Four pileated gibbons (Hylobates pileatus) died acutely during two separate disease outbreaks. The animals presented diarrhea, vomiting and severe apathy. Virology, bacteriology and parasitology on feces did not reveal any pathogen and blood cell count and extensive biochemistry did not show any sign of metabolic disorder. Only histopathology revealed the presence of intraluminal argyrophilic bacteria in the severe proliferative enteropathy lesions observed at necropsy. Specific PCR on feces associated with severe enteritis observed at necropsy and histopathological findings led to the final diagnosis of Lawsonia intracellularis.
After this episode, a prospective epidemiological study was initiated to better understand the contamination process and the prevalence among primates housed at the zoo. Thirty-four real-time PCRs (LSI Vetmax, Lawsonia Kit, Fischer scientific) were conducted on fecal samples of primate groups from 31 species (1 Atelidae, 2 Pithecidae, 2 Cebidae, 9 Callithrichidae, 3 Cercopithecidae, 4 Hylobatidae, 9 Lemuridae, 1 Indridae) and 14 PCRs were carried out on digestive content from small mammals (Mus musculus, Apodemus sylvaticus, Sorex araeus) trapped in monkey houses and their surroundings.
Sixty-two percent of all primates came out positive for L. intracellularis (with highest prevalence in the Lemuridae: 92%) and 57% of small mammals were infected (with highest prevalence in rodents: 78%). None of the tested primates presented any sign of disease before sampling.
The study helped identifying rodents as asymptomatic carriers and a potential source of infection for the zoo primates and exposed that numerous primate species as asymptomatic carriers.
To this day, L. intracellularis has mostly been described in pigs even if reported in a broad range of mammalian species including primates (Macaca fuscata and M. mulatta).1,2 L. intracellularis may be underdiagnosed in zoos as it requires a PCR for feces identification and silver staining for histological visualization.4 As this bacterium’s spread in zoo primates seems to be wider than first thought, one should consider adding L. intracellularis to the differential diagnosis of severe diarrhea in primates. The study results emphasize the potential emerging disease risk that L. intracellularis could pose in Western Europe.3
1. Klein EC, Gebhart CJ, Duhamel GE. Fatal outbreaks of proliferative enteritis caused by Lawsonia intracellularis in young colony-raised rhesus macaques. J Med Primatol. 1999;28(1):11–8.
2. Lafortune M, Wellehan JF, Jacobson ER, Troutman JM, Gebhart CJ, Thompson MS. Proliferative enteritis associated with Lawsonia intracellularis in a Japanese macaque (Macaca fuscata). J Zoo Wildl Med. 2004;35(4):549–52.
3. Vannucci FA, Pusterla N, Mapes SM, Gebhart C. Evidence of host adaptation in Lawsonia intracellularis infections. Vet Res. 2012;43:53.
4. Vannucci FA, Gebhart CJ. Recent advances in understanding the pathogenesis of Lawsonia intracellularis infections. Vet Pathol. 2014;51(2):465–477.