Trial design to estimate the effect of vaccination on tuberculosis incidence in badgers

The principal wildlife reservoir of Mycobacterium bovis in Ireland is the European badger. Studies in the Republic of Ireland (RoI) have shown that badgers culled in association with cattle herd tuberculosis breakdowns (focal culling) have a higher prevalence of infection than the badger population at large. This observation is one rationale for the medium term national strategy of focal badger culling. A vaccination strategy for the control of bovine tuberculosis (bTB) in badgers is a preferred long-term option. The Bacillus Calmette-Guérin (BCG) vaccine has been shown to decrease disease severity in captive badgers under controlled conditions. As the vaccine has been tested in a controlled environment with precise information on infection pressure, it cannot be assumed a priori that the effects of vaccination are similar in the wild, where other environmental and/or ecological factors prevail. For this reason we have designed a vaccine field trial to assess the impact of vaccination on the incidence of TB infection in a wild badger population. The selected study area for the vaccine trial (approximately 755 square kilometers) is divided into three zones each of which has similar characteristics in terms of size, number of main badger setts, cattle herds, cattle and land classification type. Three vaccination levels (100%, 50% and 0%) will be allocated to the three zones in a way that a gradient of vaccination coverage North to South is achieved. The middle zone (zone B) will be vaccinated at a 50% coverage but zone A and C will be randomly allocated with 100% or 0% vaccination coverage. Vaccination within zone B will be done randomly at individual badger level. The objective of this paper is to describe the design of a field tuberculosis vaccination trial for badgers, the epidemiological methods that were used to design the trial and the subsequent data analysis. The analysis will enable us to quantify the magnitude of the observed vaccination effect on M. bovis transmission in badgers under field conditions and to improve our knowledge of the biological effects of vaccination on susceptibility and infectiousness.     

Antidiabetic potential of Phyllanthus reticulatus in alloxan-induced diabetic mice

The plant Phyllanthus reticulatus is claimed to have antidiabetic activity in tribal area. To validate the tribal claim, the petroleum ether and ethanolic extracts of leaves of the P. reticulatus were orally tested at 500 and 1000 mg/kg for hypoglycemic effect in alloxan induces diabetic mice. It shows antidiabetic activity at the dose of 1000 mg/kg. The phytochemical screening of the residues revealed the presence of terpenoids glycosides, protein, carbohydrates and absence of alkaloids and steroids.     

Dissociative anaesthesia in free-ranging male koalas and selected marsupials in captivity

Forty seven free-ranging, adult, male koalas were captured and administered an intramuscular injection of the dissociative anaesthetic, Telazol (tiletamine HCl plus zolazepam HCl), at dose rates of 5.0 to 7.7 mg/kg body weight. Anaesthesia induction was rapid and smooth and resulted in a surgical plane of anaesthesia lasting 30 to 45 min. There was no depression of heart rate or respiration. Mild salivation occurred in most animals, but was not a problem because the swallowing reflex was retained. There was no mortality or morbidity and the anaesthesia level was sufficient to allow electroejaculation and multiple blood sampling with no apparent animal discomfort. For 10 of 19 males in which anaesthesia was required for a 90 min protocol, a supplementary Telazol injection (average, 2.5 mg/kg) was necessary. All koalas recovered completely within 3 to 4 h of the initial injection. The results suggest that the optimal Telazol dosage for the adult male koala is 7.0 mg/kg body weight. The retrospective analysis of 259 anaesthesia records involving 14 species indicated that Telazol was equally effective and safe in other captive marsupials.     

Enzymes of oxidant defence system of leucocytes and erythrocytes in bovine anaplasmosis

The glutathione oxidant defence system in leucocytes and erythrocytes of six Anaplasma marginale-infected calves was examined by assaying glutathione peroxidase (GSH-px), glutathione reductase (GSSG-R), reduced glutathione (GSH) and superoxide dismutase (SOD). In addition, GSH-S-transferase and arginase levels were measured in leucocytes. There was a significant decline in the activities of leucocyte GSH-px, GSSG-R and SOD in the post-patent period; whereas arginase activity rose significantly following the patent period of anaplasmosis. The activity of erythrocyte SOD declined in the post-patent stage. The infection also caused a decline in red cell GSH (P less than 0.05). The results suggest that the glutathione oxidant defence system of peripheral blood cells is significantly influenced by the Anaplasma infection.     

Bovine viral diarrhoea virus seroprevalence and vaccination usage in dairy and beef herds in the Republic of Ireland

Background

Bovine viral diarrhoea (BVD) is an infectious disease of cattle with a worldwide distribution. Herd-level prevalence varies among European Union (EU) member states, and prevalence information facilitates decision-making and monitoring of progress in control and eradication programmes. The primary objective of the present study was to address significant knowledge gaps regarding herd BVD seroprevalence (based on pooled sera) and control on Irish farms, including vaccine usage.

Methods

Preliminary validation of an indirect BVD antibody ELISA test (Svanova, Biotech AB, Uppsala, Sweden) using pooled sera was a novel and important aspect of the present study. Serum pools were constructed from serum samples of known seropositivity and pools were analysed using the same test in laboratory replicates. The output from this indirect ELISA was expressed as a percentage positivity (PP) value. Results were used to guide selection of a proposed cut-off (PCO) PP. This indirect ELISA was applied to randomly constructed within-herd serum pools, in a cross-sectional study of a stratified random sample of 1,171 Irish dairy and beef cow herds in 2009, for which vaccination status was determined by telephone survey. The herd-level prevalence of BVD in Ireland (percentage positive herds) was estimated in non-vaccinating herds, where herds were classified positive when herd pool result exceeded PCO PP. Vaccinated herds were excluded because of the potential impact of vaccination on herd classification status. Comparison of herd-level classification was conducted in a subset of 111 non-vaccinating dairy herds using the same ELISA on bulk milk tank (BMT) samples. Associations between possible risk factors (herd size (quartiles)) and herd-level prevalence were determined using chi-squared analysis.

Results

Receiver Operating Characteristics Analysis of replicate results in the preliminary validation study yielded an optimal cut-off PP (Proposed Cut-off percentage positivity - PCO PP) of 7.58%. This PCO PP gave a relative sensitivity (Se) and specificity (Sp) of 98.57% and 100% respectively, relative to the use of the ELISA on individual sera, and was chosen as the optimal cut-off since it resulted in maximization of the prevalence independent Youden’s Index.The herd-level BVD prevalence in non-vaccinating herds was 98.7% (95% CI - 98.3-99.5%) in the cross-sectional study with no significant difference between dairy and beef herds (98.3% vs 98.8%, respectively, p = 0.595).An agreement of 95.4% was found on Kappa analysis of herd serological classification when bulk milk and serum pool results were compared in non-vaccinating herds. 19.2 percent of farmers used BVDV vaccine; 81% of vaccinated herds were dairy. A significant association was found between seroprevalence (quartiles) and herd size (quartiles) (p < 0.01), though no association was found between herd size (quartiles) and herd-level classification based on PCO (p = 0.548).

Conclusions

The results from this study indicate that the true herd-level seroprevalence to Bovine Virus Diarrhoea (BVD) virus in Ireland is approaching 100%. The results of the present study will assist with national policy development, particularly with respect to the national BVD eradication programme which commenced recently.     

A review of Ireland's waterbirds,with emphasis on wintering migrants and reference to H5N1 avian influenza

Ireland is characterised by its diversity and large abundance of wetlands, making it attractive to a wide variety of waterbirds throughout the year. This paper presents an overview of Ireland's waterbirds, including ecological factors relevant to the potential introduction, maintenance, transmission and spread of infectious agents, including the H5N1 avian influenza virus, in Ireland. Particular emphasis is placed on five groups of wintering migrants (dabbling and sieving wildfowl, grazing wildfowl, diving wildfowl, waders and gulls), noting that the H5N1 avian influenza virus has mainly been isolated from this subset of waterbirds. Ireland's wetlands are visited during the spring and summer months by hundreds of thousands of waterbirds which come to breed, predominantly from southern latitudes, and during the autumn and winter by waterbirds which come from a variety of origins (predominantly northern latitudes), and which are widely distributed and often congregate in mixed-species flocks. The distribution, feeding habits and social interactions of the five groups of wintering migrants are considered in detail. Throughout Ireland, there is interaction between different waterbird populations (breeding migrants, the wintering migrants and resident waterbird populations). There is also a regular and complex pattern of movement between feeding and roosting areas, and between wetlands and farmland. These interactions are likely to facilitate the rapid transmission and spread of the H5N1 avian influenza virus, if it were present in Ireland.     

Survival and dispersal of a defined cohort of Irish cattle

An understanding of livestock movement is critical to effective disease prevention, control and prediction. However, livestock movement in Ireland has not yet been quantified. This study has sought to define the survival and dispersal of a defined cohort of cattle born in Co. Kerry during 2000. The cohort was observed for a maximum of four years, from January 1, 2000 to December 31, 2004. Beef and dairy animals moved an average 1.31 and 0.83 times, respectively. At study end, 18.8% of the beef animals remained alive on Irish farms, including 6.7% at the farm-of-birth, compared with 48.6% and 27.7% for dairy animals respectively. Beef animals werae dispersed to all Irish counties, but mainly to Cork, Limerick, Tipperary and Galway. Dairy animals mainly moved to Cork, Limerick, and Tipperary, with less animals going to Galway, Meath and Kilkenny. The four-year survival probability was 0.07 (male beef animals), 0.25 (male dairy), 0.38 (female beef), and 0.72 (female dairy). Although there was considerable dispersal, the number of moves per animal was less than expected.     

Farm management factors associated with bulk tank total bacterial count in Irish dairy herds during 2006/07

Research has shown that total bacterial count (TBC), which is the bacterial growth per ml of milk over a fixed period of time, can be decreased by good hygiene and farm management practices. The objective of the current study was to quantify the associations between herd management factors and bulk tank TBC in Irish spring calving, grass-based dairy herds. The relationship between bulk tank TBC and farm management and infrastructure was examined using data from 400 randomly selected Irish dairy farms where the basal diet was grazed grass. Herd management factors associated with bulk tank TBC were identified using linear models with herd annual total bacterial score (i.e., arithmetic mean of the natural logarithm of bulk tank TBC) included as the dependent variable. All herd management factors were individually analysed in a separate regression model, that included an adjustment for geographical location of the farm. A multiple stepwise regression model was subsequently developed. Median bulk tank TBC for the sample herds was 18,483 cells/ml ranging from 10,441 to 130,458 cells/ml. Results from the multivariate analysis indicated that the following management practices were associated with low TBC; use of heated water in the milking parlour; participation in a milk recording scheme; and tail clipping of cows at a frequency greater than once per year. Increased level of hygiene of the parlour and cubicles were also associated with lower TBC. Herd management factors associated with bulk tank TBC in Irish grazing herds were generally in agreement with most previous studies from confinement systems of milk production.     

A serological survey of bovine babesiosis in northern and eastern Zimbabwe

The geographical distribution of Babesia bovis and Babesia bigemina antibodies in communal herds in northern and eastern Zimbabwe was determined using the ELISA technique. The animals in different herds in the study region had different levels of natural exposure to B. bovis (mean 32%, range 0-79%) and B. bigemina (mean 52%, range 5-92%) infections. The majority of herds (90%) were endemically unstable for B. bigemina and 62% were unstable for B. bovis. Natural region 5 and Manicaland province had the highest seroprevalence of B. bovis infection, while natural region 5 and Masvingo province had the highest seroprevalence of B. bigemina infection.