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Title: Apicomplexa


1
Apicomplexa
  • Chapters 10-14

2
Phylum Apicomplexa
  • All species are parasitic
  • Many of important health and veterinary
    significance.
  • Without cilia or flagella (usually).
  • Single type of nucleus.
  • Complex sexual life cycles.
  • Unique and distinct apical complex.

3
Sporozoite or Merozoite
Oocyst
4
Life Cycle Terms
  • Sporogony multiple fission of a zygote such as
    cell is the sporont.
  • Sporozoite Daughter cell resulting from
    sporogony.
  • Oocyst cystic form resulting from sporogony
    may be covered by hardened membrane.
  • Merogony Schizogony fission of sporozoites
    where multiple mitoses take place followed by
    simultaneous cytokineses, resulting in a whole
    mess of daughter cells all at once.
  • Gametogony Production of gametes.
  • Zygote fusion of gametes (meiosis may occur
    after fusion).

5
Typical Life Cycle
SCHIZOGONY
6
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7
Phylum Apicomplexa
  • Gregarinia
  • Coccidia
  • Haemosporida (Haemosporidians)
  • Piroplasmida (Piroplasmids) 

8
Phylum Apicomplexa
  • Class Gregarinia genera include Gregarina,
    Monocystis, Ophriocystis, Pseudomonocystis
  • Parasites of annelids and arthropods.
  • Many very specific.
  • If there are millions
  • of species of insects,
  • are there millions of
  • species of Gregarina?

9
Phylum Apicomplexa
  • Class Coccidia
  • Order Eimerida
  • Genera include Besnoitia, Caryospora,
    Cryptosporidium, Eimeria, Frenkelia, Hammondia,
    Hepatozoon, Isospora, Lankesterella, Neospora,
    Sarcocystis, Toxoplasma
  • (Know genera in green)

10
Phylum Apicomplexa (cont.)
  • Class Coccidia
  • Order Haemosporida
  • Plasmodium
  • Order Piroplasmida
  • Bebesia
  • (What do green names mean?)

11
Coccidia
  • Small parasites with intracellular reproduction.
  • Monoxenous or heteroxenous.
  • Important parasites of vertebrates.
  • Often a predator disease requiring consumption
    of infected tissue.
  • Usually attack intestinal wall at some stage.
  • Three major phases
  • merogony
  • gametogony
  • sporogony (produced from zygote)

12
A Coccidian
Heptozoon caesbiane Parasite of bullfrogs
Fertilization
13
Coccidia Eimeria and Isosphora spp.
  • Important parasites of chickens, sheep, goats,
    pigs, dogs, cats.
  • Oocysts are infectivous stage, go through several
    generations (merozoites) within host, then
    produce new oocysts to continue cycle.
  • Reproduction is rapid and production of oocysts
    can be astronomical (possibly into the millions
    from a single individual).

14
Coccidia Eimeria and Isosphora spp.
  • These parasites are monoxenous and usually highly
    specific, even for tissues types in their hosts.
  • The diseases caused by these parasites are
    collectively referred to as coccidiosis, and they
    vary in virulence.

15
Eimeria and Isosphora
  • Although Eimeria and Isosphora can produce
    millions of individuals
  • Their only saving grace is that they are SELF
    LIMITING, in that they only run through a set
    number of generations.

1 ? 900 ? ( x 300_at_) 270,000 ? 20 _at_ 5.4
million ? Oocysts ? Stop
1st Gen. 2nd Gen.
3rd Gen. Zygotes
16
Oocysts
Isospora cyst
Eimeria oocyst
17
Life Cycle of Eimeria and Isospora spp
18
Eimeria tenella
  • One of the most serious diseases of poultry.
  • Mortality higher in younger birds.
  • 250 - 300 million spent annually for
    prophylactic treatment with coccidiastats. (A
    normal additive to feed)
  • Must use these prophylactic methods because once
    infected, there is no known treatment of disease.

19
Pathogenesis and Symptoms
  • In all animals, Eimeria and Isospora protozoans
    are intestinal parasites of the intestinal wall
    causing diarrhea, weight loss, and emaciation.
  • Normally, younger animals are more affected and
    adults may be resistant and/or asymptomatic to
    continued infections.

20
Diagnosis and Treatment
  • Detected by examining stool.
  • Chemical treatments are normally available.
  • Sulfa drugs and other anticoccidials

21
Other species of Eimeria and Isospora
  • Isospora belli is only reported human parasite of
    these genera.
  • Rare
  • The infection causes nausea, pain, and chronic
    diarrhea. 
  • Like other coccidia, the infection is
    self-limiting, except in those individuals with
    compromised immune systems.

Isospora belli oocysts
22
Family SarcocystidaeSarcocystis, Toxoplasma
  • These are somewhat similar to Eimeria and
    Isospora but
  • are heteroxenous
  • and can infect many tissues types (although
    usually infect intestinal cells as some stage).

23
Sarcocystis cruzi and related parasites
  • In Sarcocystis cruzi, the intermediate host is
    usually a ruminant, and the definitive host is a
    dog or other canine.
  • May be common and benign, although heavy
    infestations may cause death to ruminants.

Sarcocystis cruzi oocysts in the feces of an
infected dog
A section of cattle tongue showing three
sarcocysts
24
Life Cycle ofSarcocystis cruzi
25
Family SarcocystidaeToxoplasma and Toxoplasmosis
  • Toxoplasma gondii
  • Parasite of many tissues and intestinal
    epithelium
  • The non-cat stage of parasite has very low host
    specificity, and it will probably infect almost
    any mammal. 

26
Toxoplasma gondii
  • Has two phases
  • 1) intestinal (or enteroepithelial) and 2)
    extraintestinal phases. 
  • The intestinal phase occurs in felines
    (definitive host)
  • The extraintestinal phase can occur in many
    hosts. 

Are you lookin at me?
27
Life Cycle Cat Phase
Infects Mammals
Infects Mammals
6
1
5
2
3
4
28
From Cat get Oocytes or Bradyzoites from eating
Infected animal
29
Toxoplasma and Toxoplasmosis
  • Two routes of infection for mammals.
  • Through ingestion of oocytes
  • Through consumption of infected tissues
    containing bradyzoites or sporozoites of
    Toxoplasma.

30
Toxoplasma and Toxoplasmosis
  • In Humans
  • In most humans infected with Toxoplasma, the
    disease is asymptomatic. 
  • However, under some conditions, toxoplasmosis can
    cause serious pathology, including hepatitis,
    pneumonia, blindness, and severe neurological
    disorders. 
  • This is especially true in individuals whose
    immune systems are compromised (e.g., AIDS
    patients). 

31
Toxoplasma and Toxoplasmosis
  • In Humans (cont.)
  • Toxoplasmosis can also be transmitted
    transplacentally resulting in a spontaneous
    abortion, a still born, or a child that is
    severely handicapped mentally and/or physically.

32
Human Infection Rates
  • United States 0.5 1 of population
  • Much higher in Central American and other
    countries of the world.
  • Once infected, the non-definitive hosts have
    bradyzoites (Brady meaning slow) and will
    probably be infected for life.

33
Cryptosporidium
  • Common parasite in vertebrates, with very low
    specificity.
  • More common in humans with AIDS or immune
    problems.
  • Symptoms include watery diarrhea, sometimes
    lasting months in immune deficient persons.
  • In animals, fairly common and may be the cause of
    short term outbreaks of diarrhea.

34
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35
Phylum ApicomplexaClass CoccideaOrder
Haemosporida
  • Genera include Haemoproteus, Hepatocystis,
    Plasmodium.

36
Malaria
  • The most important disease in the world today in
    terms of lives lost and the economic burden it
    imposes.

37
Malaria
38
Malaria
  • WHO Definition of
  • A parasitic infection characterized by cycles of
    chills, fever, sweating, anemia, enlarged spleen
    and a chronic relapsing course. Four types of
    parasites affect man, through infection by the
    Anopheles mosquitos. Most malarious areas are in
    the tropics. Disasters, like floods and refugee
    encampments, are conducive to the propagation of
    the disease.

39
Anopheles mosquito
40
Data concerning Malaria
  • Recent estimates are that over 450 million
    persons are infected annually. (US population
    300 million).
  • Estimated deaths annually 1.5 to 2.7 million
  • Percentage of African children killed by malaria
    5 percent, or almost 3,000 each day. Most common
    age at death 4 years

41
Data concerning Malaria
  • In the early 1960s, only 10 the world's
    population was at risk of contracting malaria.
    This rose to 40 as mosquitoes developed
    resistance to pesticides and malaria parasites
    developed resistance to treatment drugs. Malaria
    is now spreading to areas previously free of the
    disease

42
Data concerning Malaria
With greater international travel, the incidence
of malaria is increasing in developed countries.
43
However, this can be controlled!
Data from the Netherlands from 2000-2007 van
Rijckevorsel et al. Malaria Journal 2010 9300
Total
Year Plasmodium
2000 535
2001 547
2002 396
2003 340
2004 293
2005 298
2006 241
2007 197
44
History of Malaria
  • Written references from Egyptians (3500 B.C.) and
    Greeks (2500 BC) clearly refer to the ravages of
    malaria.
  • Mentioned in the Iliad
  • More Crusaders died of malaria than warfare.

45
History of Malaria
  • Thought to have come to the New World with the
    conquest (Spanish and their slaves).
  • Based on speculation that the great civilizations
    that arose in tropical environments of the
    Americas (Olmecs, Mayans) would not have been
    able to flourish if malaria had been around.

46
Discovery of the Vectors and the Disease Causing
Parasites
  • There has always been a realization of the
    association between swamps (mosquito habitat) and
    malaria.

47
Discovery of the Vectors and the Disease Causing
Parasites
  • Mal aire from Latin roots.
  • Also, paludism is another term for the disease.
    Its commonly used in various languages
    (paludismo Spanish, Italian), from the Latin
    root word palus meaning marsh.

48
Discovery of the Vectors and the Disease Causing
Parasites
  • Lots of speculation.
  • Unusual granules observed in red blood cells of
    infected persons (Mackel 1847), but werent sure
    whether related to illness (or result of).

49
Discovery of the Vectors and the Disease Causing
Parasites
  • With the emergence of germ theory, assumed that
    malaria was also a bacteria.
  • Alphonse Laveran discovered the parasitic nature
    of the disease, observing the so-called
    granules in red blood cells suddenly transform
    to male gametes.
  • Initially, his results were met with skepticism.

50
Discovery of the Vectors and the Disease Causing
Parasites
  • The mode of transmission was still unknown.
  • Patrick Manson was the first to discover
    (1877-79) that the mosquito can host a developing
    parasite worm that causes the human disease,
    filariasis.
  • He then made the hypothesis that mosquitoes
    might also transmit malaria.

51
Discovery of the Vectors and the Disease Causing
Parasites
  • Manson convinced Major Ronald Ross, working in
    India, of his idea.
  • In his spare time, Ross worked with mosquitoes
    and malaria from 1892-1897.
  • First worked with the wrong mosquitoes (Culex
    and others)
  • Secondly, he was led astray by gregarine
    parasites.

52
Discovery of the Vectors and the Disease Causing
Parasites
  • At last, he investigated Anopheles mosquitoes,
    having them feed on a malaria-infected person,
    and then dissecting the mosquitoes later, and
    found the infective stages in the mid-gut.
  • Earned Nobel Prize in Medicine in 1902

Anopheles mosquito
53
Oocysts What Ross saw in external tissues of
gut of mosquito.
54
The night after Ross discovered the growing
oocysts he wrote
  • This day relenting God
  • hath placed within my hand
  • A wondrous thing, and God
  • Be praised. At this command
  • Seeking His secret deeds
  • with tears and toiling breath,
  • I find thy cunning seeds,
  • Oh million-murdering Death.

55
Distribution of Malaria
56
Life Cycle and Morphology
57
Sexual
Asexual
58
Life Cycle Plasmodium of Malaria Exoerythrocytic
Phase
  • Sporozoites injected into bloodstream via saliva
    of mosquito.
  • Travel to liver, where protein recognition allows
    sporozoite to penetrate liver cells (lt 1 hour).
  • In cell, parasite develops into a feeding
    trophozoite.
  • After a week, asexual reproduction occurs
    (schizogony) transforming the parasite into a
    schizont.

59
In mosquito
60
Life Cycle Plasmodium of MalariaExoerythrocytic
Phase
  • Through repeated, asexual divisions, a single
    schizont can produce thousands of merozoites, the
    next infective stage.
  • Also, hypnozoites can also be produced, living
    parasitical time bombs that can erupt many years
    later.
  • The merozoites do not invade liver cells but red
    blood cells (erythrocytes) and so begins the
    erythrocytic phase.

61
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62
Life Cycle Plasmodium of Malaria Erythrocytic
phase.
  • Released merozoites invade red blood cells
    (erythrocytes), where they develop into
    trophozoites. After a period of growth, the
    trophozoites divide and develop, eventually
    forming 8-24 merozoites in each red blood cell.
  • When this process is complete, the host red blood
    cells rupture, releasing mature merozoites.
  • The symptoms associated with malaria occur at
    this point.

63
Life Cycle Plasmodium of Malaria Erythrocytic
phase.
  • The merozoites then invade fresh erythrocytes and
    another generation of parasites develops in the
    same manner and the process is repeated.
  • In the early stages of infection there is no
    characteristic periodicity.
  • Later, the cycle (erythrocytic schizogony
    development cycle) becomes synchronized, and the
    febrile paroxysms (periodic fever) become more
    consistent.

64
Vector stage
  • After a number of erythrocytic schizogony
    development cycles, some merozoites differentiate
    into sexual forms (female macrogametocytes, male
    microgametocytes)
  • These are the infective stages and, if not picked
    up by a mosquito, will die.
  • Once in the stomach of the mosquito, the
    micorgametocytes develop into microgametes. This
    occurs rapidly in a process called
    exflagellation.

65
There are five important Plasmodium species which
infect humans causing malaria.
  • P. vivax - benign tertian (3 day cycle) malaria -
    accounts for 43 of cases
  • Worldwide in tropical and some temperate zones
  • P. falciparum - malignant tertian malaria
    accounts for 50 cases.
  • tropical Africa, Asia and Latin America
  • P. malariae - quartan malaria (4 day cycle) -
    accounts for 7 of cases
  • worldwide but very patchy distribution 
  • P. ovale - mild tertian malaria - accounts for gt
    1 of cases ( mainly in tropical west Africa)
  • P. knowesi malignant quarten malaria (fairly
    new and not well documented yet).

66
Species of Malaria
  • Of the five human malaria strains, Plasmodium
    falciparum is the most common and deadly form. It
    is responsible for about 95 of malaria deaths
    worldwide. Plasmodium knowlesi is coming in
    second, making up 80 of case in Borneo that
    require hospitalization.

67
Fever cycles with the various species of malaria.
68
Pathogenesis
  • Two manifestations
  • Inflammatory response due to large release of
    antigens in blood at cell lysis. Thought that
    hemozoin (the dregs of hemoglobin) might
    initiate major fever response.
  • Anemia also created due to red blood cell
    destruction.

69
Various manifestations of malaria
  • Normal sequence of fevers and chills
  • Cerebral malaria progressive headache leading
    to coma and rapid death.
  • Pulmonary edema
  • Algid malaria onset of shock.
  • Blackwater fever- massive lysis of erythrocytes
    resulting in blood and blood products in urine

70
Relapses
  • Exoerythrocytic forms that become crytozoites
    or hypnozoites
  • Can remain dormant for many years.
  • Only P. vivax and P. ovale are capable of
    production of true hypnozoites.

71
Epidemiology Considerations
  • Reservoir How many people are infected?
  • What are the levels of parasitism?
  • Are simple actions taken like isolating the sick
    individual with mosquito netting? Isolation from
    the other family members?
  • Are anti-malarials available to the infected
    population?

Man is tested for malaria in Jinotega, Nicaragua
72
Epidemiology Considerations
  • What are the vectors? What are their requirements
    and ecophysiological limitations?
  • Local climatic conditions, and availability of
    mosquito breeding areas?
  • Times of floods, and other natural disasters are
    conducive to major malarial outbreaks.

73
Insecticidal spraying
  • Almost eliminated malaria with effective and
    organized program of DDT spraying over much of
    the world during the 1960s.
  • DDT was very effective for a time with a single
    application of the interior of a house. A
    mosquito landing on the wall would die and this
    effect lasted for up to three years!

74
Antimalarial drugs
  • Botanical based.
  • Chinese had several plant extracts that were
    effective drugs (eg. Dichroa febrifuga)
  • The alkaloid, Quinine, from the Peruvian tree,
    was dependable and effective.

Cinchona Tree.  . This plant's bark is the source
of quinine, a highly effective drug for treatment
of malaria.
75
Antimalarial drugs
  • Synthetic drugs
  • Chloroquine developed after quinine production
    captured by Japanese during WWII.
  • Others have been developed, only primaquine
    effective against all.
  • Chloroquine still most effective against P.
    falciparum.

76
Resistance to Antimalarial drugs
  • Plasmodium falciparum now resistant to
    Chloroquine in Asia, Africa, and South America.
  • Resistance popping up for virtually all drug
    treatments.
  • Travelers to malarial areas recommended to take
    mefloquine regularly, but serious side effects
    are common.
  • Problem in prophylaxis treatment of malaria is
    that it may hide symptoms. Symptoms then appear
    after returning home and the travelers stop
    taking the drug.

77
New Research Directions for Control
  • A vaccine or induced resistance is fleeting
    because membrane antigens of Plasmodium are
    continually changing in populations (remember
    they have sexual stages).
  • Trying to produce a non-transmissive Anopheles
    with molecular genetic technology. Would this
    work ?

78
Anopheles mosquitoes
  • 390 species
  • Worldwide distribution
  • Standing water or Permanent water mosquitoes
  • Species vary in their ability to transmit
    malaria, and all species have their unique
    ecological requirements.

79
A brief overview of mosquito biology
Anopheles annulipes
80
Anopheles mosquitoes
  • 390 species of Anopheles worldwide.
  • Ecology is distinct for each species, as expected
    for good species.

81
Anopheles mosquitoes
  • Where adults place eggs, which defines larval
    habitats, is probably most limiting factor as to
    where Anophles can occur.

82
Standing Water or Container-breeding Mosquitoes
Mosquitoes
  • All Anopheles species lay single eggs on the
    water surface and the egg has a built-in set of
    floats (on the side) to prevent it from sinking.
  • Culex lay eggs on water surface as well, but
    in rafts.

83
Flood water mosquitoes
  • Aedes lays single eggs on moist ground. When
    rains come they are already in position.
    Sometimes the can wait out long periods of dry
    weather.

84
Different mosquito larvae
85
Difference in position below water surface
Siphon tube
Anopheles larvae lay close to surface. They lack
siphon tube
Aedes aegypti larva
86
  • Most larvae are filter feeders that collect bits
    of suspended organic debris, using their mouth
    brushes to strain the food out of the water.

87
  • The larvae quickly wiggle to the bottom when
    disturbed, and thus are commonly called
    wrigglers.

88
Anopheles instars (larvae stages).  Mosquito
larvae go through 4 growth stages known as
instars, before molting to the pupal stage.
89
Pupal Stage (Also on water surface)
Pupae can move!
90
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91
Plumose antenna
Male mosquito
92
Biological ControlGambusia spp. Mosquito-eating
fish
Questionably effective.
93
Biological ControlMosquito-eating mosquitoes
The larvae of Toxorhynchites speciosus. This
mosquito larvae (as for all Toxorhynchites
larvae) is predacious on other mosquito larvae
94
Biological ControlProtozoan parasites Phlyum
Microspora
95
Cultural ControlSource reductions
  • Drainage and management of water sources

96
Source reductions
97
Source Reductions
98
Source Reductions
99
Chemical ControlBack pack sprayer
100
Chemical ControlAerial spraying
101
Order Piroplasmida Parasites of ticks and mammals
  • Phylum Apicomplexa
  • Order Piroplasmida
  • Family Babesiidae
  • Family Theileriidae

102
Family Babesiidae
  • Most important parasite is Babesia bigemina,
    cause of babesiosis.
  • Many other common names including, Texas
    Red-water fever, Tick fever, or infuriating
    for Texans, Texas Fever.

103
Texas cattle fever(Texas red-water fever)
  • Cattle drives to northern markets from Texas and
    further west, started in earnest in 1866.
  • Famous Chisholm Trail, various trails north.
  • By 1870s, the railroads moved the cattle north.

104
Texas cattle fever
  • In 1868, nearly 75,000 Texas Longhorns were
    driven to Abilene, Kansas, where they were
    shipped by rail to the Midwest and East.
  • Within a month of arrival, local northern cattle
    began dying in droves.
  • Nobody wanted Texas Cattle.
  • Settlers along the trails guarded their property
    with rifles.

105
Texas cattle fever
  • Northerners claimed that Texas cattle carried the
    disease
  • But Texans countered that their cattle werent
    sick.
  • Turns out that the Texan longhorn cattle were
    resistant to this protozoan parasite, carried by
    Rhipicephalus (Boophilus) ticks.

106
Texas cattle fever
  • When Longhorn cattle from the south were put in
    pastures with northern stock, the ticks would
    fall off, and infect the susceptible Yankee
    cattle.

107
  • Theobald Smith and Kilbourne proved in 1880s
    that the tick, Rhipicephalus (Boophilus)
    annulatus, was the vector of a tiny protozoan
    parasite causing Texas fever, Babesia bigemina
  • At the time, many scientists were skeptical that
    disease would be spread by bloodsucking
    arthropods

108
Theobald Smiths discoveries
  • One of the first to find evidence of an arthropod
    borne disease
  • Opened the door to further discoveries of the
    importance of arthropods as vectors of disease.
    (Remember malaria?)

109
Life Cycle of a One Host Tick
Adult Rhipicephalus (Boophilus) tick feeds on
host
Babesia parasites pass to eggs (transovarian
transmission)
Gravid (eggs mature) adult releases and falls
off
110
Life Cycle of a One Host Tick
Female lays egg in huge mass
Six legged nymph hatches and searches for host
111
Stages of a Tick
112
Not Happy!!!
113
Babesia bigemina
  • Sporozoites injected into host through liquids
    injected from salivary glands.
  • Unlike malaria, there is no exoerythrocytic
    phase, and sporozoites move directly to infect
    blood cells.
  • Asexual cycles continues indefinitely.
  • Host resistance develops if they survive the
    infection.

114
Babesia bigemina
  • Ticks are infected from some of the parasites
    within blood cells that developed as gametocytes
  • These are ingested by tick and develop into ray
    bodies.

115
Babesia bigemina
  • These strangely shaped ray bodies fuse to form
    the zygote called the kinete.

116
Babesia bigemina
  • Kinetes penetrate various cell types, transform
    and some of then enter the salivary glands of the
    host tick.
  • Through multiple fission, produce thousands of
    sporozoites that are injected into vertebrate
    host.

Hypostoma
117
Babesia bigemina
  • Biggest problem in controlling disease is that
    part of its transmission from tick to tick is
    transovarial.
  • Transovarian transmisson means that the protozoa
    enters the eggs while still in reproductive
    system before oviposition.

If female is infected, the eggs are already
infected
118
Babesia bigemina pathogenesis
  • Affects older animals more than calves.
  • Incubation of 8 to 15 days, followed by fever.
  • 75 of eurythrocytes may be destroyed in fatal
    cases, and less infected animals suffer from
    severe anemia.
  • If host survives attack, it will be immune.

119
Best control method is through control of vector
by dipping cattle.
120
Other Babesia spp.
  • Babesia microtis infects humans on very rare
    occasions.
  • Other Babesia species attack cattle in Europe,
    Asia, and Africa

121
Other Babesia spp.
  • Babesia canis attacks dogs and has very similar
    life cycle to that of B. bigeminia.
  • Transmission is primarily by the brown dog tick
    (Rhipicephalus sanguineus).
  • Babesia felis is a rare parasite that can produce
    a regenerative anemia, lethargy and anorexia in
    cats.

122
Phylum Microspora
  • Previously in Subphylum Sporozoa with
    Apicomplexa.
  • Produces spores like Apicomplexa, but other
    differences including unique coiled, polar bodies
    in the anterior end of organism.
  • Thought to be more related to Cnidaria than other
    protozoa!!

123
Phylum Microspora
  • Nosema apis Disease of honey bees, called
    nosema disease, bee dysentary, or May
    sickness.

Entrance to hive with bees with dysentery
124
Phylum Microspora
  • Encephalitosoon cuniculi parasite of mammals
    (especially rabbits), occasionally infecting
    humans. Ubiquitous but easily defended against by
    person with normal immune system.

125
Phylum Myxozoa
  • Of multicellular origins.
  • Annelids are needed as intermediate hosts.
  • Parasites of fish and amphibians and reptiles.

126
One more parasite to go
  • Phylum Myxozoa
  • Class Myxosporea
  • Order Bivalvulida
  • Suborder Platysporina
  • Myxobolus ( Myxosoma) sp. ("whirling disease")

127
Myxobolus cerebralis
128
Spores in minnow
129
Myxobolus cerebralis life cycle
  • The lifecycle of M. cerebralis alternates between
    salmonid fish and aquatic oligochaete worms.
  • Myxospores are released into the sediment from
    decomposing infected salmonids, or from the feces
    of predators who have eaten infected fish.

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Two to four months later, waterborne
triactinomyxon (TAM) spores are released from the
worm which attack the fish
Tubifex tubifex (oligochaetes) eat myxospores in
detritus
Myxospores
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Myxobolus cerebralis
  • When the triactinomyxon comes into contact with
    the fish, it attaches to the skin
  • The parasite reproduces in the skin, and then
    migrates to the central nervous tissue and
    surrounding cartilage. Here they eat cartilage,
    before forming the trophozoite stage.

Cartilage deformation
132
Myxobolus cerebralisblack tail symptom
133
Symptoms
134
Whirling disease
  • The parasite Myxobolus cerebralis is not native
    to the U.S., but is native to Europe.
  • Introduced in 1956.
  • Most important in Colorado and Montana, although
    in many other states.

135
Whirling disease
  • The significant problem is that while in the
    spore stage (myoxspore), M.cerebralis is
    virtually indestructible. The spore can withstand
    freezing and desiccation, and can survive in a
    stream for 20 to 30 years. This provides lots of
    chances to be eaten by worms.

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Ranges of susceptibility to M.cerebralis among salmonids Ranges of susceptibility to M.cerebralis among salmonids

Species Susceptibility
Rainbow trout Highest
Huchen High
Sockeye salmon High
Chinook salmon Intermediate
Cutthroat trout Intermediate
Brook trout Intermediate
Atlantic salmon Intermediate
Brown trout Low
Coho salmon Low
Bull trout Low
Arctic grayling Not
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