause serious illness
✓ devastating disease in immunocompromised / immunosuppressed
individuals = toxoplasmosis in immunocompromised patients
✓ it can cause blindness and mental retardation in congenitally infected
children = congenital toxoplasmosis
✓ in approx. 10 % of postnatally infected immunocompetent persons = clinical
human toxoplasmosis
✓ manipulation of host behaviour = manipulation hypothesis
Toxoplasmosis in immunocompromised patients
• encephalitis - most important manifestation in immunosuppressed patients
(in 40% of AIDS patients)
• exacerbation of infection (from bradyzoites to tachyzoites)
• disseminated toxoplasmosis, leads to death of patients with AIDS
• prophylactic TMX-sulfa (trimethoprim-sulfamethoxazole) treatment
Congenital toxoplasmosis
• occuring only when a woman becomes infected during pregnancy
✓ if T. gondii infection occurs 4-6 months before pregnancy – mother's
protective immunity protects against transplacental (vertical) infection of
the foetus
✓ if infection occurs during pregnancy - multiplication of tachyzoites in the
placenta and subsequent infection of the foetus
• mother rarely has symptoms of infection  testing of all pregnant women for T.
gondii infection is compulsory in some European countries (France, Austria)
• acquired during the first trimester is more severe than that acquired in the
second and third trimester
• incidence of congenital toxoplasmosis 1-10 / 10 000 new-born children
• wide spectrum of clinical diseases occur in congenitally infected children
• hydrocephalus is the least common but most dramatic lesion of toxoplasmosis
Congenital toxoplasmosis
Congenital toxoplasmosis
Manipulation of host behaviour by Toxoplasma gondii
https://doi.org/10.1371/journal.pone.0028925
https://doi.org/10.1017/S0031182001007624
https://doi.org/10.1016/j.pt.2013.01.004
Manipulation of host behaviour by Toxoplasma gondii
https://www.sci.news/biology/dorm
ant-toxoplasma-10407.html
Original research paper:
https://doi.org/10.1016/j.chom.2021.11.012
Manipulation of host behaviour by Toxoplasma gondii
https://www.theatlantic.com/magazine/archive/20
12/03/how-your-cat-is-making-you-crazy/308873/
..“if Flegr is right, the “latent” parasite may be quietly
tweaking the connections between our neurons, changing
our response to frightening situations, our trust in others,
how outgoing we are, and even our preference for certain
scents. And that’s not all. He also believes that the
organism contributes to car crashes, suicides, and mental
disorders such as schizophrenia. When you add up all the
different ways it can harm us, says Flegr, “Toxoplasma
might even kill as many people as malaria, or at least a
million people a year.”
https://www.forbes.com/sites/frederickallen/2012/02/
09/house-cats-said-to-lead-to-car-crashes-suicides-
and-mental-disorders/?sh=2130abbc5a1b
Source of postnatally acquired Toxoplasma gondii infection
Three infectious stages: tachyzoites, bradyzoites and sporozoites
Humans become infected by ingesting:
✓ tachyzoites in unpasteurized milk (?)
✓ tissue cysts in under cooked or uncooked meat
✓ food and water contaminated with oocysts from infected cat faeces
https://doi.org/10.1016/j.pt.2013.01.004
Facultatively heteroxenous
character of T. gondii:
✓can spread without DH
✓can spread without MH
Toxoplasma gondii is a very
successful parasite
Meat as a source of Toxoplasma gondii infection
https://doi.org/10.1136/bmj.321.7254.142
Naples
Lausanne
Copenhagen
Oslo
Brussels
Milan
Tachyzoites of Toxoplasma gondii
• tachyzoites demonstrated in the milk of sheep, goats and cows in the acute phase of
infection
• prerequisites for toxoplasmosis after ingestion of milk with tachyzoites:
✓ acute infection (parasitaemia)
✓ temperature-sensitive tachyzoites - unpasteurised milk
✓ tachyzoites are sensitive to low pH and pepsin - penetration of the mucous
membrane of the oral cavity and oesophagus
✓ importance of tachyzoite infection in milk is minimal (only few publications)
Bradyzoites of Toxoplasma gondii
• cysts develop as early as a week after infection and are infectious throughout the lifetime
of the IH
• in different IH, different localisation of cysts and different number of cysts
• ranking according to the frequency of T. gondii cysts:
1. pig, sheep, goat
2. rabbit, burrowing fowl
3. horses
4. cattle
Bradyzoites of Toxoplasma gondii
Survival of tissue cysts in meat - low temperatures:
✓ at a temperature of 1 to 4 °C for 3 weeks
✓ at a temperature of -1 to - 8 °C for 1 week
✓ at a temperature of -12 °C, bradyzoites in tissue cysts die immediately
Survival of tissue cysts in meat - high temperatures:
✓ at a temperature of 67 °C, bradyzoites in tissue cysts die immediately
✓ at a temperature of 60 °C, bradyzoites in tissue cysts die in 4 minutes
✓ at a temperature of 50 °C, bradyzoites in tissue cysts die in 10 minutes
Survival of tissue cysts in meat - salting
✓ 6% NaCl solution - bradyzoites in tissue cysts die immediately
✓ 3% NaCl solution - bradyzoites in tissue cysts die in 3-7 days
Survival of tissue cysts in meat - smoking
✓ they survive "cold" smoking
Survival of tissue cysts in meat - irradiation (USA)
✓ γ radiation - 1 kGy - bradyzoites in tissue cysts die immediately
Oocysts of Toxoplasma gondii
• asymptomatic shedding of T. gondii oocysts
• only about 1 % of cats in a population are found to be shedding oocysts at
any given time
• oocysts are shed for only a short period (1-2 weeks) in the life of the cat
• sporulation finished in 2-5 days, importance of burying of faeces
Oocysts of Toxoplasma gondii
✓ sporulated oocysts survive for long periods under most ordinary environmental
conditions
✓ sporulated oocysts survive in moist soil for years
✓ sporulated oocysts survive in 4 °C for 54 months
✓ sporulated oocysts survive in -10 °C for 106 days
✓ sporulated oocysts die at 55 - 60 °C in 1-2 minutes
✓ flies, cockroaches, dung beetles, earthworms, etc. can mechanically spread oocysts
https://doi.org/10.1016/j.tcsw.2018.100016
• started simultaneously in several districts of Moravia at the beginning of 1994 (December
1993) and lasted until April 1994, distinctly local character
• detected 722 cases of clinical toxoplasmosis (lymphadenopathy, prolonged angina)
during the first 3 months of 1994
• total number of infected not determined
• source of infection not proven
• hypothesis - the source of infection is raisins, nuts... contaminated with cat feces with
Toxoplasma gondii oocysts
✓ especially in the city
✓ Christmas season
✓ local occurrence (1-2 distribution companies)
• the second largest proven epidemic (larger epidemic was the water-borne
toxoplasmosis in Canada with 2 900-7 700 cases in 1995 )
Toxoplasmosis epidemic in Moravia 1994
Neospora caninum
• DH: Canidae
• IH: birds and mammals = warm-blooded vertebrates (no human infection)
• structural and antigenic similarity to Toxoplasma gondii
• 3 types of infectious stages:
tachyzoites - endodyogeny
bradyzoites - endopolygeny
sporozoites in fully sporulated oocyst
• bradyzoites  tachyzoites - immunologically mediated (IFN-γ)
• in vitro cultivation
• neosporosis - clinical disease of dogs and cattle
• transmitted from infected cows to offspring by congenital infection
• major cause of abortion in dairy cattle worldwide
• important cause of reproductive failure in cattle
Life cycle of Neospora caninum
intermediate hosts
Clinical signs of neosporosis
Pelvic limb hyperextension in a young dog with
neosporosis
Bovine abortion of neosporosis
• DH: dogs mostly asymptomatic, clinical signs in congenitally infected dogs, most severe
cases in young puppies – ataxia, partial but progressive paralysis of hind legs; in adult
dogs - inflammation of brain, spinal cord, liver and hearth, dermatitis with sores, pneumonia
• IH: abortion (mostly in 5 and 6 months of pregnancy; stillbirth or premature calf; clinical
signs in congenitally infected calves (neurological deficits)
Developmental stages of Neospora caninum
Tachyzoites and tissue cysts in
naturally infected dogs. A) Tissue cyst
from the cerebellum of a dog. HE. B) Large
group of tachyzoites (arrows) in skeletal
muscle of the same dog. HE. C) Tissue
cyst from the brain. Toluidine blue. D) A
group of tachyzoites (arrow) in the brain.
Giemsa stain. E) Tachyzoites (arrows) from
the liver of dog stained with polyclonal
antibodies to N. caninum.
https://doi.org/10.1016/S0020-7519(02)00094-2
Developmental stages of Neospora caninum
A) Impression smear of the liver of an experimentally infected mouse with tachyzoites varying in dimension, depending
on the stage of division. a - slender tachyzoite, b - tachyzoite before division, c - 3 dividing tachyzoites, arrow - red
blood cell. Giemsa. B) Sectioned tissue cyst inside a neuron in the spinal cord of a congenitally infected calf. HE. Thick
cyst wall (opposing arrowheads) encloses slender bradyzoites (open triangle). C) Unsporulated oocyst in the dog
faeces. D) Sporulated oocyst with 2 sporocysts. https://doi.org/10.1128/CMR.00031-06
Pathology of neosporosis
Microscopic lesions in brain of lambs naturally infected with N. caninum. A) Focus of gliosis (arrowhead) at the cerebral
cortex. HE. B) Diffuse congestion, mainly seen at the white matter of the corona radiata and a focus of necrosis with peripheral
gliosis. HE. C) Tissue cyst containing structures compatible with bradyzoites. HE. D) Positive labelling of tissue cyst. IHC.
genus Besnoitia
• cause of pedunculated lesions in the skin, nasal cavity and larynx of animals
• 10 described species
Besnoitia besnoiti
• new emerging parasitic disease in Europe, responsible for significant losses in the
cattle industry of Africa and Mediterranean countries
• DH and infection source unknown
• acute disease - fever, subcutaneous oedema, conjunctivitis, nasal discharge,
salivation, lameness, and depression
• chronic bovine besnoitiosis - parasite cysts in connective tissues, especially the
dermis and the non-intestinal mucosa; superficially located cysts in the scleral
conjunctivae, mucous membranes in nasal cavity and vestibulum vaginae = pinhead
sized white protuberances are pathognomonic for bovine besnoitiosis
• chronic non-reversible besnoitiosis - hyper-scleroderma, hyperkeratosis, alopecia; in
bulls - atrophy, sclerosis and focal necrosis causing irreversible lesions in testis
• no vaccines and chemotherapeutical drugs available
Clinical signs and pathology in chronic bovine besnoitiosis
A) tissue cysts in scleral conjunctiva
B) tissue cysts in a vulvar biopsy
C) elephant skin and alopecia
D) nodules in udder and teats
Chronology of disease progression:
https://doi.org/10.1186/s12917-015-0344-6
Pathology in chronic bovine besnoitiosis
Histological sections of skin. A) Scrotal skin transition
from more normal to area of epidermal and dermal necrosis.
B) Deep subcutaneous vessels containing thromboses. HE.
Ventral view of the bull with skin and scrotal lesions
http://www.bioone.org/doi/full/10.1645/12-128.1
Cyst morphology and pathology of besnoitiosis
A) numerous tissue cysts in the dermis and epithelial desquamation; B) cyst with three-layered wall: outermost connective
tissue, middle layer containing host cell nuclei and inner parasitophorous vacuole membrane surrounding the bradyzoites; C)
infiltration with histiocytes and eosinophilic granulocytes around cysts; D) occlusion of sebaceous gland duct
Besnoitia besnoiti in Europe
World-wide distribution of Besnoitia spp. infections in ungulates
Inlay: chronological expansion of B. besnoiti in Europe. Crosses: before 1900; triangles: 1991–2000;
circles: 2001–2012
Apicomplexa
Aconoidasida•••
• apical complex lacking conoid in asexual motile stages; some diploid motile
zygotes (ookinetes); macrogametes and microgametes forming independently;
heteroxenous
Haemospororida••••
• zygote motile as ookinete with conoid; ciliated microgametes produced by
merogony; oocyst formed in which sporozoites develop
• Haemoproteus, Leucocytozoon, Mesnilium, Plasmodium
Piroplasmorida••••
• piriform, round, rod-shaped or amoeboid; conoid and cilia absent in all stages;
polar ring present; without oocyst
• Babesia, Theileria
Apicomplexa
Aconoidasida (previously Hematozoea)
• dixenous parasites – vertebrate host and arthropod vector
• merogony in vertebrate erythrocytes (with some exceptions)
• development of gametocytes in vertebrate blood cells
• gamogony and sporogony in arthropod vectors
• sporozoite inoculation with vector saliva
• small number of microgamonts
• motile elongated zygote - ookinete
Haemospororida
Plasmodiidae
genus Haemoproteus
• merogony not in erythrocytes but in endothelial cells of blood vessels
• “halter-shaped” gamocytes  displacement of the host nucleus
• gamogony and sporogony in blood sucking insects - sporozoites in their salivary glands
Haemoproteus columbae
• transmitted by pigeon louse fly Pseudolynchia canariensis
• heavy infection  cell granuloma and massive destruction of the parenchyma of liver
and lungs leading to severe illness or even death of the pigeons
Gametocytes from the blood of Columba livia. a-b) macrogametocytes, c-d) microgametocytes
Haemospororida
Plasmodiidae
genus Leucocytozoon
• about 60 species in various birds
• transmitted by black flies (Simulium), biting midges
(Culicoides)
• no merogony in erythrocytes, but in endothelial cells
of blood vessels of parenchymatous organs
• development of gamonts in leucocytes
• gamonts mostly elongated with long tapering
extremities, in some species round
Leucocytozoon simondi
• duck, geese
L. smithi
• turkeys
Life cycle of
Leucocytozoon simondi
sporogony
merogony
gamogony
Haemospororida
Plasmodiidae
genus Plasmodium
• about 200 species (birds 45 species, mammals 55
species, reptiles 70 species)
• sporozoites in vector salivary glands
• first exoerythrocytic merogony:
➢ birds - endothelial cells of blood vessels
➢ mammals - hepatocytes
• merogony in erythrocytes
• gamogony and sporogony in mosquitoes
➢ birds - Aedes, Culex, Mansonia
➢ mammals - Anopheles
• „mal-aria“ = bad air in swamp (mosquitoe biotope)
• first evidence of malaria found in mosquitoes
preserved in amber from Palaeogene period (cca
30 million years old)
Avian malaria
Plasmodium gallinaceum
• poultry
P. lophurae
• chikens, ducks
P. cathemerium
• passerine, pathogenic for canaries
P. relictum
• passerine, pathogenic for pigeons
https://doi.org/10.1016/j.ijpara.2017.09.005
Rodent malaria
Plasmodium berghei
• rodents, originally isolated from thicket
rats Grammomys surdaster
• laboratory model
• vector: Anopheles dureni
P. vinckei
P. chabaudi
P. yoelli
• laboratory model
• vector. Anopheles stephensi
Malaria in non-human primates
• 7 species can be experimentally transferred to humans
Plasmodium brasilianum
• platyrrhine monkeys of South and Central America
P. cynomolgi
• macaques, capuchin monkeys, transferable to human
P. knowlesi
• macaques, transferable to human
P. swetzi
• chimpanzee, gorilla
P. rodhaini
• chimpanzee
Plasmodium species infecting humans
Plasmodium falciparum
• malignant tertian malaria
• single generation of hepatic merogony
• recrudescence  reinfection
• attacked erythrocytes adhere to vessel walls
Plasmodium vivax
• most frequent cause of benign tertian malaria
• multiple generations of hepatic merogony, hypnozoite
formation
• frequent relapses even after several years
Plasmodium ovale
• less frequent cause of benign tertian malaria
• multiple generations of hepatic merogony, hypnozoite
formation
• long prepatent period - up to 4 years
Plasmodium malariae
• benign quartan malaria
• low parasitaemia, attacking only mature erythrocytes
Plasmodium species infecting humans
Life cycle of human Plasmodium spp.
https://www.youtube.com/watch?v=1v55yg0RfoY
https://www.youtube.com/watch?v=MxiWp8vkRFI
Morphology of Plasmodium falciparum stages
ring stages
meront gametocyte
trophozoites
Morphology of Plasmodium falciparum merozoite
Morphology of Plasmodium falciparum early ring stage
Morphology of Plasmodium falciparum trophozoite
Morphology of Plasmodium falciparum meront
Symptoms of uncomplicated malaria
Symptoms and physical findings in
uncomplicated malaria
• host is repeatedly exposed to the effects of toxins, metabolic products and
antigens (immunogens)  cascade of indirect pathological reactions leading to
circulatory disorders, pathological immune reactions and a general disruption of
metabolism
• immunocomplexes
• cerebral malaria - coma
• anaemia due to haemolysis
• abnormalities in blood coagulation
• haemoglobinuria
• acute kidney injury
• hepatosplenomegaly
• acute respiratory distress syndrome
• low blood pressure caused by cardiovascular collapse
• metabolic acidosis often in association with hypoglycemia
Manifestations of severe malaria
Cerebral malaria
Plasmodium falciparum
• abnormal behaviour
• impairment of consciousness
• seizures, coma, or other
neurologic abnormalities
• opisthotonus (opisthotonos)
Petechial hemorrhages in white matter, compression of lateral and third
ventricles due to edema, vascular changes and thrombus
Diagnosis of malaria
✓ clinical symptoms
✓ microscopic detection
✓ QBC (quantitative buffy coat) capillary tube test
✓ antigen detection – rapid diagnostic tests
✓ PCR - malaria species identification
✓ serology (IFA, ELISA) - does not detect current
infection but measures past exposure
✓ drug resistance tests
Epidemiology and prevention of malaria
Immune mechanisms in malaria
https://doi.org/10.1038/nm.3083
* There is strong evidence that drugs listed in
parentheses are active against designated
stage of parasite life cycle.
¶ Quinoline derivatives are blood stage
schizonticides with the exception of
primaquine.
Δ Primaquine is a blood stage schizonticide
with activity against schizonts of P. vivax but
not those of P. falciparum.
Quinoline derivatives include chloroquine,
amodiaquine, quinine, quinidine, mefloquine,
primaquine, lumefantrine, and halofantrine.
Antifolates include sulfadoxine-pyrimethamine
and atovaquone-proguanil. Antimicrobials
include tetracycline, doxycycline, and
clindamycin.
Plasmodium life cycle drug targets
Drugs used for malaria chemoprophylaxis
Piroplasmorida
• apical complex without conoid and pellicular microtubules
• zygote = motile stage – kinete
• parasites of vertebrate erythrocytes and lymphocytes (IH)
• vectors are ticks belonging to Ixodidae and Argasidae (DH)
Babesiidae
• development restricted to vertebrate erythrocytes
• transovarial transmission in vectors
• more than 100 species
Theileriidae
• development in vertebrate erythrocytes and in lymphocytes = Koch´s bodies
• transstadial transmission in vectors only
Babesiidae
genus Babesia
• infecting livestock worldwide, wild and domestic vertebrate animals, and occasionally
humans
• transmitted by ticks
Babesia canis
• IH: Canidae
• DH: hard ticks - Dermacentor reticulatus for
subspecies B. canis canis (Europe),
Rhipicephalus sanquineus for B. canis vogeli
(subtropics, tropics), Haemaphysalis leachi for
B. canis rossi (south Africa)
• clinical signs - lethargy, weakness, vomiting,
anorexia, fever, pale mucous membranes, and
dark discoloration of urine
• incubation period 10-20 days, mortality to 100%
in untreated dogs
• imported / autochthonous cases in Czechia
Rhipicephalus sanguineus
Babesia canis in erythrocytes of a dog (Giemsa)
Life cycle of Babesia canis
Babesia bigemina
• IH: Bovidae
• DH: Rhipicephalus ticks
• Texas cattle fever - mortality in acute
untreated cattle 50-90 %
• rapid rise in temperature, fever
persisting for a week or more  loss of
appetite, dull, listless  severe
anaemia due to rapid loss of
erythrocytes  infected erythrocytes
adhere to vasculature of organs
• cattle may die within 3-8 days
https://doi.org/10.1016/j.exppara.2009.03.011
Developmental stages of B. bigemina in Ixodes scapularis tick cell
line. G-H) Masses of uninucleated sporokinetes. I-J) Extracellular ring form
adhered to the cell. K-L) Intra- and extracellular degeneration of
sporokinetes. Giemsa.
Babesia bigemina in cattle blood
Urine of uninfected animals (left) and Babesia-infected
animals showing haematuria
• infections with B. bovis, B. bigemina, B. divergens, and B. ovis, mainly adult animals
showed intense pathogenic effects, which lead often to death
• some Babesia species (e.g. B. ovis, B. bigemina, B. bovis, B. divergens) may introduce
mortality rates of up to 50 %
Clinical signs of livestock babesiosis
• leading symptom is bloody urine, since
reproduction of the parasites inside the red
blood cells leads to the destruction of the host
cell
• infection mostly starts with fever (40–42 C),
diarrhoea, apathy, nonfeeding, paresis, and
spasms followed by anaemia, icterus and
often severe haemoglobinuria, erythropenia,
and leucocytosis
Babesia microti
• IH: rodents (primarily
Peromyscus leucopus)
• DH: Ixodes ticks
• possible misidentification - also
classified as Theileria microti
• genome sequencing showed
that it does not belong to either
Babesia or Theileria, but to a
separate genus
• zoonosis
Life cycles of
Ixodes scapularis
and Babesia microti
https://doi.org/10.1128/JCM.00504-17
• primary species infecting humans: Babesia microti, B. divergens, B. duncani, B. venatorum
• hallmarks of babesiosis - fever and fatigue
• infection can be asymptomatic or range from an influenza-like illness to severe disease (depending
on host immune status) with end-organ compromise (renal failure, acute respiratory distress
syndrome, disseminated intravascular coagulation, or splenic infarction or rupture), might be fatal
• relapsing disease and treatment failures are primarily observed among patients with asplenia
and/or other immune deficits
Human babesiosis
Theileriidae
genus Theileria
• infecting cattle and ungulates
• theileriosis transmitted by ticks
Theileria parva
• IH: Bovidae
• DH: Rhipicephalus appendiculatus
• „East Coast Fever“ of cattle in sub-Saharan Africa
• meronts in lymphocytes (Koch’s blue bodies)
circular or irregularly shaped
• rod-shaped stages in erythrocytes
• high mortality (in imported stock mortality up to
100%)
• zebu (Bos indicus) is naturally resistant
• vaccination with attenuated strains
• East Coast fever results from
infected lymphocytes
• symptoms include anorexia, fever,
enlarged lymph nodes near the tick
bites (or even lymphadenopathy),
diarrhoea, laboured breathing due to
pulmonary oedema, corneal opacity,
nasal discharge and anaemia
• rarely a "turning sickness" disorder
develops - when the parasites in
cells block blood vessels in brain
and cause brain damage – usually
results in death
• respiratory failure and death of
African cattle
Symptoms and life cycle
of Theileria parva
https://doi.org/10.1371/journal.pone.0156004
Theileria annulata
• IH: Bovidae
• DH: Hyalomma ticks
• causal agent of tropical theileriosis
• indistinguishable from T. parva
• north Africa, Mediterranean coastal area,
Middle East, India, former USSR, Asia
• incubation period 9-25 days
• infects mainly bovine B-cells and macrophages
• lymphoproliferative disease with clinical
features similar to some human leukaemia
• acute disease in all breeds and all age group of
cattle, including buffalo and zebu
• fever, depression, lacrimation, nasal discharge,
swelling of superficial lymph nodes
• rapid emaciation and haemoglobinuria
• mortality of up to 90 % Koch´s bodies
A) Blood smear showing three ring forms of T. annulata in
red blood cells. B) Lymph node smear showing a meront in
mononuclear cell. Giemsa.
Life cycle of Theileria annulata
Pathology of Theileria annulata
A) Widespread haemorrhagic nodules in subcutaneous tissue and abdominal muscles
of calf. B) Pale and haemorrhagic nodules are inserted in the tongue and the laryngeal
and pharyngeal mucosa.
Lymphoid neoplastic-like cells (A) in a nodule infiltrating the skeletal muscle (HE),
with indistinct cell-membrane, high nuclear/cytoplasmic ratio and occasionally indented
nuclei (B) (HE).
• acute lethal infection of calves
(≤ 4 months of age) - calves
had enlarged lymph nodes and
developed multifocal to
coalescent nodular skin
lesions, similar to multicentric
malignant lymphoma
• at necropsy, haemorrhagic
nodules or nodules with
haemorrhagic halo were found,
particularly in the skin,
subcutaneous tissue, skeletal
and cardiac muscles, pharynx,
trachea and intestinal serosa
https://doi.org/10.4142/jvs.2010.11.1.27
https://doi.org/10.1016/j.pt.2021.11.001
https://doi.org/10.3389/fcimb.2018.00248
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