protists Flashcards
what are protozoa
single celled eukaryotic organisms that feed heterotrophically and have diverse motility mechanisms
how do protists feed
- 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
list important veterinary protists that are zoonotic
- giardiasis
- cryptosporidiosis
- toxoplasmosis
- babesiosis
- trypanosomiasis
what is a trophozoite
feeding form of a protist
outline reproduction in protozoa
- 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
outline the life cycle of coccidia
outline the lifecycle of toxoplasma gondii
what is an oocyst
“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
how do protozoa cause disease
- compete with normal commensals changing gut microbiota
- produce toxins
- cause host immune response (major reason)
- damage cells and tiussues (major)
how do you diagnose protozoa
- 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
list GI protozoal diseases
- coccidiosis
- cryptosporidiosis
- toxoplasmosis
- neosporosis
- giardiasis
- trichomoniasis
- histomoniasis
- balantidiasis
- spironucleasis
what are the most important genera of coccidiosis
eimeria spp or isospora spp
discuss coccidiosis infection in poultry
- 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
how is coccidiosis diagnosed and controlled in birds
- Diagnosis – oocysts in faeces and necropsy
- Control measures include: coccidiostats, coccidiocides, vaccines (live, attenuated), biosecurity/disinfection
discuss coccidiosis in lambs
- 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
how is coccidia diagnosed/controlled in lambs
- 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
outline the lifecycle of cryptosporidiosis
which strain of cryptosporidiosis is zoonotic
C. parvum
how is crypto controlled/treated
- no treatment for non-human animals as is self limiting
- no vaccine
outline the lifecycle of toxoplasmosis
what is the definitivie host for toxoplasmosis
cats - dont show disease
oocysts are mainly shed by younger cats
what is the intermediate host of toxoplasmosis
rodents - get tissue cysts which are eaten by cats
can transmit vertically
disease of toxoplasmosis in accidental hosts manifests as
sheep: abortion, stillbirths or weakly lambs
humans: abortion, systemic/neurologic disease
outline the life cycle of neosporosis
what is the clinical relevence of neospora caninum
- important cause of abortion in cattle
- dogs eat raw meat/placenta (vertical transmission occurs in cattle) and poops in field
- dogs only definitive host
how is neosporosis diagnosed and controlled
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
where are common locations to find giardia spp
water environments contaminated by human, livestock or wildlife
what are the clinical signs of giardia
diarrhea (mainly in humans and dogs, rarely in any other species)
outline the clinical significance of trichomoniasis
- 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)
what is the significance of histomoniasis
- 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
outlinenthe lifecycle of histomoniasis
what is the clinical significance of balantidium spp
- 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
what is the significance of spironucleosis
- 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
