Coelioscopic Investigation in European Eels (Anguilla anguilla)

Coelioscopy is a surgical technique in which small incisions are made into the coelomic cavity through which specific instrumentation is inserted to evaluate the internal structures within. For this reason, coelioscopy must be considered a less-invasive surgical method than traditional abdominal surgery. This study was aimed at evaluating and adapting the general coelioscopic principles of the technique to teleosts (10 European eels [Anguilla anguilla]). All the examined fish were anaesthetized with tricaine methanesulfonate solution. The coelioscopic procedures were performed with a rigid, 30° offset, 1.9-mm diameter endoscope connected to a portable video system. The results confirm that coelioscopy represents an imaging technique with high sensitivity in evaluating the coelomic organs in European eels.     

谷氨酰胺对黄颡鱼幼鱼抗氧化能力和非特异性免疫力的影响

本试验旨在研究谷氨酰胺对黄颡鱼幼鱼抗氧化能力及非特异性免疫力的影响。选取平均体重为(2.49±0.04)g的黄颡鱼幼鱼240尾,随机分为4组,每组3个重复,每个重复20尾。4组试验鱼分别饲喂谷氨酰胺添加量为0(对照)、0.1%、0.2%、0.4%的等氮等能试验饲料。试验期为10周。结果表明:饲料中添加0.2%的谷氨酰胺可以显著提高黄颡鱼幼鱼的血清总蛋白、球蛋白、甘油三酯、高密度脂蛋白和低密度脂蛋白含量(P0.05);各组黄颡鱼幼鱼的血清谷丙转氨酶、谷草转氨酶和碱性磷酸酶活性差异不显著(P0.05);饲料中添加0.1%的谷氨酰胺可以显著提高黄颡鱼幼鱼肝脏中过氧化氢酶、谷胱甘肽过氧化物酶及肌肉中超氧化物歧化酶、谷胱甘肽过氧化物酶的活性(P0.05);随着饲料中谷氨酰胺添加量的增加,头肾巨噬细胞的吞噬指数呈升高趋势,且0.2%和0.4%组较对照组显著升高(P0.05),但0.2%和0.4%组间差异不显著(P0.05)。由此可见,饲料中添加0.1%~0.2%的谷氨酰胺能够提高机体的抗氧化能力和非特异性免疫力。     

氨氮胁迫下饥饿与复投喂对黄颡鱼肝脏中脂质代谢相关酶活性及相关基因表达的影响

为了研究氨氮胁迫下饥饿与复投喂对黄颡鱼脂质代谢的影响,将360尾黄颡鱼幼鱼[初始体重为(14.95±0.03)g]随机分配到12个养殖桶中,每桶30尾.对照组人工饱食投喂42 d,试验组饥饿14 d后恢复投喂28 d.对照组和试验组分别被暴露到总氨氮浓度为0(低氨氮处理,正常养殖环境)和5.70 mg/L(高氨氮处理,...     

Caprine aflatoxicosis: experimental disease and clinical pathologic changes

Groups of 8 male crossbreed domestic goats were given 3 dosage levels of aflatoxin B1 [(AFB1) mg/kg of body weight/day] orally: 0.1 for 34 days; 0.2 for 18 days; or 0.4 for 10 days. Clinical condition, feed consumption, and selected blood values were determined. Clinical signs of toxicosis included decreased feed consumption, slight-to-moderate loss of body weight, mucopurulent nasal discharge, dyspnea, coughing, lethargy, icterus, diarrhea (4 goats), and subnormal body temperature 24 to 48 hours before death. Clinicopathologic changes included increases in total RBC count, PCV, hemoglobin concentration, serum bilirubin concentration, and serum activities of aspartate aminotransferase, isocitric dehydrogenase, and ornithine carbamyl transferase. Goats given the 2 smaller dosage levels of AFB1 had slight increases of serum total protein (TP) concentration compared with control goats, but goats given the larger dosage levels of AFB1 initially had a slight decrease in TP. Aflatoxin had little effect on total WBC count. Serum alanine aminotransferase (ALT) activities in goats given the 2 larger dosage levels of AFB1 were similar to those of control goats, but goats given the smallest dosage level of AFB1 had increased serum ALT activities. Aflatoxin did not produce consistent dose-related changes in serum alkaline phosphatase activities. Seemingly, goats are susceptible to aflatoxin. Onset of clinical signs was dose-related. Onset and magnitude of increases in PCV, hemoglobin concentration, serum bilirubin concentration, and activities of serum aspartate aminotransferase, ornithine carbamyl transferase, and isocitric dehydrogenase were dose-related. Changes in TP and activities of serum ALT and alkaline phosphatase were neither dose-related nor were they potentially useful indicators of toxicosis.     

Serum liver enzyme and histopathologic changes in calves with chronic and chronic-delayed Senecio jacobaea toxicosis.

Progressive changes in serum enzyme activity and liver histologic features were monitored in calves fed tansy ragwort (Senecio jacobaea)-contaminated pellets. The experiments were designed to simulate natural intoxicant ingestion conditions in relationship to the dose and duration of exposure to the toxic plant to correlate early laboratory diagnostic changes with the natural progression of the disease, thereby facilitating early diagnosis and intervention by veterinary clinicians. Eight calves were fed tansy ragwort and 4 additional calves served as controls. In group 1, 4 calves were continuously fed dried tansy ragwort mixed in a pelleted feed at a 5% concentration by dry weight until terminal liver disease developed. Serum liver enzyme (alkaline phosphatase, glutamate dehydrogenase, and gamma-glutamyltransferase) activities were monitored at weekly intervals in these calves and in the 2 controls. In group 2, 4 calves were fed the same contaminated feed for only 60 days, with return to normal feed for the duration of the trial. Two additional calves served as controls. Their liver enzyme activities were monitored every other week in conjunction with percutaneous liver biopsies. All 8 calves fed tansy ragwort-contaminated pellets developed terminal hepatopathy in either a chronic pattern (n = 6) or a chronic-delayed pattern (n = 2), with the onset of a moribund state or sudden death at 11 to 17 weeks and 27 to 51 weeks, respectively. The calves were euthanatized when classic terminal signs of hepatic encephalopathy first became evident. The clinicopathologic patterns of chronic and chronic-delayed toxicoses were typical of over 5,000 cases of field tansy toxicosis diagnosed at the diagnostic laboratory. Serum glutamate dehydrogenase was the first enzyme to increase in most animals, with a short-term increase to peak values followed by a rapid return to normal. This enzyme change was followed by increases in alkaline phosphatase and gamma-glutamyltransferase. Serum enzyme changes preceded development of recognizable histologic lesions. Vacuolar changes in hepatocyte nuclei, biliary hyperplasia, and fibrosis sequentially developed in liver biopsy specimens from each animal, whereas megalocytosis was not a predominant feature until necropsy. On the basis of our findings, we suggest that the optimal tests for diagnosis of pyrrolizidine alkaloid intoxication should consist of liver biopsy and determination of concurrent serum liver-enzyme activities.     

Comparison of biopsy samples obtained using standard endoscopic instruments and the harmonic scalpel during laparoscopic and laparoscopic-assisted surgery in normal dogs

Objectives— To compare tissue specimens of canine abdominal organs collected by standard techniques (ST) and harmonic scalpel (HS) and to determine the effect of each technique on wound healing.
Study Design— Experimental.
Animals— Twelve dogs.
Methods— Paired biopsy samples (ST, HS) were collected from liver, spleen, adrenal gland, pancreas, stomach, jejunum, and bladder using laparoscopic or laparoscopic-assisted methods. Hemorrhage at biopsy sites was assessed (present or absent). Specimens were evaluated for diagnostic quality and histologic changes. Dogs were necropsied at 4 or 14 days postoperatively.
Results— HS incision caused less frequent hemorrhage of all organs except spleen. HS specimens had more coagulation necrosis than ST specimens, but both techniques yielded specimens that were sized similarly and were of diagnostic quality. At necropsy, HS biopsy sites of the stomach, jejunum, bladder, adrenal gland, and pancreas were more hyperemic than ST sites. There were more adhesions at jejunal and pancreatic ST biopsy sites. HS biopsy sites had more coagulation necrosis at days 4 and 14 postoperatively. Differences in fibrin deposition, inflammation, and fibrosis were present at biopsy sites of some organs at days 4 or 14 and in comparisons between days 4 and 14.
Conclusions— Diagnostic quality biopsy specimens were obtained with HS and ST. Although HS-induced gross and histologic changes during the first 2 postoperative weeks, no clinical complications were observed.
Clinical Relevance— Both HS and ST can yield specimens with minimal hemorrhage and HS resulted in no apparent postoperative problems in normal dogs. Although HS caused more inflammation and adhesions at biopsy sites of the pancreas, adrenal gland, and jejunum, no clinical complications occurred.     

Survival and prognostic indicators for dogs with intrahepatic portosystemic shunts: 32 cases (1990-2000)

OBJECTIVE: To determine prognostic indicators for short-term outcome and long-term survival for dogs with intrahepatic portosystemic shunts (IPSS). STUDY DESIGN: Retrospective study. ANIMALS: Thirty-two dogs of various breeds. METHODS: Clinical data extracted from medical records of dogs with IPSS were reviewed and included gender, age at surgery, weight, preoperative packed cell volume (PCV), total plasma protein concentration (TP), albumin (ALB), serum activities of alanine aminotransferase (ALT) and alkaline phosphatase (ALP), preprandial and postprandial bile acid concentrations (pre-BA, post-BA), blood urea nitrogen (BUN), glucose concentration, band neutrophils, per-rectal nuclear scintigraphy shunt fraction, whether an angiogram was performed, shunt location at surgery, whether a partial or complete attenuation of the shunt was performed, rectal temperature at the end of surgery, and duration of surgical procedure. Follow-up was determined from visits to the veterinary teaching hospital or by telephone communications with the owner or referring veterinarian. RESULTS: Median survival time was 35.68 months, and 1- and 2-year probabilities of survival were 60% and 55%, respectively. Body weight, TP, ALB, and BUN were identified as prognostic indicators for short-term outcome. PCV and TP were identified as prognostic indicators for long-term survival. CONCLUSIONS: PCV and TP were identified as prognostic indicators for long-term survival, whereas body weight, TP, ALB, and BUN were identified as indicators for short-term outcome in dogs with IPSS. Shunt location at surgery did not have any effect on short-term outcome and long-term survival. CLINICAL RELEVANCE: Total protein, ALB, BUN, and PCV can be used to determine prognosis of dogs with intrahepatic shunt.     

Development and validation of a SYBR green real-time PCR for the quantification of porcine circovirus type 2 in serum, buffy coat, feces, and multiple tissues

The emergence of multiple genotypes of PCV2, as demonstrated by phylogenetic analysis of whole genome or capsid sequences, makes it necessary to have quantitative diagnostic assays that perform equally well on all strains. The objectives of this study were to develop and validate a novel real-time polymerase chain reaction (PCR) assay targeting the highly conserved rep gene (ORF1) and investigate the effects of diagnostic specimen choice on its performance. The assay was tested in naturally infected conventional pigs, experimentally infected gnotobiotic pigs, and plasmid-spiked negative serum, lung tissue, and feces and found to have a linear detection range of 2.2x10(3) to 2.2x10(10) copies of PCV2 per mL. The assay successfully detected and quantified PCV2 DNA in serum, buffy coat, feces, and multiple lymphoid (bronchial, mesenteric, and superficial inguinal lymph nodes; thymus; tonsil; ileal Peyer's patches; and spleen), and non-lymphoid (myocardium; lung; kidney; liver; and gluteal muscle) tissues from naturally infected pigs. Across all tissues and sera of naturally infected pigs, the mean PCV2 concentration was 3.0logs higher in wasting versus non-wasting pigs. PCV2 concentration measured by tissue culture and immunohistochemical staining in homogenized liver samples of experimentally infected gnotobiotic pigs were compared to the concentrations estimated by quantitative PCR. Similar trends were noted with increasing PCV2 concentration detected in subclinically infected to severely PMWS-affected pigs across all assays. Our diagnostic assay was developed with a conserved target sequence, and performed efficiently in quantification of PCV2 in a variety of tissues from naturally and experimentally infected pigs.     

Milk transfer of pyrrolizidine alkoloids in cattle.

A study was conducted to determine if pyrrolizidine alkaloids from Senecio jacobaea (tansy ragwort) are passed into milk of lactating cows. Four cows were given dried tansy ragwort via rumen cannula at a dosage of 10 g/kg/day for 2 weeks. Chemical assay of pyrrolizidine alkaloid content in the dried plants averaged 0.16% by weight. By use of thin-layer chromatography, 5 alkaloids were isolated from the plant materials. The only alkaloid isolated from the milk was jacoline. Condition of the cows and nursing calves was monitored via measurement of blood leukocyte count, and serum protein, albumin, and globulin content. Sorbitol dehydrogenase values and liver biopsy specimens were used to assess liver function. In the cows, marked changes were observed in blood leukocyte count, sorbitol dehydrogenase values, and liver biopsy findings. No changes of any type were observed in the calves. Pyrrolizidine alkaloid content of the milk ranged from 9.4 to 16.7 mug/100 ml of milk.     

Complications of exploratory coeliotomy in 70 cats

Records of all cats that had undergone exploratory coeliotomy at the University of Edinburgh during the period November 1995 to July 2002 were reviewed. Seventy records were retrieved. There were 30 cats in which infection or inflammatory disorders predominated, 17 cats with neoplasia, three cats with trauma and 20 cats with other disorders. Exploratory coeliotomy was performed for diagnostic purposes in 28 cats (40 per cent), treatment in 34 cats (49 per cent) and for diagnosis and treatment in eight cats (11 per cent). Methods of intraoperative diagnosis included incisional biopsy of abdominal organs (52 cats), cytology (two cats), microbiology (17 cats) and gross appearance (17 cats). Fifty-eight cats (83 per cent) survived the hospitalisation period. Complications occurred in 18 cats (26 per cent) and were related to anaesthesia (four cats), the underlying disease process (15 cats), surgery (five cats) and were undetermined in one cat.     

Prognostic Indicators Of Survival In High-Risk Canine Surgery Patients

Canine high-risk surgical patients were identified, and the variables that distinguished between survivors and nonsurvivors were determined. Fifty-two nonsurvivors and 176 survivors were randomly drawn from a population of 615 dogs undergoing general surgical procedures and entering the intensive care unit. Forty-two variables were examined to determine which variables were significantly different between nonsurvivors and survivors. Properative variables that were significantly different were age, hospital days prior to surgery, the number of concurrent diseases, American Society of Anesthesiologists (ASA) status, PCV, TP, platelet count, albumin concentration, alkaline phosphatase activity, bilirubin concentration, and surgery site (laparotomy = highest risk). Age, PCV, TP, platelet count, albumin concentration, alkaline phosphatase activity, and bilirubin concentration were then examined, using stepwise logistic regression for their ability to predict mortality in a separate population of 169 canine patients undergoing laparotomy. Age, TP, and platelet count were identified as predictive variables.     

Biochemical evaluation of mitochondrial respiratory chain enzymes in canine skeletal muscle

OBJECTIVE: To perform respiratory chain enzymatic activity assays on canine skeletal muscle biopsy specimens and establish reference range values of skeletal muscle enzyme activities for dogs. SAMPLE POPULATION: Biopsy specimens from the vastus lateralis muscle were obtained from 24 dogs (8 sexually intact males and 14 sexually intact females) ranging from 15 months to 6 years of age. PROCEDURE: Mean values of citrate synthase, cytochrome-c oxidase, succinate dehydrogenase, succinate dehydrogenase-cytochrome-c reductase, nicotinamide adenine dinucleotide (NADH) dehydrogenase, and NADH dehydrogenase-cytochrome-c reductase activities were established by use of 6 standard spectrophotometric assays for respiratory chain enzyme analysis. RESULTS: Compared with published data for skeletal muscle enzyme activities in humans, skeletal muscle enzyme activities in dogs were 2- to 4-fold higher. Additionally, citrate synthase activity, a marker for mitochondrial volume, was positively correlated with age in dogs, suggesting that mitochondrial volume increases with age, although no apparent change in respiratory chain enzymatic activity with an increase in age was found. CONCLUSIONS AND CLINICAL RELEVANCE: Reference range values for skeletal muscle enzyme activities of dogs are needed to accurately interpret results of respiratory chain enzymatic activity assays. During investigation of metabolic myopathies, if skeletal muscle biopsy specimens are evaluated for respiratory chain enzyme kinetics, they should be performed and evaluated in concert with skeletal muscle biopsy specimens from clinically normal animals of the same species.     

Comparison of liver cytology and biopsy diagnoses in dogs and cats: 56 cases

Abstract: The results of liver cytology and corresponding biopsy specimens submitted to the Pathology Department at Angell Memorial Animal Hospital during 1998 were retrospectively reviewed to objectively assess the diagnostic value of liver cytology. A "corresponding" biopsy was defined as a biopsy specimen obtained within 1 day of the cytology specimen. Fifty-six cases were reviewed, including 25 from dogs and 31 from cats. Results were in complete agreement in 34 cases, in partial agreement in 11 cases, and in disagreement in 11 cases. Agreement occurred most often in cases of fatty change (10 cases) and neoplasia (7 cases of lymphoma and 3 cases of epithelial tumor). Disagreement was most common in cases of hepatitis (6 cases) in which inflammation was not seen in cytologic specimens. Other causes for disagreement included fibrosis (2 cases), and 1 case each of amyloidosis, hemangiosarcoma, and lymphoma. Three cytologic specimens were considered suggestive of hepatitis because of leukocytosis in the background, although clinicians were advised to compare cytologic observation to CBC results. Cytologic evaluation of the liver was useful for determining disease processes, especially when disease distribution was diffuse.     

Usefulness of Ki-67 proliferation marker in the cytologic identification of liver tumors in dogs

BACKGROUND: Performing a biopsy is currently the best method of diagnosing liver disease. To reduce possible risk factors resulting from a biopsy, liver cytology can provide an alternative technique. The diagnostic accuracy of cytology for identifying liver tumors is, however, limited. The results of cytology might be improved by using immunochemistry for Ki-67, a proliferation marker, on liver cytology specimens. OBJECTIVES: The purpose of this study was to investigate the value of Ki-67 immunochemistry on liver cytologic specimens from dogs for identifying neoplastic diseases of the liver, by comparing the results to histologic findings. METHODS: Liver biopsy and cytology samples were obtained from 30 dogs with hepatic disease. All samples were evaluated by an anatomic pathologist and a cytopathologist. Parallel Ki-67 immunochemistry of histologic and cytologic samples was performed. The gradation of Ki-67 expression in histologic and cytologic samples was assessed. RESULTS: Cytologic specimens of liver tumors (n = 9) showed <50% Ki-67-positive cells. Twenty of 21 cases of non-neoplastic liver disease had no or few single Ki-67-positive cells. Using Ki-67, the diagnostic accuracy of cytologic evaluation was increased from 78% to 100% for malignant neoplasia. CONCLUSIONS: Based on the results of this study, the cytologic evaluation of liver together with Ki-67 immunochemistry can improve the diagnostic accuracy of cytology for liver neoplasia.     

Surgical removal of an ovarian tumour in a koi carp (Cyprinus carpio)

Ultrasonography, radiography and exploratory coeliotomy were used to diagnose and treat a large intracoelomic neoplasm from a female koi carp (Cyprinus carpio) presented for abdominal enlargement of several months duration. Feed was withheld for 1 week immediately prior to surgery and the fish was sedated with isoeugenol (AQUI-S) at a dose rate of 10 mL/L to facilitate diagnostic imaging techniques. Surgical anaesthesia was induced by adding tricaine (MS-222) 50 mg/L to the water and an exploratory coeliotomy and tumour removal was performed. The fish was allowed to recover in fresh water at 18 degrees C and salt was added slowly to the water over a period of 1 hour to a concentration of 5 g/L This concentration was maintained in a recovery pond for 1 week postoperatively. Enrofloxacin was administered intramuscularly (10 mg/kg) immediately, 3 days and 1 week postoperatively. A diagnosis of undifferentiated ovarian carcinoma was made on the basis of the histological appearance of the neoplasm and immunohistochemical staining.     

Evaluation of ornithine carbamoyl transferase and other serum and liver-derived analytes in diagnosis of fatty liver and postsurgical outcome of left-displaced abomasum in dairy cows

OBJECTIVE: To evaluate postsurgical outcome in dairy cows with left-displaced abomasum (LDA) with regard to severity of fatty liver and assess the usefulness of preoperative determination of serum ornithine carbamoyl transferase (OCT) activity, bile acids concentration, and other variables for evaluating liver function during the postsurgical convalescence period. DESIGN: Prospective study. ANIMALS: 68 Holstein cows. PROCEDURES: Blood and liver biopsy specimens were obtained during standing LDA surgery. Liver tissue was examined histologically and classified by severity of fatty change. Serum activities of liver-derived enzymes and concentrations of total lipids, triglycerides, bile acids, glucose, beta-hydroxybutyric acid, bilirubin, and nonesterified fatty acids were determined. RESULTS: Most cows with LDA and cows with severe fatty liver were detected within the first month after calving. Postsurgical outcome was related to severity of fatty liver. All cows that died had severe fatty liver. Serum activities of OCT, aspartate aminotransferase, and glutamate dehydrogenase and serum total bilirubin concentration were sensitive indicators of fatty liver. Serum bile acids concentration was not an accurate indicator of fatty liver. CONCLUSIONS AND CLINICAL RELEVANCE: Postsurgical outcome of cows undergoing surgery to correct LDA was related to fatty liver severity. Assessment of serum activities of OCT, aspartate aminotransferase, and glutamate dehydrogenase and serum total bilirubin concentration is recommended for diagnosis of fatty liver in dairy cows with LDA, whereas determination of bile acids concentration is not. The strong correlation between OCT activity and degree of hepatocellular damage supports use of this enzyme for assessing severity of fatty liver and predicting postsurgical outcome in cows with LDA.     

Genital neoplasms treated by en bloc resection and penile retroversion in horses: 10 cases (1977-1986)

The medical records of 10 horses with invasive neoplasms of the penis, prepuce, and/or superficial inguinal lymph nodes in which treatment involved en bloc resection and penile retroversion were reviewed. All were geldings and ranged in age from 12 to 25 years (mean, 19 years). Evaluation of biopsy specimens obtained before surgery confirmed lymphosarcoma in 1 horse and squamous cell carcinoma in 9 horses. Typical history included swelling, ulceration, and abscessation of the penis and prepuce and large superficial inguinal lymph nodes. Complications after surgery included dehiscence of the urethrostomy site (4 horses), dehiscence of the ventral skin incision (1 horse), urine scalding of 1 hind limb (1 horse), cystitis (1 horse), severe hemorrhage (1 horse), and diarrhea (1 horse). One horse was euthanatized during hospitalization, because of severe dehydration secondary to diarrhea. At necropsy, firm nodules were scattered in the pulmonary parenchyma, myocardium, thyroid gland, parathyroid glands, cranial mediastinum, kidneys, and hilar lymph nodes. Microscopic examination of the nodules revealed undifferentiated carcinoma. Nine horses were discharged from the hospital between 1 and 5 weeks after surgery. The mean follow-up interval was 27 months (range, 6 to 96 months). Eight horses had no evidence of recurrence. One horse had recurrence of neoplasm at 6 months and was euthanatized 12 months later.     

The Effect of Extended Preoperative Fasting in Mares Undergoing Surgery of the Perineal Region

Horses with third-degree perineal lacerations require surgical treatment. To reduce the risk of postoperative dehiscence of the surgical site caused by tension, bacterial contamination, and mechanical abrasion, a preoperative and postoperative fasting up to 14 days was performed. A complete blood cell count, concentrations of electrolytes, urea, creatinine, glucose, lactate, cholesterol, triglycerides, total protein, and the activities of aspartate aminotransferase, glutamate dehydrogenase, γ-glutamyl transferase, creatine kinase, and alkaline phosphatase were determined. Fasting resulted in a marked decrease in intestinal motility and an increase in the concentrations of triglycerides and cholesterol. The activity of the glutamate dehydrogenase increased three-fold during the presurgical period. The other biochemical values showed few fluctuations. Based on these data, we concluded that presurgical and postsurgical fasting causes no severe imbalances in the metabolism in mares.     

Successful wound healing over exposed metal implants using vacuum‐assisted wound closure in a dog

An eight‐month‐old Labrador retriever was presented with a grade IIIb open shearing injury of the left tarsus. Acute severe surgical site infection developed 2 days after pan‐tarsal arthrodesis, resulting in wound dehiscence. Vacuum‐assisted wound therapy was carried out for 12 days to treat an extensive full‐thickness soft tissue defect with exposure of metal implants. New granulation tissue formation covering most of the defect was achieved by day 10 of this therapy. Epithelialization was achieved by second intention healing with open wound management. To the authors’ knowledge, this is the first veterinary clinical case report documenting complete healing over exposed metal implants without any requirement for surgical revision.     

Parasitism by protozoan Ichthyophthirius multifiliis enhanced invasion of Aeromonas hydrophila in tissues of channel catfish

Protozoan Ichthyophthirius multifiliis Fouquet (Ich) and bacterium Aeromonas hydrophila are two common pathogens of cultured fish, which cause high fish mortality. Currently there is no information available for the effect of parasitism by Ich on survival of channel catfish and invasion of A. hydrophila in fish tissues following exposure to A. hydrophila. A trial was conducted in this study to: (1) determine whether A. hydrophila increased fish mortality in Ich-parasitized channel catfish; and (2) compare the bacterial quantity in different tissues between non-parasitized and Ich-parasitized catfish by real-time polymerase chain reaction (qPCR). The results demonstrated that the Ich-parasitized catfish showed significantly (P<0.05) higher mortality (80%) when exposed to A. hydrophila by immersion than non-parasitized fish (22%). Low mortality was observed in catfish exposed to Ich alone (35%) or A. hydrophila alone (22%). A. hydrophila in fish tissues were quantified by qPCR using a pair of gene-specific primers and reported as genome equivalents per mg of tissue (GEs/mg). Skin, gill, kidney, liver and spleen in Ich-parasitized fish showed significantly higher load of A. hydrophila (9400-188,300 GEs/mg) than non-parasitized fish (4700-42,100 GEs/mg) after exposure to A. hydrophila. This study provides evidence that parasite infections enhance bacterial invasion and cause high fish mortality.