Hola a todos,En el día de ayer, mis fuentes me enviaron un estudio de la ''University of Florida'', sobre Cryptobia iubilans en Cíclidos, de la mano de Ruth Francis Floyd y Roy Yanong:Link: http://edis.ifas.ufl.edu/VM077Este artículo tiene mucho que ver con el ''bloat''.
Cryptobia iubilansin CichlidsRuth Francis Floyd and Roy Yanong
What is Cryptobia?Cryptobia is a flagellated protozoan, closely related to
Hexamita and
Spironucleus, but not nearly as well understood.
Like
Hexamita and
Spironucleus,
Cryptobia is a very tiny (single-celled) organism and, consequently, can be difficult to identify and study. There have been 52 species of
Cryptobia identified in fish; however, because of its small size and difficult taxonomy, these may not all be separate species.
Of the 52 species that have been identified, five are classified as ectoparasites that infect the gills and skin; seven are classified as enteric parasites that infect the gastrointestinal system; and 40 are classified as hemoflagellates which are found in the bloodstream. It has recently been proposed that the hemoflagellates be assigned to a subgenus called
Trypanoplasma.
The hemoflagellates have an indirect life cycle and are transmitted by leeches, whereas the gastrointestinal and ectoparasitic forms have direct life cycles.
Cryptobia iubilans and CichlidsCryptobia iubilans was first recognized in cichlids some 20 years ago. The organism is typically associated with granulomas (a tissue reaction) in the stomach, but systemic infections that involve the organism in blood and organ systems (including liver, gall bladder, kidney, ovary, brain, and eye) have been reported.
It is not known how the organism is able to spread from the intestinal tract to other organs, or what causes the internal spread. Mortalities associated with the systemic form may exceed 50% of the infected population.
The gastrointestinal form of
Cryptobia has been reported in East African and Central American cichlids, including:
Herichththys cyanoguttatus,
Cichlasoma meeki,
Cichlasoma nigrofasciatum, and
Cichlasoma octofasciatum. Our laboratories have found it in some additional species, but most of the work has been done with
Pseudotropheus zebra (Department of Fisheries and Aquatic Sciences, Gainesville, FL) and
Symphysodon spp. (Tropical Aquaculture Laboratory, Ruskin, FL).
In the summer of 1995, there was an outbreak of the systemic form of
Cryptobia iubilans in cichlids at the Chicago Shedd Aquarium. The outbreak resulted in loss of 50% of the collection of East African cichlids including
Cyphotilapia frontosa,
Dimidiochromis compressiceps, and
Aulonocara stuartgranti. The outbreak seemed to originate with the
Aulonocara that had been purchased from a midwest wholesaler. While the fish were in quarantine, the infection spread to
Cichlasoma meeki and
C. nicaraguense housed in the same tank. From there it spread to the
C. frontosa and
D. compressiceps that were housed in separate tanks but shared the same water due to a common filtration system. The sick fish went off feed for one to two days, becoming progressively more listless and withdrawing from contact with other fish.
Just prior to death, they would move to the surface of the water and their respiration rate would increase dramatically, suggesting that they were hypoxic (suffering from low dissolved oxygen). Closer examination of fish at this stage of the disease revealed severe anemia, with packed cell volumes around 5% (normal should be greater than 30%). Death usually occurred within 24 hours of the development of severe anemia.
Veterinarians at Shedd aquarium wanted to see how many species in their collection carried the parasite so they sacrificed 60 apparently healthy fish, and found evidence of
Cryptobia iubilans in all but one (98% prevalence). These fish had granulomatous gastritis (the tissue reaction in the stomach) but no evidence of the systemic disease.
The affected species included
Haplochromis macula,
Cichlasoma nicaraguense,
Labeotropheus fuelleborni,
Cichlasoma aureus,
Pseudotropheus zebra and
P. elongatus. Since the 1995 epizootic (disease outbreak), Shedd Aquarium has instituted a new quarantine protocol for all cichlids. All incoming cichlids are subjected to a minimum 60-day mandatory quarantine. A number of animals are screened for the presence of
Cryptobia; any infected cichlid is culled.
Comparing Cryptobia and Spironucleus infectionsClinical Disease:Both
Cryptobia and
Spironucleus can result in similar disease scenarios on cichlid farms. Both parasites become more serious under conditions of crowding, poor sanitation, high organic load, and handling stress. Diet also may play a role in the development of the disease.
It has been demonstrated in laboratory mice that changes in the intestinal bacterial flora, caused by changes in diet, can affect the presence of intestinal flagellates, suggesting greater potential for clinical disease.
Enteric disease from either parasite may result in low level chronic mortality, "wasting" or poor growth.
The effect of
Spironucleus is more serious in fry and very young fish. It is not known if this is also true for
Cryptobia, but there is some evidence that supports this belief. The impact of either disease on reproduction is not well understood; however, we believe that breeders heavily infected with
Spironucleus produce poor quality eggs and weak fry.
Diagnosis:Spironucleus can be tentatively identified by observing the motile trophozoites in smears of intestinal contents or feces. Identifying the parasite to genus requires both transmission and scanning electron microscopy and therefore cannot be done on a routine basis.
Cryptobia is most easily detected by identification of granulomas in thin wet mounts of stomach tissue (Figure 1). Because these granulomas are indistinguishable from the granulomas observed with
Mycobacterium, an acid-fast stain (eg. Ziehl-Nielson) should be used to rule out that important disease (see IFAS Extension Fact Sheet No. VM-96). In most instances, motile forms of
Cryptobia will not be seen on wet mounts that are examined with a light microscope. Electron microscopy is also required to confirm the identity of this organism.[url=http://edis.ifas.ufl.edu/LyraEDISServlet?command=getImageDetail&image_soid=FIGURE 1&document_soid=VM077&document_version=565796518]
[/url] Figure 1.
Typical granuloma seen in a wet mount of stomach tissue from an African cichlid with
Cryptobia iubilans infection. The section is unstained and is examined with a light microscope (100x)
Transmission:Both
Spironucleus and
Cryptobia have direct life cycles. Infective forms are shed with feces, and ingestion of these forms is thought to result in infection. Both organisms can live in the water column for at least a few hours. Always remove carcasses as quickly as possible when they are found, since both parasites may be spread by ingestion of infected tissue.
Treatment:Spironucleus usually responds well to metronidazole administered in feed or as a bath. The recommended dose in feed is 1% (4.5 grams active drug per pound of feed) fed daily for five consecutive days (see IFAS Extension Fact Sheet No. VM-67). The bath treatment is 6 mg/L (250 mg added to 10 gallons of water), followed by a water change four to eight hours after treatment, repeated daily for five days (see IFAS Extension Fact Sheet No. VM-67). These regimes have been very effective for control of
Spironucleus in cichlids for the past ten years.
Currently, there is no effective treatment for
Cryptobia. Part of the difficulty may be that the parasite seems to have an intracellular stage. Parasites are occasionally seen in phagocytic cells, called macrophages, which are part of the immune system and are supposed to destroy foreign protein by engulfing it.
Cryptobia seems to be able to live within these cells rather than being destroyed by them. This can make it difficult to treat
Cryptobia because most drugs are not able to penetrate the cell wall of a macrophage.
Some Florida farms have used a sulfa drug (sulfadimethoxine) that seems to help control mortalities in some cases, but has not eliminated the parasite. Experiments are in progress at the Tropical Aquaculture Laboratory (Ruskin, FL) to find an effective therapeutic agent.
SummaryCryptobia iubilans is not a new parasite of cichlids but has received significant attention in the past few years.
It seems to be widespread in East African cichlids and has been found in
Pseudotropheus zebra immediately following importation from Lake Malawi, suggesting that it occurs naturally in wild fish. It has also been found in some South American cichlids, most notably, discus.
The parasite usually causes a granulomatous gastritis and may be associated with chronic low-level mortality. A systemic form of the disease has been reported in captive East African and Central American cichlids. This form was associated with acute mortalities and loss of 50% of affected animals. Currently there is no effective treatment for
Cryptobia. Water quality, stocking density and diet may all effect the severity of infection. Work is in progress at the University of Florida to learn more about this common, but important, cichlid parasite.
Footnotes1.
This document is VM104, one of a series of the Veterinary Medicine-Pathobiology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date January 1, 1999. Revised April 12, 2002. Visit the EDIS Web Site at http://edis.ifas.ufl.edu.
2.
Ruth Francis Floyd, DVM, MS, Extension Veterinarian for Fisheries and Aquatic Sciences and Professor, Department of Large Animal Clinical Sciences and Roy Yanong, VMD, Assistant Professor for Department of Fisheries and Aquatic Sciences, Tropical Aquaculture Laboratory, 1408 24th St. S E, Ruskin, FL 33570
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.
U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim Dean.
Índice 
Portal 
Galería 
Buscar 
Registrarse 
Atlas trophero 
Conectarse 
Lun Oct 26, 2009 4:37 pm
