Zusammenfassung der Ressource
Protozoan infections
- Protozoa are unicellular eukaryotes that undergo
morphological changes as they develop. They are
non pathogenic commensals (rumen) in many
circumstances. They undergo both sexual and
asexual repro
- Amoebae, Apicomplexans, Flagellates and Ciliiates
- Apicomplexans are obligate intracellular
parasites that will only be found outside the cell
when they are 'migrating'. They hi-jack the host
mechanisms
- The Lifecycle of Protozoa
- Eimeria: Oocyst contains
four sporocysts, eac
containing 2 sporozoite after
sporogony (1-3d): always a
DIRECT LC
- Isospora: Oocyst contains two
sporocyst, each containing 4
sporozoites after sporogony
(1-3d). These have an optional
indirect lc
- Ingestion of the oocysts
after sporulation allows
the sporozoites to be
liberated
- SCHZOGONY (asexual): First generaton
shizonts produced intracellularly
and shizozoites released into
surrounding tissue, then second
generation
- GAMETOGONY: A second generation shizozoite
enters and becomes either Male (microgametocyte)
or Female (Macro).There are many males,
fertlisation (gamete fusion) produces an oocyst
which is released into faeces
- Sporogony in the environmnet
- POLYP formation: the 2nd generation sporozoites
have delayed sexual maturity (PROMEGATOCYTES) -
these live at the apical surface and induce maturation
as they divide and
- Coccidia
- These are often non pathogenic commensal
organisms in the GIT of many species- under
normal conditions oocytsts will be picked up in
env and devlop immunity within 1-2 weeks
- TRANSMISSION: oocysts will survive for LONG periods of
time (impermeable membrane) and its
when large numbers ingested that clinical
dz manifests: Malnutrition,over crowding,
poor hygiene, war,, moist conditions and
young animals
- PATH: Infection of LI is ore
pathogenic then small, crypts
more then villi, 2nd more then
1st generation shizogony and
POLYP not at all
- DIAGNOSIS: Detection of
oocyts in facees is not specific
PM: inflammation of the
intestines, mucosal scrapings to
look for shizonts and oocysts in
large nubers
- CATTLE: E. Zurnii and E. Bovis-
in animals less then 6m of age-
occasionally in adults wth BVD. Dirrohea
with TENESMUS- dehydration, anorexia,
convulsons, (Bovis) as there are
neurotoxins released
- Diagnosis: PM scrapings and
imflammation of the GIT
- Support therapy (FLUIDS) is just as
important as coccidiostats/ cidals
- Coccidiostats: polyether ionophores- Monensin
and Bovatec are used for calves in feed (post
wenaing control is the most crucial). Quinolones
inhibit mitochondrial activity and have some
efficay against sporozoites, early shizonts:
DECCOX
- Coccidiocidals: These two
products interfer with DNA
sythesis, bayxox [one off] and
Toltracox [used in combination
with antheminintics]
- PIGS: An increaisng cause of
neonatal death in US (20-25%)is ISO
suis- fluid toothpaste within 102
days
- SMALLIES: Isospora species only;
Dogs: Iso canis, Iso Ohionsis and in
cats less then 1m of age: mixed
infectiosn of I. Felis and Rivolta...!
- SHEEP/GOATS: EIMERIA is uncommon in
young sheep few are pathognic
and mortality is low. Its
common in young goats in NZ in
late Summer/ Autumn
- Cryptosporidium
- This infection is confined to the brush
border of intestinal epithelium in many
speciesp man, mammals, reptiles and birds
and apotential source of neonatal mortality
- The zoite attaches to surface, is ingested
and forms a vacuole
- There is shizogony and gametogony
(confined to 5um diameters)
- Oocytts that contain FOUR free
sporozoites are passed into the faeces and
are IMMEDIATELY infective
- Doagnose with a modifiied ZN acid fast stain
- TREATMENT is guarded- very few drugs
available- Halocur is a synthetic form or a
plant alkaloid with a small TI. There is a
anew drugsL EXAGEN which contains an
active ingredient that nterfers with oocyts
infectivity- promote recovery OR used
prophylatically
- ZOONOTIC
- Toxoplasmosis
- This is an APICOMPLEXAN which favours
indirect transmission (needs to be an ISO)
between cats (the only DH) and a range of Prey
animals. It is the DZ of MICE and MAN and ca
cause abortions in: sheep, goats, pigs and
humans
- After sporulation in the environment, the
ISOSPORAare infective to both the DH (felids) and
ALL the possible IH- they survive well in Haybarns,
on sheep silage, in gardens and sandpits
- After the sporozoites are liberated they quickly
transform into tachhy's (fast moving) and can
invade the FOETUS. Afterimmune response, IFN
will cause a transformation into a BRADYzoite-
these can sporadically revert and form infective
cysts
- The cyst is heavily glycolated and does not
provoke an immune response- the toxo brain
cysts can be seen in a PAS or HandE stain of the
brain!
- Tachys; can only cross the placenta and cause
necrosis of the foetus/ and or placentomes on
the FRST exposure to the protozoa- clincal signs
depend on stage: EED, abortions, congenital dev
- Characteritic necrosis of
the cotelydons and
multifocal calcificaion.
Fetal heart serology
- In non pregant animals there may be LN
infection with pulmonary signs, fever etc. The
proliferaing tacchys can cause necrosis of many
organs
- DIAGNOSIS: Serology of ewes can be
misinterpreted, 40d delay from infection-
abortion, PM of the foetus
- CONTROL: Toxovax one month b4 mating season
in Maiden ewes- an attenuated tacchy
- People infection- a non congenital infection
that is largely assympomatix- some link with
primiscuity and risk taking behaviour in males.
Infection via: Shellfish, poorly cooked lamb,
gardening and drinking un-pastuerised milk.
Beware when pregnant
- Neospora
- This was first diganosed in ataxic dogs and confused with TOXO
(New... Spora) - a natural infection found in cheep, goats, horses,
camels and foxes.
- The DH are dogs that release oocysts similar to toxo but FEWER of the,
"rehsedding" after first infection in dogs is nknwn
- Sporozoites liberated in DH and IH (Catlle) and then fast moving
TACCHYS spread to the CNS and myocardum predominantly
- REPEAT infection in calves can occur- some will result in abortions,
others: a congenitally infected but "NORMAL" calf - n some cases the
infection will remain in the herd for many generations BUT NOT induce
abortions
- Cattle infection: Abortion (storms) up to
30% and congenital calfs
- 1) Ingestion of
dog oocysts
- 2) CONGENITAL
ingection- an
infected cow can
given birth to a
congenitally
infected calf!
Heifers who are
infected this way
will commonly
abort as maidens
- DIAGNOSIS: Serology for antibodies may be used but titres fall
about 2-3 months so many get a lot of false NEGS. IFAT (green
speckles) may be used but cut off is also high for this
- DOGS: manifests in young dogs, pre
weaning, rare in NZ and treatable. They
have paralysis/ paresis with high titres,
Bitch breeding should stop
- Theileria
- T. Parva is the most important type- EAST
Coast Fever in Africa. T.orientalis in NZ (keda
strain is the recent one- CHITOSE is the
older). Mortality ~1.6%. The tranmission is
via the vector: HAEMOPHYLLIS
LONGICORNIS which has three live stages:
Larvae, Lymph and Adult- each feeds on a
separate DH
- Microcycts: Dogs and macrocusts in Cats:schizogony in
the endothelium and shzozoites released into the
skeletal muscle which become arrested as CYTS after
tacchy cycle does NOT occur