Heterophyid Dermatitis Notes

Heterophyid Dermatitis

  • Skin swelling and discoloration caused by infection with trematode larvae from the Heterophyidae family.
  • Common in many fish species in the North Atlantic and Southeast Asia.
  • Cryptocotyle lingua (Creplin, 1825) is a species within Heterophyidae.

Platyhelminths

  • Phylum Platyhelminthes (flatworms):
    • Class Cestoda (tapeworms)
    • Class Trematoda (flukes: endoparasites)
      • Family Heterophyidae (cold water marine fish)
      • Family Diplostomatidae (temperate and tropical freshwater fish)
    • Class Monogenea (skin flukes: ectoparasites)
    • Class Turbellaria (free-living flatworms, some parasitic forms)
      • Paravortex and Piscinquilinus (tropical marine fish (Pacific))
  • Platyhelminths are parasitic worms that cause black dermal lesions in fish.

Acanthuridae

  • Acanthurus spp.
    • A. bahianus (Ocean surgeonfish)
    • A. coeruleus (Blue tang)
    • A. chirurgus (Doctorfish)
  • Family: Acanthuridae; Surgeonfishes, tangs, unicornfishes
  • Very abundant species on reefs.
  • Important algal grazers on coral reef systems.

Emerging Disease

  • The presence of A. bahianus (Ocean surgeonfish), A. coeruleus (Blue tang), and A. chirurgus (Doctorfish) with skin lesions raises the question of whether this is an emerging disease or phenomenon.

Sampling Methods

  • Fish were either purchased at markets in St. Kitts or speared directly from the reefs.
  • Fish with noticeable skin lesions were not typically present at the fish markets, so the diseased fish were mostly speared.

Postmortem Examination

  • Twenty-nine dermatopathy-affected acanthurids were sampled by spearfishing for comprehensive postmortem examination.

Metacercaria

  • Encapsulated metacercaria.
  • Metacercaria removed from capsule.

Scaphanocephalus spp.

  • Scaphanocephalus spp.
  • S. expansus:
    • Hindbody broad, rounded posteriorly.
    • Testes not branchy.
    • Anterior Testis (AT) > Posterior Testis (PT)
  • S. australis:
    • Hindbody slender, pointed posteriorly.
    • Testes branchy.
    • AT ≤ PT
  • S. adamsi life cycle:
    • 1: Final host (bird)
    • 2: First intermediate host (gastropod)
    • 3: Second intermediate host (numerous fish)

Cysts

  • Cyst in epidermis, with surrounding inflammation.
  • Cyst in skeletal muscle.

PCR/Sequencing

  • Two genotypes were found to be 97% similar over the D1-D3 variable region in the LSU rDNA, suggesting they represent two distinct species.
  • There are 29 species of fishborne heterophyid trematodes that infect humans worldwide, belonging to 13 genera.

Scaphanocephalus-associated dermatitis

  • Scaphanocephalus-associated dermatitis as the basis for black spot disease in Acanthuridae of St. Kitts, West Indies.

Assumed/proposed Scaphanocephalus sp. life cycle

  • Definitive bird host depositing eggs into the sea.
  • Infection of unknown 1st intermediate host (gastropod).
  • Infection of unknown 2nd intermediate hosts (numerous fish).
  • Mature trematodes develop in the bird intestine.
  • Typically, a narrow host range for definitive host (bird).
  • Typically, a broad host range for intermediate hosts (gastropod and fish).
  • Zoonosis is a possibility.