Biology 625
ANIMAL PARASITOLOGY
Fall semester lecture note outline

Updated: 24 September 1999

The text below simply represents a crude lecture outline of one of the topics covered in class. It is not meant to substitute for attending lectures or ignoring the textbook. Additional material, including line drawings, kodachromes, and more extensive information on life-cycles and basic biology, will be supplied in the lectures.

TOPIC #6: Order: Strigeiformes


About nine superfamilies; select groups as follows:

SUPERFAMILY: Strigeoidea

  1. bodies divided into distinct anterior and posterior portions; often spoon-like
  2. accessory "pseudosuckers" on each side of the oral sucker
  3. behind acetabulum a tribocytic organ, thought to secrete proteolytic enzymes for mucosal digestion
  4. hindbody usually contains the reproductive organs
  5. genital pore posterior

Posthodiplostomum minimum (family: Diplostomidae)

  1. adults in the intestine, predominately in Ciconiiformes and Charadriiformes (i.e. herons, gulls, ternd). However, many other species of birds, and even some mammals, reptiles, and amphibia, have been shown experimentally to be suitable hosts
  2. metacercariae in bluegills, crappie, and other related fish; even cyprinids
  3. life-cycle
    1. adults in gut
    2. eggs out with feces
    3. hatches
    4. miricidium penetrates snail (Physa)
    5. 2 sporocyst generations
    6. cercariae exit snail
    7. penetrate fish and form metacercariae throughout viscera
    8. infected fish eaten by bird
  4. similar species
    1. Hysteromorpha triloba
      1. adults in herons, egrets, pelicans, cormorants
      2. metacercariae in bullhead catfish
    2. Diplostomum spathaceum
      1. adults in gulls and terns
      2. metacercariae in eye of cottids, salmonids, suckers
    3. Uvulifer ambloplites
      1. adults in kingfishers
      2. metacercariae; skin "black spot" in bass, perch, pike, sunfish
    4. Crassiphiala bulboglossa
      1. adults in kingfishers
      2. metacercariae; skin "black spot" in perch, chub, minnows, pike
    5. Fibricola texensis
      1. adults in raccoons
      2. metacercariae in muscles of ranid tadpoles
    6. Neodiplostomum intermedium
      1. adults in Rattus spp.
      2. metacercariae in tadpoles of Hyla spp.
Alaria americana (family: Diplostomidae)
  1. adults in intestine of canids
  2. forebody with pair of ventral flaps anteriorly
  3. pointed structures, termed "lappets" flank anterior sucker
  4. tribocytic organ large
  5. numerous hosts common
  6. life-cycle
    1. adults in gut
    2. unembryonated eggs passed in feces
    3. embryonates in about 2 weeks in environment
    4. hatch
    5. miricidium penetrates planorbid snail
    6. 2 sporocyst generations
    7. furcocercous cercariae escape in daylight; to surface
    8. penetrate tadpole via skin
    9. tadpole transforms into adult frog
    10. mesocercariae (unencysted larva)
    11. infective for next host
      1. definitive host
        1. mesocercariae penetrate gut
        2. migrate across diaphragm to lungs
        3. about 5 weeks maturation
        4. transform into metacercariae
        5. migrate up trachea
        6. mature to adults in gut
      2. paratenic host (i.e. snakes)
        1. mesocercariae can be transferred and accumulate in tissues
        2. if eaten by definitive host, same migration as above
    12. In Alaria marcianae (raccoons), mesocercariae can be transmitted to offspring in milk via lactation
  7. Epidemiology of Alaria spp. (esp Alaria marcianae) in Louisiana
    1. frogs 30-100%
    2. fish 0%
    3. snakes (Agkistrodon piscivorus, Nerodia spp., Coluber constrictor, Thamnophis proximus) 98%
    4. can also be transmitted experimentally to alligators and green anoles
    5. opossums 60%
    6. raccoons 60%

Cotylurus flabelliformis (family: Strigeidae)

  1. common in ducks in North America
  2. adults 0.5-1.0 mm
  3. forebody cup-shaped, hindbody short and stout, curved dorsally
  4. life-cycle
    1. adults in small intestine
    2. unembryonated eggs out with feces
    3. hatch in about 3 weeks
    4. miricidia infect snails in the family Lymnaeidae
    5. 2 sporocyst generations
    6. furcocercous cercariae released
      1. contact snails in family Lymnaeidae
        1. migrates to ovotestes
        2. metacercariae form
        3. eaten by duck
        4. mature in gut in about 1 week
      2. contact snails of families Planorbidae or Physidae
        1. attacks and penetrates sporocysts and rediae of other fluke species
        2. metacercariae forms
        3. eaten by duck
        4. mature in gut in about 1 week


SUPERFAMILY: Clinostomatoidea

  1. large, fleshy worms
  2. anterior and posterior suckers closely associated
  3. no muscular pharynx
  4. secondary network of ramified lacunae present for excretion besides protonephridia

Clinostomum marginatum (family: Clinostomatidae)

  1. adults in mouth, pharynx, esophagus of herons and other fish eating birds
  2. life-cycle
    1. adults in oral area of birds
    2. eggs into water directly or pass out with feces
    3. hatch
    4. miricidia penetrate Helisoma snails
    5. one sporocyst and two redial generations
    6. cercariae liberated and penetrate cyprinids, bluegills, bass, trout, catfish
    7. metacercariae ("yellow grub") throughout dermis and muscles
    8. eaten by bird; matures
  3. similar species (taxonomy poorly known)
    1. Clinostomum attenuatum (birds/frogs, fish)
    2. Clinostomum complanatum (birds/fish)


SUPERFAMILY: Brachylaemoidea

  1. Genital pore in posterior one-half of body
  2. often large suckers
  3. a representative species as follows:

Leucochloridium macrostomum (family: Leucochloridiidae)

  1. testes posterior
  2. large suckers
  3. predominately in Europe
  4. life-cycle
    1. adults in cloaca and bursa of various birds
    2. embryonated eggs passed in feces
    3. eaten by snails (genus Succinea mainly) and slugs
    4. miricidium hatches
    5. 2 sporocyst generations
    6. daughter sporocysts become branched; brightly colored, often with rings
    7. migrates anteriorly into tentacles
    8. tentacles become expanded and pulsate; may rupture off
    9. eaten by birds
    10. cercariae released; to cloaca; mature


SUPERFAMILY: Bucephaloidea

  1. mouth mid-ventral (gasterostomes)
  2. acetabulum absent
  3. fish and amphibia only
  4. anterior sucker may or may not be present
  5. anterior end often with rhyncus (muscular holdfast organ)

Bucephalus polymorphus (family: Bucephalidae)

  1. lives in intestine or stomach of carnivorous fish
  2. 1-6 mm long
  3. rhyncus with 7 tentacles
  4. life-cycle
    1. adults in gut
    2. eggs out with feces
    3. miricidium hatches
    4. penetrates freshewater clams; some snails
    5. highly branched sporocysts in digestive gland
    6. furcocercous cercariae (short tail; long furci)
    7. furci become entangled in fins of small fish
    8. metacercariae under scales
    9. eaten by larger fish
    10. excyst in gut; mature
  5. similar genera; defined often by anterior holdfast structures
    1. Bucephalopsis
    2. Prosorhynchus
    3. Rhipidocotyle


SUPERFAMILY: Schistosomatoidea

  1. mature in blood vascular system
  2. no second intermediate host; cercariae enter final host directly with encystation
  3. most species dioecious, but with some exceptions
  4. no pharynx generally

Spirorchis elegans (family: Spirorchiidae)

  1. Family consists of small, monecious monostomes and distomes, with a small oral sucker, no pharynx, and occurring in reptilian heart and blood vascular system
  2. multiple species in genus
  3. this species in Chrysemys, Trachemys (Emydid turtles)
  4. about 10 testes
  5. posterior ovary
  6. life-cycle
    1. adults in heart; large arteries
    2. eggs embryonated, circulate through blood stream, lodge in walls of small blood vessels
    3. escape through endothelium, enter surrounding tissue
    4. those in gut wall enter lumen and pass out with feces
    5. miricidia hatch
    6. penetrate freshwater snails
    7. 2 sporocyst generations
    8. furcocercous cercariae released at night
    9. penetrate skin of turtle (esp mucus membranes, eye, nostrils, mouth)
    10. migrate to blood vascular system
  7. disseminated eggs of some species result in significant morbidity and mortality in turtles due to local granulomatous reactions. Clincal signs are varied but include lethargy, irregular swimming behavior, necrotic lesions on the carapace, and necrosis of various visceral organs. Eggs in various stages of decomposition can be found in virtually all tissues of the body (1998, Lab Anim Sci 48: 340-343).

Cardicola davisi (family: Sanguinicolidae)

  1. Family consists of monecious species, with intestinal cecae arranged in H- or X-shape; no suckers; no pharynx; live in heart or blood vessels (rarely liver) of freshwater fish
  2. one of two important genera
    1. Cardicola (1 large testes)
    2. Sanguinicola (several testes arranged in two regular rows)
  3. in trout of North America; may cause severe mortality
  4. life-cycle
    1. adults in main gill capillaries
    2. non-operculate eggs released and lodge in gill filament capillaries
    3. miricidium develops in egg; hatches
    4. ruptures out through epithelium into water
    5. enters freshwater snail (Oxytrema circumlineata)
    6. 2 sporocyst and one redial generations
    7. furcocercous cercariae
    8. penetrates skin of trout
    9. enters vein; through blood system to heart, then gills
  5. similar species
    1. Cardicola klamathensis (trout)
    2. Cardicola alseae (trout)
    3. Sanguinocola inermis (carp in Europe)

Schistosoma and other spp. and genera (family: Schistosomatidae)

  1. elongate bodies
  2. no pharynx
  3. in birds (many genera); mammals (3 genera)
  4. eggs non-operculate
  5. live in blood vessels, especially mesenteric blood vessels
  6. Schistosoma spp. (in mammals; 4 groups)
    1. Schistosoma haematobium group
      1. 7 species
      2. most use Bulinus snails
      3. indigenous to Africa and adjacent regions
      4. most with posterior spine on egg
      5. S. haematobium, S. intercalatum, S. mattheei in primates. Available evidence suggests that S. haematobium can cause urinary bladder carcinoma
      6. S. mattheei, S. bovis, S. curassoni, S. margrebowiei, S. leiperi in artiodactyla
    2. Schistosoma mansoni group
      1. 4 species
      2. most used Biophalaria snails
      3. indigenous to Africa; introduced to the Caribbean and South America
      4. most with large, sublateral spine of egg
      5. S. mansoni in primates and rodents
      6. S. rodhaini in carnivores and rodents
      7. S. edwardiense, S. hippopotami in artiodactyla
    3. Schistosoma indicum group
      1. 4 species
      2. most species use Indoplanorbis snails
      3. indigenous to Asian countries
      4. Most species have egg with terminal spine
      5. S. indicum, S. spindale, S. nasale in artiodactyla
      6. S. incognitum in rodents, carnivores, and artiodactyla
    4. Schistosoma japonicum group
      1. 4 species
      2. variety of snails
      3. indigenous to Asian countries
      4. most eggs spherical or subspherical, with small spine
      5. S. japonicum in primates, rodents, and carnivores. Evidence suggests that this parasite may cause hepatic carcinoma.
      6. S. mekongi in primates and carnivores
      7. S. sinensium, S. malayensis in rodents
  7. life-cycle of Schistosoma spp.
    1. adults in veins in visceral region; females inch down into venioles to release eggs
    2. eggs trapped in capillaries; granuloma; out with feces or urine or remain trapped
    3. embryonate en route
    4. hatch
    5. miricidium penetrates snail
    6. two sporocyst generations
    7. furcocercous cercariae released
    8. penetrate skin of definitive host
    9. schistosomule migrates; blood vessels; heart; liver
    10. matures in about three weeks
    11. migrate down veins to sites of infection; en route males and females pair
  8. pathology and immunology
    1. adults evade imune system by coating themselves with host proteins
    2. adults cause little damage
    3. most pathology associated with eggs; many carried to exotic sites
    4. delayed type hypersensitivity around egg granulomas; leaking antigens; eosinophilia; neutrophilia
    5. blood vessel occlusion; fibrosis; bloody diarrhea; bloody urine; edema; ascites; cirrhosis
  9. a few reports have suggested that the pharaoh Akhenaton may have had Schistosoma haematobium
  10. some historical reports have suggested that Napoleon Bonaparte, who had chronic dysuria, may have acquired Schistosoma haematobium during his Egyptian campaign of 1798.
  11. other genera and species
    1. Schistosomatium douthitti
      1. rodents and lagomorphs in far North America
      2. hepatic portal system
    2. Heterobilharzia americanum
      1. medium sized mammals; carnivores; in North America
      2. in raccoons in Kansas 1991, J. Wildlf. Dis. 27: 156-160. Introduced into Lyon County by transport of infected raccoons from SE United States
    3. Gigantobilharzia, Bilharziella, Trichobilharzia, Microbilharzia, etc.
      1. birds
      2. many cause swimmer's itch, where cercariae penetrate skin, die, and cause inflammation in abnormal hosts
      3. review 1971, J. Helminthol. 45: 289-320.

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