Haemophilus parasuis or HPS is a bacterial disease that can cause death or chronic lameness, and is often referred to as a “high-health disease.”

Many conventional herds have reduced the level of other bacterial organisms via modern management practices, and in doing so, have elevated the potential for HPS to become increasingly prevalent.

Case Study No. 1

A client purchased weaner pigs and discontinued buying feeder pigs. The change was sparked by the need to increase the number of pigs on feed. The opportunity to purchase the weekly production of weaner pigs from a new, 1,200-sow, breed-to-wean unit had significant appeal.

Pigs were placed weekly into wean-to-finish (W-F) facilities at 17-22 days of age. The new sow herd was sourced with gilts naïve for porcine reproductive and respiratory syndrome (PRRS) and positive for Mycoplasmal pneumonia.

The first 1,000-head W-F barn filled with pigs in February got off to a good start, but developed a mild cough during week two. On Day 12, the client called to report three pigs died overnight. The producer adjusted the ventilation settings. Three days later I received a call that one good pig died and three more the next morning.

I arrived at the W-F barn to find a mild, widespread cough in the pigs, moderate swelling to the hock joints and many lethargic pigs. Two pigs were euthanized for tissue collection. I told the producer that either Streptococcus suis or HPS was the cause of this outbreak. Treatment plan included individual injections to the visibly sick pigs and water medication for the next five days.

Tissue results from the diagnostic lab isolated an HPS organism from the brain, lung and joint of the first pig and the lung and brain of the second pig.

We started pigs on water medication the second week after filling the barn and implemented aggressive individual pig treatments.

Case Study No. 2

A 2,400-sow unit recently doubled in size. The producer signed a new contract that required him to change genetics. The current sow population was PRRS-naïve and mycoplasma-positive. Production was 22.6 pigs sold/mated female/year with very few health challenges.

The incoming gilts were purchased from a user group recommended by the company buying the pigs. The gilts were isolated in an off-site barn 3.5 miles from the sow unit. New gilts were vaccinated in isolation. Cull sows were introduced 4-5 weeks after the gilts arrived. Gilts entered the sow unit eight weeks after arrival.

The producer called to say three gilts had died.

Walking through the isolation barn, the owner found gilts lethargic with 10-15% of the 300 gilts showing signs of respiratory distress. Water consumption had dropped 20%.

The owner and barn caretaker performed necropsies. All three gilts were found to have fluid in the thoracic cavity with a white film covering the outer surface of the lungs. The stomachs contained feed and the intestinal tract appeared to be normal.

I diagnosed an acute respiratory outbreak and advised the producer to inject all 300 gilts with an antibiotic. When I toured the isolation barn the next afternoon, no more gilts had died, but the group was still slightly depressed and 5-6 were heard coughing. Lung samples preserved by the producer were sent to the diagnostic lab for testing.

During my walkthrough of the isolation barn, the owner said problems started when the cull sows arrived. We concluded they must have been carrying a strain of HPS pathogenic for the gilts.

I recommended all incoming gilts receive two doses of HPS vaccine on weeks one and three after arrival to immunize the gilts and avoid another outbreak in the isolation barn. More importantly, the ultimate goal was to avoid an HPS break in the gilts after entry to the sow unit.

The diagnostic lab confirmed HPS on two of the three lung samples submitted. The vaccination program on the incoming gilts has worked well. The plan is to continue using the vaccine until all of the original sows are replaced with the new source. Then the producer will attempt to drop the HPS vaccine.


HPS is becoming more prevalent, often compounded by stress that creates the opportunity for disease expression.

Clinical signs vary depending upon the presence of other pathogens. Mixing multiple sources of pigs can occasionally cause difficulties. High-health animals are generally at more risk.

Consult your veterinarian to discuss a plan for HPS.