Edwardsiella ictaluri as the Causative Agent of Mortality in Cultured Nile Tilapia

Abstract

Edwardsiella ictaluri was consistently isolated from the spleens, livers, and head kidneys of diseased Nile tilapia Oreochromis niloticus from a farm experiencing mortality events in several culture ponds. We describe the first published outbreak of E. ictaluri–induced edwardsiellosis in Nile tilapia. Pure cultures of the isolated bacteria were characterized both biochemically and molecularly. Biochemical analysis was performed using the API-20E and RapID One systems, and antimicrobial susceptibility was determined by the broth microdilution method. Molecular analysis involved sequencing of the 16S rRNA gene, species-specific real-time polymerase chain reaction (PCR), and PCR-mediated genomic fingerprinting (rep-PCR). Pairwise sequence analysis of the 16S rRNA gene identified the case isolates to be a 100% match to E. ictaluri cultured from channel catfish in the southeastern United States. However, rep-PCR analysis identified the case isolates to be genetically different from representative strains isolated from disease outbreaks in cultured channel catfish in Mississippi. Infectivity challenges (intraperitoneal injection and immersion) demonstrated that a representative E. ictaluri strain isolated from tilapia was pathogenic to naïve tilapia, reproducing clinical signs and mortality, thereby establishing Koch's postulates.

Received August 30, 2011; accepted January 30, 2012     

Diagnosis of tuberculosis due to Mycobacterium bovis in New Zealand red deer (Cervus elaphus) using a composite blood test and antibody assays

A blood test for tuberculosis in deer was developed as an ancillary test to clarify the status of skin test-positive deer, with non-specific sensitisation following exposure to saprophytic mycobacteria. The blood test incorporates the measurement of the relative humoral and cellular immunological responses to Mycobacterium bovis and M. avium antigens to provia composite test with high levels of sensitivity (>95%) and specificity (>98%). The specificity of the test has allowed it to be used in parallel with the skin test to salvage thousands of tuberculosis-free deer with non-specific skin test-positive reactions, while its high sensitivity has consistently identified M. bovis-specific reactivity in tuberculous skin test-positive animals. The rules for establishing the diagnostic parameters for the cellular and antibody assays were developed by retrospective analysis of the laboratory results using blood samples from many thousand tuberculous or disease-free deer. The sensitivity of the blood test was tested in this study using 150 animals with tuberculosis diagnosed by the isolation of M. bovis. It had sensitivity values of 95.7–95.9% in herds with a low (<2.0% ) or a high (>30.0%) incidence of tuberculosis. The test had a specificity of 98.0% when tested on 218 disease-free animals, 118 of which were skin test-positive.

An antibody test was developed to diagnose M. bovis in skin test-negative “anergic” deer from tuberculosis infected herds. When this test was used with deer blood taken 10 days after reading the skin test, it had a sensitivity of 85.3% for 102 M. bovis-positive deer. When used in combination with skin test, the antibody test complemented the skin test to raise the sensitivity of the combined tests to 95.0%) when antibody-positive or skin test-positive tests were used to diagnose tuberculosis. The specificity of the antibody test was 100% when used to evaluate 218 disease-free deer from non-infected herds.     

The nutritional management of gastrointestinal tract disorders in companion animals

Dietary protein, carbohydrates, fats and fibre have marked influences on gastrointestinal tract function and dysfunction. This article reviews the nutritional management of common gastrointestinal disorders in companion animals and introduces some of the current areas of research including probiotics, prebiotics, protein-hydrolysate diets, immunonutrition and dietary fibre.

Nutritional management of oesophageal disease revolves around varying the consistency of the diet and feeding the animal from an elevated container. Provision of bowel rest remains the mainstay of the management of acute gastroenteritis but food-based oral rehydration solutions are a useful adjunct. The recommended diet for chronic small bowel diarrhoea is a highly digestible, hypoallergenic, gluten-free, low-lactose and low-fat diet with modest amounts of fermentable fibre. The use of probiotics in the management of diarrhoea in companion animals has not yet been shown to be beneficial. It is likely that prebiotics will prove more effective than probiotics in the prevention of enteropathogenic infections.

Approximately 50% of cats in New Zealand that suffer from chronic idiopathic vomiting or diarrhoea will respond to a novel-protein-elimination diet and approximately 30% meet the diagnostic criteria for food sensitivity. Growing evidence supports the use of protein-hydrolysate diets in the management of inflammatory bowel disease and further advances in immunonutrition are expected. The dietary management of colitis should include a hypoallergenic diet with a fermentable fibre source.

Manipulation of the diet provides clinicians a powerful therapeutic strategy to be used alone or concurrently with drug therapy in the management of gastrointestinal disorders.     

The ACVD task force on canine atopic dermatitis (XXI): antihistamine pharmacotherapy.

Antihistamines frequently are recommended by veterinary dermatologists for symptomatic treatment of pruritus associated with canine atopic dermatitis (AD), perhaps because of their moderate success in some human patients with AD. A critical review of the literature describing antihistamine use in canine AD reveals that the majority of published, peer-reviewed studies are open, uncontrolled or partially-controlled trials. Such studies vary widely in reported efficacy, from perhaps 0 to 75% of patients, even using the same drug. The few blinded placebo-controlled trials available have failed to confirm efficacy of these drugs to relieve the pruritus of canine AD. Some studies indicate that synergistic effects could occur with concurrent use of essential fatty acid supplements. Consequently, at the time of this writing, there is insufficient evidence to conclude for or against the efficacy of antihistamines for treatment of canine AD. Additional blinded, randomized and controlled trials with larger numbers of patients are necessary to establish which of the antihistamine drugs currently available, if any, are truly efficacious for canine AD. Nevertheless, present clinician consensus suggests that several different antihistamine drugs should be evaluated in sequence, for 7-14 days each, in canine patients with AD.     

Modelling the demographics of the Irish cattle population

In recent years, national authorities have committed very substantial resources to the creation and maintenance of databases capable of recording important animal event data, such as births, deaths and movements. This has primarily been driven by the need to ensure the quality and safety of animal products. However, it can also be used to assist policy makers in decision making. Despite the abundance of animal event data, as yet there is little published information about the use of these data to better understand the demography of cattle populations. This study reports the development of, and outputs from, a demographic model using data routinely collected from the Irish cattle population. The demographic model was based on a series of life tables detailing age-specific probabilities of survival up to a maximum of 17 years. These outputs were used to determine characteristics of the Irish cattle population, including estimated mortality rates, life expectancies and age profiles, and estimated cattle numbers by age and date. Separate life tables were developed for each of the 204 monthly birth cohorts born between January 1989 and December 2005. Within the Irish cattle population, the peak estimated mortality rate occurs at 29–33 months. The estimated life expectancy at birth of cattle in Ireland was 42 months. When the survival rates for all the cohorts within a population are calculated, then it is possible to use these rates as a model for determining future population size and answering cohort specific queries.     

Comparison of femoral and auricular arterial blood pressure monitoring in pigs

Objective To compare arterial blood pressure measurements obtained from the femoral and auricular arteries in anaesthetized pigs. Study design Prospective experimental study. Animals Fifteen female Large White pigs were used weighing 21.3 ± 2.3 kg. Methods The pigs were anaesthetized with tiletamine/zolazepam and xylazine administered intramuscularly, and anaesthesia maintained with isoflurane delivered in oxygen/nitrogen. Arterial oxygen partial pressures were maintained between 11.3 and 13.3 kPa and PaCO₂ between 4.6 and 6.0 kPa. Monitoring included electrocardiogram, capnography and invasive blood pressure. The auricular and femoral arteries were catheterized for continuous systolic (SAP), diastolic (DAP) and mean arterial pressure (MAP) measurements. Measurements were recorded every 15 minutes. Statistical analysis involved a Bland–Altman plot analysis. Results The mean difference ± confidence intervals between the femoral and the auricular arterial diastolic, systolic and mean blood pressure measurements during hypotension were 2 ± 7, 2 ± 5 and 2 ± 5 mmHg respectively. In conditions of normotension mean difference ± confidence intervals, of femoral and auricular arterial blood pressure measurements of diastolic, systolic and mean blood pressure were 4 ± 5, 3 ± 7 and 4 ± 4 mmHg respectively. In conditions of increased arterial blood pressure, mean difference ± confidence intervals, of femoral and auricular arterial blood pressure measurements of diastolic, systolic and mean blood pressure were 4 ± 5, 3 ± 8 and 4 ± 4 mmHg respectively. Conclusion Auricular artery catheterization is easier and quicker to perform. Pressure measurements from the auricular artery compared well with the femoral artery. Clinical relevance We found that auricular arterial blood pressures were similar to femoral arterial values under the conditions of this experiment. We did not test extremes of blood pressure or significant alterations in body temperature.     

Beta glucuronidase activity in skin components of children with cystic fibrosis

As compared to that in normal children a decreased activity of beta gliucuronidase, a lysosomal enzyme associated with mucopolysaccharide metabolism and with salt transport, has been detected in the epidermis and sweat gland tissues of children with cystic fibrosis.     

The frequency of meteorite falls on the Earth

Photographic observations from a network of 60 cameras in western Canada are used to derive the influx rate of meteorites on the earth's surface, the first time instrumental data have been used for this purpose. Forty-three observed events are believed to have dropped between 0.1 and 12 kilograms of meteorites each. The flux values are corrected for a minor latitude effect and agree with earlier estimates near 10 kilograms but vary more slowly with mass. Eight events per year drop at least 1 kilogram of meteorites in an area of 10(6) square kilometers.