Enzootic bovine leukosis

In order to develop a molecular method for detection and identification of Xanthomonas campestris pv. viticola (Xcv) the causal agent of grapevine bacterial canker, primers were designed based on the partial sequence of the hrpB gene. Primer pairs Xcv1F/Xcv3R and RST2/Xcv3R, which amplified 243- and 340-bp fragments, respectively, were tested for specificity and sensitivity in detecting DNA from Xcv. Amplification was positive with DNA from 44 Xcv strains and with DNA from four strains of X. campestris pv. mangiferaeindicae and five strains of X. axonopodis pv. passiflorae, with both primer pairs. However, the enzymatic digestion of PCR products could differentiate Xcv strains from the others. None of the primer pairs amplified DNA from grapevine, from 20 strains of nonpathogenic bacteria from grape leaves and 10 strains from six representative genera of plant pathogenic bacteria. Sensitivity of primers Xcv1F/Xcv3R and RST2/Xcv3R was 10 pg and 1 pg of purified Xcv DNA, respectively. Detection limit of primers RST2/Xcv3R was 104 CFU/ml, but this limit could be lowered to 102 CFU/ml with a second round of amplification using the internal primer Xcv1F. Presence of Xcv in tissues of grapevine petioles previously inoculated with Xcv could not be detected by PCR using macerated extract added directly in the reaction. However, amplification was positive with the introduction of an agar plating step prior to PCR. Xcv could be detected in 1 µl of the plate wash and from a cell suspension obtained from a single colony. Bacterium identity was confirmed by RFLP analysis of the RST2/Xcv3R amplification products digested with Hae III.

/pdf/development-of-a-molecular-method-for-detection-and-2xfkg6j4ns.pdf

Development of a molecular method for detection and identification of Xanthomonas campestris pv. viticola

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis (EBL). Although efficient eradication programs have been successfully implemented in most European countries and Oceania, BLV infection rates are still high worldwide. BLV naturally infects cattle, inducing a persistent infection with diverse clinical outcomes. The virus infects lymphocytes and integrates a DNA intermediate as a provirus into the genome of the cells. Therefore, exposure to biological fluids contaminated with infected lymphocytes potentially spreads the virus. Vertical transmission may occur in utero or during delivery, and about 10% of calves born to BLV-infected dams are already infected at birth. Most frequently, transmission from dams to their offspring occurs through the ingestion of infected colostrum or milk. Therefore, although EBL is not a disease specific to the neonatal period, during this period the calves are at special risk of becoming infected, especially in dairy farms, where they ingest colostrum and/or raw milk either naturally or artificially. Calves infected during the first week of life could play an active role in early propagation of BLV to susceptible animals. This review discusses the main factors that contribute to neonatal BLV infection in dairy herds, as well as different approaches and management practices that could be implemented to reduce the risk of BLV transmission during this period, aiming to decrease BLV infection in dairy herds.

/pdf/bovine-leukemia-virus-infection-in-neonatal-calves-risk-3iiryn3scq.pdf

Bovine Leukemia Virus Infection in Neonatal Calves. Risk Factors and Control Measures.

Development of a PCR to diagnose BLV genome in frozen semen samples.

A three-year prospective study involving 244 calves was undertaken on a California dairy to evaluate the protective role of colostral antibodies against bovine leukemia virus (BLV) infection in calves. Calves were followed from birth to the time they left their individual hutch (TLIH), at about 90 days of age. The probability of being infected at TLIH and the daily risk of infection between birth and TLIH were modelled using the logistic and the Cox models, respectively. Calves with no detectable antibodies during the first week of life were up to 2.00 and 2.75 times more likely to be infected at TLIH compared to calves with low and high concentrations of antibodies during the first week of life, respectively (p = 0.01). When the daily risk was modelled, calves without antibodies at the estimated day of infection were up to 3.4 and 11.6 times more likely to become infected than calves with low and high concentrations of antibodies on that day, respectively (p less than 0.001). Results indicated that calfhood infection may be reduced by about 45% through the feeding of colostrum with BLV antibodies. Further reduction in infection may be possible by feeding calves milk powder, milk replacer, and/or milk from noninfected cows. Results also indicated that quantification of the effect of a time-dependent risk factor, such as colostral antibody concentration, might be affected if treated as a fixed factor.

Protection of colostral antibodies against bovine leukemia virus infection in calves on a California dairy.

Nineteen calves born to dams free of bovine leukaemia virus (BLV) did not possess maternally derived precipitating antibody to BLV in their sera after the ingestion of colostrum. Eight of these calves remained serologically negative after being fed milk from BLV-free cows while three (27.3%) of 11 similar calves that had been fed milk from BLV-infected cows developed antibody. Forty-four of 47 calves born to BLV-infected dams acquired maternal antibody to BLV after ingesting colostrum. Two (8.7%) of the 23 calves fed milk from BLV-free cows developed antibody to BLV probably as a result of transplacental or colostrum infection whereas four (16.7%) of the 24 calves fed milk from BLV-infected cows developed antibody. It is concluded that milk transmission of BLV is responsible in part for the high rates of infection encountered in our dairy herds and that calves lacking specific maternal antibody are more susceptible to BLV infection through the ingestion of milk than are calves with maternal antibody.

Transmission of bovine leukaemia virus in milk.

O objetivo deste trabalho foi a producao de anticorpos policlonais contra Xanthomonas campestris pv. viticola e sua caracterizacao pelo metodo Elisa indireto. Os resultados apontaram a qualidade dos anticorpos policlonais produzidos, os quais mostraram-se altamente reativos e especificos para o patovar com potencial para ser empregado no diagnostico da doenca e em programas de certificacao.

/pdf/producao-e-caracterizacao-de-anticorpos-policlonais-contra-320n19sn10.pdf

Produção e caracterização de anticorpos policlonais contra Xanthomonas campestris pv. viticola

Arbor Vitae (Thuja occidentalis) is widely used in homoeopathic and phytotherapic treatments,either for human or for animals. Its immunestimulating and antiviral properties have been described and its empiric use in the treatment of the avian poxvirosis is recommended by animal breeders and veterinarians. To evaluate the therapeutic potential of Arbor Vitae in these infections, two groups (control and test) of 10 young birds were inoculated by scarification with a field sample of avian poxvirus. When lesions were first observed the test group received the Arbor Vitae alcoholic extract diluted in the drinking water. The birds were examined daily, from the beginning and evolution of the lesions to the healing. The results indicated that, in our experimental conditions, the use of T. occidentalis did not favor the regression or restriction in the development of the skin lesions promoted by the experimental infection.

/pdf/ineficiencia-da-thuja-occidentalis-no-tratamento-dos-qno4wf5kkj.pdf

Ineficiência da Thuja occidentalis no tratamento dos poxvirus aviários

The flea Ctenocephalides felis felis is a parasite that causes allergic dermatitis and also may transmit etiologic agents to domestic animals and humans. This study investigated by scanning electron microscopy the development of entomopathogenic fungi on flea cuticle. Fleas were exposed to conidia (10(8) ml(-1)) of Metarhizium anisopliae (isolate 959) or Beauveria bassiana (isolate 986). Following standard protocols for electron microscopy, the specimens were prepared 2, 15, 26 and 96 h after infection. The micrography revealed that 2 h after fungus exposure, conidia attachments encompassed the entire flea cuticle, especially on abdominal intersegmental membranes. The emergence of germ tubes and appressoria formation occurred at 15 h, thickening and branching of hyphae on the flea cuticle was noted at 26 h. Therefore, both of these fungal isolates were able to develop on cuticular surfaces of C. f. felis.

http://www.scielo.br/pdf/rbpv/v16n3/a11v16n3.pdf

[Development of the fungi Metarhizium anisopliae (Metschnikoff, 1879) Sorokin, 1883 and Beauveria bassiana (Balsamo) Vuillemin, 1912 on the Ctenophephalides felis felis (Bouché, 1835)].

Geraldo Baêta da Cruz

Papers

Transmission of bovine leukaemia virus in milk.

Produção e caracterização de anticorpos policlonais contra Xanthomonas campestris pv. viticola

Ineficiência da Thuja occidentalis no tratamento dos poxvirus aviários

[Development of the fungi Metarhizium anisopliae (Metschnikoff, 1879) Sorokin, 1883 and Beauveria bassiana (Balsamo) Vuillemin, 1912 on the Ctenophephalides felis felis (Bouché, 1835)].