Isolation of Acanthamoeba sp. from a Greyhound with Pneumonia and Granulomatous Amebic Encephalitis

Abstract

Abstract. Acanthamoeba were isolated from a naturally occurring animal infection of granulomatous amebic encephalitis. The amebas were grown from lung lesions from a 1-year-old greyhound puppy, which was 1 of several dogs in a kennel that was affected by a progressive fatal neurologic and respiratory disease. The Centers for Disease Control, Atlanta, Georgia, confirmed the disease to be acanthamebiasis and specifically identified the amebas as Acanthamoeba culbertsoni by fluorescent antibody testing on brain tissue from the dog. The amebas were cultured initially on potato dextrose agar and on nonnutrient agar plates that were seeded with a lawn of nonpathogenic Escherichia coli. The isolate was then transferred to nonnutrient agar plates containing killed Enterobacter aerogenes and subsequently to axenic medium and cell cultures. The isolate was highly pathogenic by intranasal inoculation into 2-week-old mice.Acanthamebiasis is an infection by a free-living ameba, Acanthamoeba, which was proven pathogenic in 1958 by Culbertson et al. 10,11 The name granulomatous amebic encephalitis (GAE) was given to Acanthamoeba infections to differentiate this disease from another encephalitic amebic disease called primary amebic meningoencephalitis (PAM), which is caused by a closely related genus, Naegleria, 5,27 The first reported free-living amebic infection was in 1965, and although believed to be caused by Acanthamoeba at the time of the report, it is now thought to have been caused by Naegleria.14 The first confirmed human case of acanthamebiasis was not reported until 1972, 19 but other cases that occurred at earlier dates have been retrospectively diagnosed as Acanthamoeba infections. 22,28,39 16,19,[24][25][26]38 The clinical course of the disease in humans is usually prolonged, with an insidious onset and an extended course of weeks to months. 15,27,36 The pathogenesis of acanthamebiasis is still unclear, partly because the disease is commonly diagnosed late in the infection. Proposed routes of infection include inhalation of the organisms from the air or exposure of the organisms to the nasal cavity from swimming in contaminated water. 27 In the upper respiratory tract, the organisms can replicate and either infect the brain directly by migration up the olfactory nerves or indirectly by hematogenous spread from a primary lung infection. 24,27,36 Some reports have suggested hematogenous spread to the brain from external wound contamination. 17,22,33 Besides an encephalitis and pneumonia, Acanthamoeba can cause eye infection in humans, which is usually associated with soft contact lens wear. 30,34 Therefore, extension of the organisms via the optic nerve from eye infections could be another possible pathogenesis of encephalitis. 20 Cases of acanthamebiasis in animals usually have been reported as individual isolated cases, 2,12,29,32 but there are reports of multiple cases in greyhounds. 15,18 Acanthamoeba have been isolated in a few human cases, 36 but there are no reports of isolation from animal infe...

Systemic acanthamoebiasis associated with canine distemper in dogs in the semiarid region of Paraíba, Brazil

“…infection. Similar findings have been described in elsewhere (Ayers et al 1972, Pearce et al 1985, Bauer et al 1993, Dubey et al 2005, Reed et al 2010, Kent et al 2011.…”

“…is rare in dogs and is generally associated with immunosuppressive conditions such as canine distemper (Reed et al 2010), as seen in the three cases of this report, and corticosteroid therapy (Foreman et al 2004). However, some cases were described with absence of characteristic signs of immunosuppression (Ayers et al 1972, Bauer et al 1993.…”

“…In dogs, cases of infections by Acanthamoeba spp. and Balamuthia mandrillaris have been reported in Vietnam and several regions of the United States (Ayers et al 1972, Pearce et al 1985, Bauer et al 1993, Foreman et al 2004, Dubey et al 2005, Reed et al 2010, Kent et al 2011. Such infections showed acute or chronic systemic involvement mainly characterized by granulomatous inflammation associated with necrosis and hemorrhage in the lungs, heart, kidneys and brain.…”

Diagnostic Exercise

“…1,5 Systemic acanthamoebiasis is opportunistic and typically a result of inhalation of cysts from the air or exposure to the organisms while swimming in contaminated water. Spread to the brain can occur via the olfactory nerves or hematogenously from a primary lung infection.…”

“…are free-living protists, commonly found in fresh water, salt water, soil, dust, and sewage. 1,6 The life cycle consists of a free-living cyst and a vegetative trophozoite that feeds on bacteria in aquatic environments and acts as an opportunistic pathogen. Canine infections are caused by Acanthamoeba castellanii, Acanthamoeba culbertsoni, and Acanthamoeba sp.…”