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44 Cards in this Set
- Front
- Back
5 Groups of Protozoan Parasites |
1. Flagellates - all possess flagella at some life stage 2. Ciliates - all possess cilia at some life stage 3. Amoebae - all use pseudopodia for locomotion at some life stage 4. Apicomplexa - the coccidians & hemosporidians 5. Microsporida - Highly specialized (protozoa-like) fungi - dominant life stage is a spore |
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Flagellates |
- all possess flagella at some life stage 1. Giardiasis 2. Spironucleosis (Hexamitosis) 3. Trichomoniasis - Bovine, Avian, and Feline 4. Histomoniasis |
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Ciliates |
- all possess flagella at some life stage 1. Balantidiosis |
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Amoebae |
- all use pseudopodia for locomotion at some life stage 1. Intestinal amoebiasis - mammals 2. Intestinal amoebiasis - reptiles 3. Amoebic meningoencephalitis |
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Apicomplexa |
- The coccidians & hemosporidians 1. Enteric Coccidians - Avian, Bovine, Ovine/Caprine, Equine, Rabbit, Swine, Canine, Feline 2. Cryptosporidiosis 3. Tissue cyst-forming cociccidians - Toxoplasmosis - Neosporosis - Sarcocystosis - EPM |
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Microsporida |
- Highly specialized (protozoa-like) fungi - dominant life stage is a spore 1. Encephalitozoonosis |
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Protozoan Parasites: General Characteristics |
- protozoa are a heterogenous group of approximately 50, 000 known species, many of which are parasitic - protozoa are responsible for some of the most important diseases of animals & humans - protozoan parasites kill, debilitate & mutilate more people in the world than any other group of disease organisms |
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Host Range |
- all animals are susceptible - some protozoan parasites have highly specific host ranges (e.g. Eimeria) - Others are less discriminate and will infect any host e.g. Giardia & Cryptosporidium |
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Site of Infection |
- most organs & tissues e.g. intestine, muscle, brain, liver & blood - some live free within the intestine or blood while others are intracellular |
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Morphology |
- single-celled eukaryotes & therefore most have a typical complement of organelles (nucleus, mitochondria, endoplasmic reticulum, golgi apparatus) surrounded by a plasma membrane - simple appearance but some have developed complexity through specialized organelles that aid in attachment, locomotion, feeding & cell entry - Glycosomes (contain glycolytic enzymes) - Kinetoplasts (contain extrachromosomal DNA - modified mitochondria) - Rhoptries (cell invasion) - Locomotion occurs by the use of flagella, cilia, pseudopodia or other specialized methods |
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Life Cycle |
- Reproduction can be asexual, sexual or a combination of both - Asexual e.g. budding, binary fission or schizogony (multiple fission) - Sexual reproduction involves fusion of identical gametes (isogametes) or gametes that differ in size (anisogametes) - Some have a cyst stage (infective or resting stage) with a resistant covering that protects from environmental factors. Some protozoa also encyst within the host's tissue (e.g. Toxoplasma) - Life cycles may be simple occurring with a single host (e.g. Isopora) while others are complex and involve multiple hosts (intermediate & paratenic) - Some infect hosts directly while others rely on a vector (e.g. insects) for successful transmission |
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GI Protozoa Parasites: Dog |
- Giardia Small Intestine - Cryptosporidium Small Intestine - Isopora Small Intestine - Sarcocystis Small Intestine - Neospora Small Intestine - Entamoeba Colon - Balantidium Colon |
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GI Protozoa Parasites: Cat |
- Giardia Small Intestine - Trichomonas Large Intestine - Cryptosporidium Small Intestine - Isospora Small Intestine - Sacrocystis Small Intestine - Toxoplasma Small Intestine - Besnoitia Small Intestine - Entamoeba Colon |
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GI Protozoa Parasites: Cattle |
- Giardia Small Intestine - Trichomonas Reproductive Tract - Cryptosporidium Small Intestine & Abomasum - Eimeria Small & Large Intestine |
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GI Protozoa Parasites: Sheep & Goats |
- Giardia Small Intestine - Cryptosporidium Small Intestine - Eimeria Small & Large Intestine |
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GI Protozoa Parasites: Swine |
- Giardia Small Intestine - Cryptosporidium Small Intestine - Eimeria Small Intestine - Entamoeba Colon - Balantidium Colon |
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GI Protozoa Parasites: Horses |
Giardia Small Intestine Cryptosporidium Small Intestine Eimeria Small Intestine |
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GI Protozoa Parasites: Pet Birds |
Giardia Small Intestine Trichomonas Crop Cryptosporidium Small Intestine/Airways Eimeria Small Intestine |
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GI Protozoa Parasites: Poultry |
Giardia Small Intestine Trichomonas Crop Hexamita Small Intestine Histomonas Cecum & Liver Cryptosporidium Small Intestine Eimeria Small & Large Intestine, Cecum |
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GI Protozoa Parasites: Rodents & Rabbits |
Giardia Small Intestine Cryptosporidium Small Intestine Encephalitozoom Kidney, liver, brain |
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GI Protozoa Parasites: Reptiles & Amphibians |
Giardia Small Intestine Entamoeba Intestine Cryptosporidium Stomach/SI |
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Giardiasis: Agent & Host Range |
- common intestinal disease of mammals& birds found worldwide (cosmopolitan), esp. in warmed climates, causes by various Giardia spp. - Giardiasis is recognized zoonosis - Often called "beaver fever" in humans Broad host range: Giardia duodenalis = intestinalis = lamblia - most important species of Giardia in vet med - wide range: dogs, cats, cattle, sheep, birds & humans - animals = potential reservoir for human infections and vice versa |
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Giardiasis: Site of Infection |
- duodenum & upper small intestine - Giardia attached to the brush border of epithelial cells by a ventral sucking/adhesive disk |
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Giardiasis: Morphology (Trophozoite) |
- 2 life stages: Trophozoite & Cyst Trophozoite - motile feeding stage, non-infectious - bilaterally symmetrical, pyriform to ellipsoidal in shape, convex dorsal surface, a ventral sucking/adhesive disk, axostyle & 2 median bodies (specialized microtubules) - approimately 12-20um long, by 7-10 um wide - 4 pairs of flagella, binucleate (2 diploide nuclei) "Monkey Face" |
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Giardiasis: Morphology (Cyst) |
- infectious stage (immediately infectious to host)
- environmentally resistant ~2 months w/ideal conditions (temp/hum) - oval shaped, 9-12um long by 7-9um wide - internal structures visible with light microscopy - contains 4 nuclei (ie. 2 trophozoites/cyst) - axostyle - median bodies - karyogamy (fusion of nuclei) ie. "Sex in the cyst" |
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Giardiasis: Life Cycle |
- simple direct life cycle, cysts ingested by the host & excyst after exposure to both acid of stomach & alkaline of small intestine to release 2 trophozoites into duodenum
- trophozoites reproduce by asexual binary fission & feed & colonize SI - severity of disease is dependant on the number of feeding trophozoites - trophozoites encyst in response to increasing conc. of bile in feces ---> ie. reabsorption of water, dehydrated feces as it passes through intestine towards, rectum, therefore bile conc. increase at same time as free cholesterol decreases - both cysts & more rarely, trophozoites can be passed in feces - cysts resistant & survive (infectious stage), where as trophozoites are fragile & die quickly (non-infectious) - 10^6 cysts per g of feces - intermittent shedding of cysts - PPP = 7-10 days |
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Giardiasis: Transmission |
- via cysts (immediately infectious) - direct: fecal-oral route is most important - waterborne transmission common in human outbreaks - cysts highly contagious & ingestion of a few as 10-100 cysts can establish an infection - cysts are susceptible to desiccation but remain viable in cool moist areas for ~2 months - cysts are resistant to "conventional" water disinfectants (ie. chlorination, filtration) |
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Giardiasis: Prevalence |
- ubiquitous in the environment but varies among populations and geographic regions
- infections are most common in young animals (including humans) & exacerbated by stressful situations, poor sanitation/hygiene & crowded confinement conditions (eg. barnyards, kennels, catteries, shelters, pet stores, puppy mills & for humans, day care facilities) Dogs & Cats Livestock Birds |
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Giardiasis: Pathogenesis |
- highly variable & still controversial in some species as both parasite & host factors contribute to disease - severity of disease dependent on dose of infection ie. number of cysts ingested - trophozoites do not invade tissue (normally) but instead attach to the brush border of the mucosal epithelium of the duodenum & upper small intestine - trophozoite colonies result in diffuse shortening of microvilli (sometimes villus atrophy) which reduces the absorptive surface area (malabsorption) of the SI & results in decreased intestinal enzyme activity (eg. disaccharidases) & malabsorption of nutrients (glucose esp.), electrolytes and water ---> results in increased intestinal motility of digesta (decreased transit time) - in some animals, enterocyte injury by the parasite disrupting tight junctions thereby increasing intestinal permeability & destruction of enterocytes - this may lead to more severe chronic intestinal disorders eg. Inflammatory bowel disease, Chron's disease & food allergies by exposing immune system to novel antigens |
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Giardiasis: Clinical Signs |
- most infection are asymptomatic - if so; typically small bowel diarrhea (usually self-limiting) but can be acute of chronic & often will reoccur - clinical signs range from slight abdominal discomfort to severe abdominal pain and cramping, explosive water, pale, foul-smelling diarrhea with malabsorption - steatorrhea (fat in stool) is common as is anorexia & some vomiting - in people, acute giardiasis develops after 1-14 days (avg ~7 days) & can last 1-3 weeks - dogs, PPP 1-2 weeks & can last 1 day to months - extra-intestinal signs of urticaria & pruritus (allergic diseases) have been reported in both dogs, humans & birds Eg. feather picking (allergic disease) in cockatiels (associated with giardiasis) |
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Giardiasis: Diagnosis |
- "most commonly mis, under or over diagnosed parasite in vets" - Requires multiple fecal samples (3 consecutive or 3 over 5 days) as cyst shedding is intermittent |
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Giardiasis: Fecal Flotation |
- Gold Standard: fecal flotation with centrifugation in ZnSO4 (with or without Lugol's iodine stain) - cytoplasm within cysts collapses producing a crescent shaped refractile osmotic artifact |
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Giardiasis: Direct Smear |
- saline smear of fresh diarrhea, trophozoites movement (via flagella) - "falling leaf" - trophozoites die quickly so sample must be observed soon after collection (ie. per rectum sample collection) or within ~20-30 mins of 'deposit' & kept at body temperature in humid environment to avoid desiccation - cysts may be observed in high number - Lugol's iodine can be used to stain both trophozoites & cysts |
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Giardiasis: Antigen Detection |
- detect Giardia - specific antigen - ProSpec T Fecal ELISA (micro plate - multiple samples) - detect infections in cats & dogs (100 & 96%, sensitivity & specificity respectively) - IDEXX SNAP Giardia test (lateral flow ELISA - individuals samples) - based on cyst wall protein released into the feces during encystation - approvved for cats & dogs (>90% sensitivity & specificity) |
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Giardiasis: Treatment |
- no licensed treatments - anti-giardial therapy focuses on the trophozoite stage not the cyst - (Panacur) & (Flagyl) used off-label alone or combo - Dtrol Plus is effective - most current treatment protocols recommend fenbendazole - clinical resistance - many ases of treatment failure are most likely cause by re-infection |
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Giardiasis: Vaccination |
- Giardia Vax to aid in prevention of disease & cyst shedding by Giardia in dogs
- Claim of 1 year protection in healthy animals 8 weeks of age & older - Contains killed Giardia. Dosage: 1ml dose subcutaneously - 2nd dose is given 2-4 weeks after 1st vaccination - annual re-vaccination is recommended - vaccinated dogs may still shed viable cysts & therefore owners should continue to use proper hygiene & sanitation practices - a few studies showing variable efficacy (no significant differences between vaccinated animals & controls), dogs cats and cows! - not recommended by American Animal Hospital Association 2006 |
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Giardiasis: Control |
- good hygiene & proper sanitation to limit exposure to infectious cysts
- remove or reduce stressful situations if possible - cysts can stick to the fur & be a source of re-infection, the positive animal should receive a bath at least once during treatment - disinfectant on surfaces - bleach & Lysol (VIM) with high contact times: - 15-20 minutes to ensure inactivation of cysts - hot, soapy water also works |
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Spironucleosis (Hexamitiasis or Hexamitosis) |
General Taxonomy: Flagellate Agent & Host Range: - Spironucleus (Hexamita) meleagridis - turkeys & game birds - Spironucleus (Hexamita) columbae - pigeons - hexamitosis = infectious catarrhal enteritis of birds (turkeys, pigeons, quail, pheasants, partridge, ducks & peafowl) |
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Spironucleosis: Morphology |
Trophozoites
- oval shaped, 6-12um long - bilaterally symmetrical with 8 flagella - binucleate with prominent nucleoli Cyst - rarely formed |
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Spironucleosis: Life Cycle |
- direct life cycle: trophozoites is the infectious stage, reproduce via binary fission
- fecal-oral route of transmission (feces containing trophozoites or cysts contaminate food or water) - trophozoites colonize crypts of duodenum & upper jejunum - disease of young birds (1-9 weeks old) recovered adults act as asymptomatic carriers - heavy losses in outbreaks in ring-necked pheasants - chickens not typically affected - hexamitosis is a problem in every commercial turkey-producing area - major problems occur in localized areas during a particular year, followed by one or more years in which incidence is low |
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Spironucleosis: Pathogenesis |
- catarrhal enteritis (inflammation of the mucous membranes) and atony
- results in distension of upper small intestine - swollen, bulbous, liquid filled small intestine |
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Spironucleosis: Clinical Signs |
- listlessness, inappetence, anorexia - birds huddle together near heat source & chirp constantly (pain?) - greenish-yellow, foamy or watery diarrhea - rapid weight loss due to diarrhea (dehydration) - convulsions due to lowered blood glucose levels shortly procede death - affected birds that survive remain stunted |
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Spironucleosis: Diagnosis |
- history, clinical signs & microscopic examination of intestinal contents
- trophozoites detected in fresh wet mounts of intestinal contents of the duodenum - confounding flagellate organisms in the cecae are not disease producers |
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Spironucleosis: Treatment & Control` |
- remove carrier birds & disinfect buildings, feeders & waterers
- separate adult & young birds or use an all-in/all-out strategy - biosecurity: prevent contact between turkey poults & captive/wild birds - chlortetracycline & oxytetracycline used w/food animals: variable success - Drugs** for non-food animals (pet birds) - treatment does not substitute for adequate sanitation & management programs |