VLA: Coal Tar Poisoning

UK - Coal tar poisoning in young pigs as the result of using straw that had been kept on a recently resurfaced road was one of the highlights of the Veterinary Laboratories Agency (VLA) Monthly Scanning Surveillance Report for January 2011.
calendar icon 11 April 2011
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Alimentary Tract Diseases

Swine dysentery

Swine dysentery was diagnosed in a six-month-old Tamworth pig submitted to Sutton Bonington for necropsy. The animal was from a small breeding and finishing unit of around 50 pigs which also buys in pigs for finishing. Necropsy revealed necrotic typhlitis and colitis from which a Brachyspira spp organism, was isolated. There was strong evidence the disease had been introduced by a purchased pig. Advice was provided with regards to the hygienic precautions required to minimise the impact of this condition and how to break the cycle of infection.

Respiratory Diseases


Bury diagnosed porcine reproductive and respiratory syndrome virus (PRRSV) infection in a group of 1,050 seven-week-old pigs on a large continuous nursery-finisher unit on which 15 per cent were coughing and 13 had died. Three dead pigs were submitted for necropsy in two of which there was a fibrinous polyserositis and bronchopneumonia and in the third pig, which was markedly anaemic, there was significant haemorrhage from a gastric ulcer. PRRSV was detected by PCR on the spleen and Pasteurella multocida and Streptococcus suis type 7 were isolated from the lungs. No swine influenza virus or PCV2-associated disease was detected. Gastric ulceration associated with active PRRSV infection has been noted in previous submissions, sometimes in older finisher pigs. Interruption of feed intake due to inappetence is a recognised risk factor for the development of gastric ulcers and may have been involved in this case.

Streptococcal septicaemia

Thirsk investigated an ongoing problem presenting as 50 per cent morbidity and some mortality in recently weaned pigs on a breeder-finishing unit. It affected mainly gilt litters. Affected pigs were described as just going to sleep and not waking up. Post mortem examination of two affected piglets revealed a polyserositis with fibrinous pericarditis and pneumonia with much pleural fluid and fibrin clots and beige to purple consolidation affecting 25 per cent of the cranio-dependent portions of the lungs. Culture produced a growth in septicaemic distribution of Streptococcus dysgalactiae ssp equisimilis together with sparse growth from the lung of Streptococcus suis Serotype1/2, Mycoplasma hyopneumoniae was also identified using DGGE. Advice was given about hygiene, and avoidance of sources of abrasion and ways of avoiding or minimising tail biting which were thought to be predisposing factors.

Swine influenza

Truro investigated a herd in which all sows in the farrowing house had developed anorexia, five had aborted and two had died. There had also been 25 per cent pre-weaning mortality over a seven-day period. All staff working on the farm also had been off sick with respiratory disease over the preceding two weeks. Necropsy on lung specimens revealed evidence of respiratory pathology and Pasteurella multocida was isolated from both lungs. H1N1 2009 influenza virus was also confirmed by PCR and this was consistent with evidence of a multifocal, acute, suppurative and necrotising bronchiolitis and mild granulomatous pneumonia found on histopathology.

Other Diseases

Coal tar poisoning

Thirsk diagnosed coal tar poisoning as the cause of of malaise, recumbency and ataxia, affecting a group of 400 pigs in a straw yard nursery system. Thirty-five animals had died by the time animals were submitted for necropsy. Post-mortem examination revealed a severe, diffuse hepatopathy featuring random beige, purple and brown discolouration of individual liver lobules. These changes extended throughout the parenchyma (see figure). There was also severe oedema of the musocolon and greater curvature of the stomach. Further history revealed that the animal had been bedded on straw which was over a base of road clippings from a road that had been re-surfaced. The owner agreed to withdraw the animals from the human food chain for 30 days after last exposure to the presumptive toxin.

Diffuse multifocal hepatopathy in coal tar poisoning associated with access to road planings in eight-week-old pigs

Suspected cardiac myopathy caused by bracken

Two fattening pigs grazing on moorland were found dead and were submitted to Truro for post mortem examination. Necropsy findings included serosanguineous exudates and fibrin tagging in body cavities, widespread visceral congestion and haemorrhages. Histopathology revealed myocardial necrosis in the left ventricle of one pig. Differentials including mulberry heart disease, porcine stress syndrome, excessive catecholamine production and toxic injury were ruled out. Bracken poisoning, which has been reported in pigs grazing woodland and other rough pasture, was suspected. Discussion with the farmers and their vet revealed that the land on which the pigs had been grazing had been frozen and then started to thaw, which may have exposed new bracken shoots to the pigs.

Neurological Diseases

Otitis interna

Bury diagnosed osteomyelitis affecting the inner ear as the cause of a head tilt in a boar which had developed six weeks previously. The boar had remained mobile and was eating but was nervous, excitable and sometimes violent in its reactions and the head tilt did not resolve leading to the decision to cull. The boar was the only one affected from a group of 84. Post mortem examination revealed infection involving middle and inner ears associated with a focus of osteomyelitis. Solid green exudate was also filling the external ear canal. Pasteurella pneumotropica was isolated.

Congenital tremor

A farm had recently been experiencing a high morbidity of newborn pigs from gilt litters affected with congenital trembling. Two live pigs were submitted to investigate the problem. Following necropsy histopathology revealed a deficiency of myelin in the spinal cord, consistent with congenital tremor type A2. This form of the disease is believed to be caused by a virus, but the precise aetiology is uncertain.

Further Reading

- You can view the full report by clicking here.

Further Reading

- Find out more information on the diseases mentioned in this article by clicking here.
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