GI Parasites Flashcards
describe parasitic mechanisms of disease
- trauma:
-direct destruction of host cells or tissues: cystiospora, haemonchus, small strongyles
-indirect destruction of host cells or tissues: giardia, tritrichomonas
-organ occlusion: parascaris
- nutrient robbing: tapeworms
- excretion of toxins or other pathogens: nanophyetus
- interactions with host immune/inflammatory responses: dirofilaria immitus, fleas
describe giardia
- coccidian protozoan
- the more fluid the stool, the more trophozoites (active, motile stage), the more solid the stool, the more custs
describe the life cycle of giardia
primary host:
1. many species
2. colonize SI on mucosal surface
tranmission: fecal-oral
1. ingest cysts via feces or contaminated water, food, fomites, self-grooming
2. NOT trophozoites: will not survive the stomach
stages:
1. trophozoite: active, noninfective
2. cysts: dormant, infective
reproduction: binary fission of trophozoites
describe pathogenesis of giardia
- indirect destruction:
-trophozoite attaches to surface of SI, damages epithelial cells and enterocytes, decreasing GI permeability and blunting intestinal villi and microvilli, resulting in reduced surface area so
-maldigestion, malabsorption, hypersecretion: DIARRHEA
describe clinical disease of giardia
- persistent diarrhea: mucoid, pale, soft, loose, fatty (blood is uncommon), typical of small bowel diarrhea
-can be acute, intermittent, or chronic - +/- vomiting, anorexia, dehydratio
- some animals are subclinical shedders
- malabsorption syndrome:
-signs of poor nutrition: lethargy, weight loss, etc.
describe diagnosis of giardia
- direct microscopic fecal analysis
-loose stool: motile trophozoites on fresh wet mounts - fecal float centrifugation:
-solid stool: cysts stage (don’t confuse with yeast)
-use fecal float centrifugation with ZINC SULFATE solution
-recommended for routine creening - antigen (cysts) detection kits, ELIDA
-rapid in house, high specificity
-NOT rec for routine screening - PCR:
-increased Se and Sp
-not rec for routine screening unless owner concerned (immunosuppressed)
describe treatment for giardia
- fenbendazole FIRST
-or metronidazole but do NOT start with metro - probiotics and fiber/psyllium
- treatment duration depends on drug but rage 3-8days
- follow up with strict environmental decontamination, bathing the animal, etc. bc can reinfect themselves!!
- treat only symptomatic dogs and cats to decrease development of resistance to antiprotozoals
- some animals will persistently shed cysts despite treatment and resolution of clinical signs
describe control of giarfia
- strict prevention of fecal contamination
- outdoor environment: pick up and dispose of feces
- indoor env: clean (soap and water), disinfect, dry out cysts
- bathe contaminated fur
- cysts can survive for months
describe zoonotic implications of giardia
- contains some molecular assemblages that are host specific so zoonosis is rare but
- concern for immunocompromised people:
-humans: assemblages A and B
-canines: C and D
-felines: assemblage F
describe cytsoisospora
- oocysts:
-species specific size and shape, unsporulated when passes - sporulated oocysts contains 2 sporocysts with 4 sporozoites each
- 8 sporozoites total
describe the life cycle of cystoisospora
- definitive host: asexual and sexual replication occurs
-unsporulated oocysts pass in feces - sporulate in 2-3 days
-ingestion by paratenic host, encyst in tissue, forming a cystozoite (does not directly cause dz in paratenic host) - direct host ingests paratenic host
describe pathogensis of cystoisospora
- direct destruction of enterocytes (SI):
-destruction of epi lining (rare hemorrhagic ulcers)
-villous atrophy
-malabsorption
-increased permeability, loss of fluids, +/- blood
-immune response causes hyper-secretion
describe clinical disease of cystoisospora
- mild to moderate diarrhea
-loose, mucoid, sometimes watery
-sometimes bloody (rare) - most often reported in nursing or recently weaned pets
- large infective dose of sporulated oocysts = worse clinical disease
describe diagnosis of cystoisospora
- animal age and history:
-young, immunocompromised, stress - fecal float centrifugation:
-look for unsporulated oocysts in fresh sample
-sporulated oocysts in older sample
-diarrhea may occur prior to oocysts excretion (prepatent period)
-may need to differentiate between eimeria (coprophagy) vs cystoisospora - PCR
describe treatment of cystoisospora
- anticoccidials:
-sulfa drugs: static (albon, bactrovet, tribrissen); unclear efficacy against acute disease
-ponazuril (cidal): marquis, ponalrestat; may be more effective
- supportive therapy for symptoms
- once infected, have immunity against that species
describe control of cystoisospora
- sanitation:
-sporulated oocysts are resistant, can survive (up to a year) in moist protected environments
-susceptible to freezing or extremely high temperatures and ammonia solution - prevent access to paratenic hosts
-mainly rodents - good nutrition is important
- keep stress low
describe canine cystoisospora
- puppy diarrhea!
-copious, watery, may persist for weeks (small bowel diarrhea) - cystoisospora canis:
-large, oval oocyst
-low pathogenicity in adult dogs - C. ohioensis complex:
-small-medium sized spherical oocyst
- +/- diarrhea
describe feline cystoisospora
- kitten diarrhea! small bowel diarrhea
- cystoisospora felis: large, oval oocyst
+/- pathogenic for kittens - C. rivolta: small-medium spherical oocyst
-small bowel diarrhea in newborn kittens
list the 4 most common hookworms
- ancyclostoma caninum: dogs
- ancyclostoma tubaeforme: cats
- uncinaria stenocephala: dogs and cats
- ancyclostoma braziliense: dogs and cats
describe the life cycle of ancyclostoma caninum
- adult worms live in small intestine of dogs
- eggs passed in feces, develop, hatch
- L1 and L2 in the environment develop to infective L3
- transmision:
-skin penetration of L3
-ingestion of L3
-ingestion of infected paratenic host
-transmammary transmission: female to puppies
describe diagnostics and treatment nof ancyclostoma caninum
diagnostics:
1. clin signs: pale MM and anemia, ill thrift, failure to gain weight, poor hair coat, dehydration, dark tarry feces (melena) +/- diarrhea
- dx tests:
-fecal float centrifugation
-fecal antigen tests: detect PPP infections
-PCR tests: detect PPP infections and MDR strains - regular testing to check program efficacy
-adult dogs at least 2x/year
-puppies at least 4x in 1st year of life
treatment:
1. puppies: at 2-3wks of age with a drug that controls hookworms and ascarids, repeat every 2 weeks until 2 months when put on HW prevention program
- dams: deworm close to whelping to minimize transmammary transmission to puppies
-fenbendazole daily starting at 40th day of gestation until 2 weeks post whelping
-selamectin during periparturient period and at whelping - multidrug resistance = common issue
describe control and zoonosis of ancyclostoma caninum
control:
1. monthly HW prophylactic that is also effective against GI nematodes
- sanitation:
-prompt removal of feces will minimize contamination of environment
-keeping habitat dry allows for rapid dessication of larvae - prevent predation to avoid infection via paratenic hosts
zoonosis:
1. cutaneous larval migrations
-intensely pruritic serpentine lesions of skin
-caused by skin penetration of infective L3 in contaminated habitats (parks, beaches, etc.)
- eosinophilic gastroenteritis (very rare)
describe the life cycle of ancyclostoma tubaeforme
- adult worms live in small intestine of cats
- eggs passed in feces, hatch
- L1 and L2 in environment develop to infective L3 stage
- transmission:
-skin penetration of L3s
-ingestion of L3s
-ingestion of infected paratenic host
-NO transmammary transmission
describe diagnostics and treatment of ancyclostoma tubaeforme
diagnostics:
1. clinical signs: pale MM and anemia, ill thrift
2. dx:
-fecal float centrifugation
-fecal antigen tests
-PCR tests
3. regular testing to check program efficacy
-adults at least 2x/yr
-kittens at least 4x/1st year of life
treatment:
1. kittens at 2-3 weeks of age with drug that control hookworms and ascarids, repeat every 2 weeks until can be put on HW prevention
control:
1. monthly HW prophylactic also effective against GI nematodes
2. sanitation: like for dog one
3. prevent predation to avoid infection via paratenic
zoonosis: cutaneous larval migrans like dog one
describe uncinaria stenocephala
- has cutting plates (not fangs)
- less common hookworm of dogs, cats, and foxes
- found in northern cooler regions
- relatively non-pathogenic
- transmission: only via ingestion of L3
describe ascarids in general
- large adult worms live in small intestine
-non-bursate
-mouth surrounded by 3 fleshy lips - host specific adult stage
-toxocara canis in dogs, cati in cats
-baylisascaris procyonis in raccoons
-parascaris equorum in horses
-ascaris suum in pigs
-ascaris lumbricoides in humans - larval stage can infect other hosts, including humans
- eggs:
-distinct appearance: thick-walled, many have textured outer coat
-highly resistance: can persist in soil for years
-female worms extremely fecund: approx 200,000 eggs/day; ascarids flood environment with eggs to ensure infection of next host
describe toxocara canis
- SI ascarid in dogs
- thick, white, large (10-15cm) adult worms
- anterior end: moderate cervical alae
- life cycle:
-adult worms in SI
-take approx 4 weeks to infective eggs
-routes of infection:
–ingest infective eggs: followed by tracheal migration in puppies, somatic migration in mature dogs
–transuterine to pups (MAJOR)
–transmammary to pups (minor)
–paratenic hosts to adult dogs
-prepatent period: 3 weeks transuterine, 5 weeks egg ingestion
- zoonotic: visceral larval migrans
describe toxocara cati
- SI ascarid of cats
- thick, white, large (4-12 cm) adult worms
- anterior end: prominent cervical alae
- life cycle:
-adult worms in small intestine, take approx 4 weeks to develop infective eggs
-routes of infection
–ingest infective egg: followed by tracheal migration in kittens, somatic migration in mature cats
–NO transuterine!! transmammary to kittens possible but still minor
–paratenic hosts to adult cats
-prepatent period: 8 weeks via egg ingestion
- zoonotic: visceral larvae migrans
describe pathology of toxocara canis and toxocara cati
- nutrient robbing (ingest host food)
- enteritis:
-inflam of intestine
-hypersensitivity: ascarids and their excretions are hyperallergenic - verminous pneumonia (rare): due to tracheal migration of larvae through lungs causing traumatic damage with hemorrhage and inflammation
- intestinal obstruction/intussusception (rare)
-due to very large burden of adult worms
describe clinical signs of toxocara canis and toxocara cati
- often subclinical, esp in adults
- mainly disease of young puppies/kittens
-lack of growth, loss of condition
-ill-thrift, dull coat
-abdominal pain, pot-bellied
- +/- fetid, mucoid diarrhea
-contributor to fading puppy/kitten syndrome: feline less severe due to lack of transuterine transmission
describe diagnostics of toxocara canis and toxocara cati
- discovery diagnostics: to confirm a suspect infection
-observation of clinical signs
-fecal float with centrifugation
-fecal antigen tests
-adult worms in vomit or feces - fecal monitoring (CAPC)
-confirm efficacy of deworming program (during routine health checks)
-fecal float with centrifugation and fecal antigen tests
-puppies and kittens: 4x/1st year
-older dogs and cats: 2x/year - fecal egg reduction test (FERT):
-to verify reduction/elimination of an infection
-to confirm efficacy of specific dewormer vs resistant worm population: check fecal 7-14d after tx
describe treatment of toxocara canis and toxocara cati
treat an active infection:
1. to eliminate: many dewormers effective against adults, few against migrating or arrested larvae
2. plan:
-2 treatments: 1st to elim standing adult pop, 2nd to elim recently matured adult worms
-fecal check 7-14d after 2nd tx to confirm efficacy, warn owner about dead worms in poop
prophylactic deworming:
1. deworm female dog to decrease transuterine transmission: fenbendazole starting at 40th day of gestation until 2 weeks post whelping
OR selamectin effectively kills larvae that have migrated to puppies when mother is treated at or near parturition
- deworm newborn kittens/puppies
-start at 2-3 wks old, repeat every 2 weeks until 2 months old and can start monthly HW and intestinal worm prophy: liquid pyrantel is more palatable/preferred for nursing babies
-deworm dams at same time as deworming nursing puppies/kittent to ensure no transmammary transmission
describe control and zoonosis of toxocara canis and toxocara cati
- environmental:
-good sanitation practices: prompt feces disposal (before rains/dung beetles disperse feces and worm eggs)
-clean surfaces, dispose of feces
-wash hands thoroughly after handling (ZOONOTIC) - routine fecal checks
-confirm efficacy of dewormer
-check for gaps in control program
-check for gaps in owner compliance - routine dewormer control:
-use monthly (HW) preventative that also has efficacy intestinal worms
-eliminate worms prior to maturity/production of eggs that contaminate environment
ZOONOSIS:
1. migration of larvae in tissues of aberrant host (humans)
2. ingestion of infective egg: beware sandboxes and gardens
3. ocular larvae migrans: in children, larvae may settle in retina and cause granulomatous reaction
4. 14% of people have antibodies to toxocara sp.
describe trichuris/whipworms in general
- in cecum and LI
- worms: anterior thin, posterior thick
-anterior end embedded in epithelial cels of gut - egg: bipolar plugs, smooth shell
-very hardy, can survive many years
-resistant to dessication, high temps and UV light
-very difficult to control - species:
-trichuris ovis: sheep and goats, asymptomatic
-trichuris discolor: cattle, asymptomatic
-trichuris vulpis: canid, pathogenic
-trichuris suis: swine, pathogenic
describe life cycle of trichruis vulpis
- transmission: fecal-oral; ingestion of infective egg ONLY
- in host:
-eggs hatch in SI
-larvae penetrate mucosa of SI and develop in 8-10 days
-juvenile worms return to lumen of gut and migrate down to cecum and colon: juvenile worms resistant to most dewormers
-adults in cecum and colon mature and produce ova: adults susceptible to most dewormers
describe pathology, clinical signs, and diagnosis of trichuris vulpis
pathology and clinical signs:
1. animals older than neonate
2. lesions of cecum and large intestine: inflammation, hemorrhagic foci, pathology by immature and mature adults
- number of worms:
-few worms: asymptomatic in most cases
-many worms: hemorrhagic cecum and colon (intermittent diarrhea with mucus and blood)
-severe infections: hella bloody diarrhea, dehydration, death (rare)
diagnosis:
1. fecal float with centrifugation
-eggs are heavy, slow to float with passive floatation
-false negatives: prepatent infection (but showing clin signs), intermittent shedders, poor technique to find heavy eggs
- commercial fecal antigen tests: good for dx poor egg shedders and prepatent infections
- diagnostic clues: dogs on dirt lots, yards, unsanitary kennels, intermittent bloody diarrhea
describe treatment and prophylactic control of trichuris vulpis
basic treatment:
1. remove from contaminated area
2. deworm every month for 3 months: juvenile and immature adults resistant for 1st two months
3. recheck fecal
prophylactic control:
-utilize a monthly HW preventative that is also effective against whipworms, esp if owner cannot remove dog from contam area
