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Disease surveillance in England and Wales, August 2019

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APHA disease Surveillance report headlines

  • Neosporosis responsible for an abortion outbreak in a housed dairy herd

  • Unusual skin lesions in sheep

  • Tapeworms in chickens

  • Focus on avian botulism

Highlights from the scanning surveillance network

Cattle

Neosporosis

An abortion outbreak caused by neosporosis was investigated at the APHA Carmarthen veterinary investigation centre (VIC). More than 30 cows aborted over a period of three weeks in a 500-cow dairy herd that calves throughout the year. Five of the aborted calves were examined at the VIC.

No specific gross pathology was identified but Neospora caninum DNA was detected by PCR in the brains of all five calves. Histopathology indicated a non-suppurative encephalitis and myocarditis, confirming neosporosis as the cause of the abortions (Fig 1).

Fig 1: Haematoxylin and eosin-stained section of brainstem of a calf affected with Neospora caninum. There is a focal aggregate of glial cells surrounding a degenerate neuron (glial nodule)

Cattle can be infected by N caninum through ingestion of oocysts passed by dogs, which are the definitive hosts (this is known as ‘exogenous’ infection), or in utero from chronically infected dams (‘endogenous’ infection) – this latter route is considered to be much more common.

When a cluster of abortions due to neosporosis occurs, a thorough investigation of the herd feeding and management practices should be undertaken, going back at least two months before the first abortion occurred, as the incubation period following exposure to the protozoan pathogen is several weeks. This investigation, together with serology on cohorts and offspring or dams of affected cows, may indicate the most likely source of infection, and enable appropriate control measures.

This recent outbreak occurred in a herd that is housed all through the year. From April fresh grass was harvested to feed in a total mixed ration. The introduction of N caninum oocysts in the fresh grass was considered a possible explanation for the outbreak.

About this report

This report is produced each month by the APHA Surveillance Intelligence Unit and the six Species Expert Groups (livestock and wildlife). The international horizon-scanning summaries are produced by …

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