Production changes have brought the emergence of new pig diseases such as porcine enteroviruses.
With management changes have come eradication of major diseases like hog cholera and pseudorabies from our domestic swine herds.
As those diseases have been conquered, new challenges have emerged, notably porcine reproductive and res piratory syndrome (PRRS) and porcine circovirus, the agent responsible for postweaning multi-systemic wasting syndrome.
Porcine enteroviruses have resurfaced, and are now appearing as Teschen Disease, Talfan Disease and Agent X.
Case Study No. 1
A 1,000-sow, farrow-to-wean farm experienced increasing sow deaths. The farm has pen gestation with 4-7 animals/pen.
A few sows were seen pushing their heads in the corners of the pens or against the walls, but most of the animals that died did not show signs of illness prior to their deaths.
Several sows were autopsied, and tissues were submitted to a diagnostic lab. No lesions were observed on postmortem examination. Lab testing revealed that Agent X, an RNA virus, was found in the brains.
In response, the farm increased the isolation time for incoming gilts. A more intense manure/material feedback protocol was initiated to expose the incoming animals and to maintain exposure within the herd. For feedback, manure was collected from farrowing rooms and taken to sows prefarrowing. Materials from all areas of the farm were provided to gilts in isolation. No downstream pig customers reported unusual clinical disease in their nursery or finisher buildings.
Problems have continued to occur sporadically in the sow herd.
Case Study No. 2
A 1,250-crated sow farm selling weaner and feeder pigs experienced increased sow mortality. The farm had used numerous sources for incoming gilts and several different semen suppliers over the past several years. Sow mortality at the farm was seasonal, but 6-9% annual death rate was common.
Last fall, the farm staff noticed more sows chewing on bars and head banging on the crates. Sows that went down were unable to rise and died very soon after showing clinical signs. Postmortem examinations on several affected animals revealed no visible infectious lesions.
Brains from several acute deaths were submitted to a diagnostic lab. The diagnosis was fluorescent antibody (FA)-positive for Agent X and polymerase chain reaction-positive for porcine encephalomyelitis virus (PEV). The PEV organism is an enterovirus thought to cause Teschen Disease. The downstream customers of the farm reported no clinical signs of encephalitis in weaners or finishers.
The sow farm increased gilt acclimation time and intensified feedback within the herd. No sows have shown clinical signs for over six months.
Case Study No. 3
A 3,000-sow, farrow-to-wean system experienced increased encephalitis in the nursery system in 2005. Initially, the cause was thought to be Strep “brainers.” These are pigs with Streptococcus suis infections in their brains that are found down on their sides and paddling.
On closer examination, pigs were in excellent health at weaning and nursery mortality was under 1%. But after four weeks in the nursery, pigs were found down on their sides and non-responsive to antibiotics. Live pigs were taken to a diagnostic lab. Pigs were FA positive for Agent X, and a federal diagnostic lab isolated a porcine enterovirus group 1 virus from the brain.
Several management changes were made throughout production: longer exposure and acclimation of incoming gilts, more intense feedback within the herd, limiting crossfostering and euthanizing the “fall-behinds.” The farm has been producing PRRS-negative pigs, which have stayed PRRS negative through the nursery phase.
Even after these changes, the nursery continues to experience 2-3% mortality with sudden onset of encephalitis. Recently, a sow that died suddenly was autopsied and the brain was positive for Agent X. As of this writing, the disease is still ongoing in the herd.
Control or eradication of major disease organisms has led to normal disease organisms in pigs causing “new” diseases.
It is vital to utilize good husbandry practices and keep good records to establish benchmarks for your farm.
If unusual disease signs occur, work closely with a veterinarian to determine the cause and implement appropriate prevention or control procedures.