Protozoa

Question 1

Protozoa

Answer 1

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

Question 2

Protozoa sub groups

Answer 2

Rhizopod
Ciliate
Flagelate
Sporozoan

Question 3

Rhizopod

Answer 3

Amoeba like
Move using pseudopodia
EC 
Feed by phagocytosis
Cycle between trophozoite and cyst forms
Mainly asexual repro binary fission
Direct lifecycle
Entamoeba histolytica

Question 4

Ciliate

Answer 4

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

Question 5

Flagellate

Answer 5

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

Question 6

Sporozoan

Answer 6

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

Question 7

Shizogeny

Answer 7

Asexual repro involving multinuclear division

Question 8

Direct lifecycle (monoxenous)

Answer 8

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

Question 9

Cyst/oocyst

Answer 9

Repro stage
Enviro res 
Able to survive outside host
And are infective
Shed into enviro
Infective stage

Question 10

Trophozoite

Answer 10

Feeding stage

In host

Question 11

EC monoxenous

Answer 11

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

Question 12

Entamoeba

Answer 12

Rhizopod
Esp affect dogs esp puppies
Triphozoite in gut
Cysts passed out with faeces to infect other dogs

Question 13

Balantidium

Answer 13

Ciliate
Affects pigs
Zoonotic
Trophozoite in gut
Cysts passed out with faeces to infect other pigs
Only cause dis in v large no

Question 14

Giarda

Answer 14

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

Question 15

Trichomonas

Answer 15

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

Question 16

Trichomonas foetus

Answer 16

Flagellate
Vagina of cattle and migrate to uterus to cause abortion
Controlled by resticting breeding to uninfected animals

Question 17

Trypanosoma equiperdum

Answer 17

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

Question 18

IC monoxenous (gut dwelling coccidia)

Answer 18

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

Question 19

Coccidian protozoa

Answer 19

IC and found in a parasitophorous vacuole

Question 20

Coccidia cycle

Answer 20

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

Question 21

Eimeria

Answer 21

Main coccidiosis cause worldwide
Key in intensive poultry and farmed rabbit units
Seasonally important in lambs and calves
High host and site specificity

Question 22

Poultry coccidiosis

Answer 22

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

Question 23

Ovine coccidiosis

Answer 23

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

Question 24

Caprine coccidiosis

Answer 24

9 species but only 4 highly patjogenic
All affect small intestine
Effects of poor hygiene

Question 25

Bovine coccidiosis

Answer 25

Usually affect animal less than a yr old Unhygienic enviro eg around water trough 13 species only 3 patjogenic Infect caecum and colon

Question 26

Rabbit coccidiosis

Answer 26

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

Question 27

Isospora

Answer 27

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

Question 28

Crypto

Answer 28

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

Question 29

Crypto parvum

Answer 29

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

Question 30

Indirect lifecycle protozoa

Answer 30

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

Question 31

T gondii

Answer 31

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

Question 32

Lifecycle mouse t gondii

Answer 32

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

Question 33

T gondii infection spreadg

Answer 33

Can spread vert in micr | Bradyzoite cysts in brain disrupt normal cat avoidance behaviour incr parasite transmission chances

Question 34

Lifecycle cat t gondii

Answer 34

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

Question 35

Abortion die to t gondii

Answer 35

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

Question 36

T gondii epidemiology

Answer 36

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

Question 37

T gondii sheep cycle

Answer 37

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

Question 38

Eqe t gondii infect when preg outcome

Answer 38

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

Question 39

Alternative t gondii lifecycle

Answer 39

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

Question 40

Precautions against human t gondii

Answer 40

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

Question 41

T gondii affecting sea lions

Answer 41

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

Question 42

Ovine imm resp to t gondii

Answer 42

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

Question 43

T gondii inpork

Answer 43

High prevalence of tissue cysts in pig m Human risk if pork undercooked Encouraging work on vacc piglets with some tachyzoites

Question 44

Neopspora caninum

Answer 44

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

Question 45

Sarcocystis

Answer 45

V common in livestock but dis only seen sporadically in sheep Diff species have diff spec host pairings Dog sheep Cat sheep Dog goat

Question 46

Sarcocystis cycle

Answer 46

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

Question 47

Sarcocystis clin signs

Answer 47

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