Biological, serological, and molecular variability suggest three distinct polerovirus species infecting beet or rape

Yellowing diseases of sugar beet can be caused by a range of strains classified as Beet mild yellowing virus (BMYV) or Beet western yellows virus (BWYV), both belonging to the genus Polerovirus of the family Luteoviridae. Host range, genomic, and serological studies have shown that isolates of these viruses can be grouped into three distinct species. Within these species, the coat protein amino acid sequences are highly conserved (more than 90% homology), whereas the P0 sequences (open reading frame, ORF 0) are variable (about 30% homology). Based on these results, we propose a new classification of BMYV and BWYV into three distinct species. Two of these species are presented for the first time and are not yet recognized by the International Committee on Taxonomy of Viruses. The first species, BMYV, infects sugar beet and Capsella bursa-pastoris. The second species, Brassica yellowing virus, does not infect beet, but infects a large number of plants belonging to the genus Brassica within the family Brassicaceae. The third species, Beet chlorosis virus, infects beet and Chenopodium capitatum, but not Capsella bursa-pastoris.     

Acute onset of pulmonary necrotising arteritis in a dog with a left-to-right patent ductus arteriosus

A 12-week-old, clinically normal Chihuahua was referred for investigation for a continuous heart murmur. Cardiac evaluation revealed an anatomically and haemodynamically typical left-to-right shunting patent ductus arteriosus. The continuous wave Doppler measurement of peak ductal jet velocity of 5.6 m/s was suggestive of a normal pulmonary to systemic arterial pressure ratio. The dog returned 16 days later with right heart failure and severe pulmonary hypertension. Marked reduction in left-to-right shunting was demonstrated and the ductal jet velocity had decreased to 2.5 m/s. Immediate ductus ligation, oxygen therapy before and after the operation, and administration of hydralazine failed to reduce pulmonary hypertension, and the dog was euthanased. Histopathological examination of the lung showed pulmonary necrotising arteritis with acute and chronic arterial lesions. Chronic pulmonary vascular changes related to high flow have been associated with altered nitric oxide and endothelin responses. These changes may be responsible for the acute onset of pulmonary hypertension due to relatively minor vascular insults in some human and veterinary patients with left-to-right shunts. The potential for acute progression supports the recommendations for early ductus ligation and the prognostic importance of detecting pulmonary hypertension presurgically in patent ductus arteriosus patients.     

Cytochemical reactions in cells from leukemic dogs

Leukemic cells from 17 dogs with spontaneous leukemia were stained with leukocyte alkaline phosphatase, alpha naphthyl acetate esterase with and without fluoride, peroxidase, and periodic acid-Schiff. Cytochemistry was necessary for identification or confirmation of leukemic cell type in most dogs and resulted in changing the light microscopic morphologic diagnosis in eight of 17 dogs. Leukemic cell types diagnosed were myelomonocytic leukemia in seven dogs, monocytic leukemia in five dogs, lymphocytic leukemia in four dogs, and myelocytic leukemia in one dog.     

Detection of calves persistently infected with bovine pestivirus in a sample of dairy calves in south-eastern Queensland

Objective To determine the proportion and incidence of calves persistently infected with bovine pestivirus in calves (n = 1521) supplied to the Tick Fever Research Centre and to assess the test regime to detect calves persistently infected with bovine pestivirus.
Design Calves, 1 to 6 weeks old, selected for use in the production of the tick fever vaccine were collected from 21 properties in 56 separate groups between October 1990 and December 1996. Each group was examined for the presence of calves persistently infected with bovine pestivirus.
Procedure All calves were routinely tested for antibody to bovine pestivirus and bovine pestivirus antigen using a serum neutralisation test and an antigen-capture ELISA, respectively. Pooled lymphocyte samples from calves were also monitored for bovine pestivirus by inoculation of sheep. Whole herd testing was carried out in eight herds, using a serum neutralisation test as a screen test followed by an antigen-capture ELISA of cattle with a serum neutralisation test titre of less than 32.
Results Fourteen of the 1521 calves tested (0.9%), were detected as persistently infected and the incidence ranged from 0.0 to 3.0 % per year over 6 years. Persistently infected calves were found in 13 of the 59 groups and originated from 7 of the 21 herds used. In whole herd testing on the properties of origin, cattle persistently infected with bovine pestivirus were detected in four of the eight herds tested
Conclusions The proportion of calves persistently infected with bovine pestivirus is similar to that in other countries and indicates that bovine pestivirus could be a significant cause of economic loss in Australian cattle herds. In detecting calves persistently infected with bovine pestivirus, the combination of sheep inoculation, paired antigen-capture ELISA and serum neutralisation tests appeared to be highly sensitive and specific.     

Effect of brucellosis vaccination and dehorning on transmission of bovine leukemia virus in heifers on a California dairy.

Brucellosis vaccination and dehorning were examined for an association with bovine leukemia virus (BLV) infection in heifers on a California dairy between April 1984 and June 1987. Between December 1985 and June 1986, weaned heifers were dehorned using the gouge method at the time of brucellosis vaccination. Using logistic regression, the estimated probability for a nondehorned heifer to seroconvert within three months after brucellosis vaccination (0.08) was significantly less than that for heifers dehorned after a noninfected heifer (0.46) or than that for heifers dehorned after an infected heifer (0.85) (p = 0.039 and p less than 0.001, respectively). To evaluate risk of transmission by brucellosis vaccination, which was usually done within one month postweaning, cumulative proportions of heifers remaining uninfected were computed among heifers that did not seroconvert three months after dehorning. Because results of a Cox model analysis indicated that groups of heifers were 6.6 times more at risk of becoming infected if placed in pens holding gouge-dehorned heifers (where prevalence varied between 50 and 70%) (p less than 0.001) than other groups placed in pens without gouge-dehorned heifers (where prevalence varied between 10 and 30%), cumulative proportions of heifers remaining uninfected were computed for each type of group. The cumulative proportion of heifers remaining uninfected from weaning to first calving was 0.60 for the high prevalence group and 0.96 for the low prevalence group. No change in slope of cumulative proportions was observed before and after one month postweaning, suggesting that brucellosis vaccination was not an effective means of transmission.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growth, Survival, and Feed Conversion Rates of Hatchery-Reared Mutton Snapper Lutjanus analis Cultured in Floating Net Cages

Abstract.— The aquaculture performance of mutton snapper Lutjanus analis raised in floating net cages was assessed by measuring their growth, survival, and feed conversion rates during a growout trial conducted in a 3.2‐ha saltwater lake in the Florida Keys, Florida, USA. Approximately 10,500 hatchery‐reared finger‐lings were stocked in two circular, high‐density polyethylene (HDPE) net cages of 7‐m diameter × 7‐m deep (300 m²) and 10‐m diameter × 7‐m deep (600 m³) dimensions. Cages were stocked at 25 fish/m³ (3.2 kg/m³) and 5 fish/m³ (0.72 kg/m³), respectively. Fish grew from a mean of 16.5 g to 302.8 g (25.6 cm TL) in 246 days in the former cage and from a mean of 42.3 g to 245.6 g (23.8 cm TL) in 178 d in the latter cage. Growth rates in weight were best expressed by the following exponential equations: cage 1 (high stocking density): W = 20.716 e^0.0112x (r²= 0.83); cage 2 (low stocking density): W = 38.848 e^0.0118x (r²= 0.81). Length‐weight data indicate that hatcheryraised, cage‐cultured mutton snapper are heavier per unit length than their wild counterparts. There was no significant difference (P < 0.05) between the slopes of the two lines, indicating that fish in the two cages grew at the same rate. The length‐weight relationships for mutton snapper stocked in cages 1 and 2 are expressed, respectively, by the equations W = 0.000009 L ^3.11 (r²= 0.99) and W = 0.000005 L ^3.22 (r²= 0.97). Overall feed conversion rate for both cages combined was 1.4. Approximately 10% of the fish sampled exhibited some degree of deformity, particularly scoliosis. Overall survival rate was 70%. Results suggest that L. analis has potential for aquaculture development in net cage systems.