Characterization of susceptibility and carrier status of burbot,Lota lota (L.), to IHNV,IPNV, Flavobacterium psychrophilum,Aeromonas salmonicida and Renibacterium salmoninarum

In this study, susceptibility and potential carrier status of burbot, Lota lota, were assessed for five important fish pathogens. Burbot demonstrated susceptibility and elevated mortality following challenge with infectious haematopoietic necrosis virus (IHNV) by immersion and to Aeromonas salmonicida by intraperitoneal (i.p.) injection. IHNV persisted in fish for at least 28 days, whereas A. salmonicida was not re-isolated beyond 17 days post-challenge. In contrast, burbot appeared refractory to Flavobacterium psychrophilum following intramuscular (i.m.) injection and to infectious pancreatic necrosis virus (IPNV) by immersion. However, i.p injection of IPNV resulted in re-isolation of virus from fish for the duration of the 28 day challenge. Renibacterium salmoninarum appeared to induce an asymptomatic carrier state in burbot following i.p. injection, but overt manifestation of disease was not apparent. Viable bacteria persisted in fish for at least 41 days, and bacterial DNA isolated by diagnostic polymerase chain reaction was detected from burbot kidney tissue 90 days after initial exposure. This study is the first to investigate susceptibility of burbot to selected fish pathogens, and this information will aid in efforts to culture and manage this species.     

Trends in the use of pesticides and pestiside residues on Queensland wool

Objective To determine the amounts of organophosphorous and synthetic pyrethroid residues on Queensland wool sampled between 1995 and 1997, and to study if pesticide use changed during the period.
Design Estimated amounts of residues were obtained from a survey of Queensland wool clips, and information on pesticide use was obtained from a trace-back postal survey of flock managers.
Procedure Trends in amounts of residues over time were assessed using analysis of variance and simple linear regression models, and changes in pesticide use was assessed using x² tests.
Results Significant linear reductions in organophosphorous (P = 0.0012), synthetic pyrethroid (P = 0.0044) and total (P = 0.0002) residues were detected. The proportion of woolgrowers treating for louse infestation (P = 0.0046) treating twice or more (P = 0.0006) and treating more than 4 months after shearing (P = 0.0001) decreased between 1994 and 1997. However, the proportion of growers who treated for blowfly strike (P = 0.0124) and used insect growth regulator pesticides increased (P < 0.0001). The use of handjetting to apply pesticides for blowfly strike control increased and the use of dips decreased (P < 0.0001).
Conclusion Residues of organophosphorous compounds and synthetic pyrethroids reduced in Queensland wool between 1994 and 1997. Although woolgrowers treated for louse infestation less, pesticide use to control blowfly strike increased. The increasing use of insect growth regulators in the industry needs to be monitored.     

Regulation of Corpus Luteum-function in the Bitch

Functional lifespan of the corpus luteum (CL) in non-pregnant dogs exceeds that of pregnant animals and may last for more than 80 days. Prolactin and LH act luteotropic, however, luteolytic mechanisms are poorly understood. Other than in life stock there is no uterine luteolysine and it was postulated that local paracrine/autocrine mechanisms might play a major role. In following this hypothesis the present investigations have clearly demonstrated that up-regulation of prostaglandin synthesis in the CL as indicated by the expression of cyclo-oxygenase II occurs with its formation and not regression, pointing towards a luteotropic rather than luteolytic action. Throughout dioestrus luteal and other cells of the CL express the oestrogen (ERalpha) and progesterone receptor (PR). While ERalpha expression was not cycle-related, PR concentrations were high in the early and late-luteal phase and a regulatory role of both steroids on CL-function is assumed. As in other species also in the dog the immune system seems to participate in the mechanisms regulating CL-function as an increased presence of lymphocytes within the CL could be detected at the beginning [CD4- CD8-, major histocompatibility complex (MHC)II-antigen expressing cells] and during the latter half of dioestrus (CD8- and MHCII-antigen expressing cells). Thus, leucocyte-derived cytokines may be important and the expression of the mRNA for interleukin (IL)8, IL10, IL12, tumour necrosis factor (TNF)alpha and transforming growth factor (TGF) beta1 was observed throughout dioestrus. Electron microscopy confirmed the slow process of luteolysis; first distinct signs of degeneration were seen on day 60, accompanied by some apoptotic events. From these data it is concluded that luteal regression as monitored by the gradual decrease of systemic progesterone concentrations in the dog is not an actively regulated but rather a permissive process. Immune-mediated events may play a key role. Changes in the vascular supply, as indicated by the expression of endoglin, seem to be of lower importance.     

Infection of cattle in Queensland with bluetongue viruses: 1. prevalence of antibodies

SUMMARY A survey of nearly 20 000 cattle in Queensland was conducted to describe the prevalence and distribution of infection by serotypes of bluetongue virus. The overall prevalence of serum antibodies to one or more bluetongue viruses was 8.7% (95% confidence interval 8.3 to 9.1). Sera from cattle contained neutralising activity against 2 serotypes, 1 and 21. No evidence was found of infection with other serotypes previously isolated in Australia. The overall prevalence of serotype 1 antibodies was 7.7% (95% CI 7.3 to 8.0) and the prevalence of serotype 21 antibodies was 3.3% (95% CI 3.1 to 3.6). The prevalence of serotype 1 antibodies was significantly (P < 0.05) higher than that of serotype 21 in every region of the State, except in the central highlands and south-west Queensland. Overall, 3 significantly (P < 0.05) different zones of prevalence were found: high prevalence (> 20%) in far north Queensland, moderate (5 to 20%) in north-west, northern and southern coastal Queensland, and low (< 5%) in the central highlands, Darling Downs and south-west Queensland.