Lectin Binding Patterns and Immunohistochemical Antigen Detection in the Genitalia of Tritrichomonas foetus-infected Heifers

Heifers inoculated intra-vaginally with Tritrichomonas foetus were examined after long-term infection (70 days) and short-term infection (20 days) by lectin-histochemical, immunohistochemical and cultural techniques. The organism was recovered from the genital tract and T. foetus antigens were detected immunohistochemically in the lumina of uterine glands and cytoplasm of vaginal subepithelial macrophages. An increase of galactosylated residues (galactose and N-acetyl galactose), binding to PNA, was observed in the genital epithelium (vagina, uterus and oviduct) from infected animals. In the oviductal epithelium of short- but not long-term infected heifers, mannose (binding to Con A) was detected, suggesting that the persistent presence of T. foetus and its virulence factors or inflammatory processes result in a change in the glycoproteins of the epithelial surface. The findings have implications for the adhesion of T. foetus to cells and for the pathogenesis of bovine trichomonosis.

Humoral response and susceptibility of five full-sib families of Atlantic salmon, Salmo salar L., to the haemoflagellate, Cryptobia salmositica

Susceptibility and antibody production against pathogenic and vaccine strains of the haemoflagellate, Cryptobia salmositica were investigated in five full-sib families (A-E) of Atlantic salmon, Salmo salar. Humoral response and susceptibility of families were compared within three treatments: infection, vaccination and vaccination followed by challenge. Parasitaemias caused by the vaccine strain of C. salmositica were considerably lower than those caused by the pathogenic strain. All vaccinated families were protected when challenged with the pathogenic strain. Family B had significantly lower parasitaemias (with both strains) than the other families. When naïve fish were infected with the pathogenic strain, this family had a significantly lower and earlier peak parasitaemia (4.3 +/-1.3 x 10(6) parasites mL(-1) blood at 3 weeks post-infection; w.p.i.) than the other families. Family C had the highest peak (11.1 +/- 1.2 x 10(6) parasites mL(-1) blood), which occurred at 4 w.p.i. Antibodies against C. salmositica were detected earlier in Family B (3 w.p.i.) than in Family C (5 w.p.i.). This demonstrates an association of increased susceptibility with a delayed antibody response. Western immunoblot identified antibodies against 112, 181 and 200 kDa antigens earlier in more resistant fish (Family B). Antigenic stimulation leading to a stronger antibody response was shown with the vaccine strain and in the later stages of infection.

The induction of laboratory-based amoebic gill disease revisited

Previous work in our laboratory defined a method of inducing laboratory-based amoebic gill disease (AGD) in Atlantic salmon, Salmo salar L. Gills of AGD-affected fish were scraped and the debris placed into fish-holding systems, eliciting AGD in naïve Atlantic salmon. While this method is consistently successful in inducing AGD, variability in the kinetics and severity of infections has been observed. It is believed that the infections are influenced by inherently variable viability of post-harvest amoeba trophozoites. Here, a new method of experimental induction of AGD is presented that redefines the infection model including the minimum infective dose. Amoebae were partially purified from the gills of AGD-affected Atlantic salmon. Trophozoites were characterized by light microscopy and immunocytochemistry and designated Neoparamoeba sp., possibly Neoparamoeba pemaquidensis. Cells were placed into experimental infection systems ranging in concentration from 0 to 500 cells L(-1). AGD was detected by gross and histological examination in fish held in all systems inoculated with amoebae. The number of gross and histological AGD lesions per gill was proportional to the inoculating concentration of amoebae indicating that the severity of disease is a function of amoeba density in the water column. The implications of these observations are discussed in the context of the existing AGD literature base as well as Atlantic salmon farming in south-eastern Tasmania.

Prevalence of and risk factors for feline Tritrichomonas foetus and giardia infection

Data were gathered for 117 cats from 89 catteries at an international cat show to examine prevalence and risk factors for feline Tritrichomonas foetus and Giardia infection. Prevalence of T. foetus was 31% among cats (36 out of 117) and catteries (28 out of 89) based on results of fecal smear examination (5 out of 36), fecal culture in modified Diamond's medium (9 out of 36), fecal culture in In Pouch TF medium (20 out of 36), or PCR amplification of the ribosomal RNA gene from feces with T. foetus-specific primers (34 out of 36). Catteries in which T. foetus was identified were more likely to have had a recent history of diarrhea, historical diagnosis of coccidia infection in adult cats, and a decreased number of square feet of facility per cat. Evidence did not exist for the ongoing transmission of T. foetus by water, food, or contact with other species.

Some immune parameters in carp cyprinus Carpio susceptible and resistant to the haemoflagellate Trypanoplasma borreli

The present study addresses aspects of the (specific) immune response of carp to the haemoflagellate Trypanoplasma borreli. Sera of resistant carp contained antibodies, which agglutinated the flagellates in vitro. When flagellates were incubated in fish sera from resistant carp, binding of antibodies to flagellates could be demonstrated by flow cytometry, and T. borreli were effectively killed. Heat-treatment of the sera prevented killing, indicating that complement activation is important for the control of a T. borreli infection. Sera of carp that were highly susceptible to infection with T. borreli contained no antibodies capable of binding to or killing the parasite. Furthermore, specific antibodies were not generated after experimental infection. This lack of antibody production in susceptible carp is not due to a general unresponsiveness of lymphoid cells, since peripheral blood leukocytes (PBL) from susceptible and resistant carp responded to mitogenic stimuli in vitro with lymphocyte proliferation in a similar manner. However, viable flagellates were significantly less able to stimulate proliferation of PBL from susceptible carp. In vitro-produced culture supernatants of freshly isolated PBL from both carp lines (but not those of head kidney cells) differentially modulated the mitogen-induced proliferation of PBL from susceptible and resistant carp. The supernatants enhanced the proliferation of leukocytes obtained from individuals from the same carp line, but suppressed the mitogen-induced proliferation of PBL from the other line tested. This indicates that lymphoid cells from susceptible and resistant carp differ in their spectrum of spontaneously produced immunomodulatory mediators. Whether this is decisive for a T. borreli-specific and successful immune response is discussed.

18S ribosomal DNA-based PCR identification of Neoparamoeba pemaquidensis, the agent of amoebic gill disease in sea-farmed salmonids

Neoparamoeba pemaquidensis is a parasomal amoeboid protozoan identified as the agent of amoebic gill disease (AGD) in Atlantic salmon Salmo salar reared in sea-pens in Tasmania, Australia, and coho salmon Oncorhynchus kisutch farmed on the west coast of the USA. Outbreaks of AGD caused by immunologically cross-reactive paramoebae have also been reported in sea-farmed salmonids in several other countries. Complete 18S rDNA sequences were determined for respective paramoebae isolated from infected gills of salmon from Tasmania and Ireland, and N. pemaquidensis isolates from the USA and UK, including representative free-living isolates. Alignments over 2110 bp revealed 98.1 to 99.0% sequence similarities among isolates, confirming that paramoebae implicated in AGD in geographically distant countries were homologous and belonged to the same species, N. pemaquidensis. The results supported previous findings that N. pemaquidensis exists as a widely distributed, amphizoic marine protozoan. Partial 18S rDNA sequences were obtained for the ultrastructurally similar species, N. aestuarina, and for the morphologically similar but non-parasomal amoeba Pseudoparamoeba pagei. N. aestuarina had 95.3 to 95.7% sequence similarities with N. pemaquidensis strains, which distinguished 2 closely related but separate species. Neoparamoeba spp. were not analogous to P. pagei or to other marine Gymnamoebia. We designed 4 oligonucleotide primers based on elucidated 18S rDNA sequences and applied them to single-step and nested 2-step PCR protocols developed to identify N. pemaquidensis to the exclusion of apparently closely related and non-related protistan taxa. Nested PCR was able to detect the AGD parasite from non-purified, culture-enriched net microfouling samples from Atlantic salmon sea-pens in Tasmania, and confirmed that N. pemaquidensis was also responsible for AGD in chinook salmon O. tshawytscha in New Zealand. Our sequence and PCR analyses have now shown that AGD affecting 3 different salmonid species farmed in 4 countries are associated with N. pemaquidensis. A species-specific diagnostic PCR provides for the first time, a highly specific detection and identification assay for N. pemaquidensis that will facilitate future ecological and epidemiological studies of AGD.

Cryptobia iubilans infection in juvenile discus

Four commercial producers of discus (Symphysodon aequifasciatus) were found to have fish infested with the flagellate Cryptobia iubilans. Affected fish had granulomatous gastritis, and many also had granulomatous disease of other organs. The parasite had to be differentiated from the related flagellates Spironucleus spp, which induce different lesions. Transmission electron microscopy was found to be useful in detecting and identifying the parasite. Morbidity and mortality rates in the various fish populations appeared to be linked to a number of variables, including water quality, presence of other parasites and bacteria, diet, species, size, and age of the fish, and optimization of husbandry appeared to be important in alleviating the severity of disease. Metronidazole was not effective for treatment of C iubilans, but bath treatments with dimetridazole (80 mg/L for 24 hours, repeated daily for 3 days) or 2-amino-5-nitrothiazol (10 mg/L for 24 hours, repeated daily for 3 days) may be useful in decreasing the prevalence of infestation.

Identification of a serine protease gene expressed by Myxobolus cerebralis during development in rainbow trout Oncorhynchus mykiss

Serine proteases have been recognized as key factors in parasite physiology and disease development. We have identified a serine protease gene from Myxobolus cerebralis, MyxSP-1, the myxozoan parasite causing whirling disease in salmonid fishes. The amino acid sequence, as deduced from the cDNA sequence, included a catalytic residue arrangement similar to that of the chymotrypsin family of serine proteases. A real-time TaqMan polymerase chain reaction (PCR) analysis revealed differences in the transcription levels for the chymotrypsin-like protease as found in early, intermediate, and late developmental stages of the parasite in experimentally-infected rainbow trout Oncorhynchus mykiss. MyxSP-1 transcription differed between individual tissues at each sampling point and in the same tissues over time (p < 0.0001). A nonradioactive mRNA in situ hybridization (ISH) protocol was developed to detect MyxSP-1 transcripts. Using a mixture of 3 digoxigenin-labeled antisense mRNA probes, MyxSP-1 transcription was observed in developmental stages of the parasite during the acute and chronic phases of the disease over a 240 d time period in infected rainbow trout tissues. MyxSP-1 transcription observed by ISH in cartilage and as associated with cartilage destruction was consistent with our real-time TaqMan PCR findings that demonstrated high levels of MyxSP-1 transcription during lesion development. Identifying genes encoding these enzymes and characterization of their functions can lead to the development of new chemotherapeutic protocols and vaccine approaches to control parasitic diseases.

Intraoligochaete development of Myxobolus intimus (Myxosporea: Myxobolidae), a gill myxosporean of the roach (Rutilus rutilus)

The infection with Myxobolus intimus Zaika, 1965 in the gills of the roach Rutilus rutilus (L.) from Lake Balaton was recorded in 28 out of the 39 fish examined. Developing and mature plasmodia were detected on the gills exclusively in the spring. The Myxobolus intimus infection was found only in 2- to 3-year-old fish. In histological sections, young plasmodia were found in capillaries of the secondary lamellae. More mature, round plasmodia 0.4-0.6 mm in diameter, deformed the respiratory lamellae. The intraoligochaete development of M. intimus was studied in experimentally infected oligochaetes. In two experiments, uninfected Tubifex tubifex Müller and Limnodrilus hoffmeisteri (Claparède) were exposed to mature myxospores of M. intimus. In both experiments, typical triactinospores developed in T. tubifex specimens but no infection was found in L. hoffmeisteri. In semithin sections, developmental stages, pansporocysts and actinospores, were found within the proliferated gut epithelium of T. tubifex. Triactinospores were first released from oligochaetes 37 and 58 days after initial exposure in the two experiments, respectively. Each triactinospore had three pyriform polar capsules and a cylindrical sporoplasm with 32 secondary cells. The spore body joined the 3 caudal projections with a moderately long style.

Advances in the knowledge of amphizoic amoebae infecting fish

Free-living amoebae infecting freshwater and marine fish include those described thus far as agents of fish diseases, associated with other disease conditions and isolated from organs of asymptomatic fish. This survey is based on information from the literature as well as on our own data on strains isolated from freshwater and marine fish. Evidence is provided for diverse fish-infecting amphizoic amoebae. Recent progress in the understanding of the biology of Neoparamoeba spp., agents responsible for significant direct losses in Atlantic salmon and turbot industry, is presented. Specific requirements of diagnostic procedures detecting amoebic infections in fish and taxonomic criteria available for generic and species determination of amphizoic amoebae are analysed. The limits of morphological and non-morphological approaches in species determination are exemplified by Neoparamoeba, Vannella and Platyamoeba spp., which are the most common amoebae isolated from fish gills, Acanthamoeba and Naegleria spp. isolated from various organs of freshwater fish, and by other unique fish isolates of the genera Nuclearia, Thecamoeba and Filamoeba. Advances in molecular characterisation of SSU rRNA genes and phylogenetic analyses based on their sequences are summarised. Attention is particularly given to specific diagnostic tools for fish-infecting amphizoic amoebae and ways for their further development.

Development of a simulation model to evaluate the effect of vaccination against Tritrichomonas foetus on reproductive efficiency in beef herds

OBJECTIVE

To develop a model to evaluate the effect of vaccination against Tritrichomonas foetus on reproductive efficiency in beef herds.

SAMPLE POPULATION

A beef herd of 300 cows and 12 bulls (8 bulls < or = 3 years old and 4 bulls > 3 years old).

PROCEDURE

The model was developed by use of data for various risk factors and vaccine efficacy. The reference herd was considered to be one in which T. foetus had been diagnosed and bulls were tested for T. foetus before the breeding season. Five thousand iterations were run for each of 13 simulations, with each simulation representing a separate combination of risk factors.

RESULTS

In all simulations, vaccination resulted in significantly higher calving incidence than nonvaccination. Shared grazing was found to be the most significant risk factor for a decrease in calving incidence attributable to T. foetus infection, followed in importance by lack of testing before the breeding season and a higher proportion of old bulls. Combinations of risk factors contributed to a loss of income of up to 22%, some of which could be blunted by vaccination.

CONCLUSIONS AND CLINICAL RELEVANCE

Highest calving incidence is achieved when all bulls are tested for T. foetus before the breeding season and all bulls with positive culture results are culled. Avoiding all risk factors is better than vaccinating, but when this is not feasible for a given herd, the results of this simulation indicate that proper vaccination can decrease economic losses attributable to abortions caused by T. foetus.

Epidemiology of Tritrichomonas foetus in beef bull populations in Florida

The objectives of this study were to estimate the prevalence of herd and individual bull infection with Tritrichomonas foetus in a survey of beef bulls in the state of Florida and to perform an epidemiological investigation of risk factors for the disease. Bulls were tested for T. foetus colonization by a single preputial scraping and culture. Bull infection prevalence within herds was calculated and relationships with bull, herd factors, and production measurements were determined. The survey included 1984 beef bulls in 59 herds throughout Florida; nine bulls in three small herds (<100 cows) were later excluded from the models. An overall prevalence for T. foetus-infected bulls was 6.0% (within-herd prevalence ranged from 0 to 27%). The herd prevalence was 30.4% (i.e. at least one infected bull); infected bulls were found in 11.1 and 39.5% of herds sampled in North and South Florida, respectively. The likelihood of disease was greatest in larger herds in more extensive management settings (> or = 500 cows, 53.9% prevalence; medium-sized herds of 100-499 cows, 10.0% prevalence). Tritrichomonas foetus infection was associated with several bull factors, including age, breed, herd, and herd management practices (bull-to-cow ratio, bulls per breeding group). Tritrichomonas foetus infection continues to be prevalent in beef herds in Florida that use natural service.

Failure to establish infection with Tetratrichomonas sp. in the reproductive tracts of heifers and bulls

Experimental infection of the reproductive tracts of heifers and bulls with Tetratrichomonas sp. isolated from preputial smegma of virgin bulls was attempted. Nine heifers and four bulls were challenged by inoculation of 7 x 10(6) Tetratrichomonas sp. into the vaginal lumen and preputial cavity, respectively. Vaginal mucus and preputial smegma samples were collected and cultured for Tetratrichomonas sp. Heifers were slaughtered in groups of three at 2, 9 and 21 days after inoculation. Two heifers and two bulls infected with Tritrichomonas foetus and two uninfected heifers were used as controls for the model infection. Tetratrichomonas sp. were only isolated in vaginal mucus of 7/9 inoculated heifers at 6h post-inoculation, and genital secretions taken at slaughter time from vagina, uterus and oviduct were cultural negative. Bulls challenged with Tetratrichomonas sp. remained cultural negative. Since Tetratrichomonas sp. survived only a few hours in the female genitalia and did not survive in the male genitalia after experimental challenge, Tetratrichomonas sp. did not colonize the genital tract. These were likely trichomonads from the digestive tract. Collection of clean samples without fecal contamination from the reproductive tract is proposed as a measure to avoid Tetratrichomonas sp. transitory genital infection.

Experimental amoebic gill disease of Atlantic salmon, Salmo salar L.: further evidence for the primary pathogenic role of Neoparamoeba sp. (Page, 1987)

Amoebic gill disease (AGD) has been attributed to infection by Neoparamoeba sp. The causal mechanisms for AGD lesion development and the primary pathogenic role of Neoparamoeba sp. require elucidation. Three groups of Atlantic salmon were exposed to viable gill isolated amoebae, to sonicated amoebae, or to sea water containing viable amoebae without direct contact with gill epithelia. Fish were removed 8 days post-exposure and the gills assessed histologically for AGD. AGD occurred only when fish were exposed to viable trophozoites. Consequently, in an accompanying experiment, infection was evaluated histologically at 12, 24 and 48 h post-exposure in three groups of salmon, one group being mechanically injured 12 h prior to exposure. A progressive host response and significant increase (P < 0.001) in the numbers of attached amoebae was apparent over the 48-h duration in undamaged hemibranchs in both treatment groups. There were no significant differences to mucous cell populations. Attachment of Neoparamoeba sp. to damaged gill filaments was significantly reduced (P < 0.05) by 48 h post-exposure. These data further confirm and describe the primary pathogenic role of Neoparamoeba sp. and the early host response in AGD. Preliminary evidence suggests that lesions resulting from physical gill damage are not preferentially colonized by Neoparamoeba sp.

Presence of anti-Neoparamoeba sp. antibodies in Tasmanian cultured Atlantic salmon, Salmo salar L

Previous studies have indicated that when Atlantic salmon, Salmo salar L., are exposed to Neoparamoeba sp. the fish produce anti-Neoparamoeba sp. antibodies. It appears unlikely that these antibodies elicit any specific protection against amoebic gill disease (AGD) as fish with demonstrable activities have been affected by AGD. Experiments were conducted on Atlantic salmon cultured throughout Tasmania to assess the natural production of antibodies towards Neoparamoeba sp. Fish were sampled from areas where AGD was prevalent and from areas where there had been no reported cases. An enzyme-linked immunosorbent assay (ELISA) was used to measure anti-Neoparamoeba sp. antibody activities in serum. All fish from sea water had antibody activities greater than the negative control fish, including fish from areas with no reported cases of AGD. Time trial samples indicated that time after transfer to sea water did not appear to be a significant (P > 0.05) factor in antibody activity, however location was (P < 0.05). There was no agreement (corrected kappa value, 0.16) between the ELISA result and the isolation of Neoparamoeba sp. from the gills of the same fish. The results suggest that Atlantic salmon in seawater culture in Tasmania produce anti-Neoparamoeba sp. antibodies regardless of infection history, suggesting the presence of Neoparamoeba sp. in the environment.

Effect of Cryptobia salmositica-induced anorexia on feeding behavior and immune response in juvenile rainbow trout Oncorhynchus mykiss

At 10 degrees C, rainbow trout Oncorhynchus mykiss (n = 13 per group) infected with Cryptobia salmositica Katz, 1951 became anorexic at 3 wk post-infection (w.p.i.), with feed-intake decreasing significantly from 1.33 to 0.94% body weight (b.w.). Anorexia was most severe at 4 w.p.i. (0.80% b.w.), coinciding with peak parasitemia (9.2 x 10(6) parasites ml blood(-1)) and anemia. At 8 w.p.i., fish had recovered their appetite although they still had contained detectable parasites (6.8 x 10(5) parasites ml(-1)) and were anemic (pack cell volume, PCV, of 24.4%). However at 5 degrees C, anorexia occurred at 5 w.p.i. (0.81% b.w.), and was most severe at 7 w.p.i. (0.40% b.w.). At 8 w.p.i. (0.43% b.w.), fish displayed high parasitemia (4.6 x 10(6) parasites ml(-1)) and low PCV (10.8%). Fish at 5 degrees C had lower gastric evacuation (GE) rates (GE48h) than 10 degrees C fish, however there were no differences between infected and naive fish at both temperatures. Before anorexia, there was no significant correlation between mean share of meal (MSM, a measure of how food was partitioned within a group) and coefficient of variation in feeding but this became significant during anorexia (p = 0.02 and p = 0.0002 at 10 and 5 degrees C respectively). Significant correlations were detected between b.w. and MSM before onset of anorexia at 10 degrees C (p = 0.005) and 5 degrees C (p = 0.02); this was maintained at 10 degrees C (p = 0.001) but not at 5 degrees C (p = 0.98). Fish on an anorexic diet (0.93% b.w.) responded well at 10 degrees C to a live C. salmositica vaccine; this could partly be due to constant antigenic stimulation by the live vaccine.

Ichthyobodo necator (Kinetoplastida)--a complex of sibling species

Ichthyobodo necator is a parasitic flagellate that attacks fishes, causing disease problems in freshwater worldwide. Findings of similar flagellates in strictly marine fishes have indicated that ichthyobodiosis may be caused by more than 1 flagellate species. We obtained partial small subunit rDNA (ssu rDNA) sequences of 14 Ichthyobodo isolates originating from fishes in Norway, Japan, Singapore, South Africa and Brazil, and identified 8 strains or species, including 2 species infecting cultured salmon in Norway. An Ichthyobodo species isolated from the skin of Atlantic salmon parr in freshwater is suggested to represent L. necator sensu stricto, while another species, showing particular affinity for the gills, infects salmon in both fresh- and seawater. Atlantic cod is infected with a marine Ichthyobodo species unrelated to those infecting salmonids; 2 cyprinids originating from different parts of the world had related Ichthyobodo strains/species, and 2 isolates from unrelated North and South American fishes were also closely related. The phylogenetic relationships of the Ichthyobodo isolates is described, and the implications of the molecular findings on past and future morphological studies of Ichthyobodo spp. are discussed.

Tritrichomonas foetus: a scanning electron microscopy study of erythrocyte adhesion associated with hemolytic activity

The in vitro hemolytic activity of Tritrichomonas foetus was investigated. The parasite was tested against human erythrocytes of groups A, B, AB, and O, and against erythrocytes of nine adult animals of different species (the rabbit, rat, chicken, cat, dog, swine, horse, bovine, and sheep). The results showed that T. foetus strains (ATCC KV1, K, PAL, 5022, RJ, 90) did not present any hemolytic activity against any human erythrocyte group nor against rabbit, rat, chicken, cat, dog and swine erythrocytes. T. foetus strains, however, lysed horse, bovine, and sheep erythrocytes. No hemolysin released by the parasites could be identified. Hemolysis did not occur with trichomonad culture supernatants, with sonicated extracts of T. foetus, nor with killed organisms. Scanning electron microscopy (SEM) showed that human erythrocytes did not adhere to the trophozoites, in contrast horse erythrocytes adhered to the surface of the parasites and were phagocytosed for up to 90 min. The parasites are able to exert their cytopathic effects through: (a) physical contact established between the two cell surfaces, (b) toxins released from parasites into the interaction media, or (c) the association of both mechanisms. Further studies are necessary to clarify the importance of the hemolytic activity in the biology of T. foetus.

Protozoal and epitheliocystis-like infections in the introduced bluestripe snapper Lutjanus kasmira in Hawaii

The bluestripe snapper, or taape, was introduced into Hawaii in the 1950s and has since become very abundant throughout the archipelago. As part of a health survey of reef fish in Hawaii, we necropsied 120 taape collected from various coastal areas south of Oahu and examined fish histology for extraintestinal organisms. Forty-seven percent of taape were infected with an apicomplexan protozoan compatible with a coccidian. Infection was evident mainly in the spleen and, less commonly, the kidney. Prevalence of this coccidian increased with size of fish, and we saw no significant pathology associated with the organism. Twenty-six percent of taape were also infected with an epitheliocystis-like organism that occurred mainly in the kidney and, less commonly, the spleen. In contrast to the coccidian, fish mounted a notable inflammatory response to the epitheliocystis-like organism, and this inflammation appeared to increase in severity with age. Prevalence of the epitheliocystis-like organism infection increased with age, but infection was not seen in fish greater than 26.5 cm fork length. The high prevalence of coccidial infection in introduced taape prompts the concern that these organisms, along with the epitheliocystis-like organism, have the potential to be transmitted to native reef fish. Given the impact of other introduced microbial organisms on native Hawaiian fauna, there is a clear need to assess whether protozoa and bacteria are endemic to Hawaii, and whether they negatively impact native reef fish that closely associate with taape.

Minor effect of depletion of resident macrophages from peritoneal cavity on resistance of common carp Cyprinus carpio to blood flagellates

Carp Cyprinus carpio macrophages were depleted by intraperitoneal (i.p.) injection of clodronate-liposomes for the in vivo study of the effect of macrophage depletion on the resistance of carp to infection with blood flagellate parasites. Clodronate released inside the cell induces apoptosis of (murine) macrophages. Following i.p. injection of carp with liposomes alone, but not with Trypanoplasma borreli, neutrophilic granulocytes rapidly migrated from the head kidney to the peritoneal cavity. The majority of liposomes in the peritoneal cavity were not taken up by newly arrived neutrophilic granulocytes, however, but by resident macrophages. After 2 i.p. injections of clodronate-liposomes, the percentage of macrophages present in the peritoneal cavity was significantly reduced, as evaluated by flow cytometry. Macrophage-depleted carp that were infected i.p. with T. borreli suffered from high mortality. However, these fish did not show lethal parasitaemia but did show clear bacteraemia. Macrophage-depleted carp that were infected i.p. with Trypanosoma carassii showed a minor increase in parasitaemia. In addition, macrophage-depleted carp, immune to T. borreli as a result of having survived a prior infection, remained immune to i.p. reinfection with T. borreli. Succesful depletion of peritoneal macrophages seemed to have a minor effect on the resistance of carp against blood flagellates. However, carp macrophages are essential as a first line of defence against (bacterial) infection.

Electron microscopic study of Tetratrichomonas didelphidis and its interaction with a prokaryotic cell

Tetratrichomonas didelphidis is a flagellate protozoan found in the intestine of the opossum. The parasite lives in a hostile and stressed environment, where it interacts with microorganisms and can survive under extreme conditions for growth, involving strict anaerobiosis or equilibration with air and abundance or absence of nutrients. The in vitro cultivation of this protozoan depends upon Escherichia coli as a growth-promoting partner. In this study, we used scanning and transmission electron microscopy to observe the phagocytosis of bacteria by the protozoan, confirming the strong association between both cells and the growth dependence of T. didelphidis upon E. coli. After adherence to the protozoan surface, the bacteria induced the appearance of crater-like depressions and the ingested bacteria were intracellularly degraded.

Ultrastructural study of a tetratrichomonad species isolated from prepucial smegma of virgin bulls

We present observations on an unusual tetratrichomonad species isolated from preputial smegma of virgin bulls. Ultrastructural studies were performed using scanning and electron microscopy techniques. This protozoan presents four anterior flagella of unequal length and a recurrent one forming the undulating membrane. It shows one anterior nucleus, a Golgi complex, an axostyle, and a costa. The hydrogenosomes are rather elongated, seen in groups, and presenting different electron densities. Vacuoles of different sizes containing bacteria and material in process of digestion were frequently found. PCR was also used in order to compare the species herein described with other trichomonad species. The amplification products were seen only with primers TFR1 and TFR2 (specific to trichomonads), but not with TFR3 and TFR4 (specific to Tritrichomonas foetus), suggesting that although collected from the genital tract of the bull, this protist was not T. foetus. We propose that the appearance of these tetratrichomonads were probably due to the sodomy practiced among bulls. Concomitant contamination of preputial cavity with feces could explain the presence of the opportunistic organism. The observations presented here show the importance of the correct diagnostic when investigating samples obtained from the urogenital tract of cattle. We also suggest that this flagellate belongs to the species Tetratrichomonas buttreyi.

Cryptobia (Trypanoplasma) salmositica and salmonid cryptobiosis

Salmonid cryptobiosis is caused by Cryptobia (Trypanoplasma) salmositica. The haemoflagellate has been reported from all species of Pacific Oncorhynchus spp. on the west coast of North America. It is normally transmitted by the freshwater leech, Piscicola salmositica, in streams and rivers, and sculpins, Cottus spp., are considered important reservoir hosts. The pathogen can also survive on the body surface of fish because it has a contractile vacuole to osmoregulate when the fish is in fresh water. This allows for direct transmission between fish, especially in aquaculture facilities. The parasite divides rapidly by binary fission in the blood to cause disease, the severity of which is directly related to parasitaemia. Cryptobia salmositica has a mitochondrium and it normally undergoes aerobic respiration; however, if its mitochondrium is damaged it will switch to glycolysis. Its glycolytic enzymes and catalase are contained in glycosomes. Cysteine protease is a metabolic enzyme, and its neutralization inhibits oxygen consumption and multiplication of the parasite. An important virulent factor in cryptobiosis is a secretory metalloprotease. The protective mechanism involves production of complement fixing antibodies, phagocytosis by macrophages, and cell-mediated cytotoxicity. Recovered fish are protected, probably for life as the immunity is non-sterile. Clinical signs of the disease include anaemia, anorexia, splenomegaly, general oedema and abdominal distension with ascites. The metabolism and swimming performance of infected fish are significantly reduced and the bioenergetic cost of the disease is very considerable. Fish are susceptible to hypoxia and their immune system is depressed during acute cryptobiosis. Severity of the disease and mortality rates vary significantly between species and stocks of salmon. Protective strategies include selective breeding of Cryptobia-resistant fish. This is innate resistance to infection and it is controlled by a dominant Mendelian locus. In these fish the parasite is lysed via the alternative pathway of complement activation. In Cryptobia-tolerant fish (infected with the pathogen but which do not suffer from disease) the metalloprotease secreted by the parasite is neutralized by alpha2 macroglobulin. Hence, the production of a transgenic Cryptobia-tolerant salmon is an option. This strategy has the advantage in that human intervention (e.g. vaccination, chemotherapy) is not required once the transgenic fish is produced. Acquired immunity is another option; a single dose of the attenuated live vaccine protects fish for at least 2 years. The protective mechanism in vaccinated fish is similar to that in recovered fish. The trypanocidal drug, isometamidium chloride, is an effective therapeutic and prophylactic agent. It accumulates in the mitochondrium of the parasite and significantly disrupts aerobic respiration by causing lesions in the organelle. Efficacy of the drug is significantly increased after its conjugation to antibodies. This immuno-chemotherapeutic strategy has the advantage in that it will lower the drug dosage and hence side-effects of chemotherapy. It will probably reduce the accumulation of the drug in fish, an important consideration in food fish.