Variation amongst the neutralizing epitopes of bluetongue viruses isolated in the United States in 1979-1981.

Neutralizing epitopes present on field isolates of bluetongue virus (BTV) serotypes 10, 11, 13 and 17 were evaluated with a panel of polyclonal and neutralizing monoclonal antibodies (MAbs). A total of 91 field isolates were evaluated, including 15 isolates of BTV-10, 29 isolates of BTV-11, 26 isolates of BTV-13, and 21 isolates of BTV-17. The viruses were isolated from cattle, goats, sheep, elk and deer in Idaho, Louisiana, Nebraska and, predominantly, California, in the years 1979, 1980 and 1981. The isolates were analyzed and compared using a panel of neutralizing MAbs which included five MAbs raised against BTV-2, seven against BTV-10, five against BTV-13, and six against BTV-17. Neutralization patterns obtained with the MAb panel and individual field isolates were compared to those obtained with prototype viruses of each serotype. All field isolates were neutralized by at least some of the MAbs raised against the prototype virus of the same serotype. All field isolates of BTV-10 were neutralized by the seven MAbs raised to BTV-10, whereas the field isolates of BTV-11, BTV-13 and BTV-17 were not consistently neutralized by all of the MAbs raised against the prototype virus of the same serotype. Variation in neutralizing epitopes recognized by the MAb panel was most pronounced amongst the field isolates of BTV-17. A one-way cross neutralization was evident between BTV-10 and BTV-17 as all field isolates of BTV-17 were neutralized by four of the MAbs raised against BTV-10. In contrast, no BTV-10 isolates were neutralized by the MAbs raised against BTV-17. Differences in the MAb neutralization patterns of field isolates of BTV-11, BTV-13 and BTV-17 suggest that the immunogenic domain responsible for their neutralization is plastic, such that individual epitopes within the domain may vary in their significance to the neutralization of different viruses, even of the same serotype. The apparent conservation of neutralizing epitopes on field isolates of BTV-10 suggests that the field isolates may be derived from the modified-live vaccine strain of BTV-10.     

Seroprevalence of antibodies against bluetongue virus in animals imported to Poland from EU countries

The aim of this study was to determine the seroprevalence of BTV-specific antibodies in animals imported to Poland from EU countries after 15 June 2006. From 1 January 2007 to 22 January 2008, a total of 10719 samples of sera collected from cattle, goats and fallow deer were tested. Sera were screened using the highly sensitive and specific c-ELISA test and positive results were confirmed by the AGID assay. Out of 10719 sera, 30 (0.28% of the total number of samples) were found to be positive in both tests applied. All of 21 seropositive cattle specimens were imported to Poland from Germany whereas 9 seropositive fallow deer were of Dutch origin. In conclusion, it can be stated that because BTV situation in Europe is getting worse, implemented surveillance studies should be continued to monitor the actual BT status in Poland.     

Gastrointestinal protozoa in non-human primates of four zoological gardens in Belgium

Gastrointestinal parasites are important infectious causes of diarrhoea in captive non-human primates (NHP). However, prevalence data of gastrointestinal parasites in zoological gardens are scarce. Therefore, a cross-sectional survey was conducted to estimate the occurrence of gastrointestinal parasites in NHP of four zoological gardens in Belgium. Between August 2004 and April 2006, 910 faecal samples were collected from 222 animals housed in 39 groups. The 31 species involved were representatives of prosimians, New World (NW) monkeys, Old World (OW) monkeys and apes. Because individual sampling was impossible, a statistical simulation was performed to estimate a sufficient sample size. All samples were microscopically examined after an acetic acid-ether concentration. Differences in host species susceptibility were examined by non-parametric tests. Entamoeba spp. (44%) and Giardia spp. (41%) were the most prevalent species. Other parasites detected were Endolimax nana (36%), Chilomastix mesnili (21%), Balantidium coli (13%), Trichuris spp. (10%), Iodamoeba bütschlii (5%) and Strongyloides spp. (5%). Parasites for which a significant difference in susceptibility at the level of host taxonomy was noted were Entamoeba spp. (p<0.001) and C. mesnili (p<0.05). Samples containing Entamoeba spp. were the most prevalent in OW monkeys (p<0.0083). Samples collected from OW monkeys contained the highest number of parasite species (p<0.0083).     

Animal genetic resource trade flows: The utilization of newly imported breeds and the gene flow of imported animals in the United States of America

Animal germplasm exchange has recently received attention as a product of the FAO's State of the World's Animal Genetic Resources effort. Some have advocated a need to explore policies and regulations on the exchange of germplasm (e.g., Hiemstra, S.J., Drucker, A., Tvedt, M., Louwaars, N., Oldenbroek, J., Awgichew, K., Kebede, S., Bhat, P., da Silva Mariante, A. 2006. Exchange, use and conservation of animal genetic resources: policies and regulatory options. Centre for Genetic Resources. Wageningen Univ., the Netherlands, pp. 1­43). However, there has been little comprehensive assessment of either the economic or genetic impact of introduced germplasm into national populations. As a result, much of the discussion of gene flows has been based on assumptions and generalizations. The objective of this paper is to evaluate the genetic impact of germplasm imported into the United States during the last 25 to 50 years. The paper considers both new breeds (Meishan pigs, Tuli cattle, and Boer goats) and new animals within existing breeds (Limousin and Jersey cattle). Of the new breeds recently imported only one had an impact on US animal agriculture. Neither the Tuli nor the Meishan has impacted the US livestock industry. It appears that these breeds were initially viewed as attractive because of single traits, but producers did not find it attractive to adopt the new breeds based on these specific traits. In the end, these breeds did not prove competitive in the US under the current set of market conditions. This result would indicate that importation of new genetic resources due to a single trait of interest is not a viable importation strategy. By contrast, the Boer goat exhibited a number of production characteristics which made it desirable to US producers and thereby allowed the breed to become well established. A second portion of the study evaluated the importation and parentage pattern of Limousin cattle as they became established in the U. S. and the gene flow of imported Jersey cattle since the 1950′s. In both cases, the study relied on pedigree analysis. Over the past fifty years, Jersey cattle have been sporadically imported from various countries, but no imported animal has had an overpowering effect on the population. It appears that by the great-grand progeny level, the genes from imported animals are diminishing rather than increasing in the population. In evaluating the predicted transmitting abilities for imported cattle relative to high and moderately ranked domestically bred cattle, there were significant differences between these groups for milk production. This would be sufficient to explain why the impact of the imported cattle diminished. The results of our analysis at both the breed and individual level underscore the speculative nature of germplasm importation — even within breeds where there is a great deal of information available about production characteristics. From this analysis, we conclude that successful importation of new breeds into the US must be based on a large number of production characteristics; importation for a single characteristic (e.g., high prolificacy) while the breed is deficient in other areas does not lead to the breed's adoption. While not fully explored in this work, it appears that initial interest and acceptance from the private sector is crucial for breed acceptance, as the Boer goat demonstrates. Within an existing breed, importation of individual animals still appears to have a relatively high degree of risk and is dependent upon the importer's ability to pick viable candidates. However, once animals are imported their progeny must effectively compete with the domestic population, or else their genetic contribution will rapidly diminish.     

Regional risk of exporting cattle seropositive for bluetongue virus from the United States

OBJECTIVE: To create a stochastic model to quantify the risk that shipments of cattle from regions within the United States would contain animals seropositive for bluetongue virus and to determine shipment-level accuracy of serologic testing by use of a competitive ELISA (c-ELISA). SAMPLE POPULATION: 19,216 shipments containing 528,918 cattle and calves. PROCEDURE: Data were obtained on number of animals and state of origin of cattle in export shipments originating within the United States between January 1994 and March 2002. Probability distributions for size of export shipments were determined for all states within the United States, and distributions for agar gel immunodiffusion and c-ELISA accuracy (sensitivity and specificity) were determined from expert opinion and review of the literature. The model simulated selection of a shipment and then determined the probability that a threshold number or percentage of cattle within that shipment would have a positive c-ELISA result. Shipment-level sensitivity, specificity, positive-predictive value, and negative-predictive value were calculated. RESULTS: Substantial differences were evident in the regional probability of a shipment being declared positive, with shipments from northeastern states having the lowest probability and shipments from southwestern states having the highest probability. The c-ELISA had variable predictive values at the shipment level, depending on the threshold used and the prevalence of antibody-positive cattle within the region. CONCLUSIONS AND CLINICAL RELEVANCE: Results from this study will aid importers in making scientifically based decisions regarding risk of importing antibody-positive cattle.     

Serogrouping of United States and some African serotypes of bluetongue virus using RT-PCR

The diagnostic potential of RT-PCR for detection of bluetongue virus (BTV) ribonucleic acid (RNA) sequence in cell culture and tissue samples from infected ruminants from United States, Sudan, South Africa and Senegal, was evaluated. The non structural protein 1 (NS1) gene of North American BTV serotype 11 was targeted for PCR amplification. The United States BTV serotypes 2, 10, 11, 13 and 17 and the Sudanese BTV serotypes 1, 2, 4 and 16 and BTV serotype 4 from South Africa and BTV serotype 2 from Senegal were studied. RNAs from all BTV field isolates used in this study, propagated in cell cultures, were detected by the described RT-PCR-based assay. The first specific 790bp BTV PCR products were amplified using a pair of outer primers (BTV1 and BTV2). Specificity of the PCR products was confirmed by a nested amplification of a 520bp PCR product using a pair of internal (nested) primers (BTV3 and BTV4). The BTV PCR products were visualized on ethidium bromide-stained agarose gels. Amplification products were not detected when the RT-PCR-based assay was applied to RNAs from closely related orbiviruses including, epizootic hemorrhagic disease virus (EHDV) prototypes serotypes 1, 2, 4; RNA from Sudanese isolate of palyam orbiviruses serogroup and total nucleic acid extracts from uninfected Vero cells. Application of the nested BTV RT-PCR to clinical samples resulted in amplification of BTV RNA from blood and serum samples from goats experimentally infected with BTV4 and from naturally infected sheep, goats, cattle and deer. The results of this study indicated that this RT-PCR assay could be applied for rapid detection of BTV, in cell culture and clinical samples from susceptible ruminants during an outbreak of the disease, in the United States and African.     

Exotic ticks introduced into the United States on imported reptiles from 1962 to 2001 and their potential roles in international dissemination of diseases

Since 1962, a total of 29 species of exotic ticks have been introduced into the United States on imported reptiles, with 17 species from the genus Amblyomma, 11 from the genus Aponomma and one from the genus Hyalomma. In the absence of measures to control introduction of these importations, some exotic tick species will develop breeding colonies and become established as indigenous species and some tickborne diseases may be introduced to wreak havoc among susceptible native populations. However, formulation of risk assessments and rational control measures have been hampered by a lack of knowledge of these exotic ticks, with much of the available data published in older and relatively obscure publications. This report is an attempt to collate information for all 29 exotic tick species, including previously unpublished data from our laboratory, with particular reference to their geographical distribution, hosts, life cycles and vector potential, and to review methods to minimize their global dissemination.     

United States food and drug laws and ratites as emerging food animals.

The ratite practitioner must balance the need to treat patients with the obligation to minimize the risk of drug residues. If a practitioner treats birds intended for market, the possibility of residues should be considered before administering therapeutic agents. Improved management practices can and will preclude the need in many instances for drug therapy. Practitioners should be aware of the conditions that must be met in order to justify extralabel use. When treating ratites intended for food, practitioners should comply with the documentation requirements listed in these regulations and be aware of the list of prohibited drugs. The Food Animal Residue Avoidance Databank (FARAD), at 1-888-US-FARAD (1-888-873-2723) or by electronic mail at farad@ucdavis.edu or farad@ncsu.edu, is a valuable source of information regarding residue avoidance. Emergence of ratites as food species should stimulate research to provide answers to questions concerning pharmacokinetics and tissue depletion in order to improve the quality of veterinary services for flock owners, to obtain approval for drugs for these species, and to provide information by which to establish appropriate withdrawal periods.     

Temporal appearance, geographic distribution, and species of origin of bluetongue virus serotypes in the United States.

Beginning in 1973, all available laboratory and field strains of bluetongue virus (BTV) from the United States were serotyped. Of the viral strains serotyped, 27 were collected from 1953 through 1972; 173 were collected from 1973 through 1977. Although 20 BTV serotypes have been found worldwide, only BTV serotypes 10, 11, 13, and 17 have been found in the United States. Since 1973, serotypes 11 and 17 have been the prevalent serotypes. Samples were collected over a 24-year period in the United States and represent a wide geographic area and diverse host sources (sheep, cattle, wild ruminants, and insect vectors). The collection was not a statistical sampling.     

Isolation of an exotic serotype of bluetongue virus from imported cattle in quarantine.

In 1980, 60 zebu cattle from Brazil were admitted into quarantine in Florida for 150 days. During the 30 days between their last test in Brazil and their first test in Florida, four animals developed antibody to bluetongue virus detectable by agar gel immunodiffusion test. Within 62 days after arrival in Florida, three more seroconverted and one more was positive by the 86th day. Virus neutralizing titers of serums from the first four cattle were highest against bluetongue virus serotype 4 and 20; both of these serotypes are exotic to the United States. A bluetongue virus serotype 4 was isolated from one of these animals. The eight positive reactors were slaughtered; the other 52 cattle, which did not develop detectable antibody titers to bluetongue virus, were released into the United States.     

Spatial analysis of seroconversion of sentinel cattle to bluetongue viruses in Queensland

Objective To assess quantitatively the spatial distribution of seroconversion of Queensland cattle to bluetongue viruses.
Design A sentinel herd study. Sample population Sixty-nine sentinel herds at 30 locations.
Procedure Spatial clustering of seroconversion to blue-tongue viruses was investigated during the period from 1990 to 1994.
Results Seroconversion to only two bluetongue virus serotypes, 1 and 21, was observed. The 14 herds, in which seroconversion to bluetongue virus serotype 1 was detected, were located only along the eastern coastal and subcoastal region of Queensland, and were significantly (P < 0.05) clustered. Locations at which seroconversion to serotype 21 was detected, were not significantly clustered. The results generally agree with field observations, except for the failure to detect seroconversion to bluetongue viruses in north-western Queensland.
Conclusion Bluetongue infection of cattle in north-western Queensland may be temporally sporadic. The dominance of serotype 1 in the Queensland cattle population may be the result of differential transmission by potential vector species. Long-term surveillance programs are important for defining disease status of animal populations.