Diagnostic and Surveillance Services, Biosecurity New Zealand, Ministry for Primary Industries, Upper Hutt, New Zealand.
Tāwharau Ora - School of Veterinary Sciences, Massey University, Palmerston North, New Zealand.
N Z Vet J. 2024 Nov;72(6):347-354. doi: 10.1080/00480169.2024.2392687. Epub 2024 Aug 26.
In spring 2021, on a seasonally calving, pastorally based, Taranaki dairy farm, 12 first-calving heifers (≤ 30 days post-calving) developed similar dry, red to black, crusting lesions on the medial aspect of the teat udder junction extending down the medial teat. Some cows had multiple teats affected. Treatment was initially unrewarding and did not slow the progression of the disease. Overall, 8/12 cows recovered, and 4/12 cows were culled, with three of the cows culled after a teat sloughed and the fourth after surgical amputation of a teat. Outbreaks of the same condition, on the same farm but affecting fewer animals, occurred in spring 2022 (n = 6) and spring 2023 (n = 3).
An initial scab-like or crusting lesion progressed to resemble a thick eschar consisting of very dry and hard dead tissue. The unaffected areas of the teat felt normal but immediately under the dead tissue, there was a warm, firmer area consistent with an inflammatory reaction. Removing the scab led to profuse bleeding, with no visible bed of granulation underneath the scab. There was no leaking of milk in those cows that lost a teat, and no smell to the lesions themselves. Serology and virology ruled out the involvement of bovine alphaherpesvirus (BoHV-2) bovine gammaherpesvirus (BoHV-4), orthopoxviruses (cowpox) and parapoxviruses (pseudocowpox). Histopathology of an affected and surgically amputated teat showed multifocal erosion and ulceration of the epidermis, covered by a thick serocellular crust. In areas of ulceration, there were numerous neutrophils, and the dermis was expanded by granulation tissue with variable numbers of neutrophils, eosinophils, and lymphocytes around small blood vessels.
Based on the similarity of the history, presentation, and histopathological changes to those described for a novel disease reported in the UK, a diagnosis of ischaemic teat necrosis (ITN) was made.
If ITN is an emerging condition in New Zealand and becomes as prevalent as it has in the UK, clinicians will be confronted with a significant new welfare problem in dairy cows. Anecdotally, there have been reports of other ITN outbreaks in New Zealand, and the Ministry for Primary Industries would be interested in collating reports from other New Zealand veterinarians.
2021 年春季，在一个季节性产犊的牧场式达尼丁奶牛场，12 头初产小母牛（产后 30 天内）在乳突间的内侧出现类似的干燥、红色到黑色、结痂病变，沿内侧乳头向下延伸。一些奶牛有多个乳头受到影响。最初的治疗没有效果，也没有减缓疾病的进展。总的来说，12 头奶牛中有 8 头康复，4 头被淘汰，其中 3 头因乳头脱落，4 头因乳头切除而淘汰。2022 年春季（n=6）和 2023 年春季（n=3），同一农场但感染动物较少的情况下也发生了相同条件的疫情。
最初的痂样或结痂病变进展为类似厚厚的硬干坏死组织形成的干痂。乳头未受影响的区域感觉正常，但在死组织下方，有一个温暖、更坚硬的区域，与炎症反应一致。去除结痂会导致大量出血，结痂下没有可见的肉芽床。那些失去乳头的奶牛没有乳汁泄漏，病变本身也没有异味。血清学和病毒学排除了牛α疱疹病毒（BoHV-2）、牛γ疱疹病毒（BoHV-4）、正痘病毒（牛痘）和副痘病毒（假性牛痘）的参与。受影响和手术切除的乳头的组织病理学显示表皮多灶性侵蚀和溃疡，被厚厚的浆液细胞痂覆盖。在溃疡区域，有大量中性粒细胞，真皮扩张为肉芽组织，在小血管周围有不同数量的中性粒细胞、嗜酸性粒细胞和淋巴细胞。
根据病史、表现和组织病理学变化与英国报道的一种新疾病的相似性，诊断为缺血性乳头坏死（ITN）。
如果 ITN 在新西兰是一种新兴疾病，并像在英国那样普遍，临床医生将面临奶牛的一个重大新的福利问题。据传闻，新西兰还有其他 ITN 疫情报告，初级产业部有兴趣从其他新西兰兽医那里收集报告。
