Managing other pathogens could limit the impact of cirovirus.
The North American swine industry is in the midst of some of its greatest health challenges ever. Clinical losses due to disease are at levels never before seen.
The main disease getting all the attention is porcine circovirus-associated disease (PCVAD). This is a very tough disease, and we have not begun to fully understand all the interactions between the pig's environment, genetics and nutrition and the complex disease interactions within the pig.
Because of its complexity, we need to focus on the things we do understand. The high death losses from circovirus are the result of a pneumonia complex involving circovirus and a combination of other disease cofactors such as porcine reproductive and respiratory syndrome (PRRS), swine influenza virus, a variety of bacteria and Mycoplasmal pneumonia.
For years, mycoplasma has been part of the Swine Respiratory Disease Complex. Tried and true treatment and control protocols have been effective in keeping the effects of this disease to a minimum.
Mycoplasma continues to be a key cofactor in this disease complex that involves circovirus, and its control must be a priority.
Case Study No. 1
Our first case is a 2,500-sow, farrow-to-finish farm with three-site production. The pigs spend eight weeks in the nursery and 16 weeks in the finisher. Over the last two years, occasional postmortems and laboratory work identified lung and lymph node lesions consistent with a circovirus infection. The farm is mycoplasma-positive with a one-dose mycoplasma vaccine used for control.
Over the last six months, the incidence of clinical losses due to pneumonia has increased from 4% to almost 6%. Recent diagnostics have detected evidence of increased mycoplasma activity as well as an increase in lesions attributed to circovirus.
We reevaluated the mycoplasma control protocol to ensure we were getting adequate control, and decided to switch from one vaccination at weaning to two vaccinations. The first dose is given at two weeks postweaning and the second dose at five weeks. We also elected to add a pulse dose of lincomycin in the feed for two weeks after the third week in the finisher.
Microscopic lesions in the lung and serology indicated some mycoplasma exposure early in the finisher phase.
Death loss has improved, but with the presence of circovirus, death loss is still higher than target.
Case Study No. 2
The second farm is a 5,000-sow, farrow-to-finish farm with wean-to-finish barns. It is a PRRS-negative and mycoplasma-negative farm. Wean-to-finish death loss from group to group usually stays between 3-5%.
About six months ago, this farm saw death losses begin to exceed 5% on multiple groups. Clinically, we saw an increase in pigs treated for pneumonia and an increase in fallback pigs. Postmortem examinations and laboratory diagnostics indicated some evidence of circovirus lesions.
To determine what other disease agents might be acting as cofactors and contributing to the problem, we conducted a serological profile across the system. We tested 10 pigs from each age group starting at weaning, and also tested each group at four-week intervals up to market weight. We identified serologic conversion to mycoplasma in pigs starting at 12 weeks postweaning, consistent across multiple sites.
Since then, we have gone into the sow herd to look for serologically positive sows, and at this time have not determined that any are present. We have started vaccinating the pigs with two doses of mycoplasma vaccine. The first dose is given at weaning and the second two weeks later.
At this time, it is too early to tell if the herd will see a reduction in the clinical signs of pneumonia.
The increase in health challenges across the swine industry has highlighted the importance of knowing the different diseases involved.
Circovirus is definitely showing up more often. With the high demand for circovirus vaccine, many pork producers are unable to get an adequate supply.
In this current situation, control of the cofactors contributing to the problem is critical. Mycoplasmal pneumonia is an organism we understand. We have excellent tools available to use for control. Antibiotics, vaccines and facility management can be used separately or in combination to design a plan that works best in each situation.
Veterinarians also have access to sophisticated diagnostic procedures to help sort out primary and secondary problems.
The producers who are able to figure out the best approach to respiratory disease control will be the ones with the best chance of survival.