Encephalitozoonosis in Squirrel Monkeys (Saimiri sciureus)

Abstract

Abstract. Twenty-two cases of naturally occumng encephalitozoonosis in squirrel monkeys are reported from breeding colonies of the Delta Regional Primate Research Center, Covington, La. Characteristic foci of granulomatous inflammation and organisms were demonstrated in brains, kidneys, lungs, adrenals, and livers. Vasculitis and perivasculitis were also common lesions in several organs. At least seven cases were congenital while ten others occurred in monkeys less than nine months old. Granulomatous placentitis, previously unreported in any species due to Encephafitozoon cuniculi, was present in one monkey.Encephalitozoon cuniculi is an intracellular microsporidian parasite known to produce mild subclinical disease and occasionally clinical disease in several species of mammals, including rabbits,', lo. 15. 16. mice,'4. '' rats,'.7. l7 ground shrew^,'^ dog^,^.^.^^.^^ blue f o x e~, *~. ?~ a cat, (' monkeys,'.' and Microsporidia are small, rod shaped protozoa which possess an internal coiled tube, the polar filament, in the spore stage. This structure, visible by electron micro~copy,~' is extruded and used to penetrate host cell membranes when infecting new cells. Once inside host cells, differentiation and multiplication occur within cytoplasmic parasitophorous vacuoles termed pseudocysts.32 Development within renal tubular epithelial cells permits seeding of the urine as pseudocysts rupture into the tubular lumen." Horizontal transmission occurs following the ingestion of food contaminated with spore-containing urine from an infected animal.32 Spores extrude thin polar filaments, invade gut epithelium, and spread hematogenously to several organs-especially brain, lung, kidney, and liver.3' Vertical transmission has been demonstrated experimentally in blue foxes (Alopex lagopus),23 rabbits,'' and previously suggested in a squirrel monkey less than 24 hours old.'E. cuniculi has a long history of interfering with and complicating medical research with experimental animals. The incidence of this disease in some colonies of laboratory rodents varies between 25 and 95%." This disease has been reported only twice in a commonly used experimental primate, the squirrel monkey (Saimiri sciuyeus).'.' This report describes lesions associated with 22 naturally occumng cases of encephalitozoonosis identified over a 20-month period at Delta Regional Primate Research Center, Covington, La. Materials and MethodsAt Delta Regional Primate Research Center, approximately 250 squirrel monkeys are maintained in small breeding groups in both indoor and outdoor facilities. All animals which die receive a complete necropsy. Representative samples of all major organs were fixed in 10% neutral buffered formalin, processed routinely for histology, and stained with hematoxylin and eosin (HE). Tissues with lesions suggestive of encephalitozoonosis were stained with Taylor's bacterial For electron microscopy, formalin-fixed tissues from one case were washed in phosphate buffer, post-fixed in 3% glutaraldehyde and 1 % osmium tetroxide, dehyd...

Zoonotic Potential of the Microsporidia

“…Disseminated natural infections resulting in high morbidity and severe encephalitis caused by Encephalitozoonlike organism have been reported for stillborn and young squirrel monkeys (Saimiri sciureus) in the United States (28,337). Although parasite identification was based on electron microscopy only, which does not allow one to distinguish E. cuniculi from E. hellem, the neuropathological symptoms strongly suggested that E. cuniculi was the species involved.…”

Human microsporidial infections

“…can be transmitted transplacentally from mother to offspring (100,252). Transplacental transmission may even be important in the pathogenesis of the disease, especially in foxes, dogs, and nonhuman primates such as squirrel monkeys (137,145,252).…”

“…Four categories of host-parasite interaction have been described for mammalian and human encephalitozoonosis (192): (i) latent asymptomatic or chronic mildly symptomatic infection, known in mice and rabbits of all ages and in dogs, foxes, and squirrel monkeys infected as adults (16,45,101); (ii) acute, potentially fatal disease, observed in neonatal dogs, foxes, and squirrel monkeys (21,136,137,252); (iii) proliferation of the parasite in the absence of competent host defenses, seen in patients with cellular immunodeficiency and athymic mice in vivo and in cell cultures in vitro (81,177); and (iv) symptomatic human disease in the immunocompetent host (175 (56,194). Also, alteration of more specific immunologic responses, including enhanced killer cell activity and activation of macrophages, has been demonstrated in animals with encephalitozoonosis (142).…”

“…Since 1857, when Nageli first discussed newly identified parasitic agents in silkworms, which he termed Nosema bombycis (140), microsporidia have been recognized as a cause of disease in various animal groups, among them commercially important insects, fish, laboratory rodents, rabbits, fur-bearing animals, and primates (45,82,141,171,194,252). Indeed, their host range is extensive, including most invertebrates and all classes of vertebrates (45,(200)(201)(202)(203).…”

A case of equine abortion caused by Encephalitozoon sp.

“…Abortion and stillbirth induced by E. cuniculi were reported in single cases in horses (AFIP, 1988(AFIP, , 2004Van Rensburg et al, 1991;Patterson-Kane et al, 2003) and in squirrel monkeys (Zeman and Baskin, 1985) and have been assumed in cattle (Reetz, 1995). There are only three reports on equine placentitis and abortion caused by E. cuniculi (AFIP, 1988(AFIP, , 2004Patterson-Kane et al, 2003).…”