Possible introduction of epizootic hemorrhagic disease of deer virus (serotype 2) and bluetongue virus (serotype 11) into British Columbia in 1987 and 1988 by infected Culicoides carried on the wind.

Outbreaks of epizootic hemorrhagic disease of deer and of bluetongue began in British Columbia in August and October 1987 respectively and recrudescence of infection by both viruses was detected the following year in August. Weather records for up to 18 days before the initial outbreaks of disease, isolation of virus or seroconversion were examined to determine if the viruses could have been introduced by infected Culicoides carried on the wind. Data on temperature, rainfall, wind speed and direction and pressure together with backward trajectory analysis showed that there were suitable winds which could have introduced Culicoides infected with epizootic hemorrhagic disease of deer virus on 13 August 1987 (14 days before disease was observed), Culicoides infected with bluetongue virus on 1 October 1987 (7 days before virus was isolated and 13 days before disease in sheep) and Culicoides infected with bluetongue or epizootic hemorrhagic disease of deer viruses on 20 July 1988 (15 days before seroconversion was detected). The arrival on 13 August 1987 coincided with the passage of a cold front and rain and that on 1 October 1987 with a fall in temperature and calm winds. The source of the Culicoides before arrival could have been the Okanogan Valley as far south as the junction of the Okanogan and Columbia rivers in Washington, USA. Flight would have been at temperatures of 12.6 degrees C or higher and at heights up to 1.5 km.     

Foot-and-mouth disease in British deer: transmission of virus to cattle, sheep and deer.

After exposure for two hours to cattle with foot-and-mouth disease, each of the five species of deer found in the British countryside became infected. Clinical disease was typical and severe in the roe and muntjac deer, with some animals dying, less severe in the sika deer and usually subclinical in the fallow and red deer. Each species transmitted disease to its own species and to cattle and sheep. The amounts of virus present in the blood, and in oesophageal/pharyngeal samples and excreted as an aerosol during the course of the infection in the deer were similar to those recorded for the sheep and cattle in the same experiment. The fallow and sika deer commonly carried virus in the pharynx beyond 28 days after exposure; some red deer also became carriers. In epidemics of foot-and-mouth disease in the UK, it is likely that deer would have such intimate contact with farm animals as occurred in this study. The natural behavior of free-living deer in the UK suggests that, although the five species are susceptible to foot-and-mouth disease, they are unlikely to be an important factor in the maintenance and transmission of the virus during an epidemic of foot-and-mouth disease in domestic livestock.     

A serological comparison of the australian isolate of bluetongue virus type 20 (CSIRO 19) with bluetongue group viruses

Bluetongue virus serotype 20 (BTV20) (CSIRO 19 isolate) was compared with 17 other BTV serotypes using various serum neutralization (type antigen) tests to determine whether any serological relationships existed. Plaque-reduction neutralization tests employing 50% and 80% end-points could not clearly differentiate BTV20 from BTV4. Plaque-inhibition tests and quantal microtitre neutralization tests also showed a relationship between BTV20 and BTV4. Antisera against BTV20 and a Cyprus isolate of BTV4 (A SOT 1) showed a low level of cross-neutralization against BTV17. Investigation of plaque-reduction neutralization of virus—antiserum mixtures, by the calculation of regression curves and comparison of the area under the curves, showed that the BTV4 isolates studied could not be differentiated, and that BTV4 typing antiserum could not distinguish between BTV4 and BTV20, but that BTV20 antiserum could distinguish between BTV20 and BTV4. BTV20 did not show any significant type relationships with any of the other BTV types 1 to 17 using any of the neutralization tests. Our results suggest that BTV20 is closely related to, although not identical with, BTV4 and could be grouped as a subtype of BTV4. BTV17 appears to be distantly related to BTV20 and BTV4, but is clearly a distinct type.     

Artifactual Prolongation of the Activated Partial Thromboplastin Time Associated With Hemoconcentration in Dogs

An inappropriate blood-to-anticoagulant ratio can cause an artifactual prolongation of the activated partial thromboplastin time (APTT) and prothrombin time (PT). In a drug safety study in dogs, we observed a 4-to 5-second increase in the APTT from baseline coincident with increased hematocrit values (56% to 65%) secondary to drug-induced vomiting and diarrhea. The PT and platelet counts were unchanged, and there was no clinical evidence of bleeding associated with venipuncture. Although we were unable to sample the same dogs to investigate the possible effect of hemoconcentration on the prolonged APTT, the question was addressed by an in vitro study. The hematocrit value for citrated blood samples collected from healthy beagle dogs was increased by the addition of aliquots of red blood cell/plasma mixtures in vitro while maintaining a 9:1 blood-to-anticoagulant ratio. There was a 2-to 4-second prolongation of the APTT associated with hematocrit values of 55% to 61 %, but the PT was not prolonged. Adjustment of the blood-to-anticoagulant ratio corrected the prolongation. This study emphasizes the important relationship of the blood-to-anticoagulant ratio when measuring coagulation tests in hemoconcentrated samples.     

Use of danazol for treatment of corticosteroid-resistant immune-mediated thrombocytopenia in a dog

A routine health screen of a 7 1/2-year-old female Beagle participating as a control in a long-term study revealed thrombocytopenia. Immune thrombocytopenia was diagnosed on the basis of regenerative bone marrow findings (high number of megakaryocytes) and evidence of antiplatelet antibodies. Treatment with prednisone at dosages up to 1 mg/kg of body weight every 12 hours resulted in limited improvement, with relapses of severe thrombocytopenia thwarting attempts to taper the corticosteroid, and was further complicated by side effects of the drug. Addition of danazol to the treatment regimen (5 mg/kg, q 12 h) resulted in remission of the thrombocytopenia within 2 weeks and permitted the dosage of prednisone to gradually be reduced and discontinued. Associated with this response was a decrease in platelet-associated IgG to values comparable with control samples.     

The airborne dispersal of foot-and-mouth disease virus from vaccinated and recovered pigs, cattle and sheep after exposure to infection.

Foot-and-mouth disease virus was detected during two periods in the air of looseboxes which housed susceptible, vaccinated or recovered pigs, cattle or sheep exposed to infection. The first was 30 min to 22 h after exposure and occurred in all animals. The second was two to seven days after exposure and occurred with those susceptible and vaccinated animals which developed clinical lesions, and with vaccinated and recovered pigs and sheep, which did not develop clinical lesions. Vaccination of animals before exposure resulted in less or no virus being detected. The virus during the first period was attributed to virus trapped on the animal during exposure, and the virus during the second period to limited multiplication in the respiratory tract. Control of movement for two weeks after contact with infection is suggested as a means of preventing spread of foot-and-mouth disease in areas that contain vaccinated animals.