Researchers Track Lawsonia intracellularis Spread

Lawsonia intracellularis is being forced out of hiding and its secrets extracted largely because of the intense research efforts of scientists like Nicola Pusterla, DVM, PhD, Dipl. ACVIM, and his colleagues at the University of California, Davis, and the University of Minnesota, St. Paul.

The gram negative bacterium L. intracellularis is the causative agent of equine proliferative enteropathy (EPE), an emerging and devastating disease of weanling foals.

"The bacterium lives freely inside the cells lining the intestine causing these cells, called enterocytes, to proliferate. Over time, the intestines become thick leading to reduced absorption of nutrient and loss of protein," explained Pusterla.

Affected foals (typically 4-9 months old) are lethargic, febrile, have weight loss, diarrhea, colic, and low protein (albumin) levels in their blood.

EPE was first reported in 1982. Since then, both sporadic cases and outbreaks have been reported. It is now thought to affect foals in the United States, Canada, South America, Europe, and Australia.

Because many of Lawsonia's habits remain secret, Pusterla and colleagues established an animal model to better study EPE. Specifically, the research team sought to determine how exactly foals become infected with L. intracellularis.

Eight foals between 4 and 5 months of age were divided into one of three groups. The first group (n=3) were challenged with an intragastric inoculation of L. intracellularis organisms of equine origin. The remaining foals served as sentinels (n=3) who cohabitated with the infected foals and controls (n=2).

All foals challenged with L. intracellularis developed signs of EPE during the 90 day study period. Fecal shedding of the bacterium was noted as early as 12 days post-inoculation and persisted for 7-21 days. Seroconversion (formation of antibodies against L. intracellularis) occurred in all three challenged foals and one sentinel. The remaining two sentinels and the control foals did not seroconvert.

"These results support the hypothesis that L. intracellularis is spread by the feco-oral route," said Pusterla. "Since it appears that healthy foals with no sign of EPE can shed the bacterium exposing susceptible foals to the bacterium, infectious disease control measures will be an important consideration in preventing the spread of disease from an infected to a susceptible animal."

The study, "Oral infection of weanling foals with an equine isolate of Lawsonia intracellularis, agent of equine proliferative enteropathy," is scheduled to be published in an upcoming edition of the Journal of Veterinary Internal Medicine.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.