Kudoa amamiensis

From Fish
A fillet of yellowtail showing Kudoa infection
Fresh spores of Kudoa amamiensis

Kudoa spp are a myxosporidian parasite of the muscles of marine fish, including Yellowtail (Seriola quinqueradiata), Greater amberjack (Seriola dumerili) and Pearl-spot chromis (Chromis notata).

Clinical signs

Many spherical white cysts form within skeletal muscle. It is not fatal to host fish even in heavy infection.

In the early infection period, vegetative stages develop inside the myocytes andremarkable host reactions are not observed. As the plasmodia develop,parasites are encapsulated by fibrous connective tissue, resulting in visible cyst formation. Liquefaction of muscle tissue does not occur.

Since this parasite is not infectious to human, it is harmless in food hygiene.

Diagnosis

Diagnosis is confirmed by microscopic examination of diseased muscles, where spores are observed. Kudoa amamiensis can be distinguished from Kudoa iwatai by the spore size and shape[1]. Sample should be smeared and stained by Giemsa or Diff-Quik. The detection methods by IFAT or PCR has been developed[2].

K. amamiensis was first thought to be confined to Amami-Ohshima and a part of Okinawa in Japan, but Whipps et al(2003)[3] reported the distribution of this parasite in Great Barrier Reef in Australia. The extent of susceptibility to this disease depends on the host fish species, e.g., several hundred of cysts, several dozen of cysts and one or a few cysts (per 1 g of muscle tissue) in yellowtail, greater amberjack and pearl-spot chromis, respectively[4]. There are no effective methods to prevent this disease.

References

  1. Egusa, S. (1986) The order Multivalvulida Shulman, 1959 (Myxozoa; Myxosporea): a review. Fish Pathol 21:261-274
  2. Yokoyama, H., D. Inoue, A. Sugiyama and H. Wakabayashi (2000) Polymerase chain reaction and indirect fluorescent antibody technique for the detection of Kudoa amamiensis (Multivalvulida: Myxozoa) in yellowtail Seriola quinqueradiata. Fish Pathol 35:157-162
  3. Whipps, C. M., R. D. Adlard, M. S. Bryant, R. J. G. Lester, V. Findlay and M. L. Kent (2003) First report of three Kudoa species from eastern Australis: Kudoa thyrsites from mahi mahi (Coryphaena hippurus), Kudoa amamiensis and Kudoa minithyrsites n. sp. from sweeper (Pempheris ypsilychnus). J Eukaryot Microbiol 50:215-219
  4. Sugiyama, A., H. Yokoyama and K. Ogawa (1999) Epizootiological investigationon kudoosis amami caused by Kudoa amamiensis (Multivalvulida:Myxozoa) in Okinawa Prefecture, Japan. Fish Pathol 34:39-43