Growing evidence suggests this forgotten disease may be on the rebound.
A disease known as swine eperythrozoonosis (epe), first recognized in the 1930s and widely controlled with the use of arsanilic acid in feed up to 1986, has been largely forgotten. But there is growing concern that the disease may be a cause of sow fertility, lactation and preweaning mortality problems.
Eperythrozoon suis was reclassified in 2002 as Mycoplasma suis (M. suis), but the disease it causes is still known as swine eperythrozoonosis. This blood-borne bacterial organism has been shown to affect pigs of all ages, says Iowa State University (ISU) immunologist Erin Strait, DVM.
“It generally shows up in younger pigs in the form of ill-thrift or anemia. You can have an acute hemolytic anemia, where the pigs are very sick, or a chronic phase, where there probably won’t be any visible signs,” she says.
Less common, there can be acute deaths in sows from hypoglycemic coma caused by low blood sugar levels. During stressful times, such as gestation, a sow might be fine one day but dead the next, Strait says.
Close examination prior to death may have shown that affected sows had pale skin and were exercise-intolerant, but this can be subtle and is easy to overlook, she adds.
Recent Research Efforts
Mycoplasma suis (M. suis) has not been widely studied, but a group of European scientists in 2007 developed a polymerase chain reaction (PCR) test, which provided a much-improved diagnostic assay over previous blood-staining procedures.
This group used their more sensitive PCR test to conduct a prevalence study of normal-appearing pigs at a German slaughter facility, and found the organism in 79 out of 196 farms.
This research group also identified a field isolate of M. suis that is intra-cellular, so it is not identifiable by blood staining, only by PCR. Tetracyclines can be used to treat the condition, but those antibiotics won’t clear the organism from the pig, she states.
In follow-up work, Strait performed a small survey of pig populations, using a modified PCR test she developed in her lab at ISU, and identified M. suis in normal-appearing pigs.
Surprising Signs in Sows
As Strait continued her research, the key question was whether it would really matter to the pork industry if the organism only turned up in healthy pigs. She expected to possibly find cases of anemic young pigs not explained by iron deficiency.
But to her surprise, she was presented with a case of sows failing to lactate. In a case report, presented by Peggy Anne Hawkins, DVM, of Northfield, MN, newborn pigs were found to be starving due to lactation failure. The sows produced adequate colostrum but failed to produce milk. “It was pretty prevalent in the entire sow system; there was an acute problem in this herd,” Strait observes.
Diagnosis confirmed that affected litters came from sows that were positive for M. suis, and unaffected litters came from negative sows, Strait comments. Treatment with tetracycline resolved the issue for the most part. Hawkins says the disease surfaced about the same time the producer changed gilt sources.
“The source herd is positive for M. suis and doesn’t appear to be having problems to the same extent. One possible factor may be that sows at the source herd are fed twice a day instead of once a day, which likely helps to maintain a more constant glucose level in these animals,” Hawkins says.
In a separate herd Strait has been working with, sows appear extremely lethargic when they are placed in farrowing crates. The farm veterinarian used a glucometer to test for low blood glucose (sugar) levels. Samples were tested and M. suis was confirmed, suggesting that the pathogen at least plays a role in the reproductive problems observed in the sow herd, Strait says. M. suis has also been associated with anestrus and failure to conceive.
By diagnosing suspected cases, producers can eliminate one possible frustration in the search for causes of preweaning mortality. If the problem flares up at certain stress points, attention can be placed on avoiding these acute sow deaths or lactation failures by antibiotic therapy, feeding adjustments or management changes to reduce stress, she notes.
Since the organism is blood-borne, it’s also advisable to limit use of needles and control insect vectors, tail biting and fighting to limit disease spread.
PCR Test Required
If you aren’t specifically looking for the M. suis organism, you won’t find it using conventional diagnostic tools, Strait says. To diagnose this potentially ubiquitous organism, submit whole blood samples, liver or spleen for specific identification by PCR.
Send in whole blood samples before administering antibiotics, which could produce false negative results. PCR costs $30/test.
There are numerous reasons for sow failure to lactate – ergotamine (a fungus in small grains like wheat or rye), water deprivation, stray voltage, different infections, nutritional imbalances, etc.
“But if sows are not milking right after they farrow, even though they are eating well, and the problem doesn’t appear to be an obvious case of mastitis, then you may want to consider that it could be due to Mycoplasma suis,” Strait stresses.