Infection of cattle by airborne foot-and-mouth disease virus: minimal doses with O1 and SAT 2 strains

Equipment has been constructed and methods developed for exposing individual cattle to two strains of foot-and-mouth disease (FMD) virus in aerosols to determine the minimal infective dose by the respiratory route. The aerosols used were produced either artificially by a spinning-top aerosol generator, in which case they were of homogeneous small particle size (less than 3 micron in diameter) or else they were derived naturally from infected pigs, in which case the particles were heterogeneous in size. Two strains of FMD virus were used: an O1 strain of UK origin and a SAT 2 strain from South Africa. The lowest doses which initiated infection were 12.5 TCID50 of O1 BFS virus and 25 TCID50 of SAT 2 virus, infectivity having been assayed in primary bovine thyroid cell cultures. Following exposure to low doses of virus (range 12 to 316 TCID50) 33 per cent of the cattle exposed to O1 BFS virus and 27 per cent exposed to SAT 2 virus were infected but did not develop detectable vesicular lesions.     

Plasma concentrations of corticosterone and thyroid hormones in laying fowls from different housing systems

Plasma concentrations of corticosterone, thyroxine (T4) and triiodothyronine (T3) were measured in representative mature female domestic fowls from three housing systems: cages, covered strawyard and range. There were no between-system differences for T4 but T3 was lower in birds from range than in those from cages. Corticosterone concentrations were lower in birds from strawyards than in those from range and cages. In the strawyards there were no differences in corticosterone concentrations between normal and low-ranking hens. The latter were selected on the basis that they remained apart from the flock, were under-weight, poorly feathered and unable to feed at will. Low-ranking hens had significantly higher plasma concentrations of T3 and T4 than normal birds. This was attributed mainly to the poor feather covering of most low-ranking birds. It was concluded that, in the assessment of different housing systems, plasma corticosterone and thyroid hormones were not useful measures of long-term stress or welfare. Different factors relevant to welfare may have contrary effects on the plasma concentrations of these hormones.     

Comparison of serological tests for the detection of natural heartworm infection in cats

Serological tests were performed on 380 cats with necropsy-confirmed heartworm disease to compare the performance of currently available commercial laboratory and point-of-care heart-worm serological tests in a heartworm-endemic area. Overall, antigen tests detected 79.3% to 86.2% of heartworm infections and were highly specific. Most cats with false-negative antigen tests had a single male worm. Antibody tests detected 62.1% to 72.4% of heartworm infections and had a wider range of false-positive results (1.4% to 19.1%) than antigen tests (0.3% to 2.0%). Serological tests for feline heartworm infection varied in diagnostic performance. Combining results from antigen and antibody tests achieved greater sensitivity than using either test alone.     

Foot-and-mouth disease virus (O/UKG/2001) is poorly transmitted between sheep by the airborne route

Foot-and-mouth disease virus (FMDV) can be spread by the airborne route and therefore atmospheric dispersion models have been developed to predict where the virus might spread during a disease outbreak. Airborne transmission between sheep of the FMDV strain involved in the outbreak in Europe in 2001 (O/UKG/2001) was studied experimentally. Recipient animals were exposed to two donor sheep excreting virus for 2, 4, 6, 8 or 24 h. Although FMDV was detected in air samples collected during challenge, none of the recipient sheep became infected. These data suggest that O/UKG/2001 is not efficiently transmitted by the airborne route between sheep.     

Anaplastic astrocytoma in the spinal cord of an African pygmy hedgehog (Atelerix albiventris)

A 2-year-old, female hedgehog presented with an 8-month history of progressive, ascending paresis/paralysis and was tentatively diagnosed with wobbly hedgehog syndrome. She died awaiting further diagnostic tests, and the owners consented to postmortem examination. Grossly, the bladder was large and flaccid and the cervical and lumbar spinal cord were regionally enlarged, light grey, and friable with multifocal hemorrhages. The thoracic spinal cord was grossly normal. Microscopically all regions of the spinal cord had similar changes, although the cervical and lumbar sections were most severely affected. These regions were completely effaced by a moderately cellular infiltration of highly pleomorphic polygonal to spindle shaped cells, mineralization, and necrosis, which were most consistent with anaplastic astrocytoma. The thoracic spinal cord white matter was similarly infiltrated by the neoplastic cells, with perivascular extension into the otherwise normal grey matter. A diagnosis of anaplastic astrocytoma was confirmed using immunohistochemical stains that were positive for glial fibrillary acidic protein and S100.