Cryptosporidium and Giardia Flashcards
1
Q
Cryptosporidium and Giardia
A
- Protozoan parasites (both responsible for bad diarrhea)
- Cause serious diarrhoea in animals (and humans)
- LIfe Cycle/ prevelance of infection differ
2
Q
Cryptosporidium
A
- Minute protozoan parasite (even smaller than coccidia)
- Wide host range (+ zoonotic)
- Targets microvillus brush border of alimentary & respiratory tract epithelium -
Live in elementary tract, but can also be in respiratory tract, Unlike coccidia.
-Live in the brush border, not inside the epithelial cells, tip of the single villus
- Causes serious Diarrhea
- Most important species = C. parvum (zoonotic: domestic animals, humans), other species (birds)
- Distantly related to coccidia- similar life cycle
- Faecal- oral transmission (or via water supply)
3
Q
Recognizable Features
(cryptosporidium)
A
Recognisable Features
- Developmental stages occur within brush border, not in the enterocytes themselves (like coccidia do)
- Very small oocysts (4-5μm) (smaller than Eimeria oocysts (15-50μm)- 4 sporozoites within the oocyst
-RBC: 8 um–> over half the size of the RBC (oocysts that are passed in feces)
Coccidia can be up to 50 um, but are about 15-20 um
4
Q
Direct Life Cycle
A
Direct Life Cycle (means one host)
- sporozoite released once oocyst has been ingested
- sporozoite enters the brush border and continue to grow (look like football full of bananas)
- undergo asexual replication to form a schizont (Schizogony)
- Schizonts then rupture and release merozoites
- Gametology- micro gametocytes=male, macro= female
- sperm will rupture from microgametocyte and loo for a macro (equivalent of singla mammalian ovum) to fertilize (Gametogony)
- Once it is is formed, will form an oocyst (unsporylated)
- Unsporulated oocysts form but become sporulated inside host (unlike coccidia) so is immediately infective once excreted in faeces of host for another host! (thick walled cysts)
- thin walled: stay in the host to populate
- 2 different types of oocyst produced: release sporozoites while still in the same hosts. Same host can build up very large numbers of cryptosporidium and therefore more pathogenic!!
- Thick-walled- the infective ones which are shed- more robust, can survive in faeces
- Thin-walled- stay within host–> autoinfection- can –>massive build-up of parasites
- Short PPP (<1 week)
- Autoinfection can occur
- Oocysts already sporulated when passed in faeces
5
Q
Pathogenic Significance
(cryptosporidium)
A
Pathogenic Significance
- Causes outbreaks of diarrhoea in young animals (Particularly in calves in unsanitary and older cattle can be asymptomatic carriers)
- Common cause of calf scours (older animals = asymptomatic carriers)
- Common infection in AIDS patients (immunosuppressed) or pregnant women (immunocompromised)
Epidemiology:
- Direct faecal-oral infection: school parties visiting farms
- Water borne infection: contaminated water supply can infect thousands
6
Q
Diagnosis
A
- Fecal smears= only useful if stained (clear if not) - Ziehl-Neilsen stain (labor intensive)
- Oocysts appear red, bacteria stains blue
- oocysts are smaller than pollen grains
- Immunoassays- use specific Ab for crypto- tagged to fluorescent dye
- Oocysts appear green
Bright green are fluorescing cryptosporidium, Used in water treatment facilities
7
Q
Control
A
- Isolate / quarantine bought-in calves; treat if signs of diarrhoea
- Good hygiene, adequate bedding and disinfection of calf pens
- Prevention / treatment with halofuginone (Halocur, Intervet), oral dose –> ↓ oocyst excretion, ↓ % of calves with diarrhoea- good but not 100 effective
8
Q
Cryptosporidium Life Cycle
A
9
Q
Giardia spp.
A
- Anaerobic, Flagellate protozoan (fleshy stage)- They swim along like crawfish using flagellae
- Intestine of humans ( –> villous atrophy –> malabsorption-associated with chronic diarrhoea)
- Also found in wild and domestic animals
10
Q
Recognisable Features
A
- 15-20μm long (still small!)
- Pear-shaped
- Eight flagella
- Large adhesive disc/ventral disk (attaches to intestinal wall of host)
- Cysts: 10μm long & Oval-shaped
- There is a gap wrapped between wall of cyst and trophozoite inside which is important diagnostically!!
- Cyst-like stage: twice as large as cryptosporidium but still so small
11
Q
Life Cycle
(Giardia)
A
- Simple and direct
- Trophozoites attach to intestinal wall
- Reproduce by binary fission
- Cysts shed intermittently in faeces, immediately infective
- Sit on intestinal mucosaand cover a vast portion
- simple direct life cycles
- reproduce by binary fission: split down the middle to produce 2 new trophozoites
- immediately infective like crypto., but in different taxonomically (oocysts in cryptosporidium and cysts in giardia)
12
Q
Pathogenic Significance
(Giardia)
A
- Humans- Commonest cause of protozoal diarrhea in UK, widespread in most developed countries–> villous atrophy–> malabsorption
- Animals- Common in domestic animals, usually asymptomatic- infection may persist for weeks/ months if left untreated (One animal can act as a source for others in household or area)
- Stunting of the villi, results in malabsorption of nutrients
- reduced amount of SA and therefore the absorption of nutrients, malabsorption
- X sections of villi: -see giardia in spaces bw villi
- don’t invade villi themselves
13
Q
Epidemiology
(Giardia)
A
- Infection via :
(a) direct faecal-oral route
(b) water-borne transmission - Giardia taxonomy- 6 species (G. duodenalis–> human infections)-
Now there are known only 6 or 7 species
- Wild animals may act as source of infection for humans
- e.g. infected beavers upstream –> ‘beaver fever’ in humans. –> beavers are shitting into water source (river) where people drink it
14
Q
Diagnosis
(Giardia)
A
- Faecal examination – for Giardia cysts- using iodine counter-staining (the gap between the cyst wall and trophozoite shows as a lighter region)- make thin smear and flood with iodine (doesn’t penetrate cyst wall), see gap so they stand out a bit
- may see pollen grains or yeast cells (similar size)
- Cyst excretion= intermittent – must collect faeces for at least 3 days
- Giardia cysts= heavy – use higher density flotation fluids to float cysts (e.g. ZnSO4)- these also exert a strong osmotic effect which causes the contents of the cyst to be pulled to one side
- Commercial immunoassays available- beneficial as can screen for 2 different parasites at once
- Larger are giardia cysts
- Smaller ones could be cryptosporidium
15
Q
Control
(Giardia)
A
- Good sanitation and hygiene
- Boil/sterilise drinking water
- Avoid uncooked foodstuffs
- GOOD SANITATION!!
17
Q
Life Cycle Giardia
A
