Pinn Toby L, Forrestal Amber M, Duhamel Gerald E, Crouch Esther E, Thompson Belinda S, Lejeune Manigandan
Animal Health Diagnostic Center, College of Veterinary Medicine, Cornell University, Ithaca, NY.
Perry Vet, Perry, NY.
J Am Vet Med Assoc. 2021 Dec 9:1-7. doi: 10.2460/javma.21.09.0424.
Outbreaks of sudden death in apparently healthy weaned dairy calves due to Strongyloides papillosus parasitism were diagnosed on 2 separate and independent New York (NY) dairies.
Most calves were found dead; however, 1 calf observed while dying showed signs of tachycardia, tachypnea, vocalization, and convulsions shortly before death. In 6 affected heifers that underwent post-mortem examination, precocious bilaterally symmetric mammary gland enlargement was seen. A portion of their parasitized living cohorts also demonstrated similar mammary gland enlargement. A diagnosis of S papillosus hyperinfection was made based upon the presence of high numbers of S papillosus ova in feces, and confirmation by S papillosus-specific PCR assays. Consistent histopathological findings in affected calves included generalized mammary gland vascular congestion, interstitial edema and hemorrhage with ductal hyperplasia. Mild multifocal cardiomyocyte degeneration was found in 5 of 14 calves examined. Factors believed to contribute to the parasite's environmental amplification and host hyperinfection included group housing on wood shavings and high environmental temperatures and humidity.
Treatment of calves with doramectin pour-on stopped mortality and resolved the udder enlargement.
Similar outbreaks have previously been described in Japan and South Bohemia (Czech Republic), where researchers hypothesized that sudden death may be due to fatal arrhythmia caused by a parasite-associated cardiotoxin. This report highlights the importance of including S papillosus among the differential diagnoses for sudden death alone or together with precocious udder enlargement in calves kept in confinement housing.
在纽约州2个独立的奶牛场诊断出明显健康的断奶犊牛因乳头类圆线虫寄生而突发死亡疫情。
多数犊牛被发现死亡；然而，有1头犊牛在濒死时被观察到，在死亡前不久出现心动过速、呼吸急促、鸣叫和抽搐症状。在6头接受尸检的患病小母牛中，发现双侧乳腺早熟性对称肿大。其部分受寄生虫感染的同群牛也表现出类似的乳腺肿大。根据粪便中存在大量乳头类圆线虫虫卵，并通过乳头类圆线虫特异性聚合酶链反应检测进行确认，做出了乳头类圆线虫超感染的诊断。患病犊牛一致的组织病理学发现包括广泛性乳腺血管充血、间质水肿和出血伴导管增生。在14头接受检查的犊牛中，有5头发现轻度多灶性心肌细胞变性。据信导致寄生虫在环境中增殖和宿主超感染的因素包括在木屑上群养以及环境高温高湿。
用多拉菌素浇泼剂治疗犊牛可停止死亡并消除乳房肿大。
此前在日本和南波希米亚（捷克共和国）也曾描述过类似疫情，那里的研究人员推测猝死可能是由寄生虫相关的心脏毒素引起的致命心律失常所致。本报告强调了在对单独出现猝死或与圈养犊牛早熟性乳房肿大同时出现的情况进行鉴别诊断时，将乳头类圆线虫纳入考虑的重要性。
