Milk as a diagnostic fluid to monitor viral diseases in dairy cattle

BACKGROUND

Infectious viral diseases in dairy cattle have substantial implications for milk production, quality and overall animal health. Diagnostic tools providing reliable results are crucial for effective disease control at the farm and industry level. Pooled or bulk tank milk (BTM) can be used as a cost-effective aggregate sample to assess herd disease status in dairy farms.

FINDINGS

Detection of pathogens or specific antibodies in milk can be used for monitoring endemic diseases within-farm, region or country-level disease surveillance and to make informed decisions on farm management. The suitability of assays applied to pooled milk samples relies on validation data of fit-for-purpose tests to design an optimal testing strategy. Diverse approaches and variable scope of studies determining test accuracy need to be critically appraised before sourcing the parameters to design sampling strategies and interpreting surveys. Determining if BTM or pooled milk is the best approach for a disease management programme should carefully consider several aspects that will impact the accuracy and interpretation, for example, the size of the lactating herd, the risk of infection in the lactating and non-lactating groups, the expected within-herd prevalence, the duration of infection, the duration and concentration of antibodies in milk and use of vaccination.

CONCLUSIONS

There are examples of tests on BTM samples providing efficient assessments of the herd disease status and supporting disease control programmes for viral diseases. However, challenges arise in pooled milk testing due to the need for accurate estimates of the imperfect sensitivity and specificity of the assays. Integration of new biotechnologies could enhance multiplexing and data interpretation for comprehensive surveillance. The development of highly sensitive assays is necessary to meet the demands of larger dairy herds and improve disease detection and assessment.

Ostreid herpesvirus-1 microvariant surveillance in Pacific oysters (Magallana gigas, Thunberg, 1793) in Australia in 2011

OBJECTIVE

To demonstrate that OsHV-1 microvariant was limited to the known infected areas in New South Wales at the time of the survey in 2011.

DESIGN

A 2-stage survey to demonstrate probability of infection at 2% design prevalence within oyster growing regions and to detect at least one infected region (4% design prevalence) with 95% confidence.

SAMPLE POPULATION

Magallana gigas in nominated oyster growing regions in New South Wales, South Australia and Tasmania as approved by the Aquatic Consultative Committee on Emergency Animal Diseases and documented in a national surveillance plan.

PROCEDURE

Field sampling for active surveillance and laboratory selection of appropriate tissues using methods to minimize potential for cross contamination. Published methods for qPCR and conventional PCR for OsHV-1 microvariant. Stochastic analysis of survey results to demonstrate probability of detection in the areas tested.

RESULTS AND CONCLUSIONS

OsHV-1 microvariant was not detected in a total 4121 samples according to the case definition developed for the survey. However, in NSW a screening qPCR for OsHV-1 detected 13 samples that reacted. These samples were negative at 2 laboratories in the qPCR and conventional PCR assays used in the case definition for the survey. We concluded that oyster production areas of Australia outside the infected area in NSW met the criteria for self-declaration of freedom at the time of the survey in 2011.

CLINICAL RELEVANCE

This activity illustrated achievements in surveillance for an emerging emergency animal pathogen where epidemiological and test validation data were limited, but where data was required to inform the emergency disease response. It also illustrated the challenges faced by investigators in interpreting surveillance results using tests with limited validation. It was guided by and has informed improvements in surveillance and emergency disease preparedness.

The role of tissue type, sampling and nucleic acid purification methodology on the inferred composition of Pacific oyster (Crassostrea gigas) microbiome

AIMS

This study evaluated methods to sample and extract nucleic acids from Pacific oysters to accurately determine the microbiome associated with different tissues.

METHODS AND RESULTS

Samples were collected from haemolymph, gill, gut and adductor muscle, using swabs and homogenates of solid tissues. Nucleic acids were extracted from fresh and frozen samples using three different commercial kits. The bacterial DNA yield varied between methods (P < 0·05) and each tissue harboured a unique microbiota, except for gill and muscle. Higher bacterial DNA yields were obtained by swabbing compared to tissue homogenates and from fresh tissues compared to frozen tissues, without impacting the bacterial community composition estimated by 16S rRNA gene (V1-V3 region) sequencing. Despite the higher bacterial DNA yields with QIAamp® DNA Microbiome Kit, the E.Z.N.A.^® Mollusc DNA Kit identified twice as many operational taxonomic units (OTUs) and eliminated PCR inhibition from gut tissues.

CONCLUSIONS

Sampling and nucleic acid purification substantially affected the quantity and diversity of bacteria identified in Pacific oyster microbiome studies and a fit-for-purpose strategy is recommended.

SIGNIFICANCE AND IMPACT OF THE STUDY

Accurate identification of Pacific oyster microbial diversity is instrumental for understanding the polymicrobial aetiology of Pacific oyster mortality diseases which greatly impact oyster production.

Age dependency of nervous necrosis virus infection in barramundi Lates calcarifer (Bloch)

Age-dependent susceptibility to nervous necrosis virus (NNV) was demonstrated for barramundi (Lates calcarifer). The experiment used juvenile barramundi produced from a single spawning that were challenged consecutively by immersion with a redspotted grouper nervous necrosis virus (RGNNV) isolate. The dose and environmental conditions (35 ppt salinity and 30 °C) were constant. Fish and water were sampled longitudinally for histopathology and RT-qPCR analysis to examine the evolution of the disease, virus replication, immune response and release of virus into water. Viral nervous necrosis (VNN) disease occurred in barramundi challenged at 3 and 4 weeks of age while fish challenged at 5, 7 and 9 weeks of age developed subclinical infection. Replication of NNV occurred faster and the concentration of virus reached higher concentrations in the younger fish with clinical disease. Virus isolation and qPCR tests indicated that infectious NNV was released from carcasses into water when fish were affected with clinical disease but not when NNV infection was subclinical. Based on these observations, we consider that carcasses from clinically infected fish have a potentially important role in the horizontal transmission of NNV, and barramundi juveniles should be protected from exposure to NNV until they are 5 weeks of age and reach the disease resistance threshold.

[Psychosocial prognostic factors for refertilization or IvF after tubal sterilization]

In a psychosomatic study we interviewed 33 women who had undergone tubal anastomosis or IvF after tubal ligation. As a control group we chose a randomised sample of 45 women after elective tubal ligation. We used a semi-structured interview and the Giessen-test as psychometric instruments. According to the leading indication for reanastomosis, we allocated women to one of 2 groups: 21 patients had found a new partner (R-partner), 12 mentioned experiences of loss (R-loss). The groups were well comparable in respect of sociodemographic items, but showed relevant differences in psychological variables, like motivation for and time for deliberation to sterilisation or age difference between partners. Women of the R-partner group were highly satisfied with tubal reanastomosis as compared to R-loss subjects. Satisfaction with the procedure was basically independent of an actual pregnancy. Women experienced the two methods in different, rather specific ways. Cluster analysis of the Giessen-test result confirmed group allocation. We conclude that experiences of loss as a leading reason for tubal reanastomosis are unfavourable prognostic factors. IvF has an unfavourable prognosis in women with the intention to restore the mutilated body image. Preoperative counselling by a psychotherapeutically trained counsellor seems mandatory.

Psychological sequelae of surgical reversal or of IVF after tubal ligation

This study investigates the psychological concomitants and sequelae of surgical reversal (tubal reanastomosis) or of IVF after tubal ligation. We held semi-structured interviews and used the Giessen test and the Strauss-Appelt body image questionnaire. The sample comprised 25 women; a new partner was the leading reason for reversal in 16 cases ('New Partner'), while in 9 cases experiences of loss (of a child or of ideal values) prevailed ('Loss'). The two groups differed in a number of relevant demographic and psychological data. 'New Partner' patients showed a pattern of factors known to be associated with regret of sterilization. 'Loss' women were less satisfied with reversal than 'New Partner' subjects (P < .01). Satisfaction with reversal was independent of an achieved pregnancy. Patients considered surgical reversal to be preferable to IVF because of the "restoration of the mutilation." In the Giessen test, 'New Partner' women were more depressive (P < .05) and more submissive (P < .05) than 'Loss' subjects. Cluster analysis of the whole sample revealed four well distinguishable profiles. 'Loss' patients experienced less insecurity of their body image than both 'New Partner' women and the general female population. We conclude that reversal of sterilization helps to restore body-image and self-esteem, but it may counteract mourning. Consequences for pre-reversal counseling are discussed.

Age-related changes in carotid artery wall properties in men

Changes in distensibility and cross-sectional compliance of the common carotid artery with age were studied in 80 presumed healthy volunteers, varying in age between 20 and 69 y. The distensibility was assessed from the relative increase in arterial diameter during systole normalized with respect to the arterial pulse pressure. The cross-sectional compliance was obtained by multiplying the distensibility by the arterial diameter. The relative diameter changes of the common carotid artery during the cardiac cycle were recorded on-line with a high resolution multigate pulsed Doppler system. The arterial diameter was assessed from the width of the velocity profiles which can also be recorded on-line with this system. Arterial pulse pressure was determined from brachial artery cuff blood pressure measurements. Both distensibility and cross-sectional compliance of the common carotid artery decreased linearly with age, starting in the third age decade. The reduction in the latter parameter was less pronounced, probably as a consequence of an increase in arterial diameter with age.

Flow velocity patterns in and distensibility of the carotid artery bulb in subjects of various ages

Velocity patterns in and distensibility of the carotid artery bulb were studied in younger (20 to 30 years; n = 11) and older (50 to 60 years; n = 9) volunteers without detectable lesions of the cervical carotid arteries by means of a high-resolution, multigate, pulsed Doppler system coupled to a B mode imager. In the bulb the axial velocities were highest on the side of the flow divider, while regions of flow separation and recirculation were observed on the side opposite to this divider. Flow separation and recirculation were less pronounced and less common in the older subjects. Flow separation was not continuously present throughout the cardiac cycle. The distensibility of the carotid arteries was significantly diminished in older subjects, especially in the bulb. The velocity patterns in the carotid artery bulb of younger subjects corroborate the patterns observed in models. The diminished flow separation and recirculation in the older subjects might result from alterations in distensibility at the transition from common to internal carotid artery with increasing age.

Serum HDL/total cholesterol ratio and blood pressure in asymptomatic atherosclerotic lesions of the cervical carotid arteries in men

One hundred neurologically asymptomatic male subjects (aged 50-69 years), randomly selected through population registers, were screened for atherosclerotic lesions of the cervical carotid arteries, using a high resolution multi-gate pulsed Doppler system. In 93 subjects serum was assayed for total and HDL cholesterol. Besides, cuff arterial blood pressure measurements were made. Twenty-three of these subjects (Group III) were classified as abnormal according to the Doppler investigation (degree of narrowing less than 50% in 78% of the cases). Seven of these 23 subjects also had a history of ischemic heart disease or intermittent claudication. Of the 70 subjects with a normal Doppler examination 16 had a history of ischemic heart disease and/or intermittent claudication (Group II). The remaining 54 subjects served as controls (Group I). The frequency of asymptomatic atherosclerotic lesions of the cervical carotid arteries in the population under investigation was 23%. The HDL/total cholesterol ratio was lower and the frequency of high blood pressure higher in the Groups II and III than in Group I. The findings in this study support the idea that a low serum HDL/total cholesterol ratio and high blood pressure have a high degree of association with atherosclerotic lesions of the cervical carotid arteries. This association is already apparent at an early stage of the disease, i.e. in asymptomatic subjects with a slight to moderate degree of carotid artery narrowing.

Methods to evaluate the sample volume of pulsed Doppler systems

The spatial resolution of a pulsed Doppler system heavily depends on both the characteristics of the ultrasound transducer and the processing circuitry. The local characteristics of the ultrasound beam give the lateral sample function while the way the signals are processed affects the axial shape of the sample volume. A simple way to explore the size of the sample volume is the employment of a running string target. However, the detected Doppler signals will be the sum of all the Doppler signals returned by the string along its course through the sample volume. Therefore, it will be complicated to separate the axial and lateral contribution to the actual size of the sample volume. A scanning system capable of visualizing the cross-sectional distribution of the ultrasound intensity allows the assessment of the sample sensitivity in lateral direction. A single vibrating point target enables the exploration of both the axial and lateral sampling function. The latter approach is especially suited to evaluate routinely the spatial performance of pulsed Doppler systems in clinical practice.

Limitations of Doppler spectral broadening in the early detection of carotid artery disease due to the size of the sample volume

In the present study the criteria of spectral broadening used in pulsed Doppler systems to diagnose minor disease in the cervical carotid arteries were evaluated in relation to the size of the sample volume. For this purpose the Doppler audio spectra as recorded in asymptomatic volunteers with an ATL Duplex scanner (relatively large sample volume) and a multi-gate pulsed Doppler system (relatively small sample volume) were compared with each other. The volunteers, randomly selected from the population registers, varied in age from 20-69 yr. Only in the common carotid artery at younger age, were normal spectra recorded, especially with the multi-gate system. In the internal carotid artery the number of spectra, supposed to be associated with low grade stenosis, increased significantly, especially when recorded with the Duplex scanner. More pronounced spectral broadening was found when the spectra were recorded distally in this artery. In the cervical carotid arteries normal spectra were found only when sampled in the middle of the bloodstream. These findings indicate that for the detection of vascular lesions in the cervical carotid arteries at an early stage of the disease on the basis of spectral broadening, small sample volumes and sampling in the centre of the vessel are required.