Unusual presentation: 10% mortality in a 60-sow piggery over 16 weeks.
Time and location: Far North Queensland, Sep-2018 to Jan-2019. Note prior to 2017 it had been rare to lose any pigs although there had been some losses in 2017.
Case definition: Sows stop eating, lose body condition, some die within a day or two, others take a week or more. The case definition is deliberately broad due to the range of clinical signs and post mortem findings.
Gross post mortem findings: Twelve sows were affected between Sep-2018 and Jan-2019. Seven of the 12 cases (58%) died. Clinical signs varied from inappetence and death within 12 hours, to abortion or stillbirths, to skin blotching, to wasting.
Six of 15 gilts introduced in June 2018 were affected. The gilts had been split across two pens and 5 of 7 gilts in one pen became ill in September with diamond-shaped skin lesions. They seemed to recover but then 2 aborted and 3 subsequently died. One other introduced gilt from the second pen became ill in Jan-2019.
A moribund sow with a high temperature, swollen legs, ears and face, and severe skin blotching was euthanased and autopsied in mid November. She had farrowed 3 weeks earlier with 8 stillborn piglets and 3 live born. Two sows that had been sent for premature slaughter in the following fortnight were found to have a large (2L) liver abscess and an abdominal abscess respectively at meat inspection.
Laboratory findings: No abnormalities were seen in the brain, lung, spleen, stomach and intestine of the autopsied sow. Histopathology showed an interstitial nephritis (of uncertain significance) and skin pathology suggestive of a systemic sepsis. A pure growth of non-haemolytic E coli was cultured from the liver abscess.
Disease exclusion testing: African Swine Fever /Classical Swine Fever negative; Porcine Reproductive and Respiratory Syndrome virus negative.
Animal / management / environment risk factors: The practice organised for a pig specialist to attend the farm. He believes that several conditions were operating at one time:
- Wasting due to chronic internal abscessation (based on the two slaughter sows).
- An Erysipelas outbreak in the introduced gilts (given the diamond-shaped skin lesions in the gilts, severity of clinical signs in the autopsied sow, and no other gross pathology).
- Inappetence followed by constipation, gastric ulceration, anemia and death.
The introduction of gilts from a high health status herd to one of a lower health status without quarantine was noted as a risky practice (despite having done this for 10 years).
Possible reasons for Erysipelas vaccine breakdown were:
- Gilts assumed to have been previously vaccinated and therefore only given one dose on arrival
- A vaccine container of 125 doses used over many months due to the small number of sows vaccinated at any one time
- Issues with vaccine storage, eg if the fridge temperature was 7oC or above at any time.
Recommendations to the producer:
- To reduce risk of abscessation – attention to piggery hygiene and maintaining needle hygiene
- Add amoxicillin to all sow feed for six weeks
- Revaccinate the entire breeding herd with a new batch of Erysipelas vaccine
- New protocols for introducing gilts
- Add Epsom salts to dry sow feed
- Dose any sow not eating daily with Epsom salts and entice to eat (offer grass, milk, other feed)
- Attention to vaccine storage, drug storage and needle hygiene.