Protozoa Flashcards
Protozoa
Single celled euk organism with complex subcellular organisation that can live EC and IC with direct or indirect lifecycle and arthropod borne lifecycles
Can cause death or prod loss
Some are zoonotic
Protozoa sub groups
Rhizopod
Ciliate
Flagelate
Sporozoan
Rhizopod
Amoeba like Move using pseudopodia EC Feed by phagocytosis Cycle between trophozoite and cyst forms Mainly asexual repro binary fission Direct lifecycle Entamoeba histolytica
Ciliate
Move using cilia
EC
Feed on particulate matter using a specialised invagination of the cell mem (cytosome)
Cycle between trophozoite and cyst form
Repro asexually binary fission and sexually
Direct lifecycle
Balantidium coli
Flagellate
Move using one to five flagella Feed by taking up soluble nutrients through CM Most cycle between trophozoite and cyst form Mainly asexual repro binary fission Most EC ( a few IC living in macro) Trypanosoma Leishmania Giarda Histomonas Tritrichomonas
Sporozoan
No obvious locomotion Complex grp mainly IC with distinct phases of asex and sec repro within host to give several morphologically distinct forms during their lifecycle Asex repro is complex involving shizogeny Sex repro invovles fusion of dissimilar gametes to give an oocyst Direct and indirect lifecycle Eimeria Toxoplasma Crypto Babesia Theileria Plasmodium Sarcocystis
Shizogeny
Asexual repro involving multinuclear division
Direct lifecycle (monoxenous)
Life cycle in single host
Alternate between trophozoite and cyst stages
Assoc with body systems that have easy external access eg GIT or repro tract
Either EC in lumen of hollow organs where theyre usually motile or IC with EC stages for propagtion and infection within or between hosts
Dis assoc with conditions giving rise to high no of infective forms in enviro esp in intensive prod system or areas where animals congregate in large nos so high contam level
So to control red stocking density to red level of enviro cyst contam
Improve enviro hygiene to reduce infective challenge
Cyst/oocyst
Repro stage Enviro res Able to survive outside host And are infective Shed into enviro Infective stage
Trophozoite
Feeding stage
In host
EC monoxenous
Rel large motile protozoa Usually cycling between trophozoite and cyst forms eg in gut; entamoeba, balantidium, giarda, trichomonas Eg in repro syst Trichomonas foetus Trypanosoma equiperdum
Entamoeba
Rhizopod
Esp affect dogs esp puppies
Triphozoite in gut
Cysts passed out with faeces to infect other dogs
Balantidium
Ciliate Affects pigs Zoonotic Trophozoite in gut Cysts passed out with faeces to infect other pigs Only cause dis in v large no
Giarda
Flagellate Cause severe dis in young dogs and cats Tropjozoite in guy Cysts passed in faeces Zoonotic but role of dog form unclear Easily dispersed in water by wild animals
Trichomonas
Flagellate Cause severe dis in birds Oesophageal and intestinal forms of dis Cyst stage is undescribed Contam on water supply from crop milk often source of infect
Trichomonas foetus
Flagellate
Vagina of cattle and migrate to uterus to cause abortion
Controlled by resticting breeding to uninfected animals
Trypanosoma equiperdum
Flagellate parasite related to pathogenic vector borne trypanosomes
Causes venereally transmitted dis dourine in donkeys and horses
Result in infertility
Only ND UK protozoan parasite with statutory testing regime
Controlled by restricting breeding to uninfected animals
IC monoxenous (gut dwelling coccidia)
Wode range of hosts species
Significant economic importance to poultry and livestock industry
V small so can parasite host cells
Mainly parasite of digestive system
Coccidian protozoa
IC and found in a parasitophorous vacuole
Coccidia cycle
Oocyst break down within gut lumen releasing sporozoites which enter host cells by invagination of cell mem within which the sporozoites become physical and then grow in parasitophorous vacuole
Multiply by schizogony producing many merozoites in the schizont
Cell ruptures and merozoites are released into the gut where they enter fresh host cells and undego more cycles dep on species of schizogeny
Some enter cells and become multinucleate microgametocytes which give rise to many flagellate microgametes
Cell ruptures and microgametes released into gut
Some merozoites enter cells and grow without division to become macrohametocytes amd mature to become macrogametes
Micro and macrogamete fusion to prod a zygote that secr a protective coating and becomes an oocyst that is released in the faeces
Oocyte dev 4 sporoblasts (in eimeria)
That dev into 4 sporocysts each cont 2 sporozoites
Eimeria
Main coccidiosis cause worldwide
Key in intensive poultry and farmed rabbit units
Seasonally important in lambs and calves
High host and site specificity
Poultry coccidiosis
Caecal coccidiosis caused mainly by eimeria tenella
Intestinal coccidiosis caused by infection with one or more of 5 species
Control based on good hygiene, medicated feed, treatment of affected birds with drugs, use of att live vacc in geed or water
Shizogeny causes hypertrophy
17 species
Ovine coccidiosis
Usually weakened lambs 4-8wk
11 species but 2 highly pathogenic
All affect small intestinefirst infected by oocytes passed by chronically infected adults and then go on to prod large oocyst no that infect other lambs
Caprine coccidiosis
9 species but only 4 highly patjogenic
All affect small intestine
Effects of poor hygiene
Bovine coccidiosis
Usually affect animal less than a yr old
Unhygienic enviro eg around water trough
13 species only 3 patjogenic
Infect caecum and colon
Rabbit coccidiosis
Only prob in intensive prod syst
3 pathogenic species
One affects bile ducts (sporozoites emerge from S intestine and migrate to liver via lymph vessels cause merogeny of epi in bile ducts) and 2 affect the intestine
Wild rabbits act as source of infection for free range farmed rabbits
Isospora
Differ from eimeria as have 2 sporocysts each containing 4 sporozoites
Infect cats dogs and pigs mainly
Extra intestinal stages can occur in liver spleen and lymph nodes
Rodents can ingest oocytes and become infected with asex stages acting as reservoirs
Isually non patjogenic but high level can cause diarrhoea esp in young aanimals
Main importance is that their oocytes may be confused with Toxoplasma and other protozoa of zoonotic importance
Crypto
Key patjogen of young animals esp calves
Key cause of human food poisoning from faecal contam of meat and water source contam
Esp nasty in imm suppressed individuals eg AIDs sufferers
Crypto parvum
Sporozoites invade microbillois brush border of enterocytes
Dev at jctn between microbillous brush border and cyto of gut epi cells
Trophozoites rapidly differentiate to form meronts with 4-8 merozoites
Gametogeny follows after one or two meront generation
Prod v small sporulated oocysts (inmediately infective) within 72hrs of infection
Most passed in faeces but some release sporozoites in intestine initiating another asex repro cycle
Indirect lifecycle protozoa
All belong to coccidia
Alternating sex asex cycles with oocyst formation
Involve definitive and intermed host
Predator prey relationship
Dev of definitive host usually ltd to gut producing oocysts that infect the intermediate host
Dev in intermediate host initially in gut followed by extensive tissue migration involving tachyzoites and finally resulting in tissue cysts containing bradyzoites which are infective form for definitive host
Key due to abortion and foetal abnormalities in cattle sheep and humans
Cause neurological dis in dogs
Lead to need for slaughterhouse condemnation of meat carcasses
Sarcocysistis
Toxoplasma
Neospora caninum
T gondii
Infect and survive in warm bloods
Cause many clinical signs in diff host species and with diff strains
Esp important because of sheep abortion and as human public health concern
Cats are definitive hist and mice are natural prey intermediate
Sheep and humans affected as accidental dead end hosts
Can complete cycle in absence of intermediate host
Both intermed and defin host can dev bradyzoite cysts in them and both can be infected by oocysts
Lifecycle mouse t gondii
Mice ingest oocytes released by cats
Released sporozoites invade gut macrophages and multiply giving rise to tachyzoites
Tachyzoites invade other gut macros or are carried in blood to other sites eg lymph where they form bradyzoite cysts and bradyzoites temain in tissue cyst until ingested by cat
T gondii infection spreadg
Can spread vert in micr
Bradyzoite cysts in brain disrupt normal cat avoidance behaviour incr parasite transmission chances
Lifecycle cat t gondii
Bradyzoites freed from tissue cyst by proteolytic enz in cats GITnthen pass through several stages before gametogeny begins in s intest epi
Resultant oocytes discharged into intest lumen and passed in faeces
Lifecycle complete in 3-10 d of bradyzoite infect
Oocysts passed unsporulated and after 24hr cont 2 sporocysts each cont 4 sporozoites
Abortion die to t gondii
Ingestion of oocyte by prey result in cyst form in muscle
In preg sheep tachyzoites migrate to uterus or placenta and can cause foetal abortion or death
T gondii epidemiology
Cats infected by eating infected mice or uncooked meat cont bradyzoite cysts and pass in faeces
Shed for 8d before cat become immune so most infect pass unnoticed in cat (clinical dis usually due to overwhelming tachyzoite migr to cns and other major organs)
Young cats hunting for first time are important in epidemiology of sheep and recrudescence of infect when older cats are stressed or have another disease
Sheep ingest oocysts off pasture bedding or feed contam with cat faeces
T gondii sheep cycle
Tachyzoites released from ingested oocyst penetrate cells and multiply asex until cell ruptures, further parasitise host cells
Sheep dev hist immunity EC parasite elim and IC tachyzoite multiplication slows as they form bradyzoites in tissue cysts
Afterward sheep maintain a strong lifelong immunity while parasite survives as bradyzoite for lifetime of host
In non preg for tissue cyst in m or brain and cause no sympt
In baive preg ewes parasite multiply in placenta
Eqe t gondii infect when preg outcome
Infect during early preg can cause embryonic death and resorption - may present as barren ewe problem
During mid preg mag result in foetal death and mummification or foetal retardation due to compromised placental nutrition and foetal infection
Late preg can cause freshly dead aborted lamvs or weakly lambs eith high neonatal mortality rates
Litter mates may be affected to diff degrees combo of outcomes usually in an affected flock
Aborted ewe remain clinically normal and some not diagnosed until lambing when IDed as barren
Late lambs aborted in various decomposotion stages and placenta often autolytic having grossly visible small white focal areas of necrosis and calcification
Highest abortion rate inewe lambs and gimmers in endemically infevted flock woth no control measures if naive flock similar prevalence im all age groups
Alternative t gondii lifecycle
Ingestion of oocytes by prey animals incl sheep can result in bradyzoite cyst form in m which if uncooked can be source of infect for carnivores incl humans
Ingestion of bradyzoite cysts amd oocysts by non feline carnivores can lead to tachyzoite migration and formation of bradyzoite cysts in various body systems causing abortion bisusal disturbance amd neurological signs
Precautions against human t gondii
Wash hands before eating
After cleaning cat litter tray and clean daily because then insufficient time for oocyst sporulation
wash veg and fruit
Wask utensils in hot soapy water
Cook meat fully
Pregnant and imm compr people be v careful
T gondii affecting sea lions
Cat litter flushed into sewers sp oocysts reach sea via freshwater outflow
Heaviest sea otter infection near urban areas on californian coast
New bill passed to protect t gondii contam of oceans
Ovine imm resp to t gondii
IFN gamma
CD4 and 8 + t cells (key to control 1o infection)
Secondary challenge imm resp effectively blocks dissem of parasite via lymph and circ
T gondii inpork
High prevalence of tissue cysts in pig m
Human risk if pork undercooked
Encouraging work on vacc piglets with some tachyzoites
Neopspora caninum
Similar to t gondii in bio
Dog defin hist
Cattle intened hist
Cause dairy cattle abortion
Tachy and bradyzoites can dev in both hists
Transplacental route of infection common for cattle by oocyte ingestion by dam or bradyzoite cyst react by pregnancy
Sarcocystis
V common in livestock but dis only seen sporadically in sheep
Diff species have diff spec host pairings
Dog sheep
Cat sheep
Dog goat
Sarcocystis cycle
Sheep ingest sporocyst from feed or contam pasture
Sporozoites released and invade endo cells of gut capil
Asex repro period in gut epi parasites enter circ blood lymphocytes and carried to m or nervous tissue and then penetrate cells
Tachyzoites divide rapidly within m or n cells and form IC cysts (sarcocysts) filled with many bradyzoites
Defin host ingests part of int host cont sarcocysts and bradyzoites are released into gut
Bradyzoite invade sub epi lam prop cells - differentiate into gametes and following fertilisation give rise to thin walled oocysts passed out in faeces
Oocysts are passed sporulated and cont 2 sporocysts each with 4 bradyzoites
Sarcocystis clin signs
Rarely seen in defin host except occassional diarrhoea after large oocyst no ingestion
Sarcocysts arising from oocysts in dog faeces found in heart an skel m of most sheep in UK
Outbreaks of clin dis only occur under unusual circumstance when enviro challenge is v high
Satcocystis infect of multi organs can cause dysfx and even death and in brain and spinal cord can cause vague neurological dis incl generalised tremors compulsive nibbling recumbenct and thoracic and pelvic limb paralysis commonly in 6-12mnth old lambs
Sarcocysts from oocysts in cat faeces cause large obvious thick cysts in tongue and oesophageal m
