Bayesian evaluation of three serological tests for the diagnosis of bovine brucellosis in Bangladesh.

We evaluated the performance of three serological tests - an immunoglobulin G indirect enzyme linked immunosorbent assay (iELISA), a Rose Bengal test and a slow agglutination test (SAT) - for the diagnosis of bovine brucellosis in Bangladesh. Cattle sera (n = 1360) sourced from Mymensingh district (MD) and a Government owned dairy farm (GF) were tested in parallel. We used a Bayesian latent class model that adjusted for the conditional dependence among the three tests and assumed constant diagnostic accuracy of the three tests in both populations. The sensitivity and specificity of the three tests varied from 84.6% to 93.7%, respectively. The true prevalences of bovine brucellosis in MD and the GF were 0.6% and 20.4%, respectively. Parallel interpretation of iELISA and SAT yielded the highest negative predictive values: 99.9% in MD and 99.6% in the GF; whereas serial interpretation of both iELISA and SAT produced the highest positive predictive value (PPV): 99.9% in the GF and also high PPV (98.9%) in MD. We recommend the use of both iELISA and SAT together and serial interpretation for culling and parallel interpretation for import decisions. Removal of brucellosis positive cattle will contribute to the control of brucellosis as a public health risk in Bangladesh.

Dispersal capacity of Haematopota spp. and Stomoxys calcitrans using a mark-release-recapture approach in Belgium.

The dispersion potential of mechanical vectors is an important factor in the dissemination of pathogens. A mark-release-recapture experiment was implemented using two groups (unfed and partially fed) of the Tabanidae (Diptera) (Haematopota spp.) and biting Muscidae (Diptera) (Stomoxys calcitrans) most frequently collected in Belgium in order to evaluate their dispersion potential. In total, 2104 specimens of Haematopota spp. were collected directly from horses and 5396 S. calcitrans were collected in a cattle farm using hand-nets. Some of these insects were partially fed in vitro and all were subsequently coloured. Overall, 67 specimens of S. calcitrans (1.2%) and 17 of Haematopota spp. (0.8%) were recaptured directly on horses. Stomoxys calcitrans flew maximum distances of 150 m and 300 m when partially fed and unfed, respectively. Haematopota spp. travelled maximum distances of 100 m and 200 m when partially fed and unfed, respectively. Segregation measures seem essential in order to reduce the risk for pathogen transmission. A distance of 150 m appears to be the minimum required for segregation to avoid the risk for mechanical transmission, but in areas of higher vector density, this should probably be increased.

Study on seroprevalence and serotyping of foot and mouth disease in Chad.

Foot and mouth disease (FMD) is a highly contagious viral disease that affects all Artiodactyla. Seven immunologically distinct serotypes of FMD virus (FMDV) exist. In Chad, although FMD is included in the list of diseases monitored by the Chadian Animal Disease Surveillance Network (REPIMAT), the epidemiological situation remains unclear. A serological survey was conducted in the cattle population in eight of the nine administrative regions of the country (those regions with the highest cattle densities), to evaluate the prevalence and serotypes of circulating FMDV.A total of 796 sera from randomly selected cattle were analysed at the World Organisation for Animal Health/Food and Agriculture Organization of the United Nations FMD Reference Laboratory at the Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna(IZSLER), in Brescia (Italy). An enzyme-linked immunosorbent assay (ELISA), called 3ABC ELISA, was used to detect antibodies against non-structural proteins (NSPs), as well as a series of six competitive ELISAs to detect and serotype antibodies against the structural proteins of FMDV serotypes O, A, SAT 1, SAT 2, Asia 1 and C. Based on the detection of anti-NSP antibodies, the animal-level seroprevalence was 35.6%(95% confidence interval [CI]: 32.2-38.9) and the herd-level seroprevalence was 62.3% (95%CI: 53.0-71.5). FMD was present in all livestock administrative divisions surveyed, with a higher prevalence in southern regions, which are characterised by higher rainfall and humidity and more important transboundary animal movements. Cattle aged more than four years had a higher seroprevalence, which may be due to repeated exposure. Semi-sedentary farming and transhumance were also risk factors. Antibodies against serotypes A, O, SAT 1 and SAT 2 were detected.

La fièvre aphteuse est une maladie virale extrêmement contagieuse qui affecte l'ensemble des artiodactyles. Sept sérotypes du virus de la fièvre aphteuse ont été répertoriés, qui sont distincts au plan immunologique. Au Tchad, bien que la fièvre aphteuse figure sur la liste des maladies visées par le Réseau d'épidémiosurveillance des maladies animales du Tchad (REPIMAT), la situation épidémiologique demeure mal connue. Une enquête sérologique a été réalisée dans la population bovine de huit régions administratives sur les neuf que compte le pays (afin de couvrir les régions où la densité de la population bovine est la plus élevée), dans le but d'évaluer la prévalence du virus de la fièvre aphteuse et de caractériser les sérotypes présents. Au total, 796 sérums prélevés sur des bovins sélectionnés de manière aléatoire ont été analysés au Laboratoire de référence pour la fièvre aphteuse de l'Organisation mondiale de la santé animale/Organisation des Nations Unies pour l'alimentation et l'agriculture à l'Istituto Zooprofilattico Sperimentale dellaLombardia e dell'Emilia Romagna (IZSLER) de Brescia (Italie). Les anticorps dirigés contre les protéines non structurales ont été détectés au moyen d'une épreuve immuno-enzymatique 3ABC (ELISA 3ABC) tandis qu'une série de six ELISA de compétition a permis de détecter et de caractériser les anticorps spécifiques des protéines structurales des sérotypes O, A, SAT 1, SAT 2, Asia 1 et C du virus de la fièvre aphteuse. D'après les résultats de la détection d'anticorps dirigés contre les protéines non structurales, la prévalence sérologique à l'échelle individuelle était de35,6 % (avec un intervalle de confiance [IC] à 95 % de 32,2 à 38,9) tandis que la prévalence à l'échelle des troupeaux s'élevait à 62,3 % (IC à 95 % de 53,0 à 71,5).La fièvre aphteuse était présente dans chacune des divisions administratives étudiées, avec une prévalence plus élevée dans les régions méridionales, qui se caractérisent par des précipitations et une hygrométrie plus fortes et par l'importance des mouvements transfrontaliers d'animaux. La prévalence sérologique était plus élevée chez les bovins âgés de plus de quatre ans, ce qui s'explique probablement par un nombre répété d'expositions. Le rôle de l'élevage semi-sédentaire et de la transhumance en tant que facteurs de risque a été misen lumière. Les anticorps détectés étaient dirigés contre les sérotypes A, O, SAT 1et SAT 2.

La fiebre aftosa es una patología vírica muy contagiosa que afecta a todos los artiodáctilos. Existen siete serotipos inmunológicamente diferenciados del virus que la causa. En el Chad, aunque la fiebre aftosa figura en la lista de enfermedades sometidas a vigilancia por la Red Chadiana de Vigilancia Zoosanitaria (REPIMAT), la situación epidemiológica de la enfermedad sigue rodeada de incertidumbre. Los autores describen un estudio serológico realizado en la población vacuna de ocho de las nueve regiones administrativas del país (las que presentan la mayor densidad de ganado vacuno) con objeto de determinar la prevalencia y los serotipos del virus de la fiebre aftosa circulante. Tras seleccionar aleatoriamente un total de 796 cabezas de ganado y obtener de ellas muestras de suero, estas fueron analizadas en el Istituto Zooprofilattico Sperimentale della Lombardia e dell'EmiliaRomagna (IZSLER) de Brescia (Italia), que es el Laboratorio de Referencia de la Organización Mundial de Sanidad Animal y la Organización de las Naciones Unidas para la Alimentación y la Agricultura para la fiebre aftosa. Para detectar anticuerpos dirigidos específicamente contra proteínas no estructurales se empleó un ensayo inmunoenzimático (ELISA) denominado ELISA 3ABC, a lo que se agregó una serie de seis técnicas ELISA de competición concebidas para detectar y tipificar anticuerpos dirigidos contra las proteínas estructurales de los serotipos O, A,SAT 1, SAT 2, Asia 1 y C del virus de la fiebre aftosa. A tenor de los niveles detectados de anticuerpos contra proteínas no estructurales, la seroprevalencia individual era de un 35,6% (intervalo de confianza [IC] al 95%:32,2­38,9) y la seroprevalencia de rebaño era de un 62,3% (IC 95%: 53,0­71,5).La fiebre aftosa, presente en todas las divisiones administrativas ganaderas estudiadas, alcanzaba sus máximos niveles de prevalencia en las regiones meridionales, caracterizadas por tasas de pluviosidad y humedad más altas y por un mayor volumen de movimientos transfronterizos de animales. La seroprevalencia era más elevada en los ejemplares de más de cuatro años de edad, hecho que puede deberse a exposiciones reiteradas. La producción ganadera en régimen semisedentario y la trashumancia eran también factores de riesgo. Se detectaron anticuerpos contra los serotipos A, O, SAT 1 y SAT 2.

e-Surveillance in animal health: use and evaluation of mobile tools.

In the last decade, mobile technology offered new opportunities and challenges in animal health surveillance. It began with the use of basic mobile phones and short message service (SMS) for disease reporting, and the development of smartphones and other mobile tools has expanded the possibilities for data collection. These tools assist in the collection of data as well as geo-referenced mapping of diseases, and mapping, visualization and identification of vectors such as ticks. In this article we share our findings about new technologies in the domain of animal health surveillance, based on several projects using a wide range of mobile tools, each with their specific applicability and limitations. For each of the tools used, a comprehensive overview is given about its applicability, limitations, technical requirements, cost and also the perception of the users.The evaluation of the tools clearly shows the importance of selecting the appropriate tool depending on the envisaged data to be collected. Accessibility, visualization and cost related to data collection differ significantly among the tools tested. This paper can thus be seen as a practical guide to the currently available tools.

Estimating the prevalence of infections in vector populations using pools of samples.

Several statistical methods have been proposed for estimating the infection prevalence based on pooled samples, but these methods generally presume the application of perfect diagnostic tests, which in practice do not exist. To optimize prevalence estimation based on pooled samples, currently available and new statistical models were described and compared. Three groups were tested: (a) Frequentist models, (b) Monte Carlo Markov-Chain (MCMC) Bayesian models, and (c) Exact Bayesian Computation (EBC) models. Simulated data allowed the comparison of the models, including testing the performance under complex situations such as imperfect tests with a sensitivity varying according to the pool weight. In addition, all models were applied to data derived from the literature, to demonstrate the influence of the model on real-prevalence estimates. All models were implemented in the freely available R and OpenBUGS software and are presented in Appendix S1. Bayesian models can flexibly take into account the imperfect sensitivity and specificity of the diagnostic test (as well as the influence of pool-related or external variables) and are therefore the method of choice for calculating population prevalence based on pooled samples. However, when using such complex models, very precise information on test characteristics is needed, which may in general not be available.

[Cost estimation of an epidemiological surveillance network for animal diseases in Central Africa: a case study of the Chad network]. / Estimation du coûét d'un réseau d'épidèmiosurveillance des maladies animales en Afrique centrale: le cas du réseau tchadien.

In sub-Saharan Africa, most epidemiological surveillance networks for animal diseases were temporarily funded by foreign aid. It should be possible for national public funds to ensure the sustainability of such decision support tools. Taking the epidemiological surveillance network for animal diseases in Chad (REPIMAT) as an example, this study aims to estimate the network's cost by identifying the various costs and expenditures for each level of intervention. The network cost was estimated on the basis of an analysis of the operational organisation of REPIMAT, additional data collected in surveys and interviews with network field workers and a market price listing for Chad. These costs were then compared with those of other epidemiological surveillance networks in West Africa. The study results indicate that REPIMAT costs account for 3% of the State budget allocated to the Ministry of Livestock. In Chad in general, as in other West African countries, fixed costs outweigh variable costs at every level of intervention. The cost of surveillance principally depends on what is needed for surveillance at the local level (monitoring stations) and at the intermediate level (official livestock sectors and regional livestock delegations) and on the cost of the necessary equipment. In African countries, the cost of surveillance per square kilometre depends on livestock density.

[Detection of processed animal protein: European experience and perspectives]. / Détection des protéines animales transformées: expérience et perspectives européennes.

European Commission Regulation (EC) No. 152/2009 imposes optical microscopy as the reference method for official controls to detect traces of animal protein in animal feed. Since 1 July 2004, the one-solvent technique has been the only authorised variant of optical microscopy. Its detection limit is 0.1% of meat-and-bone meal. Other techniques--using molecular biology (polymerase chain reaction, immunology), microscopy or near-infrared imaging--have been developed in the past ten years to supplement the official method, which has certain limitations. This paper compares and discusses the different techniques, highlighting the strengths of each technique in order to propose a feasible control scheme to improve the sensitivity and specificity of the technique for the detection of processed animal protein in livestock feed.

Escherichia coli O157 prevalence in different cattle farm types and identification of potential risk factors.

Although the prevalence of Escherichia coli O157 on cattle farms has been examined extensively, the relationship between this pathogen and farm type has been established only rarely. A large-scale study was designed to determine the prevalence of E. coli O157 in the Flemish region of Belgium on farms of dairy cattle, beef cattle, mixed dairy and beef cattle, and veal calves. The effect of various factors on the occurrence at the pen level also was evaluated. In 2007, 180 farms were randomly selected based on region, farm size, and number of animals purchased and were examined using the overshoe sampling method. When possible, overshoes used in areas containing animals in three different age categories (< 8 months, 8 to 30 months, and > 30 months) were sampled on each farm. In total, 820 different pens were sampled and analyzed for the presence of E. coli O157 by enrichment, immunomagnetic separation, and plating on selective agar. Presumptive E. coli O157 colonies were identified using a multiplex PCR assay for the presence of the rfb(O157) and fliC(H7) genes. The statistical analysis was carried out with Stata SE/10.0 using a generalized linear regression model with a logit link function and a binomial error distribution. The overall farm prevalence of E. coli O157 was 37.8% (68 of 180 farms). The highest prevalence was found on dairy cattle farms (61.2%, 30 of 49 farms). The prevalences on beef, mixed dairy and beef, and veal calf farms were 22.7% (17 of 75 farms), 44.4% (20 of 45 farms), and 9.1% (1 of 11 farms), respectively. A significant positive correlation between age category and E. coli O157 prevalence was found only on mixed dairy and beef farms and dairy farms. No influence of farm size or introduction of new animals was demonstrated.

Does imidacloprid seed-treated maize have an impact on honey bee mortality?

Beekeepers suspected maize, Zea mays L., treated with imidacloprid to result in substantial loss of honey bee (Hymenoptera: Apidae) colonies in Belgium. The objective of this study was to investigate the potential impact of maize grown from imidacloprid-treated seeds on honey bee mortality. A survey of 16 apiaries was carried out, and all maize fields treated or not with imidacloprid were located within a radius of 3,000 m around the observed apiaries. Samples of honey, beeswax, and bees were collected in three colonies per apiary and analyzed for pesticide contain by liquid chromatography-tandem mass spectrometry and gas chromatography-tandem mass spectrometry. We first found a significant correlation between the number of colonies per apiary and the mortality rates in an apiary. In addition, this mortality rate was inversely correlated with the surface of maize fields treated and not with imidacloprid, suggesting that this pesticide do not interact with bees' fitness. Moreover, a very large number of our samples contained acaricides either prohibited or ineffective against Varroa destructor (Anderson & Trueman) (Acari: Varroidae), suggesting that the treatment methods used by the beekeepers to be inadequate for mite control. Our results support the hypothesis that imidacloprid seed-treated maize has no negative impact on honey bees.

Mixed Giardia duodenalis assemblage A and E infections in calves.

A molecular epidemiological study was conducted on 100 dairy (499 calves) and 50 beef (333 calves) farms in Belgium to estimate the prevalence of different Giardia duodenalis assemblages in calves younger than 10 weeks of age. Positive samples from the epidemiological study and from a previous clinical study were selected and genotyped based on the amplification of the beta-giardin gene. To investigate the occurence of mixed assemblage A and E infections in calves, a novel assemblage-specific PCR was developed based on the triose-phosphate isomerase gene. The prevalence was 22% (95% Probability Interval (PI): 12-34%) in dairy calves and 45% (95% PI: 30-64%) in beef calves. In total, 120 Giardia-positive samples from dairy and beef calves collected in the epidemiological study and from clinically affected calves were identified based on the amplification of the beta-giardin gene. Overall G. duodenalis assemblage E was more prevalent (in 64% of the samples), although the majority (59%) of the dairy calves were infected with G. duodenalis assemblage A. Furthermore, mixed G. duodenalis assemblage A and E infections were identified in 31% of the calf samples (n=101) using the assemblage-specific PCR. We believe this is the first report of mixed infections in calves, and the results of the present study indicate that calves, although mainly infected with the host-specific G. duodenalis assemblage E, are frequently infected with the zoonotic assemblage A, either as a mixed or mono-infection, suggesting that calves might be underestimated as a potential zoonotic reservoir for human infections.

A Bayesian modelling framework to estimate Campylobacter prevalence and culture methods sensitivity: application to a chicken meat survey in Belgium.

AIMS: To estimate the true prevalence of Campylobacter and the diagnostic sensitivity of routine detection methods by applying a Bayesian modelling approach. METHODS AND RESULTS: Results from a Belgium-wide survey of Campylobacter contamination in chicken meat preparations (n = 656 samples) showed that Campylobacter was detected in 24.2% of the samples by enrichment, compared with 41% detected by direct plating. Combining positive results from both methods increased the apparent prevalence to 48.02%. Bayesian model was set up in WinBUGS software, the model estimates Campylobacter prevalence as 60% (95% Credibility interval (CI): 47-82%), and the sensitivity of enrichment culture and direct plating as 41% (95% CI: 31-52%) and 69% (95% CI: 50-85%), respectively. CONCLUSIONS: The parallel use of direct plating and enrichment culture adds value for Campylobacter detection from chicken meat preparations, but the false-negative results from each culture method must be taken into account. SIGNIFICANCE AND IMPACT OF THE STUDY: Monitoring data could be strongly biased by the microbiological techniques used to generate it. To circumvent this bias, we describe an applied Bayesian framework for better interpretation of Campylobacter survey data in view of the imperfect test characteristics of routine culture methods.

A Bayesian evaluation of three diagnostic assays for the detection of Giardia duodenalis in symptomatic and asymptomatic dogs.

A Bayesian approach was used to evaluate three commonly used diagnostic assays for the detection of Giardia duodenalis in dogs: microscopical examination (ME), a commercial immunofluorescence assay (IFA: MerifluorGiardia test) and a commercial immunochromatographic assay (SNAP: Idexx SNAPGiardia test). These assays were evaluated for use in two different settings: in a cross-sectional epidemiological survey in household dogs and in a clinical survey, both conducted in the northern part of Belgium. A total of 272 faecal samples from household dogs and 141 faecal samples from clinically affected dogs were examined using these three diagnostic assays. The Bayesian analysis indicated that all tests were highly specific (specificity above 90%), and that the IFA is more sensitive than SNAP and ME, both in an epidemiological and in a clinical setting. For all three tests, the estimated sensitivity values were higher in the clinical compared to the epidemiological survey, whereas the specificity values were comparable in both studies. The results of the present study indicate that IFA is a highly specific and sensitive technique for the detection of G. duodenalis cysts, both for use in an epidemiological or clinical survey. The SNAP is a specific and fairly sensitive technique for the diagnosis of Giardia in clinically affected dogs. Overall, the ME was found to be a specific diagnostic technique, although lacking sensitivity.

Evaluating the use of packed cell volume as an indicator of trypanosomal infections in cattle in eastern Zambia.

In this study, packed cell volume-values (PCV) are evaluated as indicator of trypanosomiasis infections in cattle. A total of 734 blood samples were collected in 11 different sampling sites in eastern Zambia: 84 calves (< 1 year), 52 young females and 40 young males (between 1 and 3 years), 228 cows, 317 oxen and 13 bulls (> 3 years). All samples were subjected to three diagnostic tests: parasitological examination using the buffy coat method, PCR/RFLP and PCV determination. The results were compared and analysed in a Bayesian model, which allowed the estimation of the infection prevalence and the respective test sensitivities and specificities. The presence of a trypanosomal infection significantly reduced the PCV, independently of the age and sex of the infected animal. The estimated prevalence of trypanosomal infections in the study area was 34% (95% credibility interval: 30-38%). While the specificity of both the parasitological and the PCR/RFLP tests were set to 1, the parasitological diagnosis had a low sensitivity (37%) compared to the PCR/RFLP (96%). When using a cut-off value of 24, the PCV had a high specificity (98%) but a rather low sensitivity (53%) for identifying trypanosomiasis infections. Using 26% as a cut-off increased the sensitivity to 76% without much affecting the specificity (94%). A parallel combination of the parasitological diagnosis and the PCV improved the diagnostic sensitivity (74% and 89% for PCV cut-off values of 24% or 26%, respectively) while specificity remained high (98% and 94% for PCV cut-off values of 24% or 26%, respectively). These results suggest that such a combination could advantageously be used for the diagnosis of cattle trypanosomiasis in the field: it is much more sensitive than parasitological examination alone and it is much cheaper than molecular tests. However, the value of this approach depends largely on the determination of an appropriate cut-off value to consider a sample positive, depending on the required test sensitivities and specificities.

[Epidemiological surveillance networks for animal diseases in French-speaking West and Central Africa]. / Les réseaux d'epidémiosurveillance des maladies animales en Afrique francophone de l'Ouest et du Centre.

One of the objectives of the Pan African Programme for the Control of Epizootics (PACE) was to set up epidemiological surveillance networks in African countries. A survey based on a written questionnaire was conducted to review the technical and institutional organisation of epidemiological surveillance networks in nine French-speaking countries, including five in West Africa (Senegal, Burkina Faso, Côte d'lvoire, Togo and Guinea) and four in Central Africa (Cameroon, Central African Republic, Democratic Republic of Congo and Chad). The survey results showed that there are more similarities than differences among epidemiological surveillance networks. In general, they were found to be technically and institutionally well established. However, the two weaknesses of the majority of networks are the inadequate diagnostic capacity of laboratories and the insufficient operationality of steering committees. Epidemiological surveillance should exclusively be the domain of Veterinary Services and it is crucial for ensuring that any change in the health status of an animal population is detected rapidly. However, the networks' continuing survival after external financing ceases is generally not guaranteed because, in many cases, governments fail to fund them adequately.

The transfer of East Coast fever immunisation to veterinary paraprofessionals in Zambia.

In eastern Zambia, immunisation by 'infection and treatment' is the main method used to control East Coast fever, an acute and lethal cattle disease. This service, which requires a stringent cold chain, used to be free of charge. When a minimal user fee was introduced, attendance dropped drastically. Consequently, this complex immunisation programme was transferred to veterinary paraprofessionals working on their own account, with the aim of boosting a more sustainable distribution of vaccine. Paraprofessionals were provided with a motorbike and the required specific equipment, but fuel and drugs were at their expenses. The paraprofessionals recovered their costs, with a profit margin, by charging the cattle owners for immunisation. The reasons for the successful transfer of immunisation to paraprofessionals (despite the maintenance of a fee) are attributed mainly to the absence of information asymmetry between the paraprofessional and the livestock owner, the appreciable level of effort of the paraprofessionals and the verifiable outcome of the service provided.

Echinococcus multilocularis and Toxocara canis in urban red foxes (Vulpes vulpes) in Brussels, Belgium.

During the last decades, European red foxes (Vulpes vulpes) have been implicated in the transmission of several viral or parasitic pathogenic agents to domestic animals and humans. In urban areas, risks of zoonoses transmission are likely to increase as a result of a higher rate of intra- and inter-species contacts. Foxes occur on 35% of the Brussels-Capital Region area and local densities reach up to 4 family groups per square kilometre. According to the directive 2003/99/ECC, a first survey for the presence in foxes of Echinococcus multilocularis and Toxocara canis was conducted in Brussels from 2001 to 2004. None of 160 foxes were found to be infected with E. multilocularis and 24 of 134 foxes were found to be infected with T. canis. Considering numbers of examined foxes, the sensitivity and the specificity of tests used for diagnosis, the 95% credibility intervals for the true prevalence of E. multilocularis and T. canis were estimated in a Bayesian framework to be 0 to 1.87% (median value of 0%) and 12.7 to 26% (median value of 18.7%), respectively. For T. canis, a significantly higher risk to be a carrier occurs in cubs and a significantly lower risk in adults.

Isolation of a 14 kDa antigen from Taenia solium cyst fluid by HPLC and its evaluation in enzyme linked immunosorbent assay for diagnosis of porcine cysticercosis.

A fraction with a major band of 14kDa was obtained from crude cyst fluid of Taenia solium cysticerci by 2-step chromatography. A first fraction isolated by gel filtration (Sephacryl S-300 high resolution) was purified using an anion exchange column (Mono Q HR 5/5) on high performance liquid chromatography. Evaluation of the analytic sensitivity of this fraction (F3) was carried out in an antibody enzyme linked immunosorbent assay (Ab-ELISA-F3) using serum samples from pigs experimentally infected with different doses of T. solium eggs. The cross-reactivity of F3 was evaluated with serum samples from pigs that were naturally or experimentally infected with Taenia hydatigena, Taenia saginata asiatica, Fasciola hepatica, Trichinella spiralis, Metastrongylus apri, Trypanosoma congolense and Sarcoptes scabiei, and with serum samples of rabbits hyper-immunised with metacestode cyst fluid of T. hydatigena and T. solium. Antibody titres of lightly or heavily infected pigs differed in their kinetics. However, the increase in F3-specific antibodies could not be related to the infection level. Analysis of the specificity of the F3 showed that serum samples of pigs infected with other parasites did not recognise this antigen. Cross-reaction with T. hydatigena occurred in ELISA using cyst fluid as antigen, but the F3 antigen fraction was not recognized by rabbit hyper-immune serum samples to T. hydatigena. Evaluation of the diagnostic sensitivity and specificity of the Ab-ELISA-F3 was done by a non-parametric receiver operating characteristic (ROC) analysis using 66 serum samples from Zambian village pigs. The total number of cysticerci of these pigs was determined by dissection (28 pigs harboured T. solium cysticerci and 38 were negative at dissection). In addition, 58 serum samples from Cameroonian pigs (28 pigs from cysticercosis-free farms and 30 pigs with cysticerci at tongue inspection) were used in a separate ROC analysis. The results from the ROC analysis yielded a low diagnostic value (area under ROC curve=0.48) with the sera from the Zambian pigs while a relatively high diagnostic value was obtained with the sera from Cameroonian pigs (area under ROC curve=0.78). The main factor contributing to a low diagnostic value based on the Zambian serum samples seemed to be the false-positive reactions that were likely caused by the occurrence of transient antibodies in the non-infected animals.

Regulatory issues surrounding the temporary authorisation of animal vaccination in emergency situations: the example of bluetongue in Europe.

A marketing authorisation for a veterinary vaccine is granted after the quality, safety and efficacy of the product have been assessed in accordance with legal standards. The assessment includes complete characterisation and identification of seed material and ingredients, laboratory and host animal safety and efficacy studies, stability studies, and post-licensing monitoring of field performance. This assessment may not be possible during the emergence of a new animal disease, but several mechanisms exist to allow for the availability of products in an emergency animal health situation, e.g. autogenous biologics, conditional licences, experimental and emergency use authorisations, the importation of products in use elsewhere in the world and pre-approved vaccine banks. Using the emergence of bluetongue in northern Europe as an example, the regulatory issues regarding the temporary authorisation of animal vaccination are described. Several conditions must be fulfilled before a temporary authorisation can be granted, e.g. inactivated vaccines should be used in order to exclude reversion to virulence and reassortment between vaccine viruses and/or field strains of the bluetongue virus; decision-making must be supported by scientific evidence and risk analysis; there must be a complete census of the susceptible animals that were vaccinated; vaccination protocols must be adhered to and there must be a scheme allowing for registration, delivery and follow-up of vaccination, and monitoring, analysis and, possibly, adjustment of field use of the vaccination. This temporary authorisation must be replaced by a full authorisation as quickly as possible.

Comparison of the survival on ice of thawed Theileria parva sporozoites of different stocks cryoprotected by glycerol or sucrose.

Stabilates of Theileria parva sporozoites are mostly delivered in liquid nitrogen tanks to the East Coast fever immunization points. Using an in vitro titration model, we assessed the loss of infectivity of several stabilates when they are stored in ice baths for up to 24 h. Comparisons, with respect to rates of loss of infectivity, were made between T. parva stocks (Chitongo and Katete), cryoprotectants (sucrose and glycerol) and method of assessment (in vivo and in vitro techniques). Chitongo and Katete stabilates showed similar loss dynamics. The losses were 1-4% (depending on parasite stock) and 3% per hour of storage for glycerol and sucrose stabilates respectively, and the loss rates were not significantly different. The results suggest that Chitongo stabilates and sucrose cryoprotected suspensions can be delivered on ice as is done for Katete. A graphical relationship of in vitro effective dose at 50% infectivity (ED50) and in vivo protection rate was made. The relationship showed a 35% loss of protection for a relatively low corresponding increase of ED50 from 0.006 to 0.007 tick equivalent.

Red blood cell volume as a predictor of fatal reactions in cattle infected with Theileria parva Katete.

A comparison of mean corpuscular volume (MCV) and packed cell volume (PCV) was made between cattle undergoing lethal and non-lethal reactions following experimental infections with the apicomplexan protozoa, Theileria parva Katete. This work confirmed that anaemia occurs in infected animals. However, the fall in PCV was steeper in lethal reactions compared to non-lethal reactions. Our results show that animals with initially lower MCV values are more prone to fatal reaction, despite having normal PCV profiles. The study also found that small red blood cells are more likely to be infected with T. parva. These findings suggest that animals with a higher proportion of small red blood cells in circulation will be more likely to succumb to T. parva infections. The potential for using MCV as a predictor of the outcome of infection challenge is discussed.