Enteric infections, the role of Denagard® and the role of vectors in disease transfer were covered in a Novartis symposium held during the International Pig Veterinary Society (IPVS) Congress in Vancouver, Canada, last week.

Effect of Denagard Water Medication against Ileitis

Professor Nathan Winkelman

In his introduction, Professor Nathan Winkelman of the University of Minnesota in the USA, said that porcine proliferative enteropathy (PPE; ileitis) costs the industry between US$3 and $5 per pig affected. Ileitis is still seen quite often as non-bloody diarrhoea to the full-blown condition in finishing houses in the US, he said. Water medication against the disease has the advantages that it is easy to apply, brings about a rapid response in the pigs, affected pigs maintain water intake while feed intake decreases and it is cost-effective.

Dr Winkelmann went on to report a new challenge study with Lawsonia intracellularis, involving a dose titration with Denagard liquid concentration.

From the results, he concluded that there were no differences between the three Denagard doses used.

He said: "The 60ppm dosage is still the gold standard for treatment purposes." He added, however, that is severe cases, the 120ppm dosage may be justified over a longer period and in addition to medication of the feed in severe outbreaks to reduce faecal shedding of the pathogen.

In the challenge study, he had compared dose levels of 60, 120 and 180ppm Denagard given for five days to five-week-old pigs challenged with L. intracellularis for five days, as well as both negative (unchallenged) and positive controls (0ppm). Ileum PPE scores were better and faecal shedding was lower in the groups of pigs receiving the two higher dosage levels than for the 60ppm group. The positive controls had significantly lower final weight, average daily gain and feed conversion efficiency as well as higher PPE scores and total lesion length.

Establishment of Swine Dysentery Eradication Programmes

Dr Jake Waddilove

Swine dysentery, caused by Brachyspira hyodysenteriae, remains one of the most important pig diseases, costing an estimated £10 per pig in terms of medication and lost production, explained Dr Jake Waddilove of Eastgate Veterinary Group in the UK. He described his experiences in establishing a programme to eradiate swine dysentery in a number of farms in the UK, adding that the Swine Dysentery Producers' Charter (SDPC) achieved considerable success within a short time, and the set-backs provided useful lessons for similar programmes in the future.

In 2006, swine dysentery was introduced to East Anglia, an important pig-producing area of the UK, by the movement of 400 pigs onto an outdoor organic finishing unit. Within three years, the disease had spread to 29 farms in the area. Analysing the spread of infection, it emerged that pig movements accounted for almost half of the infections. Also important were local spread, shared staff/managers and pig transport.

SDPC is a voluntary scheme run by the British Pig Executive (BPEX), which aims to provide advice to farmers, suppliers and allied industries to prevent the spread of infection and on the most effective cleaning and disinfection protocols. It does not specify individual farm control or elimination measures, which are instead agreed between the producer and veterinarian.

Once the Charter was set up, 80 per cent of local producers signed up within a short period, and samples from post mortem and/or faecal collection were sent for diagnosis. On the basis of the results, farms were classified as 'suspect', 'active', 'controlled, establishing freedom' or 'free' of swine dysentery. Sharing this information between Charter members and their veterinarians helped them make decisions on protecting their unit from infection or control and eliminating any existing infection.

"There has been success but the job is not yet complete," Dr Waddilove said, explaining that of the 29 farms involved, 27 were declared swine dysentery-free by the end of March, and just one new case was reported in June.

Just as important, he added, is that the Charter encourages co-operation between producers to control pig diseases.

Genetic Characteristics and Antimicrobial Susceptibility of Clostridium Isolates

Dr Fabrizio Agnoletti

Several species of clostridia are involved in swine diseases, said Dr Fabrizio Agnoletti of the Instituto Zooprolifilattico in Treviso, Italy, adding that the most relevant are Clostridium perfringens and Cl. difficile. He reported at the Novartis Symposium on the genetic characterisation and the susceptibility to tiamulin and valnemulin of clostridial isolates from neonatal piglets in Denmark and Italy.

In the study, all the Cl. perfringens strains belonged to the toxin type A and more than 80 per cent were positive for the beta2 toxin gene although there were no differences between these types in drug susceptibility.

Dr Agnoletti concluded that tiamulin and particularly valnemulin showed good potency against the clostridia species involved in enteritis cases in pigs. There were some differences in the susceptibility profiles, he added, which suggest the need for local sensitivity testing before the drug is selected for therapeutic application.

Characteristics of Denagard

Dr David Burch

Pharmacokinetic (PK) and pharmacodynamic (PD) integration has become one of the cornerstones in our understanding of how antibiotics work against bacteria, said Dr David Burch of Octagon Services in the UK. Each drug has its own PK profile and PD activity, usually measured as minimum inhibitory concentration (MIC), and his paper reviewed the activity of tiamulin (Denagard) against enteric infections (swine dysentery, porcine intestinal spirochaetosis and porcine proliferative enteropathy) and respiratory conditions (enzootic pneumonia and Actinobacillus pleuropneumoniae, APP).

Tiamulin shows unique PK against these infections, concluded Dr Burch, adding that it is well absorbed from the gut and goes via the plasma to the lungs, and probably to the macrophages and neutrophils. Excretion is via the bile so active components are re-excreted in the gut, concentrating in the ileal and colonic contents.

Plasma concentrations are normally associated with efficacy against M. hyopneumoniae and administration via water gave higher lung and plasma levels of tiamulin than via the feed. High concentrations are highly effective against A. pleuropneumoniae.

Administration via the feed is thought to slow the absorption of tiamulin and reduce its bioavailability but Dr Burch found higher concentrations in the gut when the medication was given in the feed. He concluded that tiamulin is both active and effective via this route against the causes of swine dysentery, ileitis and colitis in pigs.

Role of Vectors in Disease Transfer

Professor Steven McOrist

The final paper in this IPVS satellite symposium was presented by Professor Steven McOrist of the School of Veterinary Medicine and Science at the University of Nottingham in the UK. He discussed recent studies investigating the role of insect and invertebrate vectors in the transmission of key infections such as Lawsonia, Brachyspira and the PCV2 virus. The study revealed that the pathogens were found in or on an number of the insects found commonly around the farm or feed store.

Insects and invertebrates were collected on 15 farms in the UK and Ireland were selected. The farms were mostly positive for Lawsonia and PCV2, and several were positive for Brachyspira hyodysentariae. Cockroaches were found on two of the farms. The most common fly was the house fly but the false stable fly, garbage fly, fruit fly, stable fly and hover flies are also found in considerable numbers.

The results indicate that cockroaches (Blatta orientalis) and house flies may transmit B. hyodysentariae, and that Lawsonia may be spread by house flies and hover flies. One in ten of the cockroaches on one PCV2-positive farm were carrying the PCV2 virus.

From the results, Professor McOrist concluded that measures to control cockroaches and flies should be included in programmes to reduce infection levels or post-eradication re-infections on pig farms, along with appropriate biosecurity and pig medication or vaccination.

Further Reading

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