Hepatitis E in southern Vietnam: Seroepidemiology in humans and molecular epidemiology in pigs.

Viral pathogens account for a significant proportion of the burden of emerging infectious diseases in humans. The Wellcome Trust-Vietnamese Initiative on Zoonotic Infections (WT-VIZIONS) is aiming to understand the circulation of viral zoonotic pathogens in animals that pose a potential risk to human health. Evidence suggests that human exposure and infections with hepatitis E virus (HEV) genotypes (GT) 3 and 4 results from zoonotic transmission. Hypothesising that HEV GT3 and GT4 are circulating in the Vietnamese pig population and can be transmitted to humans, we aimed to estimate the seroprevalence of HEV exposure in a population of farmers and the general population. We additionally performed sequence analysis of HEV in pig populations in the same region to address knowledge gaps regarding HEV circulation and to evaluate if pigs were a potential source of HEV exposure. We found a high prevalence of HEV GT3 viral RNA in pigs (19.1% in faecal samples and 8.2% in rectal swabs) and a high HEV seroprevalence in pig farmers (16.0%) and a hospital-attending population (31.7%) in southern Vietnam. The hospital population was recruited as a general-population proxy even though this particular population subgroup may introduce bias. The detection of HEV RNA in pigs indicates that HEV may be a zoonotic disease risk in this location, although a larger sample size is required to infer an association between HEV positivity in pigs and seroprevalence in humans.

Detection of potentially novel paramyxovirus and coronavirus viral RNA in bats and rats in the Mekong Delta region of southern Viet Nam.

Bats and rodents are being increasingly recognized as reservoirs of emerging zoonotic viruses. Various studies have investigated bat viruses in tropical regions, but to date there are no data regarding viruses with zoonotic potential that circulate in bat and rat populations in Viet Nam. To address this paucity of data, we sampled three bat farms and three wet markets trading in rat meat in the Mekong Delta region of southern Viet Nam. Faecal and urine samples were screened for the presence of RNA from paramyxoviruses, coronaviruses and filoviruses. Paramyxovirus RNA was detected in 4 of 248 (1%) and 11 of 222 (4.9%) bat faecal and urine samples, respectively. Coronavirus RNA was detected in 55 of 248 (22%) of bat faecal samples; filovirus RNA was not detected in any of the bat samples. Further, coronavirus RNA was detected in 12 of 270 (4.4%) of rat faecal samples; all samples tested negative for paramyxovirus. Phylogenetic analysis revealed that the bat paramyxoviruses and bat and rat coronaviruses were related to viruses circulating in bat and rodent populations globally, but showed no cross-species mixing of viruses between bat and rat populations within Viet Nam. Our study shows that potentially novel variants of paramyxoviruses and coronaviruses commonly circulate in bat and rat populations in Viet Nam. Further characterization of the viruses and additional human and animal surveillance is required to evaluate the likelihood of viral spillover and to assess whether these viruses pose a risk to human health.

Non-Typhoidal Salmonella Colonization in Chickens and Humans in the Mekong Delta of Vietnam.

Salmonellosis is a public health concern in both the developed and developing countries. Although the majority of human non-typhoidal Salmonella enterica (NTS) cases are the result of foodborne infections or person-to-person transmission, NTS infections may also be acquired by environmental and occupational exposure to animals. While a considerable number of studies have investigated the presence of NTS in farm animals and meat/carcasses, very few studies have investigated the risk of NTS colonization in humans as a result of direct animal exposure. We investigated asymptomatic NTS colonization in 204 backyard chicken farms, 204 farmers and 306 matched individuals not exposed to chicken farming, in southern Vietnam. Pooled chicken faeces, collected using boot or handheld swabs on backyard chicken farms, and rectal swabs from human participants were tested. NTS colonization prevalence was 45.6%, 4.4% and 2.6% for chicken farms, farmers and unexposed individuals, respectively. Our study observed a higher prevalence of NTS colonization among chicken farmers (4.4%) compared with age-, sex- and location- matched rural and urban individuals not exposed to chickens (2.9% and 2.0%). A total of 164 chicken NTS strains and 17 human NTS strains were isolated, and 28 serovars were identified. Salmonella Weltevreden was the predominant serovar in both chickens and humans. NTS isolates showed resistance (20-40%) against tetracycline, chloramphenicol, sulfamethoxazole-trimethoprim and ampicillin. Our study reflects the epidemiology of NTS colonization in chickens and humans in the Mekong delta of Vietnam and emphasizes the need of larger, preferably longitudinal studies to study the transmission dynamics of NTS between and within animal and human host populations.

Highly Pathogenic Avian Influenza Virus A/H5N1 Infection in Vaccinated Meat Duck Flocks in the Mekong Delta of Vietnam.

We investigated episodes of suspected highly pathogenic avian influenza (HPAI)-like illness among 12 meat duck flocks in two districts in Tien Giang province (Mekong Delta, Vietnam) in November 2013. In total, duck samples from 8 of 12 farms tested positive for HPAI virus subtype A/haemagglutinin 5 and neuraminidase 1 (H5N1) by real-time RT-PCR. Sequencing results confirmed clade of 2.3.2.1.c as the cause of the outbreaks. Most (7/8) laboratory-confirmed positive flocks had been vaccinated with inactivated HPAI H5N1 clade 2.3.4 vaccines <6 days prior to onset of clinical signs. A review of vaccination data in relation to estimated production in the area suggested that vaccination efforts were biased towards larger flocks and that vaccination coverage was low [21.2% ducks vaccinated with two shots (range by district 7.4-34.9%)]. The low-coverage data, the experimental evidence of lack of cross-protection conferred by the currently used vaccines based on clade 2.3.4 together with the short lifespan of meat duck flocks (60-70 days), suggest that vaccination is not likely to be effective as a tool for control of H5N1 infection in meat duck flocks in the area.

High levels of contamination and antimicrobial-resistant non-typhoidal Salmonella serovars on pig and poultry farms in the Mekong Delta of Vietnam.

We investigated the prevalence, diversity, and antimicrobial resistance (AMR) profiles of non-typhoidal Salmonella (NTS) and associated risk factors on 341 pig, chicken, and duck farms in Dong Thap province (Mekong Delta, Vietnam). Sampling was stratified by species, district (four categories), and farm size (three categories). Pooled faeces, collected using boot swabs, were tested using ISO 6575: 2002 (Annex D). Isolates were serogrouped; group B isolates were tested by polymerase chain reaction to detect S. Typhimurium and (monophasic) serovar 4,[5],12:i:- variants. The farm-level adjusted NTS prevalence was 64·7%, 94·3% and 91·3% for chicken, duck and pig farms, respectively. Factors independently associated with NTS were duck farms [odds ratio (OR) 21·2], farm with >50 pigs (OR 11·9), pig farm with 5-50 pigs (OR 4·88) (vs. chickens), and frequent rodent sightings (OR 2·3). Both S. Typhimurium and monophasic S. Typhimurium were more common in duck farms. Isolates had a high prevalence of resistance (77·6%) against tetracycline, moderate resistance (20-30%) against chloramphenicol, sulfamethoxazole-trimethoprim, ampicillin and nalidixic acid, and low resistance (<5%) against ciprofloxacin and third-generation cephalosporins. Multidrug resistance (resistance against ⩾3 classes of antimicrobial) was independently associated with monophasic S. Typhimurium and other group B isolates (excluding S. Typhimurium) and pig farms. The unusually high prevalence of NTS on Mekong Delta farms poses formidable challenges for control.

A longitudinal observational study of Salmonella shedding patterns by commercial turkeys during rearing and fattening, showing limitations of some control measures.

1. The onset and progression of Salmonella infections was investigated in commercial turkey flocks from placement at 1 d old until slaughter in "brood and move" systems using a longitudinal observational approach based on faeces and environmental sampling with subsequent culture of Salmonella. 2. Persistent Salmonella Newport contamination was found within rearing houses and on their external concrete aprons after cleaning and disinfection between crops of heavily shedding young birds. 3. Salmonella shedding was often detected by 5 d of age and the frequency of positive samples peaked at 14-35 d. Thereafter Salmonella isolations declined, especially in the later (fattening) stages. Samples were still Salmonella-positive at low prevalence in half of the intensively sampled houses at slaughter age. 4. A number of management interventions to combat Salmonella infection of flocks, including sourcing policy, competitive exclusion cultures and cleaning and disinfection, were inadequate to prevent flock infection, although improved disinfection on one unit was associated with a delay in the onset of flock infection.

An epidemiological investigation of Campylobacter in pig and poultry farms in the Mekong delta of Vietnam.

Campylobacter are zoonotic pathogens commonly associated with gastroenteritis. To assess the relevance of Campylobacter in Vietnam, an economically transitioning country in SE Asia, we conducted a survey of 343 pig and poultry farms in the Mekong delta, a region characterized by mixed species farming with limited biosecurity. The animal-level prevalence of Campylobacter was 31·9%, 23·9% and 53·7% for chickens, ducks and pigs, respectively. C. jejuni was predominant in all three host species, with the highest prevalence in pigs in high-density production areas. Campylobacter isolates demonstrated high levels of antimicrobial resistance (21% and 100% resistance against ciprofloxacin and erythromycin, respectively). Multilocus sequence type genotyping showed a high level of genetic diversity within C. jejuni, and predicted C. coli inter-species transmission. We suggest that on-going intensification of animal production systems, limited biosecurity, and increased urbanization in Vietnam is likely to result in Campylobacter becoming an increasingly significant cause of human diarrhoeal infections in coming years.

Risk factors for antimicrobial resistance in Escherichia coli found in GB turkey flocks.

Four models are presented investigating risks present on Great Britain (GB) turkey farms in breeding and fattening flocks for ciprofloxacin and cephalosporin resistance. Risk factors for ciprofloxacin resistance in fattening flocks were sourcing of feed from national compounders, antimicrobial use in the flock and evidence of mice. Disinfection of floors and walls at depopulation, older flocks and division of the flock with partitions reduced the risk. In breeding farms holding over 10,000 birds, administration of fluoroquinolones within the last year and horses on the neighbouring farm all increased the risk, whereas replenishing foot dips more than once a week reduced the risk. For cephalosporin-resistant Escherichia coli on fattening farms, being an independent farm, having a watercourse near the poultry houses, dividing the flock with partitions and providing staff with gloves reduced the risk. Factors that increased the risk included if staff worked with other livestock and if there were pigs on neighbouring farms. This work suggests that good hygiene and biosecurity, rodent control and responsible use of antimicrobials on turkey farms might help minimise the prevalence of fluoroquinolone and cephalosporin resistance in E coli, and restrict the spread of resistance genes to other organisms.

Patterns of delayed detection and persistence of bovine tuberculosis in confirmed and unconfirmed herd breakdowns in cattle and cattle herds in Great Britain.

Approximately 1500/6000 cattle farms that were depopulated during the foot and mouth epidemic in GB in 2001 had been repopulated and subjected to two unrestricted (herd considered free from bovine tuberculosis (bTB)) herd tests. Factors associated with herd breakdown(s) (HBD) and individual cattle reactor status at the second test were investigated. There were 96 HBD in total, with a 3-fold increased risk of HBD in herds that had had a HBD at the first test after restocking. Two mixed effect models were used to investigate factors associated with 324/246,060 reactor cattle at the second bTB test; 228 reactors were at confirmed HBD and 96 at unconfirmed HBD; 253 (79%) reactors at the second test were present and test negative at the first test. In confirmed HBD, the odds of cattle reacting were higher if the restocked farm had a history of bTB before 2001 and if the source and restocked farms were high frequency tested (HFT) farms (routine bTB tests at ≥1 per 2 years). Reacting cattle were more likely to have been born on the restocked farm before the first test after FMD and less likely to have been purchased from a low frequency tested (LFT) farm (routine bTB tests at 3-4 year intervals) after the first test compared with a baseline of cattle purchased from a LFT farm before the first test. Unconfirmed HBD at the second test was more likely when the first test was a confirmed HBD and when there was a history of bTB in the restocked farm. In contrast to confirmed HBD, cattle purchased from a LFT farm after the first test were at increased risk of reacting at an unconfirmed HBD at the second test. We conclude that a farm history of bTB suggests persistence of bTB on the farm. Confirmed tests indicate exposure to bTB for some time indicated by the increased risk from HFT source and restocked farms and a farm history of bTB. The risks for reactors are related to the farm and herd and duration of exposure to these risks. Therefore, the spread of bTB to naïve herds would be reduced if farmers only introduced cattle known not to have been in herds and on farms exposed to bTB. Management of bTB on farms with bTB is complicated because there is undisclosed infection in cattle and environmental contamination.

Survey of Salmonella prevalence on commercial turkey breeding and fattening farms in the UK in 2006 to 2007.

A total of 29 breeding turkey holdings and 317 fattening turkey holdings were sampled between October 2006 and September 2007 in order to establish the baseline prevalence of Salmonella in turkeys in the UK. The weighted holding level Salmonella prevalence was found to be 20.1 per cent (95 per cent confidence interval [CI] 8.6 to 40.3 per cent) in breeding turkeys and 37.7 per cent (95 per cent CI 33.4 to 42.3 per cent) in fattening turkeys. For breeding turkeys, a weighted flock-level prevalence, as more than one flock per holding was sampled, was estimated at 7.1 per cent (95 per cent CI 3.2 to 14.8 per cent). A total of 13 different serovars were identified in the survey. The most frequent serovar in both turkey flock classes was Salmonella Kottbus, which was found on two breeding holdings and 63 of the fattening holdings giving weighted prevalences of 10.4 per cent (95 per cent CI 2.6 to 34.1 per cent) and 23.0 per cent (95 per cent CI 19.3 to 27.3 per cent), respectively. On breeding holdings, a single isolate of Salmonella Typhimurium, identified as DT12 (weighted prevalence 3.5 per cent [95 per cent CI 0.7 to 15.8 per cent] [holding], 0.7 per cent [95 per cent CI 0.1 to 3.7 per cent] [flock)], was found. On fattening holdings, there were 55 isolates of S Typhimurium from 16 holdings, giving a weighted prevalence of this serovar of 5.4 per cent (95 per cent CI 3.6 to 8.0 per cent). There were no isolates of Salmonella serovars Enteritidis, Hadar, Infantis or Virchow.

A comparison of pooled and individual bird sampling for detection of Salmonella in commercial egg laying flocks.

The objective of this study was to determine the sensitivity of culturing pooled samples containing varying numbers of individual droppings for detection of Salmonella in commercial egg-laying flocks relative to the within-flock prevalence. A laboratory experiment was performed to directly measure the effect of diluting positive with negative faeces on the sensitivity of detection, and thus provide priors for a Bayesian model of pooled sampling. Pooled samples made up of different numbers of individual faecal droppings were collected from 20 flocks, and in addition bulked faeces and dust were also sampled using an in-house method that involved collecting 10 dust and 10 faeces samples into jars with buffered peptone water. The results from these flocks were analysed using Bayesian methods for diagnostic test evaluation in the absence of a gold standard, and the sensitivity of each pooled sample type was estimated relative to the within-flock prevalence. The sensitivity of pooled samples depended on the within-flock prevalence, and increased as the prevalence increased. The sensitivity of pooled sampling tended to increase with the number of droppings in the pool, and overall there was a higher proportion of positive samples from the pools of 20, 60 and the in-house faeces pooling method compared to the pools of 10, 5 and the individual droppings. Dust samples were more sensitive than the faeces samples, and so the inclusion of dust in sampling schemes is recommended.

A longitudinal study of Salmonella infection in different types of turkey flocks in Great Britain.

Salmonella is, after Campylobacter, the most reported zoonotic pathogen in the EU. Poultry are a common source of infection to humans, and turkey flocks are commonly colonized with the organism. We investigated the prevalence and risk factors of Salmonella infection in 179 houses in 60 holdings representative of turkey meat and breeder production in Great Britain. From each holding, up to four houses were chosen, and two consecutive flocks per house were sampled/tested for Salmonella to investigate the persistence, elimination and introduction of Salmonella in consecutive crops. At the first sampling, the overall flock-level Salmonella prevalence was 32.8% and 8.9% for meat and breeding flocks respectively. There was a higher prevalence of Salmonella in flocks in the rearing stage than in the fattening and breeding stages. At the first sampling, the flock-level prevalence of Salmonella was 26.8% (95% CI: 20.7-33.7%), while the prevalence level in the subsequent flock was 20.5% (95% CI: 13.6-29.7%). No houses were positive for any of the EU-regulated serovars. The most commonly encountered serovars were S. Kottbus and S. Kedougou. Carry-over of infection was observed in 44.8% of the positive houses, and introduction of new infection occurred in 8.4% of houses. Data from the questionnaires and auditing of all holdings and houses were combined and used to calculate adjusted farm- and house-adjusted risk factors. Significant risk factors were feed from a source other than a national compounder (OR = 2.4), feeder type other than pan feeders (OR = 2.4) and hygiene practices other than terminal cleaning and disinfection using power-washing with sanitizer and anteroom with boot change (OR = 2.8). The study discusses the main challenges currently faced by the industry to control Salmonella in turkey production.

Effect of delivery method on the efficacy of Salmonella vaccination in chickens.

To investigate whether the efficacy of live vaccines is influenced by the mode of vaccine delivery, a widely-used UK live commercial Salmonella Enteritidis vaccine was delivered to pullet chicks either by spray, in drinking water, or in combination with a bivalent vaccine containing inactivated Salmonella Enteritidis and Salmonella Typhimurium. The birds were subsequently challenged with 10(2) or 10(8) colony-forming units (cfu) of Salmonella Enteritidis through drinking water at either six or 20 weeks of age. Ten days after the challenge, the birds were euthanased and their caecal contents cultured for Salmonella. All of the vaccinated groups contained fewer Salmonella Enteritidis-positive birds than the unvaccinated groups. The 'spray-vaccinated' group contained significantly fewer Salmonella Enteritidis-positive birds than the 'water-vaccinated' group after challenge with 10(8) cfu at 20 weeks. However, there was little or no difference at the other challenge time points between the groups that received vaccine through different modes of delivery.

Investigation of risk factors for Salmonella on commercial egg-laying farms in Great Britain, 2004-2005.

In 2004/05, all European Union member states were required to carry out standardised prevalence surveys to establish the baseline prevalence of Salmonella in commercial laying flocks. As part of the survey in Great Britain, additional data were collected from 380 of the enrolled laying hen holdings to investigate risk factors for Salmonella at farm level. Stratified, simple random sampling was used to select holdings from which dust and boot swab samples were collected and tested for Salmonella using a modification of ISO 6579:2002. Using a multivariable logistic model weighted to account for the survey design, several factors significantly associated with Salmonella and Salmonella Enteritidis status were identified. Larger holdings (>or=30,000 birds) were found to be at higher risk of Salmonella (odds ratio [OR] 4.79, P=0.025), while vaccination (OR 0.28, P=0.013), providing foot dips with brushes (OR 0.27, P=0.042), washing and disinfecting the house at depopulation (OR 0.19, P=0.003), having a clean car park away from house (OR 0.14, P=0.001), using an independent (OR 0.19, P=0.007) or other non-company (OR 0.40, P=0.049) source of feed, being over 1 km from the nearest neighbouring farm (OR 0.45, P=0.021) and the presence of cats and dogs on the farm (OR 0.26, P=0.002) or on contiguous farms (OR 0.44, P=0.030) reduced the risk of any Salmonella serovars being present. Factors found to be associated specifically with an increased risk of S Enteritidis infection included holding size (OR 14.88, P=0.001) and frequent sightings of rats (OR 8.17, P<0.001) or mice (OR 5.78, P=0.006). Non-caged systems (OR 0.14, P=0.002), vaccination (OR 0.08, P=0.001), the use of a non-company feed source (OR 0.11, P=0.003), running the site as all-in/all-out (OR 0.06, P<0.001) and the presence of cats and dogs on the farm (OR 0.14, P=0.002) were associated with a reduced risk.

Estimation of Salmonella prevalence in UK egg-laying holdings.

As part of an EU-wide programme to reduce the prevalence of Salmonella in commercial egg-laying holdings, the EU has set for the UK an annual target of 10% reduction in the prevalence of Salmonella Enteritidis and Salmonella Typhimurium in commercial egg-laying holdings. To assist in demonstrating such a reduction, it is very important to obtain an accurate as possible baseline prevalence for Salmonella. The objective of this study was to provide a baseline estimate of the Salmonella prevalence in egg-laying holdings in the UK. Data from an EU baseline survey for Salmonella in UK commercial egg-laying flocks were therefore analysed using Bayesian methods, taking into account the sampling of only 1 flock per holding and estimates of the test sensitivity of the methods used in the EU baseline survey. In addition, in the UK the majority of the eggs come from farms which have participated in voluntary monitoring programmes for Salmonella since the early 1990s, and this data was also used, along with a prior estimate of the test sensitivity of voluntary surveillance. Results indicated that a true prevalence 14% for Salmonella Enteriditis and Typhimurium, and 18% for all serovars, both of these estimates being higher than has previously been reported from the EU baseline survey data. It is also shown that the sensitivity of voluntary surveillance is low, and it will therefore be important to compare results from "official" and "non-official" samples to check that the sampling performed in the National Control Plan is as sensitive as expected.

Investigation of risk factors for Salmonella on fattening-turkey farms.

A cross-sectional study into risk factors for Salmonella was undertaken using data gathered from 252 fattening turkey flocks in the UK. The data was derived from the EU baseline survey conducted during 2006 and 2007, in addition to a voluntary questionnaire. Multivariate logistic regression models identified significant risk factors for Salmonella spp. and Salmonella Typhimurium. A decreased risk of Salmonella spp. infection was associated with a history of intestinal illness in the sampled flock (OR 0.17), the use of wood shavings as litter (OR 0.21), use of disinfectant in the cleaning process (OR 0.25), incineration of dead birds on farm (OR 0.29), seasonal production (OR 0.31), farm staff also working with cattle (OR 0.31), and the presence of pigs on neighbouring farms (OR 0.38). The risk of isolating Salmonella spp. varied according to the company from which the poults were sourced. A reduced risk of S. Typhimurium infection was associated with the use of wax blocks to control rodents (OR 0.09), using mains water (OR 0.19) and having a Salmonella test programme (OR 0.23). An increased risk of S. Typhimurium infection was associated with storage of items around the turkey house (OR 5.20), evidence of mice (OR 4.71) and a soil surface surrounding the turkey house (OR 2.70). This study therefore identifies a number of important practical measures which can be implemented by farmers and veterinarians within the turkey industry to assist in the control of salmonellosis at the farm level.

A comparison of the efficacy of different disinfection methods in eliminating Salmonella contamination from turkey houses.

AIMS: This study aimed to compare the efficacy of different disinfection methods in eliminating Salmonella contamination from turkey houses. METHODS AND RESULTS: Fifty depopulated turkey houses which had all housed Salmonella-positive flocks were visited after cleaning and disinfection. A minimum of 45 swab samples from different surfaces were taken per house and analysed for the presence of Salmonella. The sampled surfaces included intact floor surfaces, floor cracks, walls, feeders, drinkers, anteroom, nestboxes and miscellaneous items. Houses were grouped according to the disinfectant which had been used and the efficacy of the different groups of disinfectants was compared. Sixty-eight % of houses tested positive for Salmonella after C&D. Out of 4440 samples, 207 tested positive for Salmonella, giving an overall sample prevalence of 4.7%. There was no significant difference in the level of residual contamination between breeding, rearing and finishing houses. Products containing a mixture of formaldehyde, glutaraldehyde and quaternary ammonium compounds (QAC) performed significantly better than products containing hydrogen peroxide and peracetic acid. Cleaning and disinfection was least effective in nestboxes and anterooms. CONCLUSIONS: Thorough cleaning and the choice of a suitable disinfectant are crucial if Salmonella contamination of turkey houses is to be eliminated. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows that disinfectants containing a mixture of formaldehyde, glutaraldehyde and QAC perform significantly better under field conditions than oxidising products and should therefore be the first choice for disinfection of turkey premises where Salmonella is present.

Salmonella infection in cattle in Great Britain, 2003 to 2008.

Surveillance data for clinical disease in cattle in Great Britain due to Salmonella infections were analysed for the period 2003 to 2008 in order to describe seasonality and to investigate possible associations between Salmonella diagnoses and other variables such as region, climate, age and production type. A clear seasonal pattern was shown for Salmonella infection, coinciding with the second half of the year. The incidence of Salmonella Dublin and Salmonella Typhimurium was highest in the west of the country, which has the greatest cattle density, but this was not a feature of diagnoses with other serovars. Abortion was a more common clinical sign of S Dublin infections, but was relatively unusual in the case of S Typhimurium. The observed clinical picture and age of affected animals were largely determined by the seasonality of dairy cattle calving in Great Britain.

Review of the carriage of zoonotic bacteria by arthropods, with special reference to Salmonella in mites, flies and litter beetles.

This systematic review considers the relationship between arthropods commonly found in and around livestock premises and zoonotic bacteria. The principal focus is upon insects and arachnids on poultry units, where houses, litter and manure provide good conditions for the growth, multiplication and protection of flies, beetles and mites, and where zoonotic pathogens such as Salmonella and Campylobacter are prevalent. Other members of the Enterobacteriaceae and the taxa Clostridium, Helicobacter, Erysipelas and Chlamydiaceae are also discussed. Salmonella is widely distributed in the flies of affected livestock units and is detectable to a lesser degree in beetles and mites. Persistent carriage appears to be common and there is some field and experimental evidence to support arthropod-mediated transmission between poultry flocks, particularly carry-over from one flock to the next. Campylobacter may readily be isolated from arthropods in contact with affected poultry flocks, although carriage is short-lived. There appears to be a role for flies, at least, in the breaching of biosecurity around Campylobacter-negative flocks. The carriage of other zoonotic bacteria by arthropods has been documented, but the duration and significance of such associations remain uncertain in the context of livestock production.

Sensitivity of environmental sampling methods for detecting Salmonella Enteritidis in commercial laying flocks relative to the within-flock prevalence.

The objective of this study was to estimate the sensitivity of three different sampling/testing methodologies for the detection of Salmonella Enteritidis in commercial egg-laying flocks relative to the within-flock prevalence. The following methods were compared on 21 farms: (1) The European Union (EU) baseline survey method (five faecal and two dust samples); (2) an in-house method that involved collecting 10 dust and 10 faecal samples into jars with buffered peptone water, and (3) a method involving single samples of pooled faeces and dust that has been adopted as a monitoring method for the National Control Programme across the EU (the NCP method). Testing of individual bird ovaries/oviduct and caeca was carried out on each flock, and the sensitivity of each sampling method was estimated relative to the within-flock prevalence using Bayesian methods. Results showed that the sensitivity of all the sampling methods increased as the within-flock prevalence increased, and that all were more efficient than individual bird sampling for detection of S. Enteritidis in commercial flocks. The in-house method was the most sensitive of the methods compared, with a 98% power to detect a 0.1% prevalence, and the NCP method the least sensitive, with a 93% power to detect a prevalence of 20%.