Absence of Bovine Leukosis Virus in Semen of Seropositive Bulls

Abstract

Abstract.A polymerase chain reaction (PCR)-based detection system was established to identify the presence of bovine leukosis virus (BLV) DNA in bovine semen. Seventy-nine bulls were included in the study. Serum, peripheral blood leukocytes, and semen were collected from each of the 79 bulls. The BLV-specific antibody was detected in serum by agar gel immunodiffusion and viral DNA in blood and semen by PCR. Serologically, 29 of the 79 bulls were BLV positive. Twenty-seven of the 29 seropositive bulls and 1 of the seronegative bulls had BLV DNA in peripheral blood leukocytes. All 79 bulls tested PCR negative for the presence of BLV in semen. This data is strong evidence that properly collected semen from BLV seropositive bulls will not contribute to dissemination of this viral infection.Bovine leukosis virus (BLV) is an exogenous oncogenic retrovirus associated with enzootic bovine leukosis. The infection can result in 3 different clinical states, with many animals remaining asymptomatic in an aleukemic state (AL). However, 30-70% develop a persistent lymphocytosis (PL) characterized by a polyclonal expansion of B-lymphocytes and a much smaller percent, 0.1-10%, eventually develop lymphoid tumors. 3,6,11,12 A previous survey published in 1985 suggested up to 30% of dairy cows in the United States were infected with BLV. 12 Due to the relatively short life of production cattle in the United States, the greatest economic impact of BLV infection would appear to be that associated with interference in the international movement of cattle and their germ plasm rather than clinical disease. Thus, application of molecular biology techniques, such as polymerase chain reaction (PCR), to identify the presence of BLV in semen should facilitate certification of germ plasm as being free of contaminating virus.Previous studies by numerous investigators suggested that semen from BLV-infected bulls was noninfectious for recipient cows. 4,8,9 Sheep inoculated with entire ejaculates from BLV-infected bulls remained seronegative. Cows inseminated with ejaculates from seropositive bulls have also not seroconverted nor have their progeny. In addition, a 5-year study demonstrated that use of semen derived from both BLV seropositive and seronegative donor bulls in a BLV-free closed dairy did not result in any seroconversion. Donor bulls were from multiple artificial insemination (AI) centers, with 48% being seropositive. 9 Despite the above-mentioned studies that argued strongly against the possibility of recipient cows becoming infected by using semen from BLV-positive bulls, international movement of germ plasm from BLV-infected animals is still problematic. The most common method of testing for BLV in animals is the detection of antibodies to gp51 by agar gel immunodiffusion (AGID). However, the application of PCR for identification of viral DNA has provided a sensitive test for detecting BLV in tissues such as blood. 1,2,10 This report describes the application of PCR to the detection of BLV DNA in peripheral blood leukocytes and se...

Absence of lumpy skin disease virus in semen of vaccinated bulls following vaccination and subsequent experimental infection

“…Also, different funnels were used for each animal, and between collections, these funnels were washed thoroughly with clean water and later rinsed with hot distilled water and kept in a rack to dry. Contamination of semen samples with blood during sampling has been implicated in the presence of BLV in semen [7]. No semen samples in the present study apart from samples from two unvaccinated bulls on days 13, This study provides the first evidence of the absence of LSDV in bull semen following vaccination.…”

Detection of bovine leukosis provirus in blood and semen samples of bulls

“…1 PCR products of gag and prolactin genes. Lane 1 kb+ ladder; lanes 2 and 4 products from blood and semen samples of a seropositive bull; lanes 3 and 5 products from blood and semen sample of sero-negative bulls; lane 7 product of prolactin gene; lanes 6 and 8 positive and negative control, respectively provirus in semen should facilitate certification of germ plasm as being free of contaminating virus (Choi et al 2002). PCR is the most sensitive and specific assay for diagnosis of BLV infection (Choi et al 2002).…”

“…Lane 1 kb+ ladder; lanes 2 and 4 products from blood and semen samples of a seropositive bull; lanes 3 and 5 products from blood and semen sample of sero-negative bulls; lane 7 product of prolactin gene; lanes 6 and 8 positive and negative control, respectively provirus in semen should facilitate certification of germ plasm as being free of contaminating virus (Choi et al 2002). PCR is the most sensitive and specific assay for diagnosis of BLV infection (Choi et al 2002). Several regions of the BLV genome have been assayed for developing the detection of BLV RNA or proviral DNA by PCR, such as env-gp51, gag-p24, pol, and px (Agrest et al 1993;Brandon et al 1991;Murtaugh et al 1991;Poon et al 1993;Sherman et al 1992).…”

“…The unlikely possibility of seminal transmission of BLV, even from sero-positive donor bulls, suggests that these requirements are excessive. Thus, the use of proper AI collection techniques, microscopic evaluation of semen to evaluate the presence of contaminating leukocytes, and application of PCR to detect BLV in representative straws of semen from each ejaculate should provide enough confirmation of BLV-free status (Choi et al 2002).…”

“…In some areas, where the density of hematophagous insects is important, they play a considerable role in the spread of BLV under natural conditions. Although viral antigens and proviral DNA have been identified in semen, milk, and colostrum, natural transmission through these secretions has not been demonstrated (Choi et al 2002;Kaja and Olson 1982;Monke 1986;Romero et al 1983).…”