Exam 2 - Lecture 13 Flashcards
Lecture 13
Important Gastrointestinal Nematode Parasites in Swine Production
-Parasitism in swine production impacted by raising animals in confinement:
-Limit contact w/ infective stages
-“All in all out” production segregates animals by age class, reduces risk
-Attention to hygiene and treatment protocols
-Recent trend in organic “range‐fed” production indicates need to maintain awareness about important parasitisms in swine
-Ascaris suum
-Trichuris suis
-Oesophagostomum dentatum
-Stephanurus dentatus
-Trichinella spiralis
Ascaris suum - Swine Roundworm
-Large worms living in the small intestine of swine
-Sexually dimorphic: males: 15 to 25 cm and females: up to 45 cm
-Oral opening with 3 prominent lips
-World‐wide distribution: Europe, Asia, Africa, United States
Ascaris suum - Basic lifecycle Biology
-Direct Life cycle:
-Adults live in small intestine
-Eggs passed in feces: 200,000 eggs/day
-Infective larvae develop in egg, ~ 28 days w/ optimal temperature/humidity:
-Persistent in environment, up to 7 years
-Eggs resistant to freeze‐thaw
-Susceptible host infected by ingestion of the larvated egg
-Tracheal migration to lungs via hepatic blood supply
-Prepatent period about 8 weeks
-Rodents may also serve as paratenic host
Ascaris suum - Swine Roundworm Characteristics
-Diagnosis by fecal flotation
-Eggs ~ 62 x 45μm:
-Thick, mammilated shell
-Golden brown
-Single cell (uninfective) when passed in feces
-Sticky albuminous coat
Ascaris suum - Swine Roundworm - Clinical Significance
-Stunted growth & poor feed efficiency in piglets:
-Worms consume nutrients
-Inflammation & hypoproteinemia from worm presence in gut
-Impaction in severe cases
-Grower/finishers put on contaminated pastures:
-At significant risk for disease
-No acquired immunity from previous challenge
-Pneumonia/respiratory distress from tracheal migration through the lungs:
-ADR pigs don’t eat
-Excess morbidity
-Liver condemnation from granulomatous “milk‐spots” at slaughter:
-Approximately $17/cwt
-Significant economic impact on non‐edible portion of carcass
-Sows infected while gestating on pasture:
-Ingestion of eggs
-Paratenic host
-Piglets infected by ingestion of eggs adherent to Sow’s teat while nursing
-Prevention by treatment (removal of patent infections):
-FBZ effective for removal of adults & immature stages, no withdrawal time
-Pyrantel, daily to prevent migration, 24 hrs withdrawal time
-Hygiene to provide clean nursing environment: wash Sow prior to farrowing
-Slat floors for confined growers
Ascaris suum - Swine Roundworm - Zoonotic Significance
-Case reports visceral larval migrans:
-Eosinophilic pneumonia
-Hepatic lesions
-Test specificity questionable, Ascaris sp. or Ascaris suum?
-Human Ascaris morphologically indistinguishable from swine Ascaris: close molecular relationship has
prompted many to suggest they are same
species
-Use of untreated (not composted) “swine” manure for fertilization of agricultural fields is risk factor where it occurs in foreign countries: also have high prevalence of Ascaris in human population
Trichuris suis - Swine Whipworm
-Medium‐sized worms living in the caecum & large intestine of swine
-Sexually dimorphic: males: 30 to 50mm and females: 35 to 50mm
-Stout body with whip‐like esophagus
-Cosmopolitan distribution: world‐wide where swine
production occurs
Trichuris suis - Basic lifecycle Biology
-Direct Life cycle
-Adults live in caecum & large intestine
-Eggs passed in feces
-Infective larvae develop in egg, ~ 21 days w/ optimal temperature/humidity: persistent in environment, up to 7 years and eggs resistant to freeze‐thaw
-Susceptible host infected by ingestion of the larvated egg
-Larvae develop beneath epithelium in small intestine before moving to caecum & large intestine
-Prepatent period about 7 to 9 weeks
Trichuris suis - Characteristics
-Diagnosis by fecal flotation
-Eggs ~ 55 x 25μm:
-Elongate w/ distinct polar plugs
-Golden brown
-Single cell (uninfective) when passed in feces
Trichuris suis - Clinical Significance
-Stunted growth & poor feed efficiency in piglets:
-Ages 8 to 14 weeks most affected
-Anemia, diarrhea, dehydration
-Dysorexia, weight loss
-Adult worms attachment to large intestine induce inflammatory response:
-Colitis
-Mucosal necrosis and edema
-Focal hemorrhage
-Grower/finishers put on contaminated pastures:
-At significant risk for disease
-No acquired immunity from previous challenge
Trichuris suis - Zoonotic Significance
-Human Trichuris morphologically indistinguishable from swine Trichuris: eggs on fecal examination also same size
-Close molecular relationship has prompted many to suggest they are same species
-No evidence that transmissibility of parasite results in human disease
-Recent interest and use of “induced infections “ in humans as treatment for autoimmune disorders:
-Crohn’s disease
-Autism disorders
-“Hygiene Hypothesis” microbes/parasites and humans co‐evolved to keep immunity “in‐check”
-Down regulation of inflammatory & immune mechanisms influential in the disorder
Oesophagostomum dentatum - Swine Nodular Worm
-Strongyle‐type worms living in the large intestine of swine
-Sexually dimorphic: males: 8 to 10 mm and females: 11 to 14 mm
-Typical Strongyle morphology: buccal capsule w/ leaf crown
-Cosmopolitan distribution: world‐wide where swine
production occurs
Oesophagostomum dentatum - Basic lifecycle Biology
-Direct Life cycle
-Adults live in large intestine
-Eggs passed in feces
-Infective larvae develop on pasture w/in 6 to 7 days: optimal temperature/humidity and larvae subject to desiccation/temperature extremes
-Susceptible host infected by ingestion of the L3 larval stage
-Larvae penetrate intestinal wall, develop
-Return to lumen as sub mature adult worms (so called L4 stage)
-Become adult worms and reproduce
-Prepatent period ~6 to 7 weeks
Oesophagostomum dentatum - Clinical Significance
-Stunted growth & poor feed efficiency in piglets:
-Nodule formation in gut and associated inflammation
-Enteritis
-Dysorexia,
-Blood‐stained feces
-Grower/finishers put on contaminated pastures:
at significant risk for disease and no acquired immunity from previous challenge
-Economic losses from condemned intestines used for “sausage casings”
Oesophagostomum dentatum - Characteristics
-Diagnosis by fecal flotation
-Typical Strongyle‐type eggs:
-60‐80μm x 35‐40μm
-Thin‐shelled morula
-Uninfective when passed in feces
