RESUMO
Immediate vaccination of the most susceptible and epidemiological relevant animals is a crucial part of control measures that facilitate virus elimination in case of entry of foot-and-mouth disease (FMD). The objective of this study was to evaluate the effect of cattle vaccination 7 and 14 days prior challenge using a vaccine commonly applied in systematic vaccination campaigns against transmission of FMD virus (FMDV). Transmission of FMDV was investigated in three groups of ten cattle each: one non-vaccinated group and two groups that were either vaccinated 7 days (-7/vaccinated group) or 14 days (-14/vaccinated group) before intranasal (IN) inoculation. Five cattle heads from each group were inoculated using the IN-route with the A/Argentina/2001 FMDV strain, while the remaining five cattle heads of each group were contact-exposed to inoculated cattle. Clinical signs were recorded; virus isolation and genome detection by RT-PCR were carried out on oesophageal-pharyngeal fluid (OPF) and blood. Neutralizing antibody titers and antibodies against non-structural proteins (NSP) of FMDV were also determined. Results suggest that the experimental design, virus challenge dose, and virus infectivity were appropriate and that the virus had been transmitted to naïve calves. Under the outlined experimental conditions, vaccination 7 and 14 days prior to challenge induced full clinical protection against virus inoculation. Moreover, -7/ or -14/vaccinated calves that had been contact-exposed to -7/ or -14/vaccinated IN-challenged calves, did not become infected. Consequently, no virus transmission occurred from vaccinated and subsequently infected calves to cohabitating vaccinated calves (R = 0). According to our results, early vaccination during an outbreak is effective as virus transmission can be significantly reduced using a vaccine commercially available, routinely applied in systematic vaccination campaigns.
RESUMO
Beekeepers all across the world are suffering important losses of their colonies, and the parasitic mites Varroa destructor and Nosema sp, as well as several bee viruses, are being pointed out as the possible causes of these losses, generally associated with environmental and management factors. The objective of the present study was to evaluate the presence of seven virus species (Deformed wing virus -DWV-, Acute bee paralysis virus -ABPV-, Chronic bee paralysis virus -CBPV-, Black queen cell virus -BQCV-, Kashmir bee virus -KBV-, Israeli acute bee paralysis virus -IAPV-, and Sacbrood bee virus -SBV), as well as the prevalence of Nosema sp. and Varroa destructor, and their possible associated factors, under temperate and subtropical climate conditions in Argentinean colonies. A total of 385 colonies distributed in five Argentinean eco-regions were examined after honey harvest. The final multivariable model revealed only one variable associated with the presence of DWV and two with the presence of ABPV. The apiary random effect was significant in both cases (P=0.018; P=0.006, respectively). Colonies with a Varroa infestation rate >3% showed higher presence of DWV than colonies with <3% of Varroa infestation level (OR=1.91; 95% CI: 1.02-3.57; P<0.044). The same pattern was observed for the presence of ABPV (OR=2.23; 95% CI: 1.04-4.77; P<0.039). Also, colonies where replacement of old combs was not a common practice had higher presence of ABPV (OR=6.02; 95% CI: 1.16-31.25; P<0.033). Regardless of the location of the colonies, virus presence was strongly associated with V. destructor level. Therefore, all the factors that directly or indirectly influence the levels of mites will be also influencing the presence of the viruses.
Assuntos
Abelhas/parasitologia , Abelhas/virologia , Microsporidiose/veterinária , Infestações por Ácaros/veterinária , Nosema/patogenicidade , Varroidae/virologia , Criação de Animais Domésticos , Animais , Argentina/epidemiologia , Clima , Estudos Transversais , Humanos , Modelos Lineares , Microsporidiose/epidemiologia , Infestações por Ácaros/epidemiologia , Infestações por Ácaros/virologia , Reação em Cadeia da Polimerase/veterinária , Fatores de Risco , Inquéritos e QuestionáriosRESUMO
In Argentina, bee virus studies are still incipient, and there are no studies regarding the climatic effect. The aim of this study was to assess and compare the presence of honeybee viruses in different climatic regions from Argentina. A total of 385 colonies distributed in five Argentinean eco-regions were examined to evaluate the percentage of infestation with Varroa destructor and the presence of seven virus species (Deformed wing virus, DWV; Acute bee paralysis virus, ABPV; Chronic bee paralysis virus, CBPV; Black queen cell virus, BQCV; Kashmer bee virus, KBV; Israeli acute bee paralysis virus, IAPV; and Sacbrood bee virus, SBV) after honey yield. Two viruses, KBV and IAPV, were not detected. The other five viruses were found in different prevalences: DWV (35%), ABPV (21.5%), BQCV (8.0%), CBPV (2.2%), and SBV (1.1%). We found double and triple viral associations in approximately 25% of the sampled colonies. The mean V. destructor infestation in the colonies prior to the acaricide treatment was 7.12%±8.7%. The knowledge of the prevalence of these viruses in the region and their relation with the mite and other possible influencing factors is important for preventing colony losses. Further studies are necessary to identify the risk factors associated with virus presence and its relationship with other pathogens such as V. destructor.
Assuntos
Abelhas , Varroidae , Vírus , Animais , Argentina , Abelhas/microbiologia , Abelhas/virologia , Prevalência , Vírus/isolamento & purificaçãoRESUMO
Honey bee colonies are threatened by multiple factors including complex interactions between environmental and diseases such as parasitic mites and viruses. We compared the presence of honeybee-pathogenic viruses and Varroa infestation rate in four apiaries: commercial colonies that received treatment against Varroa and non-treated colonies that did not received any treatment for the last 4 years located in temperate and subtropical climate. In addition, we evaluated the effect of climate and Varroa treatment on deformed wing virus (DWV) amounts. In both climates, DWV was the most prevalent virus, being the only present virus in subtropical colonies. Moreover, colonies from subtropical climate also showed reduced DWV amounts and lower Varroa infestation rates than colonies from temperate climate. Nevertheless, non-treated colonies in both climate conditions are able to survive several years. Environment appears as a key factor interacting with local bee populations and influencing colony survival beyond Varroa and virus presence.
Assuntos
Abelhas/parasitologia , Abelhas/virologia , Varroidae/crescimento & desenvolvimento , Vírus/classificação , Vírus/isolamento & purificação , Animais , ClimaRESUMO
A specific real time reverse transcription polymerase chain reaction (RT-PCRrt) for the detection of foot-and-mouth disease virus was validated using the LightCycler thermocycler 2.0 and its reagents as recommended by the World Organization for Animal Health and was assessed for the detection of the virus in acute infection of cattle experimentally vaccinated and challenged with virus A Argentina/2001 or A24 Cruzeiro. The technique proved to be robust, showing coefficients of variation lower than 4% for different ARN extractions, days or repetitions and was able to detect up to 0,4 TCID 50%, and/or up to 100 RNA molecules. In probang samples, diagnostic sensitivity was 93.1 (95% CI 86.5-96.6) and diagnostic specificity 100 (95% CI 96.3-100). The results of the challenge in vaccinated or multivaccinated bovines showed that although there were high levels of clinical protection in the vaccinated group, FMDV could be detected in all challenged groups. However, detection was 100 times lower in immunized animals.
Assuntos
Doenças dos Bovinos/diagnóstico , Vírus da Febre Aftosa/isolamento & purificação , Febre Aftosa/diagnóstico , Reação em Cadeia da Polimerase em Tempo Real/métodos , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos , Doença Aguda , Animais , Líquidos Corporais/virologia , Bovinos , Doenças dos Bovinos/virologia , Esôfago/virologia , Febre Aftosa/virologia , Vírus da Febre Aftosa/classificação , Vírus da Febre Aftosa/genética , Vírus da Febre Aftosa/imunologia , Faringe/virologia , RNA Viral/análise , Reação em Cadeia da Polimerase em Tempo Real/instrumentação , Reprodutibilidade dos Testes , Reação em Cadeia da Polimerase Via Transcriptase Reversa/instrumentação , Sensibilidade e Especificidade , Manejo de Espécimes , Vacinação/veterinária , Vacinas Virais/imunologiaAssuntos
Animais , Bovinos , Doenças dos Bovinos/diagnóstico , Vírus da Febre Aftosa/isolamento & purificação , Febre Aftosa/diagnóstico , Reação em Cadeia da Polimerase em Tempo Real/métodos , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos , Doença Aguda , Líquidos Corporais/virologia , Doenças dos Bovinos/virologia , Esôfago/virologia , Vírus da Febre Aftosa/classificação , Vírus da Febre Aftosa/genética , Vírus da Febre Aftosa/imunologia , Febre Aftosa/virologia , Faringe/virologia , Reprodutibilidade dos Testes , RNA Viral/análise , Reação em Cadeia da Polimerase em Tempo Real/instrumentação , Reação em Cadeia da Polimerase Via Transcriptase Reversa/instrumentação , Sensibilidade e Especificidade , Manejo de Espécimes , Vacinação/veterinária , Vacinas Virais/imunologiaRESUMO
A specific real time reverse transcription polymerase chain reaction (RT-PCRrt) for the detection of foot-and-mouth disease virus was validated using the LightCycler thermocycler 2.0 and its reagents as recommended by the World Organization for Animal Health and was assessed for the detection of the virus in acute infection of cattle experimentally vaccinated and challenged with virus A Argentina/2001 or A24 Cruzeiro. The technique proved to be robust, showing coefficients of variation lower than 4
for different ARN extractions, days or repetitions and was able to detect up to 0,4 TCID 50
, and/or up to 100 RNA molecules. In probang samples, diagnostic sensitivity was 93.1 (95
CI 86.5-96.6) and diagnostic specificity 100 (95
CI 96.3-100). The results of the challenge in vaccinated or multivaccinated bovines showed that although there were high levels of clinical protection in the vaccinated group, FMDV could be detected in all challenged groups. However, detection was 100 times lower in immunized animals.
Assuntos
Doenças dos Bovinos/diagnóstico , Vírus da Febre Aftosa/isolamento & purificação , Febre Aftosa/diagnóstico , Reação em Cadeia da Polimerase em Tempo Real/métodos , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos , Doença Aguda , Animais , Líquidos Corporais/virologia , Bovinos , Doenças dos Bovinos/virologia , Esôfago/virologia , Febre Aftosa/virologia , Vírus da Febre Aftosa/classificação , Vírus da Febre Aftosa/genética , Vírus da Febre Aftosa/imunologia , Faringe/virologia , RNA Viral/análise , Reação em Cadeia da Polimerase em Tempo Real/instrumentação , Reprodutibilidade dos Testes , Reação em Cadeia da Polimerase Via Transcriptase Reversa/instrumentação , Sensibilidade e Especificidade , Manejo de Espécimes , Vacinação/veterinária , Vacinas Virais/imunologiaRESUMO
OBJECTIVE: To determine the reference interval for WBC counts in Holstein dairy cows from herds with high seroprevalence for anti-bovine leukemia virus (BLV) antibodies, analyze the correlation of total WBC counts and blood proviral load (bPVL) in BLV-infected animals, and determine whether total WBC count can be used a hematologic marker for in vivo infection. ANIMALS: 307 lactating cows from 16 dairy herds with high BLV seroprevalence. PROCEDURES: Blood samples were collected for assessment of plasma anti-BLV p24 antibody concentration (all cows), manual determination of WBC count (161 BLV-seronegative cows from 15 herds), and evaluation of bPVL (146 cows from another herd). RESULTS: The WBC count reference interval (ie, mean ± 2 SD) for BLV-seronegative dairy cows was 2,153 to 11,493 cells/µL. Of the 146 cows used to analyze the correlation between WBC count and bPVL, 107 (73%) had WBC counts within the reference interval; of those cows, only 21 (19.6%) had high bPVL. Most cows with high WBC counts (35/39) had high bPVL. Mean WBC count for cows with high bPVL was significantly higher than values for cows with low or undetectable bPVL. White blood cell counts and bPVL were significantly (ρ = 0.71) correlated. CONCLUSIONS AND CLINICAL RELEVANCE: These data have provided an updated reference interval for WBC counts in Holstein cows from herds with high BLV seroprevalence. In dairy cattle under natural conditions, WBC count was correlated with bPVL; thus, WBC count determination could be a potential tool for monitoring BLV infection levels in attempts to control transmission.
Assuntos
Anticorpos Antivirais/sangue , Leucose Enzoótica Bovina/sangue , Vírus da Leucemia Bovina/imunologia , Contagem de Leucócitos/veterinária , Carga Viral/veterinária , Animais , Biomarcadores , Bovinos , Indústria de Laticínios , Leucose Enzoótica Bovina/imunologia , Leucose Enzoótica Bovina/virologia , FemininoRESUMO
BACKGROUND: Bovine leukemia virus (BLV) is worldwide distributed and highly endemic in Argentina. Among the strategies to prevent BLV dissemination, a control plan based on the selective segregation of animals according to their proviral load (PVL) is promising for our dairy productive system. The objective of this work was to study the relationship between the blood PVL and the antibody level, in order to identify whether the individual humoral response, i.e. the anti-p24 or anti-whole-BLV particle, could be used as a marker of the blood level of infection and thus help to recruit animals that may pose a lower risk of dissemination under natural conditions. RESULTS: The prevalence of p24 antibodies on the 15 farms studied was over 66%. The prevalence of p24 and whole-BLV antibodies and PVL quantification were analyzed in all the samples (n = 196) taken from herds T1 and 51. ROC analysis showed a higher AUC for p24 antibodies than whole-BLV antibodies (Z(reactivity): 3.55, P < 0.001; Z(titer): 2.88, P < 0.01), and as consequence a better performance to predict the proviral load status in herd 51. No significant differences were found between the performance of p24 and whole-BLV antibodies in herd T1. A significant positive correlation was observed between PVL values and p24 antibody reactivity in both farms (r (T1) = 0.7, P < 0.001, r (51) = 0.71, P < 0.0001). The analysis was extended to the whole number of weak p24 antibody reactors (n = 311) of the other 13 farms. The mean of high PVL reactors within weak p24 reactors was 17.38% (SD = 8.92). In 5/15 farms, the number of weak p24 reactors with high PVL was lower than 10%. CONCLUSIONS: We found that the humoral response reflected the level of in vivo infection, and may therefore have useful epidemiological applications. Whereas the quantitative evaluation of blood proviral load using real-time PCR is expensive and technically demanding, the measurement of antibodies in blood by ELISA is relatively straightforward and could therefore constitute a cost-effective tool in a BLV control intervention strategy, especially in highly infected herds such as Argentinean dairy ones.