protists

Question 1

what are protozoa

Answer 1

single celled eukaryotic organisms that feed heterotrophically and have diverse motility mechanisms

Question 2

how do protists feed

Answer 2

• phagocytosis, pinocytosis or simple absorption
• mouth opening may be temporary (amoeba) or permanent (ciliates)
• food particles surrounded by membranes forming a food vacuole, digestive enzymes secreted into vacuole
• soluble nutrients are absorbed into endoplasm, waste discharges through opening in plasma membrane

Question 3

list important veterinary protists that are zoonotic

Answer 3

• giardiasis
• cryptosporidiosis
• toxoplasmosis
• babesiosis
• trypanosomiasis

Question 4

what is a trophozoite

Answer 4

feeding form of a protist

Question 5

outline reproduction in protozoa

Answer 5

• often have complex lifecycles with different stages in the same ot different hosts
• asexual stages include mitotic division of parent cell into 2 or more identical offspring
• sexual reproduction = formation and fusion of gametes producing new offspring

Question 6

outline the life cycle of coccidia

Answer 6

Question 7

outline the lifecycle of toxoplasma gondii

Answer 7

Question 8

what is an oocyst

Answer 8

“egg” form of a protist
- hardy and survive in the environment
- metabolically inactive so cant be hit by drugs
- resistant to many disinfectants
- infectious (but not always immediately)
- may be detected in feces and used for diagnosis

Question 9

how do protozoa cause disease

Answer 9

• compete with normal commensals changing gut microbiota
• produce toxins
• cause host immune response (major reason)
• damage cells and tiussues (major)

Question 10

how do you diagnose protozoa

Answer 10

• look at trophozoite morphology
• oocyst morphology
• may be detected in feces
• gross and/or histopathological observation of lesions

different spp of eimeria can be dx’d by where in GIT they affect

Question 11

list GI protozoal diseases

Answer 11

• coccidiosis
• cryptosporidiosis
• toxoplasmosis
• neosporosis
• giardiasis
• trichomoniasis
• histomoniasis
• balantidiasis
• spironucleasis

Question 12

what are the most important genera of coccidiosis

Answer 12

eimeria spp or isospora spp

Question 13

discuss coccidiosis infection in poultry

Answer 13

• oocysts sporulate within 24hrs of excretion and are resilient in environment (can survive years)
• different sp infect different parts of gut and cause different clinical signs (diarrhea, poor growth and death often seen)
• disease is due to direct damage to gut mucosa and secondary bacterial infections
• big issue in young birds and rehomed layer hens (no immunity after living in strict biosecurity conditions)
• diagnose via oocysts in feces and necropsy

Question 14

how is coccidiosis diagnosed and controlled in birds

Answer 14

• Diagnosis – oocysts in faeces and necropsy
• Control measures include: coccidiostats, coccidiocides, vaccines (live, attenuated), biosecurity/disinfection

Question 15

discuss coccidiosis in lambs

Answer 15

• mainly eimeria spp
• adults act as asymptomatic sources of infection to young animals
• lambs under 6 months get diarrhea, dehydration, poor growth and death
• particularly issue in crowded and stressful conditions

Question 16

how is coccidia diagnosed/controlled in lambs

Answer 16

• Diagnosis – oocysts in faeces (but not necessarily very useful as can have high counts without disease and low counts with disease) and necropsy
• Control measures include: coccidiostats, coccidiocides, biosecurity / disinfection / rotation of pasture etc, ensure get colostrum

Question 17

outline the lifecycle of cryptosporidiosis

Answer 17

Question 18

which strain of cryptosporidiosis is zoonotic

Answer 18

C. parvum

Question 19

how is crypto controlled/treated

Answer 19

• no treatment for non-human animals as is self limiting
• no vaccine

Question 20

outline the lifecycle of toxoplasmosis

Answer 20

Question 21

what is the definitivie host for toxoplasmosis

Answer 21

cats - dont show disease
oocysts are mainly shed by younger cats

Question 22

what is the intermediate host of toxoplasmosis

Answer 22

rodents - get tissue cysts which are eaten by cats
can transmit vertically

Question 23

disease of toxoplasmosis in accidental hosts manifests as

Answer 23

sheep: abortion, stillbirths or weakly lambs
humans: abortion, systemic/neurologic disease

Question 24

outline the life cycle of neosporosis

Answer 24

Question 25

what is the clinical relevence of neospora caninum

Answer 25

- important cause of abortion in cattle - dogs eat raw meat/placenta (vertical transmission occurs in cattle) and poops in field - dogs only definitive host

Question 26

how is neosporosis diagnosed and controlled

Answer 26

diagnosis: abortion of mid/late pregnancy, necropsy of fetus and detection by immunohistology/PCR or serology of dam/fetus/dog control: no treatment of vaccine - dont let dogs eat raw placentas or raw beef, pick up dog shit in fields with cattle

Question 27

where are common locations to find giardia spp

Answer 27

water environments contaminated by human, livestock or wildlife

Question 28

what are the clinical signs of giardia

Answer 28

diarrhea (mainly in humans and dogs, rarely in any other species)

Question 29

outline the clinical significance of trichomoniasis

Answer 29

- trichomonas gallinae causes canker/frounce in birds/reptiles - common and often asymptomatic in wild pigeons, transmitted by crop milk - can cause severe upper GIT disease blocking ability to eat, drink and breath (die)

Question 30

what is the significance of histomoniasis

Answer 30

- blackhead in turkets - amoeboid in tissues but flagellated in gut lumen - can infect wide range of poultry but mainly seen in turkeys - severe necrosis of caecae and liver - yellow diarrhea, listless, high fatality - diagnosed at necropsy - controlled by deworming and biosecurity

Question 31

outlinenthe lifecycle of histomoniasis

Answer 31

Question 32

what is the clinical significance of balantidium spp

Answer 32

- ciliate protozoan that can form tough cysts to survive in environment - normal part of gut biota of many mammals but can caus diarrhea in humans and primates (mainly in tropics) - cause diarrhea in repties - treat with metronidazole - prevent with better hygiene

Question 33

what is the significance of spironucleosis

Answer 33

- live in gut and transmitted via feces - cuases diarrhea, depression and weight loss in birds - in fish causes hole in the head disease - lifecycle not understood - controlled by improved hygiene and reducing crowding - treated with metronidazole