Enzootic bovine leukosis (EBL) is a malignant B-lymphoma caused by bovine leukemia virus (BLV) and causes serious problems for the cattle industry. EBL is a typical multifactorial disease in cattle, and host, viral, and environmental factors are thought to determine susceptibility. One of the most important host factors is the polymorphism of the major histocompatibility complex (MHC) (BoLA). Several studies have identified genetic variations in BoLA-DRB3, a functionally important locus and the most highly polymorphic BoLA class II locus in cattle. To date, 386 BoLA-DRB3 alleles have been registered in the Immuno Polymorphism Database- MHC database. Importantly, the BoLA-DRB3 polymorphism influences susceptibility to BLV-induced lymphoma, and to proviral load (PVL) which is an important risk factor of virus-associated disease prediction.

In Japan, where BLV is widespread, we have proposed three new methods of EBL prevention using BoLA-DRB3 polymorphism as a marker, adding a new perspective of “individual differences in disease susceptibility” to conventional EBL control measures to promote BLV eradication while minimizing economic losses. (1) “Innovative and integrated BLV eradication strategies” to prevent new infection by resistant cattle with resistant BoLA-DRB3 alleles that place between the BLV-positive and BLV-negative cattle, and actively eliminate susceptible cattle with susceptible BoLA-DRB3 alleles in addition to conventional BLV eradication strategie. (2) “Breeding strategy” to create a population of cattle that are resistant to the disease onset and low provirus levels, and (3) “Vaccine development” targeting susceptible cattle to decrease proviral load and BLV disease progression, thereby suppressing transmission and reducing the infection rate. This presentation will introduce a new strategy to control EBL using BoLA-DRB3 polymorphism as a marker.

Bovine leukemia virus (BLV), a causative agent of enzootic bovine leukosis (EBL), is prevalent in cattle populations worldwide. While BLV infection is typically asymptomatic, a portion of infected animals progresses to persistent lymphocytosis or EBL. Beyond its oncogenic potential, BLV may exert broader impacts on the other effects such as exacerbation of mastitis. Therefore, controlling the spread of BLV remains a critical concern for the livestock industry. This study analyzed viral trait using infectious molecular clone isolated from BLV-infected cows in Japan, which is different approach compared with previous reports. First, analysis of full-length viral genomes from infected cattle revealed three genetic subgroups (A-C), with group A strains showing higher viral production than group C strains. In one farm, group A viruses were more prevalent and appeared to cluster spatially among tied cattle, suggesting that higher viral productivity enhances transmission. Next analysis identified a key nucleotide substitution at position 175 in the LTR (long terminal repeat) region as a determinant of viral replication efficiency. The LTR175C variant was associated with higher viral production and was increasingly detected over time within herds, suggesting ongoing replacement of the LTR175T genotype. Additionally, BLV isolates capable of inducing cellular transformation—a marker of oncogenic potential—were more frequently found in EBL-developed cattle. Notably, such high-pathogenicity strains shared distinct gene expression signatures despite genetic differences, suggesting convergent mechanisms of tumorigenesis. These findings indicate that specific viral genotypes are linked to both transmissibility and pathogenicity. Biomarkers such as the LTR175C mutation or host protein expression changes may be used to identify and control high-risk infections. This viral trait-based strategy offers a flexible and practical approach for controlling BLV spread and EBL onset, especially in high-prevalence herds where general measures are ineffective.

In Miyazaki Prefecture, the outbreak of foot-and-mouth disease (FMD) in 2010 was the starting point for a comprehensive initiative to establish disease-free zones. As part of this initiative, efforts have been made to eliminate Enzootic Bovine Leukosis (EBL). All seven livestock markets in the prefecture are currently involved in the EBL eradication program. Except for one market where all breeding cows have been confirmed as EBL-negative, the remaining six markets have been established a system to publicly disclose EBL-negative calves.

Miyazaki Prefecture is one of the major livestock farming areas for beef cattle breeding and dairy farming. However, in recent years, the number of cattle raised has been declining due to falling calf prices, rising costs, and the aging farming population. While the number of EBL cases continues to rise across the country, Miyazaki has seen a downward trend in EBL cases since 2022—a result attributed to the strengthening of its testing and prevention infrastructure.

The EBL testing system in Miyazaki Prefecture was significantly improved after the containment of the FMD outbreak. In collaboration with the University of Miyazaki, NOSAI (Agricultural Mutual Relief Association), and local government authorities, testing operations were consolidated at the University of Miyazaki. Furthermore, the transition from real-time PCR to digital PCR has improved both the accuracy and efficiency of testing. As a result, the number of samples tested has increased dramatically from approximately 22,000 in 2020 to more than 32,000 in 2023.

At the farm level, even in the farms with a high prevalence of EBL, various strategies such as herd segregation, revision of operational procedures, as well as routine testing and replacement of positive cattle enable the maintenance of EBL-negative herds. Even in situations where aggressive herd replacement is not feasible, consistent monitoring of viral loads and continued testing have demonstrated that disease control and elimination can be achieved.

Looking ahead, farmers, veterinarians, local government authorities, JA (Japan Agricultural Cooperatives), and the University of Miyazaki. will continue to work together to advance the regional elimination of EBL. In addition, by developing more sophisticated and cost-effective testing methods, the initiative aims to establish a sustainable system that will enable producers to confidently test their herds and bring healthy calves to market.

牛伝染性リンパ腫ウイルスは日本の牛群に広く浸潤している。ほとんどの感染牛は臨床上異常を示さないため，本病はこれまで経済的に重要ではないと考えられてきた。しかしながら近年牛伝染性リンパ腫による全部廃棄と体数は増加しており，経済的損失の大きさが示唆されている。本研究は北海道における乳用，黒毛和種，交雑種牛の牛伝染性リンパ腫由来全部廃棄による直接損失を定量化するために実施された。牛伝染性リンパ腫由来全部廃棄数は2017年1月から2021年12月までの北海道6か所，旭川市1か所，函館市1か所，計8か所の食肉衛生検査所における食肉衛生検査報告から収集した。北海道の食肉衛生検査所2か所では肉用牛の種類について報告されていないため，他の検査所の全部廃棄記録に基づきベイズ推定を用いて黒毛和種と交雑種の頭数を推定した。各牛種の標準販売価格を用いて月別直接損失を算出した。年間平均直接損失および調査期間全体の損失はそれぞれ2億3,980万円および11億9,899万円と推定された。

日本の近隣諸国ではアフリカ豚熱（以下ASF）が蔓延し，畜産業に壊滅的な影響を及ぼしている。主な感染経路は，感染した豚・イノシシとの直接的・間接的接触であるが，感染豚由来の豚肉や豚肉加工品も感染源としてリスクをもたらしている。日本では，家庭や外食産業から排出される生ごみは，地方自治体のごみ計画収集業務を通じて処理されている。本研究では，全国の自治体を対象に，家庭や外食産業から排出された生ごみを介しイノシシがアフリカ豚熱ウィルス（ASFV）に暴露され，最終的に家畜豚にASF感染が生じるリスクがあるかどうかを調査した。日本の生ごみ処理方法は自治体によって異なり，焼却，埋却，堆肥化，固形燃料化，エコフィード製造，家庭処理などがある。調査の結果，北海道および沖縄県の一部（北海道夕張市および美幌町並びに沖縄県竹富町）には，焼却せずに生ごみを埋める自治体があった。北海道ではイノシシは生息していないことから，夕張市や美幌町における生ごみを介したASFV感染のリスクは無視できると推定された。沖縄県竹富町西表島では野生イノシシが公共コンポストに廃棄された生ごみを介してASFVに暴露され，感染するリスクは無視できないと推定され，さらに，家畜豚における発生リスクも無視できないと推定された。一方，これら以外の自治体では，生ごみは直接埋却処分されていないか，イノシシが生息してないことから，家庭や外食産業から排出された生ごみを介したイノシシや家畜豚のASFV感染リスクは無視できると考えられた。

To understand how the distribution and abundance of wild birds are monitored in Japan, we conducted interviews with organizations involved in nationwide surveys and citizen science databases used by birdwatchers. Based on these interviews, we found that nationwide bird monitoring programs have been carried out by the Ministry of the Environment and various other organizations. The frequency, season, number of survey sites, and target species varied across programs. In some cases, observations were mainly conducted by locally recruited participants, including members of the Wild Bird Society of Japan. In addition, structured observation records submitted by birdwatchers through citizen science platforms serve as supplementary sources of information and are increasingly utilized in bird monitoring and related research. When interpreted with careful attention to survey design and data characteristics, both nationwide surveys and citizen-contributed records can provide valuable insights into spatial and temporal trends in wild bird populations. These data are expected to support assessments of avian influenza risk and inform broader conservation planning for avifauna.

ISVEE17 was held in Sydney, Australia from 11-15, November 2024. ISVEE is the largest international symposium on Veterinary Epidemiology and Economics. There were over 1,000 oral and poster presentations, categorized into sessions such as One Health, climate change, epidemiologic principles and methods, improving epidemiology teaching and training, simulation models, antimicrobial resistance, and epidemiology research for diseases of each animal including aquatic animals. The next ISVEE (ISVEE18) will be held in Cape Town, South Africa, in November 2027.