Modelling the links between farm characteristics, respiratory health and pig production traits.

Sustainable livestock production requires links between farm characteristics, animal performance and animal health to be recognised and understood. In the pig industry, respiratory disease is prevalent, and has negative health, welfare and economic consequences. We used national-level carcass inspection data from the Food Standards Agency to identify associations between pig respiratory disease, farm characteristics (housing type and number of source farms), and pig performance (mortality, average daily weight gain, back fat and carcass weight) from 49 all in/all out grow-to-finish farms. We took a confirmatory approach by pre-registering our hypotheses and used Bayesian multi-level modelling to quantify the uncertainty in our estimates. The study findings showed that acquiring growing pigs from multiple sources was associated with higher respiratory condition prevalence. Higher prevalence of respiratory conditions was linked with higher mortality, and lower average daily weight gain, back fat and pig carcass weight. Our results support previous literature using a range of data sources. In conclusion, we find that meat inspection data are more valuable at a finer resolution than has been previously indicated and could be a useful tool in monitoring batch-level pig health in the future.

The effect of sertraline, haloperidol and apomorphine on the behavioural manipulation of slugs (Deroceras invadens) by the nematode Phasmarhabditis hermaphrodita.

The nematode Phasmarhabditis hermaphrodita can infect and kill many species of slugs and has been formulated into a biological control agent for farmers and gardeners. P. hermaphrodita can manipulate the behaviour of slugs, making those infected move to areas where the nematode is present. Research suggests P. hermaphrodita uses manipulation of biogenic amines to achieve this, however the exact role of serotonin and dopamine needs further elucidation. Here we fed slugs Deroceras invadens (uninfected and infected with P. hermaphrodita) apomorphine, sertraline and haloperidol and observed their behaviour when given a choice between a P. hermaphrodita infested habitat, or a parasite free area of soil. In contrast to their usual P. hermaphrodita avoidance behaviour, uninfected D. invadens fed sertraline were attracted to the nematodes and conversely those fed haloperidol avoided the nematodes. D. invadens fed apomorphine were recorded equally on the control and nematode side. D. invadens pre-infected with P. hermaphrodita fed sertraline and apomorphine were found significantly more on the side with the nematodes. However, suppressing dopaminergic signalling through feeding with haloperidol abrogated this attraction and slugs were found on both sides. These results demonstrate that serotonin and dopamine are potential regulators of behavioural manipulation by P. hermaphrodita.

Longitudinal study on the occurrence in pigs of colistin-resistant Escherichia coli carrying mcr-1 following the cessation of use of colistin.

AIMS: In 2015, colistin-resistant Escherichia coli and Salmonella with the mcr-1 gene were isolated from a pig farm in Great Britain. Pigs were subsequently monitored over a ~20-month period for the occurrence of mcr-1-mediated colistin resistance and the risk of mcr-1 E. coli entering the food chain was assessed. METHODS AND RESULTS: Pig faeces and slurry were cultured for colistin-resistant E. coli and Salmonella, tested for the mcr-1 gene by PCR and selected isolates were further analysed. Seventy-eight per cent of faecal samples (n = 275) from pigs yielded mcr-1 E. coli after selective culture, but in positive samples only 0·2-1·3% of the total E. coli carried mcr-1. Twenty months after the initial sampling, faecal samples (n = 59) were negative for E. coli carrying mcr-1. CONCLUSIONS: The risk to public health from porcine E. coli carrying mcr-1 was assessed as very low. Twenty months after cessation of colistin use, E. coli carrying mcr-1 was not detected in pig faeces on a farm where it was previously present. SIGNIFICANCE AND IMPACT OF THE STUDY: The results suggest that cessation of colistin use may help over time to reduce or possibly eliminate mcr-1 E. coli on pig farms where it occurs.

Evaluation of methods for measuring coverage and representativeness of an early-warning disease surveillance system.

Early-warning surveillance provides an essential component of the evidence required to protect animal health. Assessing the proportion of the population included in surveillance systems (coverage) provides a measure of the effectiveness of early-warning surveillance, and contributes to ensuring that these systems are efficient. This paper describes an investigation of methods used for assessing the coverage and representativeness of the 'FarmFile' early-warning surveillance system. This system uses information collected with samples submitted to diagnostic laboratories by private veterinary practitioners in England and Wales. Available data on pig holdings and veterinary practices in four English counties, selected to represent a range of diverse population characteristics, were supplemented using surveys of veterinary practices. Coverage assessments were based on submissions made to FarmFile in 2009. The proportion of holdings covered varied from 5-62 per cent in Devon and Cumbria, and 16-97 per cent in Norfolk and East Riding of Yorkshire. The results suggest that while the proportion of individual pigs covered by the current early-warning surveillance system is high, small and breeding-only holdings in some regions may be poorly covered. Coverage assessments vary depending on the methods used for their assessment, and multiple assessment methods can provide a 'range' within which coverage lies.

Descriptive clinical and epidemiological characteristics of influenza A H1N1 2009 virus infections in pigs in England.

Infection of pigs with influenza A H1N1 2009 virus (A(H1N1)pdm09) was first detected in England in November 2009 following global spread of the virus in the human population. This paper describes clinical and epidemiological findings in the first English pig farms in which A(H1N1)pdm09 influenza virus was detected. These farms showed differences in disease presentation, spread and duration of infection. The factors likely to influence these features are described and relate to whether pigs were housed or outdoors, the age of the pigs, inter-current disease and the management system of the unit. Infection could be mild or clinically inapparent in breeding pigs with more typical respiratory disease being identified later in their progeny. Mortality was low where disease was uncomplicated by environmental stresses or concurrent infections. Where deaths occurred in pigs infected with A(H1N1)pdm09 influenza, they were mainly due to other infections, including streptococcal disease due to Streptococcus suis infection. This paper demonstrates the ease with which A(H1N1)pdm09 virus was transmitted horizontally and maintained in a pig population.

P-glycoproteins of Haemonchus contortus: development of real-time PCR assays for gene expression studies.

P-glycoproteins (P-gps) are proteins that function as efflux pumps, removing lipophilic xenobiotic compounds from cells. There is evidence that P-gps play a role in the resistance of parasitic nematodes to anthelmintic drugs such as benzimidazoles and macrocyclic lactones. As anthelmintic resistance becomes more common, it is important to identify candidate resistance genes with the aim of understanding the molecular basis of resistance, and of developing assays to detect these resistance-associated changes. We identified several sequences from the genome of the parasite Haemonchus contortus with convincing homology to the known P-gp coding genes of the model nematode Caenorhabditis elegans. Nine of these sequences were successfully amplified by polymerase chain reaction (PCR) and shown to be most similar to the C. elegans sequences for pgp-1, pgp-2, pgp-3, pgp-4, pgp-9, pgp-10, pgp-11, pgp-12 and pgp-14. These partial P-gp sequences from H. contortus were used to design and optimize a quantitative real-time PCR assay to investigate potential changes in the expression levels of P-gp transcripts associated with drug resistance. No significant changes in P-gp mRNA expression levels were found in a rapidly selected ivermectin-resistant parasite isolate compared to its drug-sensitive parent, but the assay has the potential to be used on other isolates in the future to further investigate resistance-associated changes in P-gp gene expression.

Salmonella serovars and antimicrobial resistance patterns on a sample of high seroprevalence pig farms in England and Wales (2003-2008).

Following the introduction of a national abattoir-based monitoring programme for Salmonella in pigs, advisory visits were made to pig farms in England and Wales with high Salmonella seroprevalence assessed by muscle tissue fluid (meat juice) ELISA. Samples (n = 15 790), including pooled pen floor faeces (n = 12 136), were collected for Salmonella culture from 296 farms, between October 2003 and February 2008. Salmonella was isolated from 4489 (28%) of all samples collected, including 3301 (27%) of pooled pen floor faecal samples, from 270 (91%) of farms visited. Salmonella Typhimurium and S. Derby were the most prevalent serovars, representing 64% and 16% of isolates serotyped, respectively. The main phage types of S. Typhimurium identified were U288 and DT193. Antimicrobial resistance (AMR) was seen in 92% of isolates tested, with the highest frequencies of resistance occurring to tetracyclines (T), sulphonamide compounds (SU), ampicillin (AM), sulphamethoxazole/trimethoprim (SXT), streptomycin (S) and chloramphenicol (C). Fifty-nine AMR patterns were observed, the most frequent of these being T, AM, SXT, C, S, SU, seen in 35% of isolates tested. Multi-drug resistance was commonly found, with 67% of isolates submitted for AMR testing showing resistance to between four and nine antimicrobials.

First Report of Anthracnose Caused by Colletotrichum acutatum on Persimmon Fruit in the United States.

Persimmon trees are important for their fruit as well as their colorful fruit and foliage in the fall. Persimmon fruit (Japanese persimmon, Diospyros kaki cv. Fuyu) were collected in November 2008 from a tree in Windsor, NC, located in the Coastal Plain. Fruit were not symptomatic on the tree but developed dark lesions after harvest. Isolations from six fruit yielded seven isolates of Colletotrichum acutatum J. H. Simmonds. After incubation at 25°C under continuous light for 15 days on potato dextrose agar (PDA), all isolates had gray aerial mycelium, but the inverse sides of the plates of six isolates were maroon and one was beige. Masses of salmon-colored conidia were formed first in the center of the colonies, then were observed scattered across the colonies in older cultures. Conidia were hyaline, one-celled, elliptic with one or both ends pointed, and measured 8.1 to 16.3 × 3.1 to 5 µm. Setae and sclerotia were not observed. There were also dark structures measuring 1 to 10 mm that were partially embedded in the agar that contained conidia. Cultural and conidial characteristics of the isolates were similar to those of C. acutatum (3). PCR amplification was performed with the species-specific primer pair CaInt2/ITS4 (2) and genomic DNA from the original isolates and isolates obtained from inoculated fruit. An amplification product of approximately 490 bp, which is specific for C. acutatum, was observed. To fulfill Koch's postulates, persimmon fruit obtained from the grocery store were surface disinfested with 0.5% sodium hypochlorite and sterile filter paper disks dipped in conidial suspensions (1 × 105 conidia/ml) of two C. acutatum isolates (maroon and beige reverse) or sterile, deionized water were placed on the fruit. Three fruit were inoculated per treatment and the disks were placed on four locations on each fruit. Parafilm was wrapped around the diameter of the fruit to keep the filter paper disks moist and in place. Fruit were placed in moist chambers and incubated at 25°C. After 3 days, the Parafilm was removed and the fruit returned to the moist chambers. Small, dark lesions were observed on fruit inoculated with each isolate of C. acutatum when the filter paper disks were removed. Ten days after inoculation, dark lesions and acervuli with salmon-colored masses of conidia were observed on fruit inoculated with both isolates of C. acutatum and the fruit were soft. After 12 days, there were abundant masses of conidia and the inoculated areas were decayed. Control fruit remained firm and did not develop symptoms. Cultures obtained from the fruit and the conidia produced were typical of the isolates used to inoculate the fruit. C. acutatum has been reported to cause fruit rot on persimmon fruit in New Zealand (1). To our knowledge, this is the first report of C. acutatum on persimmon fruit in the United States. References: (1) R. Lardner et al. Mycol. Res. 103:275, 1999. (2) S. Sreenivasaprasad et al. Plant Pathol. 45:650, 1996. (3) B. C. Sutton. Page 523 in: Coelomycetes. Commonwealth Agricultural Bureaux, Great Britain. 1980.

Re-examination of Peltaster fructicola, a member of the apple sooty blotch complex.

Peltaster fructicola is one of several fungi that causes sooty blotch on apple. Johnson et al (1996, 1997) correctly described P. fructicola but illustrated two different fungi. One is P. fructicola and the other is an unidentified ascomycete. In this paper, P. fructicola is more completely described and accurately illustrated.

Variation in Aggressiveness Among Isolates of Cercospora from Maize as a Potential Cause of Genotype-Environment Interaction in Gray Leaf Spot Trials.

The use of genetically resistant maize hybrids is the preferred means of control of gray leaf spot, caused by Cercospora zeae-maydis. One problem faced by maize breeders attempting to breed for resistance to gray leaf spot is the high degree of genotype-environment interactions observed in disease trials. In North Carolina gray leaf spot trials conducted at four locations in the western part of the state, we found consistent hybrid-location interactions over the 1995 and 1996 growing seasons. Isolates of C. zeae-maydis from those test locations were evaluated on the same hybrids used in the multilocation testing at a location in central North Carolina that does not have a history of gray leaf spot. The hybrid-isolate interactions observed in the isolate trial mirrored the hybrid-location effects seen in the multilocation testing. Most of the interactions arose from changes in the magnitude of differences between hybrids when inoculated with the isolates rather than from any change in hybrid ranking. Analysis of internal transcribed spacer-restriction fragment length polymorphisms (RFLPs) and mitochondrial rDNA RFLPs of those isolates and others revealed that both type I and type II sibling species of C. zeae-maydis, as well as C. sorghi var. maydis, are isolated from typical gray leaf spot lesions. Breeders should use the most aggressive isolates of C. zeae-maydis to maximize discrimination between genotypes in gray leaf spot trials.

Chemoprophylaxis of Theileria annulata and Theileria parva infections of calves with buparvaquone.

A clinical trial testing the prophylactic effect of a 5 mg kg-1 dose of buparvaquone on either Theileria annulata or Theileria parva experimental infections of calves demonstrated its efficacy for periods of at least seven days. The drug given 1 h or seven days before 50% lethal T. annulata sporozoite infection protected all eight calves, but prophylaxis was insufficient after 14 days to protect two out of four calves from severe reaction. When immunity was challenged by a lethal second parasite dose a month after the first, all these calves were immune. In the T. parva trial, calves given drug 1 h or seven days before a 25% lethal infection underwent minimal reaction, but some were over-protected and were susceptible to a similar challenge sporozoite dose. Although drug levels remaining 14 days after prophylaxis protected these calves from the mild challenge, some parameters measured were within the range of the 'no drug' control group. These results indicated the effectiveness of a single 5 mg kg-1 dose of buparvaquone for more than seven days but also the potential risk of its use in the infection and treatment method of immunisation. It is suggested that there may be circumstances where simple field prophylactic treatment with buparvaquone may be beneficial.

Isolation of the causative agent of heartwater (Cowdria ruminantium) from three Amblyomma species in eight Districts of Kenya.

Thirteen isolates of Cowdria ruminantium were made from eight different Districts of Kenya by four different isolation methods. Feeding adult Amblyomma species ticks derived from nymphs collected in the field and the inoculation of homogenates prepared from adult field ticks had the highest success rate. The reattachment of adult ticks collected in the field was successful on only one of five attempts, and the subinoculation of blood from suspected heartwater carriers was unsuccessful. Seven of the isolates were derived from A variegatum ticks, four from A gemma, one from A lepidum and one from a mixed pool of the last two species. This is the first report of the isolation of C ruminantium from A gemma ticks, and the first report of its transtadial transmission from nymphal to adult A gemma.

Isolation and preliminary characterisation of a previously unidentified Theileria parasite of cattle in Kenya.

A Theileria parasite was isolated from cattle on a ranch in Kenya where it caused mild theileriosis in approximately one third of the cattle exposed to natural tick challenge. The parasite was isolated by inoculation of blood into two experimental cattle. Blood from one of these cattle was used to infect two splenectomised cattle which developed high piroplasm parasitaemias and severe anaemia. A blood stabilate was prepared from one of the splenectomised cattle and produced high parasitaemias in splenectomised cattle. Immunofluorescence tests showed that the unidentified Theileria species was distinct from other African Theileria and Babesia species of cattle. The Theileria species was shown to be antigenically distinct by means of species-specific monoclonal antibodies. The piroplasma stage was relatively large for a Theileria parasite and erythrocyte infections were usually associated with veils and bars. The salivary glands of Rhipicephalus appendiculatus, R pulchellus, R evertsi and Amblyomma variegatum fed on parasitaemic cattle did not become infected and these ticks failed to transmit the parasite. It was concluded that this parasite represented a new species of cattle Theileria in Kenya.

Further evaluation of the use of buparvaquone in the infection and treatment method of immunizing cattle against Theileria parva derived from African buffalo (Syncerus caffer).

Three experiments were undertaken to determine the efficacy of different doses of buparvaquone in the infection and treatment immunization of cattle against Theileria parva derived from African buffalo (Syncerus caffer). Two of these experiments also compared buparvaquone with standard doses of long- and short-acting formulations of oxytetracycline. In addition, different dilutions of stabilates were used in the experiments. In the first experiment, a 10(-1.0) dilution of stabilate was used to infect groups of cattle treated with buparvaquone at doses of between 5 and 0.625 mg kg-1 body weight (bwt) on Day 0 after infection. All control cattle developed severe theileriosis and none of the treatment regimes (including those utilizing long-acting oxytetracycline) prevented the development of theileriosis. Treatment with buparvaquone at 2.5 mg kg-1 bwt or oxytetracycline gave the most satisfactory results. In the second experiment when the sporozoite dose was reduced to 10(-2.0) dilution, buparvaquone treatment at 5 and 2.5 mg kg-1 bwt and short- and long-acting formulations of oxytetracycline reduced reactions greatly. While all the oxytetracycline treated animals produced a serological response and were immune to a 50-fold higher challenge with the immunizing stabilate, several animals in the buparvaquone groups did not show a serological response and were not immune to challenge. In the third experiment, groups of cattle were infected with 10(-1.2), 10(-1.4) and 10(-1.6) dilutions of stabilate and were treated with 2.5 mg kg-1 bwt of buparvaquone. No animals developed severe theileriosis and all seroconverted. On homologous challenge, however, two out of 14 cattle showed severe reactions. It was concluded that further work on immunization using buparvaquone treatment at 2.5 mg kg-1 bwt and 10(-1.6) dilution of the stabilate would have to be carried out before such a system could be used in the field.