Carol House

Morbillivirus infection in cetaceans of the western Atlantic

We report serologic evidence of morbillivirus infection in eleven of fifteen species of odontocete cetaceans from the western Atlantic since 1986. Blood samples were obtained both from free-ranging and stranded animals. Virus neutralizing titers were higher against porpoise and dolphin morbilliviruses than against peste des petits ruminants virus, phocine distemper virus or canine distemper virus (CDV). Serum from five species, tested in a heterologous immunoprecipitation assay using radiolabelled CDV, precipitated the nucleocapsid (N) protein. Clinical morbillivirus infection may potentially impact already threatened species such as the harbour porpoise and precipitate mass strandings of socially cohesive odontocetes.

Morbillivirus infection in stranded common dolphins from the pacific ocean

From August 1995 to August 1997, six of 18 common dolphins (Delphinus delphis) that stranded along beaches of southern California (USA) tested antibody positive for dolphin morbillivirus (DMV). Titers ascertained by virus neutralization ranged from 1:50 to 1:910 while those determined by ELISA ranged from 1:80 to 1:195. The first individual to strand survived and was released back into the Pacific Ocean 14 mo later. Histopathologic examination of tissues from the other five dolphins did not reveal lesions characteristic of morbilliviral disease; however, morbilliviral RNA was detected in three of the five by reverse transcriptase-polymerase chain reaction testing. This is the first report of morbilliviral infection in any marine mammal species in the northern hemisphere of the Pacific Ocean. These data indicate that DMV, or a closely related morbillivirus, is present in the Pacific Ocean and infection of common dolphins may not be associated with morbillivirus disease.

Epizootiology of morbillivirus infection in harp, hooded, and ringed seals from the Canadian Arctic and western Atlantic.

Using a virus neutralization technique, we found phocine distemper virus (PDV) antibody in 130 (83% of 157) harp seals (Phoca groenlandica) from the western North Atlantic sampled between 1988 and 1993 inclusive. In contrast, only 44 (24% of 185) hooded seals (Cystophora cristata) had antibodies against PDV even though they were sympatric with harp seals and were sampled over a similar period, from 1989 to 1994 inclusive. Antibodies occurred in 106 (41%) of 259 ringed seals (Phoca hispida); this prevalence was higher than expected given the solitary behavior and territoriality characteristic of this species. Seropositive ringed seals were found at each of seven locations across Arctic Canada from Baffin Bay to Amundsen Gulf at which samples were collected between 1992 and 1994. However, the prevalence of infection was highest where ringed seals are sympatric with harp seals in the eastern Canadian Arctic.

Laboratory Diagnosis of African Horse Sickness: Comparison of Serological Techniques and Evaluation of Storage Methods of Samples for Virus Isolation:

Five serological methods of diagnosing African horse sickness were evaluated, using a battery of serum samples from experimental horses vaccinated and challenged with each serotype of African horse sickness virus (AHSV1 through AHSV9): agar gel immunodiffusion (AGID), indirect fluorescent antibody (IFA), complement fixation (CF), virus neutralization (VN), and enzyme-linked immunosorbent assay (ELISA). The 5 tests were also compared using a panel of field samples, convalescent equine sera with antibodies to domestic equine viral diseases, and sera from horses awaiting export. The ELISA described in this paper was group specific. It did not require calibration with a standard positive serum but did yield elevated values with negative sera that were repeatedly frozen and thawed or heat inactivated. The IFA test was sensitive but could not be used on some field sera as the control cells exhibited fluorescence, possibly due to the animal being recently vaccinated with cell culture material. Sixty-two experimental sera were compared by VN, CF, AGID, and ELISA. Forty sera, 10 positive and 30 negative, were correctly classified by the 5 serologic assays. The 22 remaining sera gave mixed reactions. The AGID had no false positive results but had false negative results for up to 20% of the samples, depending upon the comparison. The VN, CF, and ELISA were similar in their variability. The length of time that virus could be recovered from a viremic blood sample was compared in an evaluation of storage methods for virus isolation samples. Washed erythrocytes were held at 4 C, washed erythrocytes plus stabilizer were held at −70 C, and blood that was drawn into a preservative (oxalate/phenol/glycerol) was held at 4 C. Virus was isolated for 12 months from a sample stored as washed erythrocytes at 4 C but for only 6 months from the same blood stored by the other 2 methods.

A MORBILLIVIRUS ANTIBODY SURVEY OF ATLANTIC WALRUS, NARWHAL AND BELUGA IN CANADA

A longitudinal serologic survey was conducted for morbillivirus antibodies in Atlantic walruses (Odobenus rosmarus rosmarus), narwhal (Monodon monoceros), and beluga (Delphinapterus leucas) from the Northwest Territories, Nunavut and the St. Lawrence estuary (Canada). Sixty-five of 131 (50%) walruses sampled between 1984 and 1993 had detectable morbillivirus neutralizing antibodies. Positive walrus were identified from four of five Arctic sampling sites, to as far back as 1984. Prevalence of morbillivirus neutralizing antibodies in walruses from Foxe Basin ranged from a high of 76% (n = 21) in 1993 to a low of 22% (n = 28) in 1984. Limitations in sample acquisition may have produced underestimates for the 1984 data. There are no reports of clinical morbillivirus infection in walruses. Our results are consistent with the hypothesis that a morbillivirus similar or identical to phocine distemper virus (PDV) has circulated among walrus populations of the eastern Canadian Arctic, at least since the early 1980s. No narwhal (n = 79) or beluga (n = 445) from Arctic waters were identified as having antibodies to dolphin morbillivirus (DMV) above the threshold serum dilution of log2 4. Also, none of the beach-cast cetacean carcasses (n = 28) from the Gulf of St. Lawrence and the St. Lawrence estuary were positive for antibodies to DMV. This indicates that Gulf of St. Lawrence, St. Lawrence estuary, and Arctic cetaceans either have not been exposed to DMV or an antigenically related morbillivirus, or are not susceptible to infection.

African horse sickness and African carnivores

African horse sickness (AHS) is a disease that affects equids, and is principally transmitted by Culicoides spp. that are biological vectors of AHS viruses (AHSV). The repeated spread of AHSV from sub-Saharan Africa to the Middle East, northern Africa and the Iberian peninsula indicate that a better understanding of AHS epizootiology is needed. African horse sickness has long been known to infect and cause mortality among domestic dogs that ingest virus contaminated meat, but it is uncertain what role carnivores play in transmission of the virus. We present evidence of widespread natural AHS infection among a diversity of African carnivore species. We hypothesize that such infection resulted from ingestion of meat and organs from AHS-infected prey species. The effect of AHS on the carnivores is unknown, as is their role in the maintenance cycle of the disease.

Further studies on the efficacy of an inactivated African horse sickness serotype 4 vaccine

The immunity induced by two inoculations of a commercial inactivated African horse sickness (AHS) serotype 4 (AHSV-4) vaccine was studied. No adverse reaction was observed in five horses following vaccination. Following challenge-inoculation, no clinical signs attributable to AHS, no viraemia indicating infection, and no anamnestic response was observed in the vaccinated ponies. Two control ponies developed clinical signs typical of AHS, high levels of viraemia, and died 7 and 8 days postchallenge-inoculation. The quality of immunity induced by the two-dose regimen was compared with a one-dose regimen from a previous study; in the one-dose study following challenge-inoculation, six of nine ponies were protected from clinical signs of AHS, seven of the nine vaccinated ponies developed an anamnestic response, and one pony had a viraemia about 10(3) 50% mouse lethal dose of AHSV-4 per ml of blood for 3 days following challenge-inoculation. The utility of an efficacious inactivated AHS vaccine in the control and eradication of AHS from a non-endemic area is discussed. The lack of viraemia following vaccination with an inactivated vaccine and the prevention of vector infection by animals exposed to field virus are important in the eradication of AHS.

Viral serologic survey of bowhead whales in Alaska.

Serum samples from 21 of 36 Eskimo harvested bowhead whales (Balaena mysticetus) were positive by virus neutralization (50% endpoint titer ≥1:28 and/or 100% endpoint titer ≥1:20) for antibodies to at least one virus serotype from the calicivirus family, vesicular exanthema of swine virus (VESV) and San Miguel sea lion virus (SMSV). Many animals were positive to more than one serotype when using the Spearman-Karber (S-K) method for calculating antibody titers. The most common serotype detected was VESV F55 with 6 of 36 (17%) by the Monto and Bryan (MB) titer calculation method, and 17 of 36 (47%) by the S-K titer calculation method. Vesicular exanthema of swine virus 1934B antibody was detected in 3 of 36 (8%) and 5 of 36 (14%) whales using the MB and S-K methods, respectively. Vesicular exanthema of swine virus J56 antibody was detected in 3 of 36 (8%) by the S-K method only. All whales <8.5 m (estimated yearlings, n = 6) were seronegative for VESV J56 and 1934B while 10% and 17% of the whales >8.5 m were positive, respectively. Whales assumed to be sexually mature (>13 m) had a higher prevalence of antibody to VESV 1934B and SMSV 8 than those <13 m. Gender had an effect on seroprevalence of antibody to VESV 1934B as titers ≥1:28 (S-K method) occurred in 18% of the females and 7% of the males. Antibody to other serotypes (SMSV 8 and 12) occurred less frequently (<6%) at an antibody titer ≥1:28 by the S-K method. All 36 whale sera were negative for antibody to VESV-A48, B51, C52, D53, E54, G55, H54, 155, and K54; Tillamook calicivirus, and dolphin morbillivirus; and SMSV-1, 2, 4, 5, 6, 7, 9, 10, 11, and 13 by the S-K method.

Viral and bacterial serology of free-ranging Pacific walrus.

Serum or heparinized plasma samples were obtained between 1994 and 1996 from 20 male and 20 female adult free-ranging Pacific walrus (Odobenus rosmarus divergens) from St. Lawrence Island and Round Island, Alaska. Samples were screened for antibodies to some potentially pathogenic bacteria and viruses. No sample had detectable antibody to Brucellaspp. Three of 40 (8%) had low antibody titers to Leptospira interrogansserovars. Phocine distemper virus antibodies were not detected. Serologic responses to one or more caliciviruses (San Miguel sea lion virus 12 or vesicular exanthema of swine serotypes E54, F55, G55, 1934B) were detected in 18% (seven of 40) walrus. Antibodies to one or more subtypes of influenza A virus (H10, N2, N3, N5, N6, N7) were detected in 21% (eight of 38). Periodic screening of free-ranging populations for exposure to infectious diseases has become an important component of bio-monitoring programs to facilitate understanding and detecting trends in marine mammal populations.

Detection of Bluetongue Group-Specific Antibody by Competitive ELISA

a2 that react with the major core protein VP7 5,7 to the reference Mab 3-17-A3 b in the cELISA. 3 Three hybridomas, 7D3A.2, 8A3B.6, and 8B1B.1, a2 were prepared against BTV17, and their Mab’s were found to be reactive with BT serotypes 1-20. The Mab’s bound to VP7 (designated VP9) 2 and did not react with epizootic hemorrhagic disease (EHD) virus. The BTV group antigen 5 was prepared using baby hamster kidney (BHK-21) cell cultures infected with BTV1 and used to coat an Immulon l c plate. Dilutions of the Mab’s were reacted on the coated plate, the plates were washed, and antimouse IgG conjugated to horseradish peroxidase d was added. After incubation, the plates were washed and the substrate and chromogen, hydrogen peroxide and 2-2’azino-di(3-ethyl benzthiazaline-6 sulfonic acid) e in a citrate buffer, were added. After 15 minutes, the optical densities (OD’s) at 405 nm were recorded. The dilution of Mab fluid to achieve an OD of 0.8-1.0 was determined. The test sera, diluted 1:2, 1:4, and 15, were used in the cELISA Mab system, adding them immediately before the Mab. Positive control antiserum from the bluetongue agar gel immunodiffusion (BT-AGID) test was further diluted 2-fold from 1:10 to 1:160. Results were reported as negative when the sample at a final dilution of 1:4 did not decrease the OD of the Mab by 60% or more. Titers were expressed as the reciprocal of the highest serum dilution giving a positive result. The BT-AGID test was conducted in accordance with the package insert in the licensed test kit. Results were reported as positive (+), weak positive (W+), negative (N), or question (?) for samples of undetermined status. The microtiter virus neutralization (VN) test