Antibodies against Dictyocaulus viviparus major sperm protein in bulk tank milk: Association with clinical appearance, herd management and milk production.

The objective of this study was to conduct a comprehensive field survey using a Dictyocaulus viviparus major sperm protein ELISA on bulk tank milk samples from Belgian dairy herds to gain insights in: (1) the sensitivity (Se) and specificity (Sp) of the test under field conditions; (2) the value of the test to predict a future clinical lungworm outbreak; (3) its associations with milk production parameters and (4) its associations with herd management factors. A total of 1248 herds were sampled, with samplings occurring in the middle ("August") and towards the end ("October") of the grazing season. A completed questionnaire on potential risk factors and potentially lungworm-induced clinical signs was obtained from 587 farms and milk production records could be obtained from 343 herds. The median (25th-75th percentile) D. viviparus antibody level (ODR) was 0.25 (0.19-0.31) in "August" and 0.24 (0.19-0.32) in "October". At a threshold of 0.41 ODR, the Se and Sp were estimated using mixture models at 50 and 99%, respectively. At the same threshold, the positive and negative predictive value of the ELISA applied in "August" on the occurrence of farmer-reported lungworm symptoms in the period August-November were 65% and 69%, respectively. D. viviparus antibody levels were significantly higher in the north vs. the south of the country, in large herds and in herds that did not mow pastures or that frequently purchased new animals. An increase in the ELISA result of "August" over the interquartile range was associated with a drop in the annual average milk yield, milk protein% and milk fat% of -0.50kgcow-1day-1, 0.02 and 0.02, respectively. The relationships between the ELISA results in "October" and milk production parameters were also negative, but lower and non- or only marginally significant. We conclude that the bulk tank milk ELISA has a low value to predict lungworm disease on an individual farm based on a fixed sampling date in the middle of the grazing season. On the other hand, the test has been potential to detect subclinical production impacts and study risk factors through epidemiological surveys.

First Results in the Use of Bovine Ear Notch Tag for Bovine Viral Diarrhoea Virus Detection and Genetic Analysis.

BACKGROUND: Infection due to bovine viral diarrhoea virus (BVDV) is endemic in most cattle-producing countries throughout the world. The key elements of a BVDV control programme are biosecurity, elimination of persistently infected animals and surveillance. Bovine viral diarrhoea (BVD) is a notifiable disease in Belgium and an official eradication programme started from January 2015, based on testing ear notches sampled during the official identification and registration of calves at birth. An antigen-capture ELISA test based on the detection of BVDV Erns protein is used. Ear notch sample may also be used to characterize the genotype of the calf when appropriate elution/dilution buffer is added. Both BVDV antigen-ELISA analysis and animal traceability could be performed. METHODOLOGY: With regards to the reference protocol used in the preparation of ear notch samples, alternative procedures were tested in terms of BVDV analytic sensitivity, diagnostic sensitivity and specificity, as well as quality and purity of animal DNA. PRINCIPAL FINDINGS/SIGNIFICANCE: The Allflex DNA Buffer D showed promising results in BVDV diagnosis and genome analyses, opening new perspectives for the livestock industry by the exploitation of the animal genome. Due to the high number of cattle involved in the Belgian official BVDV eradication programme based on ear notch tags sample, a large database on both BVDV status of newborn calves and cattle genome could be created for subsequent different uses (e.g. traceability, determination of parentage, genetic signatures throughout the genome associated with particular traits) evolving through a more integrated animal health.

Single Nucleotide Polymorphism Genotyping and Distribution of Coxiella burnetii Strains from Field Samples in Belgium.

The genotypic characterization of Coxiella burnetii provides useful information about the strains circulating at the farm, region, or country level and may be used to identify the source of infection for animals and humans. The aim of the present study was to investigate the strains of C. burnetii circulating in caprine and bovine Belgian farms using a single nucleotide polymorphism (SNP) technique. Direct genotyping was applied to different samples (bulk tank milk, individual milk, vaginal swab, fetal product, and air sample). Besides the well-known SNP genotypes, unreported ones were found in bovine and caprine samples, increasing the variability of the strains found in the two species in Belgium. Moreover, multiple genotypes were detected contemporarily in caprine farms at different years of sampling and by using different samples. Interestingly, certain SNP genotypes were detected in both bovine and caprine samples, raising the question of interspecies transmission of the pathogen.

Estimation of hepatitis E virus (HEV) pig seroprevalence using ELISA and Western blot and comparison between human and pig HEV sequences in Belgium.

Zoonotic transmission of hepatitis E virus (HEV) is of special concern, particularly in high income countries were waterborne infections are less frequent than in developing countries. High HEV seroprevalences can be found in European pig populations. The aims of this study were to obtain prevalence data on HEV infection in swine in Belgium and to phylogenetically compare Belgian human HEV sequences with those obtained from swine. An ELISA screening prevalence of 73% (95% CI 68.8-77.5) was determined in Belgian pigs and a part of the results were re-evaluated by Western blot (WB). A receiver operating characteristic curve analysis was performed and scenarios varying the ELISA specificity relative to WB were analysed. The seroprevalences estimated by the different scenarios ranged between 69 and 81% and are in agreement with the high exposure of the European pig population to HEV. Pig HEV sequences were genetically compared to those detected in humans in Belgium and a predominance of genotype 3 subtype f was shown in both swine and humans. The high HEV seroprevalence in swine and the close phylogenetic relationships between pig and human HEV sequences further support the risk for zoonotic transmission of HEV between humans and pigs.

Evaluation of the Salmonella surveillance program in Belgian pig farms.

Since July 2007, Belgium has implemented a national surveillance and control program for Salmonella in pigs. Pig farms are designated as Salmonella high risk farms based on serological profiles and are obliged to subsequently take part in a Salmonella specific action plan (SSAP). The SSAP was evaluated and potential risk factors for the persistence of Salmonella on the farm were investigated. First, the Kaplan-Meier method was used in order to study the period during which a farm maintains a Salmonella high risk status. Farms recovered more slowly from their high risk status before the SSAP was implemented compared to after the program was implemented (p<0.001). However, results showed that 29% of the farms were withdrawn from the program possibly only because of sampling error. The program should thus be adapted to accommodate for this. Secondly, the influence of several risk factors (type of farm, season of entrance into the SSAP, size of farm and farm density of the municipality) on the time to withdrawal from the high risk status was evaluated using univariable methods and a Cox multiple regression model for survival data. A statistically significant association was identified between the type of farm and the time to withdrawal from the high risk status. At any point in time after the onset of the SSAP, withdrawals from the high risk status occurred at a 39% and 28% higher rate in mixed (p=0.01) and fattening farms (p=0.05), respectively, compared to closed farms. The risk attributed to closed pig farms is related to the presence of sows in this particular type of structure, which underlines the importance of implementing control measures in this category of animals.

Apparent prevalence of antibodies to Coxiella burnetii (Q fever) in bulk tank milk from dairy herds in southern Belgium.

In 2006, a cross-sectional survey was carried out in 206 herds in southern Belgium to estimate the proportion of herds with Q fever-seropositive bulk tank milk (BTM), i.e. herds with an intra-herd seroprevalence >10%. Of the tested herds, 119 (57.8%; 95% CI: 51.1-64.4%) were seropositive. Most had a low antibody titre. Of these herds, 50 were randomly subjected to a real time Coxiella burnetii PCR analysis. The proportion of herds excreting Coxiella in BTM was 30.0% with only 2.0% of herds having a high level of shedding. An additional questionnaire and logistical regression identified some factors which increased the risk of BTM seroconversion (in heifers, drinking water from watercourse or well water) and some which decreased it (in heifers, tie- and free-stalling, and animals of all age in the same shed; in heifers and cows, shed disinfection).

Q Fever: current state of knowledge and perspectives of research of a neglected zoonosis.

Q fever is an ubiquitous zoonosis caused by an resistant intracellular bacterium, Coxiella burnetii. In certain areas, Q fever can be a severe public health problem, and awareness of the disease must be promoted worldwide. Nevertheless, knowledge of Coxiella burnetii remains limited to this day. Its resistant (intracellular and environmental) and infectious properties have been poorly investigated. Further understanding of the interactions between the infected host and the bacteria is necessary. Domestic ruminants are considered as the main reservoir of bacteria. Infected animals shed highly infectious organisms in milk, feces, urine, vaginal mucus, and, very importantly, birth products. Inhalation is the main route of infection. Frequently asymptomatic in humans and animals, Q fever can cause acute or chronic infections. Financial consequences of infection can be dramatic at herd level. Vaccination with inactive whole-cell bacteria has been performed and proved effective in humans and animals. However, inactive whole-cell vaccines present several defects. Recombinant vaccines have been developed in experimental conditions and have great potential for the future. Q fever is a challenging disease for scientists as significant further investigations are necessary. Great research opportunities are available to reach a better understanding and thus a better prevention and control of the infection.

Q fever in Japan: an update review.

As neglected zoonosis for many years, Q fever is now ubiquitous in Japan. Similarly to elsewhere in the world, domestic animals are considered to be important reservoirs of the causal agent, Coxiella burnetii, a resistant intracellular bacterium. Infected animals shed bacteria in milk, feces, urine, vaginal mucous and birth products. Inhalation of bacteria present in the environment is the main route of animal and human infection. Shedding of C. burnetii in milk by domestic ruminants has a very limited impact as raw milk is seldom ingested by the Japanese population. The clinical expression of Q fever in Japan is similar to its clinical expression elsewhere. However clinical cases in children are more frequently reported in this country. Moreover, C. burnetii is specified as one of the causative organisms of atypical pneumonia in the Japanese Respiratory Society Guideline for the management of community-acquired pneumonia. In Japan, C. burnetii isolates are associated with acute illness and are mainly of moderate to low virulence. Cats are considered a significant source of C. burnetii responsible for human outbreaks in association with the presence of infected parturient cats. Since its recognition as a reportable disease in 1999, 7-46 clinical cases of Q fever have been reported by year. The epidemiology of Q fever in Japan remains to be elucidated and the exact modes of transmission are still unproven. Important further research is necessary to improve knowledge of the disease itself, the endogenous hosts and reservoirs, and the epidemiological cycle of coxiellosis in Japan.

The most likely time and place of introduction of BTV8 into Belgian ruminants.

BACKGROUND: In northern Europe, bluetongue (BT) caused by the BT virus (BTV), serotype 8, was first notified in August 2006 and numerous ruminant herds were affected in 2007 and 2008. However, the origin and the time and place of the original introduction have not yet been determined. METHODS AND PRINCIPAL FINDINGS: Four retrospective epidemiological surveys have been performed to enable determination of the initial spatiotemporal occurrence of this emerging disease in southern Belgium: investigations of the first recorded outbreaks near to the disease epicenter; a large anonymous, random postal survey of cattle herds and sheep flocks; a random historical milk tank survey of samples tested with an indirect ELISA and a follow-up survey of non-specific health indicators. The original introduction of BTV into the region probably occurred during spring 2006 near to the National Park of Hautes Fagnes and Eifel when Culicoides become active. CONCLUSIONS/SIGNIFICANCE: The determination of the most likely time and place of introduction of BTV8 into a country is of paramount importance to enhance awareness and understanding and, to improve modeling of vector-borne emerging infectious diseases.

Bluetongue in Belgium, 2006.

Bluetongue has emerged recently in Belgium. A bluetongue virus strain was isolated and characterized as serotype 8. Two new real-time reverse transcription-quantitative PCRs (RT-qPCRs) that amplified 2 different segments of bluetongue virus detected this exotic strain. These 2 RT-qPCRs detected infection earlier than a competitive ELISA for antibody detection.