Congress report on progress in pestivirus virology

Summary

This mini‐review highlights new information on various research aspects presented by specialists from all over the world at the 4th Pestivirus meeting held in Giessen (Germany) from March 15–19, 1999. Especial attention is paid towards differences in humeral and cellular immune response of naive and persistently infected calves with BVDV, and towards BVD eradication programmes m the Scandinavian countries.

The development of techniques for an early diagnosis of CSF in live pigs and the progress on both sub‐unit and MLV marker vaccines against this disease are reported.     

Differences in triglyceride and cholesterol metabolism and resistance to obesity in male and female vitamin D receptor knockout mice

A lean phenotype has been detected in vitamin D receptor (VDR) knockout mice; however, the gender differences in fat metabolism between male and female mice both with age and in response to a high‐fat diet have not been studied before. The objective of our study was to assess changes in body and fat tissue weight, food intake and serum cholesterol and triglyceride in VDR knockout mice from weaning to adulthood and after a challenge of adult animals with a high‐fat diet. Although VDR knockout mice of both sexes consumed more food than wild‐type and heterozygous littermates, their body weight and the weight of fat depots was lower after 6 months on a diet with 5% crude fat content. When adult animals were challenged with a high‐fat diet containing 21% crude fat content for 8 weeks, VDR knockout mice of both sexes had a significantly higher food intake but gained less weight than their wild‐type littermates. Cholesterol levels were higher after 2 days on the high‐fat diet in both sexes, but in the VDR knockout mice, less cholesterol was detected in the serum after 8 weeks. Wild‐type male mice showed signs of fatty liver disease at the end of the experiment, which was not detected in the other groups. In conclusion, lack of the VDR receptor results in reduced fat accumulation with age and when adult mice are fed a high‐fat diet, despite a higher food intake of VDR knockout mice relative to their wild‐type littermates. These effects can be detected in both sexes. Wild‐type male mice react with the highest weight gain and cholesterol levels of all groups and develop fatty liver disease after 8 weeks on a high‐fat diet, while male VDR knockout mice appear to be protected.     

Specific and non‐specific immunity of piglets from sows fed diets containing specific fatty acids in field conditions

The transfer of passive immunity from sows to piglets is important and it is the first immune protection of the new born piglet. Improving sows immunity by adding immuno‐stimulating product in sows diet can positively affect colostrum composition and transfer of immune molecules to piglets. The aim of the current study is to evaluate the benefit of a different solution, made of specific fatty acids from marine origin that have been used in human medicine for decades, for sows and piglets. Two trials were conducted in commercial farm, involving 240 sows at different periods of the year. Sows were divided in a control group, without supplementation, and a test group, supplemented with the feed additive from the 90th day of gestation to weaning. Sows body condition, piglets viability and growth were recorded. Milk immunoglobulin content was measured, as well as Aujeszky antibodies in sows and piglets blood as marker of specific immunity, and blood bactericidal activity, complement activity and lysozyme as markers of non specific immunity. No effect of the product was observed on piglets zootechnical criteria and specific immunity parameters but significant improvement of piglet non specific immunity, was observed. No difference was observed neither in the piglets blood PRRSV and PCV2 antibodies and viruses nor in Aujeszky antibodies. Blood complement activity seems to be an accurate indicator of immuno‐stimulating additive efficiency. Giving alkyl‐glycerol fatty acids to sows in late gestation and lactation can improve the passive immunity transfer to piglets.     

COMPUTED TOMOGRAPHIC FEATURES OF BASIHYOID ECTOPIC THYROID CARCINOMA IN DOGS

Eight dogs with a firm, nonpainful swelling in the ventral laryngeal region and with a final diagnosis of ectopic thyroid carcinoma were investigated by Computed Tomography (CT) at six different institutions. Computed Tomography findings were reviewed, focusing on lesion volume, shape, margins, relationship with surrounding structures and adjacent vessels, attenuation characteristics, and presence of metastases. Ectopic thyroid carcinomas were seen as oval‐to‐bilobed masses centered on the basihyoid bone with associated bone lysis, highly vascularized capsules with central poorly contrast enhancing areas. In all cases there was laryngeal wall infiltration, in two dogs invasion of the laryngeal lumen and in one case invasion of the ventral muscular and subcutaneous plane. Metastases were found in retropharyngeal lymph nodes (three cases) and in the lung (two cases). Ectopic thyroid carcinoma should be considered in the differential diagnosis when a mass in the basihyoid region is present. Described CT features may be typical for ectopic thyroid neoplasia and could be used to help decide the therapeutic plan.     

New method for estimating the volume and volume fractions of the nasal structures in the goose (Anser anser domesticus) using computed tomography images

1. The conchae within the nasal cavity of poultry are important for water and energy conservation, but have not been experimentally evaluated. The aim of the present study was to determine the accuracy of volume and volume fraction estimates of the conchae, nasal septum and nasal cavity.

2. The nasal cavities of 7 adult goose heads were scanned using computed tomography (CT), with images sampled randomly at a 1/5 sampling fraction. Physical sections were obtained from the same samples, using an electric saw that had an adjustable section range, and provided 14 to 15 sections with a thickness of 2.5 mm. The section surface areas of the nasal cavity, nasal septum and conchae were estimated using the Cavalieri principle. Results obtained using the CT and physical section images were compared. Volumes and volume fractions obtained from the physical sections were accepted as the gold standard and differences in the CT images were determined.

3. Multiplication of the data obtained on the CT images with the deviation percentage of the physical sections produced normalised values. No differences were observed between the gold standard data and the CT images. While it was possible to normalise the obtained data using the gold standard values, the raw data could also be used for comparative studies because the deviations from normal would be similar for all groups.

4. Our study showed that the nasal structures could be estimated in vivo using CT images.     

Multiple Induced Spawnings of the Indian Catfish Heteropneustes fossilis (Bloch) within a Prolonged Spawning Season

Abstract Singhi, the Indian catfish Heteropneustes fossilis , attained gonadal maturity repeatedly in a single spawning cycle by photothermal treatment. After the first spawning, maintenance at 30 C and 14 h light/10 h dark for 3 wk induced recruitment of the next batch of mature oocytes for subsequent spawnings. The number of eggs released declined with each spawning. However, fertilizability of the eggs was maintained until the fifth spawning. Mature fish were induced to spawn by D-Lys⁶ salmon gonadotropin-releasing hormone agonist administration. The dose of salmon gonadotropin-releasing hormone agonist for the second and subsequent spawnings was determined to be 25-fold less compared to the dose administered for the first spawning. Fish released the maximum number of eggs upon induction when they were maintained continuously at 30 C and 14 h light/10 h dark for 6 wk. The result obtained in the present study points to a possibility of obtaining multiple spawnings from those species of farmed fish which spawn once a year.     

Clinical and radiographic study of bone and joint lesions in 26 dogs with leishmaniasis

Twenty-six dogs with parasitologically confirmed leishmaniasis and abnormalities of gait were studied to determine the most common radiological patterns of bone and joint lesions. The clinical findings included either lameness, joint pain and crepitation, soft tissue swelling and/or muscle atrophy. Bone lesions were observed radiographically in 12 of the 26 dogs; the radius and ulna were affected in seven, the tibia in six and the femur in six. Joint lesions were observed radiographically in 15 of the 26 dogs; the carpus and stifle were affected in all 15, and the tarsus in nine. There was a tendency for the bones and joints to be affected bilaterally. The radiographic patterns observed were different in the long bones and the joints. In the long bones, the most common pattern was periosteal and intramedullary proliferation, involving the diaphyses and related to the nutrient foramen; in the joints, two patterns, either non-erosive or erosive polyarthritis with soft-tissue swelling, were observed. The changes observed in the synovial fluid were associated in most cases with osteolytic lesions. However, Leishmania organisms were identified in the synovial fluid from joints without bony radiographic changes.     

Susceptibility to homologous reinfection with Fasciola gigantica in goats.

Goats previously infected with 100 viable Fasciola gigantica metacercariae and treated with rafoxanide (Ranide, 7.5 mg/kg) at week 4 were not protected against subsequent homologous challenge with 250 metacercariae administered two weeks later. Reinfection resulted in more severe hepatic lesions and a higher percentage of flukes recovered as compared with primarily infected controls. However, the size of flukes originating from the second (challenge) infection was considerably reduced. The plasma enzyme activity of aspartate amino-transferase (AST), glutamate dehydrogenase (GD) and sorbitol dehydrogenase (SD) increased to a similar extent with primary and challenge infections. However, the plasma antibody response to F. gigantica was less pronounced in reinfected goats.