Disseminated infection with Balamuthia mandrillaris in a dog

Bilateral chronic granulomatous nephritis and meningoencephalitis were diagnosed on necropsy of a 2-year-old male Great Dane dog. The causative agent was identified as Balamuthia mandrillaris, based on morphologic features, immunohistochemical staining, and deoxyribonucleic acid detection using the polymerase chain reaction with newly designed primer pairs. Trophozoite and cystic forms of the amoeba were evident within the kidneys and brain parenchyma. This is the first report on a B. mandrillaris infection in a dog.     

Meningoencephalitis caused by Naegleria fowleri in cattle of northeast Brazil

Primary amoebic meningoencephalitis is an acute disease of the central nervous system of humans and animals caused by Naegleria fowleri. This report describes a case of meningoencephalitis caused by N. fowleri in a crossbred, one-year-old bovine with progressive neurological signs. At necropsy there was thickening of the meninges and multifocal areas of malacia in the thalamus, caudal and rostral colliculi, parietal and occipital cortex, and cerebellum. Histologically there was multifocal necrosupurative meningoencephalitis associated with areas of malacia containing amoebic trophozoites. Immunohistochemistry of the brain was positive for N. fowleri. The disease should be included among the differential diagnosis of diseases of the central nervous system in cattle in areas where animals are exposed to hot, stagnant water.     

Naegleria fowleri-associated encephalitis in a cow from Costa Rica

Species of Naegleria, Acanthamoeba, and Balamuthia are soil amoebae that can cause encephalitis in animals and humans. Of these, Naegleria fowleri is the cause of often fatal primary meningoencephalitis in humans. N. fowleri-associated encephalitis was diagnosed in a cow that was suspected to have rabies. Only formalin-fixed brain was available for diagnosis. There was severe meningoencephalitis involving all parts of the brain and numerous amoebic trophozoites were present in lesions. The amoebae reacted with N. fowleri-specific polyclonal antibodies in an indirect immunofluorescent antibody test. This is the first report of amoebic encephalitis in any host from Costa Rica.     

Fractures, dislocations and contusions in the Borneon orang utan (Pongo pygmaeus pygmaeus)--a review of 21 cases

The clinical features, radiographic findings and management of traumatic lesions in the orang utan are described with reference to 21 cases. Eight cases had fractures of the femur and five had humeral fractures; all the fractures were successfully treated. One case with a skull fracture (frontal parietal) died before treatment could be instigated. Five orang utans with contusions recovered with symptomatic treatment and rest.     

Cerebrospinal angiostrongyliasis in five captive tamarins (Sanguinus spp)

Four cotton-top tamarins ( Sanguinus oedipus oedipus ) and one emperor tamarin ( S imperator subgrisescens ) housed in a zoo became depressed, anorexic, paraparetic and eventually paralysed. The animals died within 5 days to 18 months of the appearance of clinical signs. Histological examination showed nonsuppurative and eosinophilic meningoencephalitis, and metastrongyle nematode larvae were found within subarachnoid spaces of all animals and within the spinal cord of one. Intact larvae with features consistent with Angiostrongylus cantonensis were recovered from the brain of one animal. This parasite is the classical cause of eosinophilic meningoencephalitis in many parts of the world and the diagnosis can be strongly suspected on clinical grounds. In endemic areas like south-east Queensland, protection of captive animals against infection with A cantonensisi s a difficult balance between providing a stimulating, natural setting and eliminating potentially infectious definitive, intermediate and paratenic hosts… This is the first report of cerebrospinal angiostrongyliasis in tamarins and nonhuman primates in Australia.     

Amebic meningoencephalitis in a sheep.

A 1.5-year-old Suffolk ewe with acute onset of incoordination and blindness unresponsive to antibiotic treatment was examined at necropsy. The meninges were congested, opaque, and thick. Microscopically, focal areas of hypercellularity in the left cortical gray matter and the meninges were observed. The inflammatory response consisted of gliosis and perivascular cuffing (lymphocytes, plasma cells, and variable numbers of eosinophils). An amebic organism in 2 life stages was found in the cerebral parenchyma. Numerous large (15 to 35 microns in diameter) organisms, interpreted as trophozoites, were characterized by vacuolated cytoplasm and small nuclei with a prominent eosinophilic nucleolus (karyosome). The smaller (10 to 17 microns in diameter) encysted stage was surrounded by a capsule-like membrane, and contained a large central body sometimes surrounded by a clear halo. Immunofluorescence studies for amebic antigens were strongly positive for an ameba recently isolated in human beings and baboons (Leptomyxid sp).     

Idiopathic eosinophilic meningoencephalitis in a Dutch Warmblood gelding

An increased content of eosinophils in cerebrospinal fluid (CSF) and eosinophilic infiltration of brain tissue are observed in eosinophilic meningoencephalitis (EME). After exclusion of various infectious diseases and further known causes of EME in other species, the diagnosis idiopathic EME was made at necropsy in the case reported here. To the authors' knowledge, this is the first report of idiopathic EME in a horse similar to the disorder occurring in dogs.     

Two rare clinical manifestations of coenurosis in sheep

Two rare clinical manifestations of coenurosis in sheep are reported. (i) A case of partial seizure disorder in a ram of 11 months old. During seizure episodes the animal lay down in lateral recumbency displaying initially a stuporous condition and subsequently began to revolve its head from the base of the cervix. At the necropsy of the case, Coenurus cerebralis cyst (young bladder worm) was found dorsally inside the brainstem, in the site of the tectum mesencephaly. (ii) The second-reported manifestation was a bacterial meningoengephalitis that was witnessed in two lambs of 6-7 weeks old. The lambs displayed lateral recumbency with seizure activity. At necropsy, meningoencephalitis with congestion and abscesses were observed in both of them. Interestingly, C. cerebralis cysts were also found in both brains. Streptococcus dysgalactiae was isolated from the abscesses. Possibly, S. dysgalactiae translocation of the blood-brain barrier was facilitated by the migration of the immature stages of C. cerebralis to and through the brain.     

COMPUTED TOMOGRAPHY OF NECROTIZING MENINGOENCEPHALITIS IN 3 YORKSHIRE TERRIERS

A necrotizing meningoencephalitis of Yorkshire terriers has recently been reported in 6 dogs in Switzerland, 1 dog in Japan and 1 dog in the United States. The purpose of this report is to describe the computed tomographic (CT) findings in 3 dogs with this disease, and to correlate the CT abnormalities with the clinical and pathologic findings in each case. Three Yorkshire Terriers between 2 and 10 years old were evaluated. Physical and neurologic examinations, complete blood count (CBC), serum biochemistry profile, cerebrospinal fluid analysis, and CT scan were performed on all 3 dogs. Brainstem auditory evoked responses (BAER) were evaluated for 2 dogs. Two dogs were euthanized at the owners' request and necropsies were performed. Neurologic examination findings were consistent with a multifocal/diffuse encephalitis involving the cerebrum and brainstem in all 3 dogs. Complete blood count and biochemistry profiles were normal. Elevated protein concentration and a mononuclear pleocytosis were demonstrated in 2 of 3 dogs on cerebrospinal fluid evaluation. Multifocal, extensive areas of decreased opacity throughout the cerebral hemispheres, asymmetric ventriculomegaly, and lack of contrast enhancement were appreciated on CT images of all three dogs. No mass effect was seen. These findings correlated well with pathologic findings at necropsy, which included multiple malacic cavitations within the brain, representing areas of locally extensive necrosis. CT abnormalities in combination with signalment, clinical findings and cerebrospinal fluid analysis should facilitate a presumptive diagnosis of Yorkshire Terrier necrotizing meningoencephalitis.     

Necrotizing meningoencephalitis and pneumonitis in a simian immunodeficiency virus-infected rhesus macaque due to Acanthamoeba

Free-living amoebae of the genus Acanthamoeba can cause a fatal disease of the brain in humans called granulomatous amoebic encephalitis. We present a case of meningoencephalitis and pneumonitis in a simian immunodeficiency virus (SIV)-infected rhesus macaque caused by Acanthamoeba sp. The animal became ill 176 days after intravenous inoculation with SIVmac251 after a short history of weight loss and a sudden onset of hind limb paresis and abnormal head movements. Histopathologic examination of hematoxylin and eosin-stained tissues revealed multifocal to coalescing necrotizing neutrophilic meningoencephalitis and pneumonitis. Immunofluorescence and polymerase chain reaction were used to identify the genus of amoeba as Acanthamoeba. Immunohistochemistry of immune cell markers was used to characterize the animal's immune response to the opportunistic amoebic infection with features of both innate and adaptive cell-mediated immunity. Although not previously reported, the potential transmission to humans, either through environmental contamination or contact with an infected animal, makes this disease a threat to laboratory animal care staff and pathologists.     

Seasonal meningoencephalitis in Holstein cattle caused by Naegleria fowleri.

Primary amoebic meningoencephalitis is a fulminant infection of the human central nervous system caused by Naegleria fowleri, a free-living amoeba that thrives in artificially or naturally heated water. The infection usually is acquired while bathing or swimming in such waters. The portal of entry is the olfactory neuroepithelium. This report describes fatal meningoencephalitis caused by N. fowleri in Holstein cattle that consumed untreated surface water in an area of California where summer temperatures at times exceed 42 degrees C. In the summers of 1998 and 1999, severe multifocal necrosuppurative hemorrhagic meningoencephalitis was observed in brain samples from nine 10-20-month-old heifers with clinical histories of acute central nervous system disease. Olfactory lobes and cerebella were most severely affected. Lesions were also evident in periventricular and submeningeal neuropil as well as olfactory nerves. Naegleria fowleri was demonstrated by immunohistochemistry in brain and olfactory nerve lesions and was isolated from one brain. Even though cultures of drinking water did not yield N. fowleri, drinking water was the likely source of the amoeba. The disease in cattle closely resembles primary amoebic meningoencephalitis in humans. Naegleria meningoencephalitis should be included among differential diagnoses of central nervous system disease in cattle during the summer season in areas with high ambient temperatures.     

POSITRON EMISSION TOMOGRAPHY FEATURES OF CANINE NECROTIZING MENINGOENCEPHALITIS

A Yorkshire terrier and a Chihuahua were referred for acute onset, generalized tonic‐clonic seizures and were suspected to have meningoencephalitis based on magnetic resonance (MR) imaging findings. Brain lesions appeared hyperintense with T2‐weighted imaging and hypointense with T1‐weighted imaging, and were characteristic of necrotizing meningoencephalitis. Both dogs were diagnosed with necrotizing meningoencephalitis based on pathologic findings. Fluorine‐18 fluorodeoxyglucose positron emission tomography (FDG‐PET) was performed on both animals before euthanasia with the permission of the owner. In FDG‐PET images, these lesions seen in MR images were characterized by multifocal or diffuse hypometabolism. Our FDG‐PET results provided evidence of glucose hypometabolism in areas of necrosis and cavitation associated with necrotizing meningoencephalitis. FDG‐PET has the potential to provide valuable diagnostic information in dogs with suspected necrotizing encephalitis.     

Brain Stem Auditory-Evoked Response Abnormalities in 14 Dogs With Confirmed Central Nervous System Lesions

Abnormal brain stem auditory-evoked responses (BAER) were recorded on 14 dogs with brain lesions confirmed by necropsy (n = 13) or magnetic resonance imaging and surgical biopsy (n = 1). Lesions included brain stem or cerebellar tumors (6 dogs), brain stem trauma (1 dog), forebrain tumors (3 dogs), hydrocephalus (2 dogs), granulomatous meningoencephalitis (1 dog), and meningoencephalitis (1 dog). Five affected dogs were comatose at the time of recording. BAER abnormalities could be classified as (1) absence of some or all of waves I to V, (2) increased latencies, with wave V being most frequently affected, or (3) a reduction in the amplitude ratio of waves V/1.     

Comparative morphologic and immunohistochemical investigation of spontaneously occurring thymomas in a colony of European hamsters

This study documents the characteristics of a large series of spontaneously occurring thymomas in a laboratory colony of European hamsters (Cricetus cricetus). Thymomas are rare organotypic neoplasms originating from the thymic epithelial compartment. Because the hamster thymomas largely resembled their human counterparts, the recent World Health Organization (WHO) classification of human thymic epithelial tumors was used. Forty hamsters of both sexes aged 3-29 months were examined macroscopically and histologically. In 22 (55%) of the 40 animals, necropsy revealed enormous whitish masses in the anterior mediastinum, with a diameter ranging from 0.5 to 4.5 cm and a lobulated structure. The anatomy of the thymus region was normal in the remaining 18 hamsters. Histologically, the tumors presented as thymuslike organoid structures with areas of medullary and cortical differentiation and a predominance of lymphoid cells. A network of epithelial cells in the cortical areas, demonstrated immunohistochemically with a cross-reactive antibody against pancytokeratin, supported the diagnosis of thymoma. Cortical lymphocytes showed positive staining with cross-reacting antibodies against CD3 and terminal deoxynucleotidyl transferase, characteristic of immature T cells. On the basis of these findings, the tumors were classified as B1 thymomas, in some cases with AB or B2 components, according to the new WHO classification for human thymic epithelial tumors.     

Rhabdomyosarcoma in 8 horses

This multi-institutional report describes 8 cases of rhabdomyosarcoma in horses. Four neoplasms were in the tongue and other areas of the mouth or head, 2 were in the abdominal wall, and 1 each was in right shoulder muscles and heart. Four rhabdomyosarcomas that were less than 10 cm in diameter were treated by surgical excision or radiation with no recurrence. Two neoplasms greater than 10 cm in diameter in the abdominal wall and the right shoulder were considered inoperable and led to decisions to euthanize the horses. Two neoplasms were incidental findings at necropsy. All the neoplasms were classified as embryonal except for 1 pleomorphic rhabdomyosarcoma. These 8 cases were evaluated with 9 published case reports of equine rhabdomyosarcoma. For all cases, the most common sites were limb muscles (5/17) and tongue (4/17). Metastasis was reported in 4 of the previously published cases; none was found in this study.     

An electron microscopic study of intra-erythrocytic stages of Babesia bovis in the brain capillaries of infected splenectomized calves.

Splenectomized vaccine donor calves undergoing primary reactions to Babesia bovis infections may develop cerebral babesiosis which leads to death if not treated in time. A brain biopsy was performed on an artificially-infected animal showing nervous symptoms and the tissue was immediately processed for electron microscopic examination. Virtually every erythrocyte in the brain capillaries sectioned was infected with B. bovis. Intra-erythrocytic merozoites, trophozoites and dividing trophozoites were indentified. Important features of the piriform merozoites included a reduced apical complex consisting of the anterior polar ring, microtubules, rhoptries and micronemes. Unidentified membrane-bound bodies, mostly spherical in shape, were observed anterior to the nucleus. The trophozoites showed very little structural differentiation and no food vacuoles or micropores could be detected. Each trophozoite produced 2 identical merozoites and the parent cell became totally incorporated in the daughter merozoites in the multiplication process. Projections were seen radiating from the surface of infected erythrocytes which appeared to adhere to other surfaces on contact. This probably resulted in the sludging of infected erythrocytes in the capillaries. The latter observations coincide with those described for Babesia argentina.     

Pilocytic astrocytoma in a cat

A 12-year-old crossbred female cat was presented for necropsy with a history of anorexia, ataxia, convulsions, and blindness. Grossly, a whitish, firm, and well-circumscribed nodule with an irregular surface of approximately 1.5 cm in diameter was observed in the right dorsal, parietal, and occipital lobes of the brain. Histologically, the tumor was composed of neoplastic astrocytes forming irregular interweaving sheets and bundles. These cells were elongated, spindle-shaped, and bipolar, and some had clear cytoplasm and a dense nuclear chromatin pattern. Extensive areas of cartilaginous and osseous metaplasia were observed. By immunohistochemistry, the neoplastic cells were found to be markedly positive for S-100 protein and glial fibrillary acidic protein. On the basis of morphologic and immunohistochemical features, the diagnosis of pilocytic astrocytoma was made.     

Clinical Parelaphostrongylus tenuis infection in two captive American bison (Bison bison)

CASE DESCRIPTION: 2 juvenile (17 and 19 months of age) male American bison (Bison bison) were examined because of acute bilateral hind limb weakness and ataxia; 1 animal also had urinary incontinence. TREATMENT AND OUTCOME: Given the clinical signs and rapid deterioration in the condition of these 2 animals, obtaining a definitive diagnosis was considered essential to minimizing the risk of disease in the remaining bison herd and among other animals at the facility. Therefore, both affected animals were euthanized. At necropsy, no gross abnormalities were seen. Histologic examination of sections of the brains from both animals revealed mild to moderate multifocal aggregates of eosinophils and mononuclear cells in perivascular regions of the meninges and gray matter of the cerebrum, cerebellum, and brainstem. Systematic examination of multiple sections of brain and spinal cord revealed evidence of nematode sections and aberrant parasite migration. CLINICAL RELEVANCE: Findings suggested that CNS migration of Parelaphostrongylus tenuis in American bison may cause clinical signs. These findings have implications for the management of captive bison and free-ranging bison sharing ranges with white-tailed deer (Odocoileus virginianus), the definitive host, and elk (Cervus elaphus canadensis).