Experimental infection of domestic swine with Baylisascaris procyonis from raccoons

Six 8-week-old ascarid-naive pigs which were experimentally infected with 72,000 embryonated Baylisascaris procyonis eggs of raccoon origin developed lesions limited to the intestines and liver. Intestinal lesions consisted of multifocal areas of inflammation by macrophages, eosinophils, and lymphocytes in the mucosa and submucosa, in association with Baylisascaris larvae; similar lesions were seen in the mesenteric lymph nodes. Typical white, granulation type, multifocal interstitial hepatitis ("milk-spots"), 1 to 5 mm in diameter, were seen in the livers by 7 days, with resolution by 47 days. Microscopically, these consisted of multifocal areas of marked periportal and interlobular edema, and influx of eosinophils, and large intralobular aggregates of eosinophils. At 47 days, hundreds to thousands of small white granulomas were seen on the serosa of the intestines; microscopically, they were discrete collections of macrophages, lymphocytes, and eosinophils in the submucosa and muscle layers surrounding nonviable remnants of Baylisascaris larvae. Larvae or lesions were not seen in other tissues, including the brain. These experiments indicated that B procyonis will undergo limited migration in swine and can produce typical white spots in the liver. The larvae were killed by cellular reactions in the intestinal wall and liver, and, unlike the situation in most other animals infected with this parasite, no somatic migration or CNS disease occurred after infection.     

Systemic mycosis caused by Scedosporium apiospermum in a stranded northern elephant seal (Mirounga angustirostris) undergoing rehabilitation.

A recently weaned, stranded, male northern elephant seal (Mirounga angustirostris) pup that had been undergoing rehabilitation was found severely obtunded with hyponatremia, hypokalemia, hypochloremia, and hypophosphatemia after a history of intermittent regurgitation. The animal was euthanatized, and gross postmortem findings included multifocal abscessation affecting brain, spleen, kidney, muscle, and subcutaneous tissue. Scedosporium apiospermum and mixed bacteria were cultured from brain, kidney, and subcutaneous tissue. Histopathologic examination revealed multiple fungal granulomas of variable size in the kidneys, brain, liver, and skeletal muscle. This is the first report of S. apiospermum infection associated with lesions in a marine mammal.     

Prevalence of psammoma bodies in meninges and choroid plexuses of raccoons (Procyon lotor) from Parramore Island, Virginia.

Microscopic evidence of multifocal mineralizations (psammoma bodies) were seen in brains of 33/53 (62%) raccoons (Procyon lotor) necropsied on Parramore Island, Virginia. Most mineralized foci had concentric laminations and were present in small capillaries of meninges of the brain (15/33), in choroid plexus (3/33), or at both these sites (13/33). In 2 raccoons, the lesions were confined to the meninges of the proximal cervical spinal cord. In most cases, the affected vessels appeared to have been completely occluded. However, no evidence of ischemic changes in the brain parenchyma was seen, and none of the raccoons had abnormal neurologic signs prior to euthanasia. The condition appears to be a common incidental histopathologic finding in raccoons from the eastern United States. Although the exact cause of this condition is not known, a primary vascular insult with resultant dystrophic mineralization of the affected vessels is suspected.     

Leptospirosis and tularaemia in raccoons (Procyon lotor) of Larimer County, [corrected] Colorado

Raccoons (Procyon lotor) are commonly implicated as carriers of many zoonotic pathogens. The purpose of this cross-sectional study was to look for Leptospira interrogans and Francisella tularensis in opportunistically sampled, free-ranging raccoons of Larimer Country, Colorado, USA. Sixty-five animals were included in the study and testing consisted of gross post-mortem examination, histopathology, and both immunohistochemistry and PCR for L. interrogans and F. tularensis. No significant gross lesions were identified and the most common histological lesions were lymphoplasmacytic interstitial nephritis and pulmonary silicosis; rare periportal hepatitis, splenic lymphoid hyperplasia and small pulmonary granulomas were also identified. Of 65 animals, 20 (30%) were positive for Leptospira on IHC but only one by PCR. Animals with inflammation in their kidneys were seven times more likely to be positive for Leptospira than animals without inflammation. The severity of inflammation was variable but often mild with minimal associated renal pathology. One animal was positive for Francisella on both IHC and PCR; IHC staining was localized to histiocytic cells within a pulmonary granuloma. In Colorado the significance and epidemiology of Leptospira is poorly understood. The high prevalence of infection in raccoons in this study population suggests that this species may be important in the regional epidemiology or could be used to estimate risk to domestic animals and humans. Identification of a single Francisella positive animal is significant as this is an uncommon disease in terrestrial animals within the state; the apparently higher prevalence in this peridomestic species implies that raccoons may be good indicators of the pathogen in the region. The results of this study suggest that raccoons may serve as effective sentinels for both Leptospira and Francisella in the state of Colorado. Further studies are needed to better characterize the prevalence and epidemiology of both organisms within the region.     

Larval toxocarosis in sheep: the immunohistochemical characterization of lesions in some affected organs

Morphological and immunohistochemical responses of lambs following oral infection with 10,000 infective Toxocara canis (T. canis) eggs were studied up to 28 days post-infection (pi). The small intestine, liver, lungs and brain of both infected and control lambs were examined using the routine histological methods for paraffin sections and immunohistochemical techniques for frozen tissue sections. Eosinophil-rich hepatic granulomas and diffuse T. canis-induced pulmonary inflammation were the most prominent pathological features. CD2+, CD4+, CD8+, IgM bearing cells, and macrophages were demonstrated in the liver granulomas. The observed histomorphologic changes were similar to other paratenic hosts. It was concluded that larval toxocarosis followed the classical migratory path in the infected lambs.     

Experimental oral administration of canine adenovirus (type 2) to raccoons (Procyon lotor).

Canine adenovirus type 2 (CAV2) has been proposed for recombinant vaccines to control rabies in wild animals. To evaluate the suitability of CAV2 as a safe vector for the genetically engineered vaccines, seven wild-caught raccoons (three males and four females) were administered CAV2 per os. Two of the animals were euthanatized on each of post-infection days 3, 6, and 14, and one was euthanatized on day 21. Two other control raccoons (a male and a female) were also euthanatized on day 21. Microscopic pulmonary lesions of multifocal necrotizing bronchiolitis with basophilic intranuclear inclusions were seen in 3/4 raccoons euthanatized on post-infection days 3 and 6. Ultrastructural examination of lungs with pulmonary lesions revealed hexagonal viral particles characteristic of adenoviruses. CAV2 is potentially pathogenic for raccoons, and this susceptibility should be of concern to developers of recombinant vaccines who intend to use CAV2 as a vaccine vector.     

Natural Heterobilharzia americana infection in horses in Texas

The schistosome Heterobilharzia americana infects dogs, raccoons, and other mammals in the southeastern United States. Migration of eggs into the liver results in parasitic granulomas with varying degrees of fibrosis and inflammation. Recently, hepatic parasitic granulomas in horses were shown to be caused by H. americana infection. In the present study, samples of liver from 11 of 12 horses with hepatic granulomas identified at necropsy (n = 11) or surgical biopsy (n = 1) were used for DNA extraction, polymerase chain reaction amplification and sequencing using primers specific for a portion of the H. americana small subunit ribosomal RNA gene. A polymerase chain reaction amplicon of the correct size was produced from the extracted DNA in 8 of the 11 horses. Amplicons from 5 of the 8 positive horses were sequenced and had 100% identity with H. americana. In all but 2 of the 12 horses, Heterobilharzia was not responsible for the primary clinical disease, and the hepatic granulomas were considered an incidental finding.     

Morphologic and immunoperoxidase study of neurologic lesions in naturally acquired rabies of raccoons.

Histopathologic (hematoxylin and eosin [HE]) and immunoperoxidase (streptavidin-biotin complex) methods were used for examination of formalin-fixed tissues of rabid raccoons from an enzootic area of Pennsylvania. Extensive morphologic lesions of rabies encephalitis were present in the cerebrum and the brain stem regions. Negri bodies were detected by both methods and were present in the brain (cerebral cortex, hippocampus, brain stem, cerebellum, and cervical spinal cord) and in the ganglia of the trigeminal nerves. The viral inclusions were also seen in ganglion cells in the tongue, parotid salivary glands, pancreas, intestines, and adrenal glands. These sites were not associated with any inflammatory cellular infiltrate. The immunoperoxidase method was superior to HE for the detection of Negri bodies. Because lesions of rabies encephalitis were consistently observed in the cerebrum, brain stem, and cervical spinal cord regions, these areas of the brain should be included when raccoons are examined by the fluorescent antibody test for rabies.     

Prevalence of Toxoplasma gondii infection in raccoons.

Serum samples from 427 raccoons (93 from Pennsylvania, 45 from New Jersey, 72 from South Carolina, 68 from Virginia, 30 from Iowa, and 119 from Ohio) were evaluated for Toxoplasma gondii antibodies in dilutions of 1:25, 1:50, and 1:500. The distribution of T gondii antibody titers was less than 1:25 for 212 raccoons (49.6%), 1:25 for 34 raccoons (7.9%), 1:50 for 117 raccoons (27.4%), and greater than or equal to 1:500 for 64 raccoons (14.9%). Tissue cysts were seen in the liver, and tachyzoites were in the brain of a raccoon with abnormal neurologic signs and concurrent infection with canine distemper virus. Organisms in the liver were stained with anti-T gondii serum, and the raccoon had a T gondii titer of 1:160 in the agglutination test.     

Morphological changes in brucellosis in guinea pigs due to experimental infection with Brucella suis

Sixty-four guinea-pigs were infected with the germs of Brucella suis. biotype 2 via the vaginal, peroral, intranasal, conjunctival and subcutaneous routes. In the subcutaneous infection the length of the trial was 151 days and in the other methods of infection 56 days. As found, guinea-pigs are highly sensitive and brucellosis lesions were detected in all cases. Brucellosis was chronical and spread locally in the guinea-pigs. In the haematogenic spreading of the disease, lesions were constantly recorded in liver, spleen and lungs. In the cases of subcutaneous infection lesions were also observed in regional lymph nodes at the places of infection. The lesions had amorphous structure and regular borders. The lesions were characterized by pronounced exudation and the exudate was subject to caseous necrosis, followed by colliquation. Secondary central colliquation was regularly observed in older granulomas, so that colliquation is considered as a characteristic morphological trait of brucellosis process in guinea-pigs. Histiocytary granuloma constituted the microscopic basis of the lesions. In older granulomas the central necroses were wide and contained a large amount of nuclear detritus, owing to the karyorhexis of cells, mainly neutrophiles. In the necroses of caseous type lipoid droplets were found and calcification was observed on the 151st day. Big cells of Langhans type occurred sometimes in the histiocytary layer of granulomas; they were present most frequently in the lesions affecting lymph nodes. Interstitial pneumonia was a characteristic symptom in liver and big cells of Sternberg type were found in the granulomas. Follicular tumor was constantly observed in spleens. Morphologically detectable lesions first developed in liver after about 7 days from conjunctival infection and subcutaneous infection, after 21 days from vaginal and intranasal infection, and after 28 days from peroral infection. In the case of subcutaneous infection, granulomas were found in the regional lymph nodes on the 14th day. The most expressive lesions in organs, mainly liver, were found from the 49th to 56th day from infection.     

Cerebrospinal nematodiasis in pheasants

Infection with larvae of Baylisascaris procyonis, the raccoon ascarid, was the cause of neurologic disease affecting young pheasants on a commercial pheasant ranch in Wisconsin. The disease was chronic and insidious, affecting 1% to 2% of the birds over a period of 2 years. Histologic lesions in the brain consisted of multifocal areas of necrosis and inflammation associated with Baylisascaris larvae. Onset of the disease at the farm correlated with introduction of chopped straw as bedding for the young birds. The straw was from a neighbor's barn and was contaminated with raccoon feces that contained B procyonis eggs. Cessation of use of the contaminated straw resulted in cessation of CNS disease in pheasants on the ranch.     

CLINICAL AND PATHOLOGICAL STUDIES OF BORDER LEICESTER RAMS NATURALLY INFECTED WITH ACTINOBACILLVS SEMINIS

Clinical examination of 31 rams with evidence of Actinobacillus seminis infection revealed 15 cases with marked lesions of the scrotal contents, two cases with very mild lesions, one with testicular atrophy but no abnormality of the epididymides, and another 13 without any palpable abnormalities of the genitalia. The rams were from a Border Leicester flock and included 27 un-mated rams from 6 to 12 months old. Histological examinations of affected epididymides showed a mixed purulent and non-purulent inflammation, with cystic hyperplasia of the ductus epididymis. Interstitial fibrosis and spermatic granulomas were seen in chronic lesions. Bilateral testicular atrophy and seminal degeneration were found in the nine rams that were autopsied. The clinical and pathological features of the disease are similar to those of ovine brucellosis. A pyelonephritis of unknown significance was found in four of the nine rams examined.     

Invasive pulmonary aspergillosis of horses: an association with acute enteritis

Invasive pulmonary aspergillosis was identified in 19 horses. In 16 cases mycotic lesions were associated with enterocolitis; 14 cases appeared to result from Salmonella infection. Pulmonary lesions included multifocal areas of acute necrosis, leukocytoclastic vasculitis, and thrombosis with fibrinosuppurative inflammation surrounding mycelial masses. Thromboemboli with fungi were in the brain and kidneys of three cases. Factors which appeared to predispose to pulmonary aspergillosis included corticosteroid therapy, disseminated neoplasms, hepatitis, pleuritis, and peritonitis. This study suggests that immunocompromise and invasion of Aspergillus sp. from damaged intestine are more important in causing equine pulmonary aspergillosis than inhalation of spores.     

Generalised granulomatous disease in a horse

A 6-year-old gelding was referred with a 3-month history of recurrent fever, inappetance, lethargy and weight loss. On clinical examination major findings were depression, thin condition, thrombophlebitis, nodules on the scrotal skin, leukocytosis, hyperfibrinogenaemia and hyperglobulinaemia. Pleural fluid and areas of lung consolidation were seen on ultrasonographic examination of the thorax. A diagnosis of chronic respiratory disease was made. Initially there was a response to antibiotic therapy but the horse was presented 3 months later with continued weight loss, recurrent fever and multifocal skin lesions, characterised by scales, crusts and nodules, affecting the nasal bridge, jugular grooves, ventral neck, withers, scrotum, prepuce, and medial gaskins. Histological evaluation of skin biopsies indicated a granulomatous reaction. On ultrasonographic examination of the thorax multiple hypoechoic lesions consistent with granulomas were seen in both lungs. A diagnosis of generalised granulomatous disease was made. The horse was euthanased at the owner's request. On necropsy examination the main findings were multiple nodules of fibrotic granulomatous inflammation in the lung, heart, liver, gastrointestinal tract and mesenteric lymph nodes, supporting the diagnosis of generalised granulomatous disease.     

Avian hepatic granuloma. A review

Hepatic granuloma is a chronic inflammatory disease characterized by a granulomatous reaction with accumulation of macrophages and/or epithelioid cells, which may fuse to form multinucleated giant cells. The hepatic granulomas typically have a surrounding rim of lymphocytes and fibrous tissues. The etiology of some hepatic granulomas in birds is well known. It could be due to viral, bacterial, fungal, protozoal, or helminthic infection. The presence of these pathogens in the liver is usually through systemic infections that might preferentially colonize the liver or be opportunistic invaders. Persistence of these pathogens infecting the liver can lead to granulomatous inflammation with different gross lesions and histopathologic patterns depending on the causative agent. This review describes the etiology, clinical signs, pathological changes, and diagnosis in a wide variety of diseases associated with hepatic granulomas in birds in which the detection of granulomatous inflammation is an aid in the differential diagnosis.     

Systemic nocardiosis in a reindeer (Rangifer tarandus tarandus).

Systemic infection by Nocardia asteroides was diagnosed in a reindeer (Rangifer tarandus tarandus). At necropsy, the animal had enlarged tracheobronchial lymph nodes, pleural and peritoneal effusions, and numerous, multifocal to coalescing, yellow, firm nodules with inspissated pus in the lung, pleura, omentum, liver, heart, adrenal glands, and left kidney. Microscopically, the nodules consisted of foci of pyogranulomatous inflammation. Microscopic lesions were present in the grossly affected organs as well as spleen and brain. Sections stained with Gram and modified Fite-Faraco histochemical stains had numerous gram-positive, variably acid fast, beaded and branching filamentous organisms in the necrotic centers. N. asteroides was isolated from the lung, bronchial lymph nodes, liver, and left kidney. To the authors' knowledge, this is the first report of systemic N. asteroides infection in a reindeer.     

Neuroaxonal dystrophy in raccoons (Procyon lotor) from Iowa.

During a 12-month period (1998-1999), microscopic evidence of neuroaxonal dystrophy (NAD) in medullae oblongata of raccoons (Procyon lotor) was observed in 17/39 (47% prevalence in adults) from Iowa, USA. Three of the animals were kits (<3 months), 26 were between 1 and 2 years, and 10 were over 7 years. Lesions were not seen in the medullae of the 3 kits. In young adults, the lesions were mild and were seen in 7 animals. More severe lesions were present in the 10 older raccoons. Grossly, the brains were unremarkable. Microscopically, NAD was confined to the dorsal caudal medulla, where certain nuclei (predominantly gracilis and cuneate) were bilaterally affected. Severely affected animals had vacuolar degeneration of neurons or neuronal loss and extensive areas of spongiosis. Tests for the presence of PrP(res) in the brain were negative. Spongiotic areas often contained axonal spheroids. Degenerate neurons and axons occasionally contained amphophilic periodic acid-Schiff-positive granular material. There was a paucity of inflammatory cells in the affected areas. Since lesions were not present in kits, were either absent or mild in young adults, and were severe in older raccoons, the findings may be related to advancing age. Neuroaxonal dystrophy has not been previously reported in raccoons. Retrospective examination of raccoon brains from the eastern and northwestern areas of the country revealed very low prevalence of NAD. Because of the apparently high prevalence of this condition at this geographic location, factors other than age (genetic, nutritional, and/or environmental) may influence this degenerative process in the brains of raccoons in Iowa.     

Cryptococcosis involving the eye and central nervous system of a dog

Cryptococcus neoformans meningoencephalitis was diagnosed as the cause of stupor and generalized seizures in a 2-year-old Cocker Spaniel. Unilateral granulomatous chorioretinitis was observed ophthalmoscopically, and isolation of C neoformans from CSF confirmed the antemortem diagnosis. The dog was euthanatized and necropsied. Multifocal lesions were seen throughout the lungs, nasal turbinates, cerebral cortex, and the optic nerve of each eye. Microscopically, the multifocal lesions were granulomas consisting of lymphocytes, macrophages, plasma cells, and cryptococcal organisms. Infection may have originated in the nasal passages and extended directly through the ethmoid plate into the meninges of the CNS and optic nerves. Although the prognosis is poor in dogs with CNS involvement, various chemotherapeutic agents are available for use by clinicians.