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
1. Amoebae, Apicomplexans, Flagellates and Ciliiates
  1. 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
1. Eimeria: Oocyst contains four sporocysts, eac containing 2 sporozoite after sporogony (1-3d): always a DIRECT LC
2. Isospora: Oocyst contains two sporocyst, each containing 4 sporozoites after sporogony (1-3d). These have an optional indirect lc
3. Ingestion of the oocysts after sporulation allows the sporozoites to be liberated
  1. SCHZOGONY (asexual): First generaton shizonts produced intracellularly and shizozoites released into surrounding tissue, then second generation
    1. 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
      1. Sporogony in the environmnet
      2. 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
1. 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
  1. 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
  2. PATH: Infection of LI is ore pathogenic then small, crypts more then villi, 2nd more then 1st generation shizogony and POLYP not at all
  3. 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
  4. 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
    1. Diagnosis: PM scrapings and imflammation of the GIT
      1. 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]
  5. PIGS: An increaisng cause of neonatal death in US (20-25%)is ISO suis- fluid toothpaste within 102 days
  6. SMALLIES: Isospora species only; Dogs: Iso canis, Iso Ohionsis and in cats less then 1m of age: mixed infectiosn of I. Felis and Rivolta...!
  7. 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
1. 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
  1. The zoite attaches to surface, is ingested and forms a vacuole
    1. There is shizogony and gametogony (confined to 5um diameters)
      1. 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
2. ZOONOTIC
Toxoplasmosis
1. 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
  1. 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
    1. 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
      1. 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!
      2. 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
      3. In non pregant animals there may be LN infection with pulmonary signs, fever etc. The proliferaing tacchys can cause necrosis of many organs
      4. 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
      5. 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
1. This was first diganosed in ataxic dogs and confused with TOXO (New... Spora) - a natural infection found in cheep, goats, horses, camels and foxes.
  1. The DH are dogs that release oocysts similar to toxo but FEWER of the, "rehsedding" after first infection in dogs is nknwn
    1. Sporozoites liberated in DH and IH (Catlle) and then fast moving TACCHYS spread to the CNS and myocardum predominantly
      1. 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
1. 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

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Protozoan infections

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	Created by rpbardoul almost 9 years ago