Eliciting preferences for attributes of Newcastle disease vaccination programmes for village poultry in Ethiopia

Newcastle disease (NCD) is an important disease of poultry, directly affecting the livelihoods of poor farmers across developing countries. Research has identified promising innovations in NCD vaccine development and field trials among village poultry have been promising. However, NCD vaccination is not currently part of village poultry extension programmes in many developing countries. Understanding the preferences for, and relative importance of, different attributes of potential vaccination programmes to prevent NCD will be crucial in designing acceptable and sustainable prevention programmes. This research employed the discrete choice experiment approach to elicit farmers’ preference for attributes of NCD vaccination programmes for village poultry in rural Ethiopia. The choice experiment survey was conducted on 450 smallholder farmers. The relative importance of attributes of NCD vaccines to farmers was estimated using a random parameter logit regression model. The preferred NCD vaccine programme had greater bird-level protection (i.e. greater capacity to reduce mortality should NCD occur in a flock), was delivered by animal health development agents, and could be administered via drinking water. Results from simulations on changes in attribute levels revealed that bird-level protection capacity and delivery of vaccine by animal heath extension affect farmers’ preferences more than other attributes. These findings suggest that it is important to ensure NCD vaccine programmes offer reasonable capacity to protect against mortality. It also suggests the need to understand farmers’ preferred vaccine delivery mechanisms and route of vaccine administration for a wider acceptance of vaccine

Validation of the ¹³C-octanoic acid breath test for measurement of equine gastric emptying rate of solids using radioscintigraphy

Reasons for performing study: Disordered gastric motility may be a significant factor in the pathogenesis of many equine conditions. Although tests for liquid phase emptying rate have been validated in the horse, there are no effective tests for solid phase emptying measurement that can be performed routinely in the field. Objectives: The objective of this study was the assessment of a novel stable isotope technique, the <sup>13</sup>C-octane acid breath test (<sup>13</sup> C-OABT), for the measurement of gastric emptying of solid ingesta, by direct comparison with the optimum method of gastric scintigraphy. Methods: To facilitate dual measurement of gastric emptying, a test meal was used containing baked egg yolk labelled with both <sup>13</sup>C-octanoic acid and (99m)technetium sulphur colloid. Simultaneous, serial lateral gastric scintigraphs and expiratory breath samples were obtained in 12 healthy horses after voluntary ingestion of the test meal. Analysis of breath (CO2)-C-13:(CO2)-C-12 ratio was performed by continuous flow isotope ratio mass spectrometry. Power regression was used to determine the gastric emptying coefficient, the gastric half-emptying time (t(1/2)) and duration of the lag phase (t(lag)). Results: Significant correlations (P < 0.001) were found between the 2 techniques for measurement of both t(1/2) and t(lag). In addition, scintigraphic left t(1/2) was correlated significantly to breath test gastric emptying coefficient (P < 0.001). Conclusions: It was concluded that the <sup>13</sup>C-octanoic acid breath test is a reliable diagnostic procedure to measure gastric emptying rate of solids in the horse. Potential relevance: Being safe, noninvasive and easy to perform, this test has potential value as; both sensitive diagnostic modality and humane research tool for motility studies

Direct and indirect contacts between cattle farms in north-west England

Little is known regarding the types and frequencies of contact that exist between farms and which of these may act as pathogen transmission routes; however it is likely that farms demonstrate considerable heterogeneity in such contacts. In this cross-sectional study, we explored the direct and indirect contact types and frequencies that exist between cattle farms within a region, focusing on potential routes of pathogen transmission. The owners/managers of 56 farms located in a 10 km by 10 km study area in north-west England were administered an interview-based questionnaire between June and September 2005. Information was obtained relating to contact types and frequencies, including those involving animal movements, equipment sharing between farms and any contractors or companies visiting the farms. The data was explored using hierarchical cluster analysis and network analysis. There was considerable variation between farms arising from different contact types. Some networks exhibited great connectivity, incorporating approximately 90% of the farms interviewed in a single component, whilst other networks were more fragmented, with multiple small components (sets of connected farms not linked with other farms). A range of factors influencing contact between farms were identified. For example, contiguous farms were more likely to be linked via other contacts, such as sharing of equipment and direct farm-to-farm animal movements (p < 0.001 and p = 0.02, respectively). The frequency of contacts was also investigated; it is likely that the amount of contact a farm receives from a company or contractor and whether or not biosecurity is performed after contact would impact on disease transmission potential. We found considerable heterogeneity in contact frequency and that many company and contractor personnel undertook little biosecurity. These findings lead to greater understanding of inter-farm contact and may aid development of appropriate biosecurity practices and control procedures, and inform mathematical modelling of infectious diseases

Infection-interactions in Ethiopian village chickens

Chickens raised under village production systems are exposed to a wide variety of pathogens, and current or previous infections may affect their susceptibility to further infections with another parasite, and/or can alter the manifestation of each infection. It is possible that co-infections may be as important as environmental risk factors. However, in cross-sectional studies, where the timing of infection is unknown, apparent associations between infections may be observed due to parasites sharing common risk factors. This study measured antibody titres to 3 viral (Newcastle disease, Marek's disease and infectious bursal disease) and 2 bacterial (Pasteurella multocida and Salmonella) diseases, and the infection prevalence of 3 families of endo- and ecto-parasites (Ascaridida, Eimeria and lice) in 1056 village chickens from two geographically distinct populations in Ethiopia. Samples were collected during 4 cross-sectional surveys, each approximately 6 months apart. Constrained ordination, a technique for analysis of ecological community data, was used to explore this complex dataset and enabled potential relationships to be uncovered and tested despite the different measurements used for the different parasites. It was found that only a small proportion of variation in the data could be explained by the risk factors measured. Very few birds (9/1280) were found to be seropositive to Newcastle disease. Positive relationships were identified between Pasteurella and Salmonella titres; and between Marek's disease and parasitic infections, and these two groups of diseases were correlated with females and males, respectively. This may suggest differences in the way that the immune systems of male and female chickens interact with these parasites. In conclusion, we find that a number of infectious pathogens and their interactions are likely to impact village chicken health and production. Control of these infections is likely to be of importance in future development planning

Detection of Cryptosporidium oocysts in fresh and frozen cattle faeces: comparison of three methods

Aims: The aim of this study was to compare the performance of three commonly used screening tests for Cryptosporidium oocysts in fresh and frozen cattle faeces. Methods and Results: Twenty‐nine freshly voided faecal samples were collected from calves from three farms in the northwest of England. Three diagnostic tests for Cryptosporidium were carried out on each sample both before and after freezing – the modified Ziehl‐Neelsen (MZN) and auramine phenol (APh) stains and a commercial enzyme immunoassay (EIA) kit, the ProSpecT Cryptosporidium Microplate assay (Remel, Lenexa, KS). Twelve samples were deemed positive by the reference standard (polymerase chain reaction, PCR). There were some discrepancies between the results of the screening tests and the levels of agreement were quantified. The sensitivity and specificity of each method was determined, with PCR as the gold standard. Sensitivity and specificity of the MZN stain was optimized when samples with fewer than two oocyst‐like bodies were classified as negative. Conclusions: All three screening methods used were effective in detecting Cryptosporidium infection in both fresh and frozen calf faeces. Significance and Impact of the Study: This study has highlighted the value of determining characteristics of tests used for diagnosis and epidemiological studies

Investigations of the reliability of observational gait analysis for the assessment of lameness in horses

The objectives of this study were to assess the reliability of a numerical rating scale (NRS) and a verbal rating scale (VRS) for the assessment of lameness in horses and to determine whether they can be used interchangeably. Sixteen independent observers graded the severity of lameness in 20 videotaped horses, and the agreement between and within observers, correlation and bias were determined for each scale. The observers agreed with each other in 56 per cent of the observations with the NRS and in 60 per cent of the observations with the VRS, and the associated Kendall coefficient of concordance was high. Similar trends were evident in the agreement between two observations by each observer. The correlation between and within observers was high for both scales. There were no significant differences (bias) among the observers’ mean scores when using either scale. There was a significant correlation between the lameness scores attributed when using the two scales, but the differences between the scores when plotted against their overall mean were unacceptable for clinical purposes. The results indicate that the NRS and VRS are only moderately reliable when used to assess lameness severity in the horse, and that they should not be used interchangeably

Recent network evolution increases the potential for large epidemics in the British cattle population

Following the foot and mouth disease epidemic in Great Britain (GB) in 2001, livestock movement bans were replaced with mandatory periods of standstill for livestock moving between premises. It was anticipated that these movement restrictions would limit each individual's contact networks, the extent of livestock movements and thus the spread of future disease outbreaks. However, the effect of behaviour changes on the global network in adapting to these restrictions is currently unknown. Here, we take a novel approach using GB cattle movement data to construct week-by-week contact networks between animal holdings (AH) to explore the evolution of the network since this policy was introduced, the first time network theory has been used for this purpose. We show that the number of AH moving cattle as part of the giant strong component (GSC), representing the region of maximal connectivity, has been increasing linearly over time. This is of epidemiological significance as the size of the GSC indicates the number of holdings potentially exposed to disease, thus giving a lower bound of maximum epidemic size. Therefore, despite restriction of cattle movements, emergent behaviour in this self-organizing system has potentially increased the size of infectious disease epidemics within the cattle industry