Experimental infection and pathology of clade 2.2 H5N1 virus in gulls

During 2006, H5N1 HPAI caused an epizootic in wild birds, resulting in a die-off of Laridae in the Novosibirsk region at Chany Lake. In the present study, we infected common gulls (Larus canus) with a high dose of the H5N1 HPAI virus isolated from a common gull to determine if severe disease could be induced over the 28 day experimental period. Moderate clinical signs including diarrhea, conjunctivitis, respiratory distress and neurological signs were observed in virus-inoculated birds, and 50% died. The most common microscopic lesions observed were necrosis of the pancreas, mild encephalitis, mild myocarditis, liver parenchymal hemorrhages, lymphocytic hepatitis, parabronchi lumen hemorrhages and interstitial pneumonia. High viral titers were shed from the oropharyngeal route and virus was still detected in one bird at 25 days after infection. In the cloaca, the virus was detected sporadically in lower titers. The virus was transmitted to direct contact gulls. Thus, infected gulls can pose a significant risk of H5N1 HPAIV transmission to other wild migratory waterfowl and pose a risk to more susceptible poultry species. These findings have important implications regarding the mode of transmission and potential risks of H5N1 HPAI spread by gulls.     

Dysentery in calves caused by an atypical strain of Escherichia coli (S102-9)

Dysentery lasting 4-8 days was produced in five 4-day-old colostrum-fed calves, after inoculation with an atypical strain of Escherichia coli S102-9; peak excretion of S102-9 occurred during the period of dysentery. Two calves were killed when clinical signs were most severe and bacteria were seen attached to the surfaces of enterocytes in the large intestine; microscopic lesions were seen in these areas. The lesions were identical to those previously reported in a natural outbreak of dysentery in calves, from which E. coli S102-9 was isolated, and to those seen in gnotobiotic calves experimentally infected with S102-9. Reinfection of the three surviving calves 16-20 days later with S102-9 and primary infection of two calves aged 24 and 51 days did not cause dysentery. Four of 659 coliforms isolated from field outbreaks of calf diarrhoea resembled the atypical strain S102-9. These four isolates and S102-9 did not produce heat-stable enterotoxin, but all produced a toxin cytopathic for Vero and HeLa cells. Two of the four isolates were inoculated alone into 4-day-old gnotobiotic calves deprived of colostrum; neither calf developed dysentery but microscopic lesions identical to those produced by S102-9 were detected in the large intestines of both animals.     

Polioencephalomalacia associated with closantel overdosage in a goat

This report describes clinical and pathological findings associated with closantel (a halogenated salicylanilide anthelmintic) overdosage in a 3-year-old goat. The clinical signs included blindness, incoordination, ataxia, depression of the palpebral and pupillary reflexes, and recumbency. No gross lesions were noted in tissue or organs at necropsy, but microscopic lesions were seen in nervous tissue and hepatic cells. Polioencephalomalacia was clearly evident. Bilaterally symmetrical status spongiosus of the white matter of the brain, bilateral laminar necrosis, microcavitations, ischaemic cell change and severe degeneration of the cerebellum were seen in nervous tissue. Fatty change and hydropic degeneration in the liver and hepato-cellular degeneration were observed histologically.     

Experimental transmission of chronic wasting disease (CWD) of elk (Cervus elaphus nelsoni), white-tailed deer (Odocoileus virginianus), and mule deer (Odocoileus hemionus hemionus) to white-tailed deer by intracerebral route

To compare clinical and pathologic findings of chronic wasting disease (CWD) in a natural host, 3 groups (n = 5) of white-tailed deer (WTD) fawns were intracerebrally inoculated with a CWD prion of WTD, mule deer, or elk origin. Three other uninoculated fawns served as controls. Approximately 10 months postinoculation (MPI), 1 deer from each of the 3 inoculated groups was necropsied and their tissues were examined for lesions of spongiform encephalopathy (SE) and for the presence of abnormal prion protein (PrP(d)) by immunohistochemistry (IHC) and Western blot (WB). The remaining deer were allowed to live until they developed clinical signs of the disease which began approximately 18 MPI. By 26 MPI, all deer were euthanatized on humane grounds. Obvious differences in clinical signs or the incubation periods were not observed between the 3 groups of deer given CWD. In 1 of 3 nonclinical deer euthanatized at 10 MPI, minimal microscopic lesions of SE were seen in the central nervous system (CNS) tissues, and PrP(d) was observed by IHC in tissues of all 3 deer. In the clinical deer, CNS lesions of SE and PrP(d) accumulations were more severe and extensive. It is concluded that the 3 sources of CWD prion did not induce significant differences in time to clinical disease or qualitative differences in signs or lesions in WTD. However, this observation does not imply that these CWD agents would necessarily behave similarly in other recipient species.     

Foot pad dermatitis develops at an early age in commercial turkeys

1. A field experiment was conducted to identify the macroscopic and histological changes associated with the development of foot pad dermatitis (FPD) in growing turkeys. Two affected and two unaffected turkeys were sampled weekly from 1 to 8 and at 10 and 21 weeks of age. 2. At one week old, birds with external signs of FPD (surface skin discolouration) showed abnormal cellular changes of the foot pad integument. As the flock aged the reactions intensified, with one sample exhibiting a fully developed macroscopic lesion at 3 weeks. 3. Major pathological changes had occurred by 6 weeks and all turkeys with external signs of lesions had fully developed microscopic inflammatory cellular lesions. From 6 weeks of age onwards lesions were increasingly numerous and became more overtly necrotic. 4. Externally normal foot pads showed microscopic evidence of lesions after the turkeys reached 4 weeks. 5. We conclude that FPD lesions become severe over a short period of time and at a very early age.     

Vitamin A deficiency in the captive African lion cub Panthera loe (Linnaeus, 1758).

Dietary, breeding and clinical histories and pathological findings are presented from 2 confirmed and 5 presumed cases of vitamin A deficiency in immature African lions. Five of the 7 animals were born in the wild while 2 were born in captivity. All animals were fed lean red meat sprinkled with a vitamin/mineral supplement. Salient clinical signs were incoordination, "star gazing", blindness and intermittent convulsions. Pathological lesions seen in 4 animals included severe thickening of the cranial bones, with consequent marked compression of the brain and partial herniation of the cerebellum. Vascular damage in the cerebellum and ensuing haemorrhages, resulting in acute increases of an already high intracranial pressure, were thought to be the cause of some of the clinical signs, particularly convulsions rather than direct pressure-necrosis and atrophy of nervous tissue.     

Clinical and pathological studies in adult sheep and goats experimentally infected with Wesselsbron disease virus

The clinical symptoms and pathology in 33 adult sheep and 31 adult goats experimentally infected with Wesselsbron disease virus are described. There was moderate to severe hyperthermia in most animals, but no other clinical signs of disease or deaths were recorded. Eleven sheep and 6 goats were sacrificed for pathological studies at various stages during the febrile response. The macroscopic and microscopic lesions in these cases are described. Microscopic studies revealed that the liver was consistently affected and showed small foci of necrosis. These were sparsely distributed and associated with a marked localized Kupffer cell response ("retothelial nodules"). In addition, acidophilic bodies and small groups of necrotic hepatocytes were evident in some lobules. Apart from the hepatic lesions, mild to moderate pyknosis and karyorrhexis of lymphocytes were seen in the spleen and lymph nodes. This report also compares the microscopic lesions in the livers of adult sheep and goats with those of new-born lambs for Wesselsbron disease as well as with those reported for Rift Valley fever in adult sheep.     

Toxicologic evaluation of chlorpyrifos in cats

Twenty-four male domestic shorthair cats were used to evaluate the acute and chronic effects of a single, toxic but sublethal, orally administered dose of chlorpyrifos. A dosage of 10 mg/kg of body weight did not induce clinical signs of toxicosis, but a dosage of 40 mg/kg induced clinical signs of toxicosis, and 1 of 12 cats died. Chlorpyrifos given at a dosage of 0.1 mg/kg to 2 cats reduced whole blood and plasma cholinesterase (Che) activities to values obtained after cats were given doses that induced clinical signs of toxicosis. Regeneration time for whole blood and plasma Che activities ranged from 7 to 28 days. Brain Che activity was considerably decreased in 1 cat that died 4.5 hours after dosing, but was normal in all others at 28 days after dosing. Other than decreased Che activity, significant changes were not seen in hematologic or serum biochemical values. Toxin-related lesions were not seen during macroscopic or microscopic examination.     

Morphological lesions in red blood cells from herring gulls and Atlantic puffins ingesting Prudhoe Bay crude oil

Red blood cells from nestling herring gulls and Atlantic puffins that had ingested 10 ml or more of a Prudhoe Bay crude oil/kg body weight/day for four to five days were examined by light and electron microscopy. In stained smears, red blood cells from oil-dosed birds were characterized by anisocytosis, poikilocytosis, reticulocytosis, and Heinz body formation. In transmission electron micrographs, affected cells had intracytoplasmic and intranuclear Heinz bodies, a variety of abnormal cytoplasmic vesicles, degenerate mitochondria, absence of circumferential microtubules, abnormal shape, and crenulation of the plasma membrane. The latter two cell surface anomalies were evident in scanning electron micrographs. Identical lesions were present in red cells from gulls injected with phenylhydrazine. Reticulocytosis was the only change evident in blood from gulls made anemic by hemorrhage. These observations support the hypothesis that the toxicity of ingested Prudhoe Bay oil to red cells was exerted by oxidant chemical compounds.     

Ruminal and plasma concentrations of 3-methylindole associated with tryptophan-induced pulmonary edema and emphysema in cattle.

Five Hereford cows were given an intraruminal dose of L-tryptophan (0.35 g/kg of body weight), and 2 cows were used as controls. Of the 5 treated cows, 3 developed clinical signs of interstitial pul monary edema, and emphysema and severe pulmonary lesions were seen at necropsy after 96 hours. Another cow developed moderate clinical signs and pulmonary lesions, and the remaining cow had few clinical signs and mild pulmonary lesions. The severity of clinical signs in each cow was related to the severity of pulmonary lesions at necropsy. The 3-methylindole (3MI) was present in ruminal fluid and plasma within 6 hours after administration of tryptophan, and the concentrations increased to 3.0 and 9.0 mug/ml within 12 to 24 hours. Severity of pulmonary lesions was related to maximal concentration and duration of 3MI in the plasma. At necropsy, gross lesions were characterized by diffuse, pulmonary edema and interstital emphysema; and the lungs were dark red, firm, and heavier than normal. Predominant microscopic changes included accumulation of proteinaceous residue, hypertrophy and hyperplasia of alveolar lining epithelium, thickening of alveolar septums, and emphysematous thickening of interstitial tissues. These changes were similar to previously reported 3MI-induced pulmonary lesions. The presence of 3MI in ruminal fluid and plasma after administration of tryptophan and the relationship between concentration of 3MI and severity of clinical signs indicate that 3MI is the principal metabolite of ruminal fermentation which leads to the development of acute pulmonary edema and emphysema in cattle given tryptophan.     

Caprine arthritis-encephalitis in the Basque country, Spain

A goat herd severely affected by arthritis was studied. The most representative clinical signs consisted of articular swelling, mainly of the carpal joints, and the subsequent locomotor disorders. Some goats also showed signs of central nervous system involvement. Examinations of joint fluid revealed an increased number of mononuclear blood cells, mostly lymphocytes. Gross and microscopic articular lesions were of inflammatory and degenerative types. Periarticular connective tissue, synovial bursae, tendons and tendon sheaths were predominantly affected. Inflammatory lesions were those of a chronic hyperplastic tenosynovitis with fibrosis of the connective tissue components. Degenerative changes consisted mainly of necrosis and mineralisation of articular-related structures. Histological lesions in the central nervous system were those of a nonpurulent encephalitis initially located in periventricular areas, but in one case extensive encephalomalacia was also seen. Of the 80 animals sampled 82.5 per cent showed seropositive reactions against an ovine progressive pneumonia virus antigen. None was seropositive to brucella and titres to chlamydia were low. Attempts to isolate chlamydia and mycoplasma from affected joints and several organs failed. Different bacteria were recovered from a few samples but did not seem significant. Syncytium-forming viral particles were isolated from several organs, mainly the lungs, synovial membranes and lymphoid tissue of almost all the slaughtered animals. These particles were identified as lentiviruses by electron microscopy. The clinical signs, lesions serological results and microbiological findings, led to a diagnosis of caprine arthritis-encephalitis. This syndrome has not been recognised in Spain previously.     

The relationship between clinical signs of respiratory system disorders and lung lesions at slaughter in veal calves

The presence and severity of lung lesions recorded post-mortem is commonly used as an indicator to assess the prevalence of respiratory problems in batches of bovines. In the context of a welfare monitoring based on on-farm measures, the recording of clinical signs on calves at the farm would be more convenient than the recording of lung lesions at slaughter. The aim of the present study was to investigate the relationship between clinical respiratory signs at farm and post-mortem analyses of lung lesions observed at slaughter in veal calves. If clinical signs were a good predictor of lung lesions it could be possible to integrate only those measures in a welfare monitoring system. One-hundred-and-seventy-four batches of calves were observed 3 times: at 3 and 13 weeks after arrival of the calves at the unit and at 2 weeks before slaughter. For each batch a maximum of 300 calves was observed and the proportions of calves showing abnormal breathing, nasal discharge and coughing were recorded. Post-mortem inspection was carried out on a sample of lungs belonging to calves from the observed batches. Each examined lung was classified according to a 4-point scale for pneumonia from healthy lung (score 0) to severe lesions (score 3). The clinical signs recorded infra vitam were significantly correlated with moderate and severe lung lesions for observations at 13 weeks and 2 weeks before slaughter and the level of the correlation was highly variable (r(sp) from 0.16 to 0.40). Receiver operating characteristic (ROC) curves were created and the area under the curves showed that batches with a high proportion of lungs with moderate or severe lesions could not be accurately detected by the three clinical signs of respiratory disorders. These results suggest that both clinical signs and post-mortem inspection of lung lesions must be included in a welfare monitoring schemes for veal calves.     

Response of pigs to recent isolates of Coxsackievirus B5

Coxsackievirus B5 (CB5) was serially passaged five times in pigs in an attempt to establish clinical disease. No clinical signs were seen although some pigs had a transient rise in rectal temperature. Viremia was not detected although virus was isolated from nasal swabs and fecal samples. No CB5 specific fluorescence or virus was detected in any tissues of five passages by immunofluorescent test and tissue culture methods, respectively.

Brain lesions were noted in all passages; extensiveness of lesions increased slightly up to the third passage although no evidence of increasing viral replication was found. No increase in brain lesions was found in the fourth and fifth passages. The development and progress of brain lesions were similar to but less extensive than those caused by swine vesicular disease virus (SVDV) in most pigs examined. Contact pigs also showed more brain lesions than inoculated pigs. In some passages, microscopic changes also were found in the heart. All pigs exposed to CB5 had positive neutralizing antibody titres against CB5 and SVDV but became ill after challenge with SVDV. There was an anamnestic response to both viruses following challenge.     

Clinical and pathologic features of neuronal ceroid-lipofuscinosis in a ferret (Mustela putorius furo)

Clinical and pathologic features of neuronal ceroid-lipofuscinosis in a 4-month-old ferret are reported. Clinical signs including neurological symptoms appeared at 3 months of age and progressed rapidly. By magnetic resonance imaging, severe cerebral atrophy was recognized. Histopathologically, there was severe neuronal loss and diffuse astrogliosis with macrophage accumulations; lesions were found predominantly in the cerebral cortex. Intracytoplasmic pigments were observed in surviving neurons and macrophages throughout the brain. The pigments were intensely positive for periodic acid-Schiff, Luxol fast blue, and Sudan black B and exhibited a green autofluorescence. Electron microscopic examination revealed the accumulation of electron-dense granular material within lysosomes of neurons and macrophages. Immunohistochemically, a large number of saposin-positive granules accumulated in the neuronal cells, astrocytes, and macrophages of the lesions, but significant immunoreactivity for subunit c of mitochondrial adenosine triphosphate synthase was not observed. Based on these findings, the animal was diagnosed as affected by neuronal ceroid-lipofuscinosis.     

Fatal necrotizing fasciitis and myositis in a captive common bottlenose dolphin (Tursiops truncatus) associated with Streptococcus agalactiae.

A common bottlenose dolphin (Tursiops truncatus) was presented for necropsy after acute onset of gastrointestinal signs and cutaneous lesions that rapidly progressed to death. Gross and microscopic findings were characterized by locally extensive severe necrohemorrhagic fasciitis and cellulitis, and severe necrotizing myositis in the head and dorsocranial thorax, with numerous disseminated gram-positive cocci. Streptococcus agalactiae was isolated from the lesions and from visceral organs (liver and lung), and it was identified by standard microbiology techniques. This communication is the first report of necrotizing fasciitis in a marine mammal associated with S. agalactiae.     

Clinical signs and pathology of accidental monensin poisoning in sheep

The clinical signs and postmortem findings in sheep from two flocks accidentally poisoned with monensin are described. Clinical signs began within 24 hours of exposure to monensin. In the acute stages they consisted of lethargy, stiffness, muscular weakness, a stilted gait and recumbency. Feed refusal was seen in one flock but not in the second. Subacute to chronic clinical signs were decreased muscle volume of the rump and thigh. When forced to run, chronically affected sheep had a stilted, stiff legged, rocking horse gait.

Gross postmortem changes were not always visible. Where visible, they affected skeletal muscles and consisted of pale streaking, with atrophy in the chronic stages. Lesions were most severe in muscles of the rump and hind limbs. Microscopically myofiber swelling and hyalinization were seen with interstitial mononuclear cell reaction and extensive sarcoplasmic mineralization in some cases. Chronic lesions consisted of fibrosis and myofiber atrophy. In lambs less than one month old, diffuse gastrointestinal hemorrhage was the only finding.

     

Comparative nephropathogenicity of infectious bronchitis virus in bursectomized and nonbursectomized chickens

A study was conducted to compare the responses of bursectomized (Bx) and nonbursectomized (non-Bx) specific-pathogen-free male chickens to Australian T strain of infectious bronchitis virus. Four chickens from each group were killed at 3, 5, 7, 14, 21, and 28 days after conjunctival inoculation of the virus. Clinical signs and gross and microscopic lesions were more severe in Bx than in non-Bx chickens. The non-Bx chickens had linear IgG deposits along the renal tubules. Virus-neutralizing titers were log10 2.74 to 4.33 for non-Bx chickens and less than log10 1.25 for the inoculated Bx and for broth-inoculated Bx and non-Bx chickens (controls). Early in the disease, renal lesions were of the same type in all infected chickens, but were more severe in Bx chickens. Later, nephritis was chronic and active in Bx chickens and was chronic in non-Bx chickens.     

Susceptibility of laughing gulls (Larus atricilla) to H5N1 and H5N3 highly pathogenic avian influenza viruses

This investigation detailed the clinical disease, gross and histologic lesions, and distribution of viral antigen in juvenile laughing gulls (Larus atricilla) intranasally inoculated with either the A/tern/South Africa/61 (H5N3) (tern/SA) influenza virus or the A/chicken/Hong Kong/220/97 (H5N1) (chicken/HK) influenza virus, which are both highly pathogenic for chickens. Neither morbidity nor mortality was observed in gulls inoculated with either virus within the 14-day investigative period. Gross lesions resultant from infection with either virus were only mild, with the tern/SA virus causing decreased lucency of the air sacs (2/6), splenomegaly (2/6), and pancreatic mottling (1/6) and the chicken/HK virus causing only decreased lucency of the air sacs (2/8) and conjunctival edema (2/8). Histologic lesions in the tern/SA-inoculated gulls included a mild to moderate heterophilic to lymphoplasmacytic airsacculitis (6/6), mild to moderate interstitial pneumonia (3/6), and moderate necrotizing pancreatitis and hepatitis at 14 days postinoculation (DPI) (2/6). Immunohistochemical demonstration of viral antigen occurred only in association with lesions in the liver and pancreas. In contrast, viral antigen was not demonstrated in any tissues from the chicken/HK-inoculated gulls, and inflammatory lesions were confined to the air sac (3/8) and lungs (3/8). Both viruses were isolated at low titers (<10(1.68) mean embryo lethal dose) from oropharyngeal and cloacal swabs up to 7 days postinoculation (DPI), from the lung and kidney of one of two tern/SA-inoculated gulls at 14 DPI, and from the lung of one of two chicken/HK-inoculated gulls at 7 DPI. Antibodies to influenza viruses as determined with the agar gel precipitin test at 14 DPI were detected only in the two tern/SA-inoculated gulls and not in the two chicken/HK-inoculated gulls.     

Tembusu virus infection in Cherry Valley ducks: The effect of age at infection

Three groups of Cherry Valley ducks at 5 day, 2 week and 5 week of age were intranasally infected with the WFCL strain of Tembusu virus (TMUV) to investigate the effect of host age on the outcome of TMUV infection. For each age group, clinical signs, gross and microscopic lesions, viral copy numbers in tissues and serum neutralizing antibody titers were recorded. Age-related differences in the resistance to TMUV infection were observed with younger ducks being more susceptible. Some ducks infected at 5 day and 2 week of age developed severe clinical signs, including severe neurological dysfunction and death. However, subclinical signs and no mortality were observed in ducks infected at 5 week of age. A decline in the severity of gross and microscopic lesions was observed as ducks mature. Systemic infections were established in the three age groups post challenge. Higher viral copy numbers in the tissues, especially in vital organs such as the brain and the heart, were developed in the ducks infected at 5 day of age than older ducks, correlating with the severity of clinical signs and lesions in the tissues. Furthermore, ducks infected at 5 week of age developed significantly higher serum neutralizing antibody titers than ducks infected at 5 day of age as determined by serum neutralization test. Therefore, age-related differences in the resistance to TMUV infection should be considered when studying the pathogenicity, pathogenesis, formulation of the vaccination and therapy strategies of TMUV infection in ducks.     

Pathologic findings in rabies-suspect, random-source, and accidentally killed skunks

To evaluate sampling biases, pathologic findings in accidentally killed skunks (ie, killed by motor vehicles) were compared with those in random-source skunks (live-trapped and euthanatized, or trap-killed during research) and skunks submitted to a public health laboratory as rabies-suspect. Presence or absence of microscopic lesions in the brain, kidneys, liver, and lungs were used to test the null hypothesis that prevalence of disease did not differ by source of collection. Brain lesions differed with the source; rabid and nonrabid skunks submitted to a public health laboratory had higher prevalences of lesions than did other skunks. Kidney, liver, and lung lesions did not differ among skunks by source of collection. Liver and lung lesions were attributed mainly to parasitism, were not severe, and did not cause debilitated condition. Lesions were seen more often in the kidneys than in other tissues. Usually, lesions were mild to severe, focal, chronic, nonsuppurative, interstitial nephritis (possibly a consequence of leptospirosis). Six of 177 skunks necropsied appeared cachectic. Aleutian disease was diagnosed in one skunk and histoplasmosis was diagnosed in another, but rabies and canine distemper virus infection were the only diseases found with the potential to cause the high population mortality. Public health surveillance cases were biased toward diseased animals (rabies and canine distemper virus infection), but random-source or accidentally killed animals provided unbiased data. Although other factors must be considered, accidentally killed skunks provided cost-effective and useful data for the evaluation of enzootic rabies.