Morrow A N, Koney E B, Heron I D
University of Edinburgh, Centre for Tropical Veterinary Medicine, Midlothian, Scotland.
Trop Anim Health Prod. 1996 May;28(2 Suppl):44S-49S; discussion 74S-86S. doi: 10.1007/BF02310698.
The occurrence of dermatophilosis on cattle in the tropics is closely associated with infestation by Amblyomma variegatum ticks. Animals that are more susceptible to the disease also tend to carry higher tick burdens. Longitudinal studies carried out on the Accra Plains suggest that N'Dama cattle acquire an enhanced degree of resistance to these ticks following initial exposure. Lesions on zebu-type Ghana Sanga cattle tend to be confined to the predilection feeding sites of adult A. variegatum even when relatively large numbers of ticks are present suggesting that these cattle are able to contain the effects of the tick. Further studies are required to investigate the nature of the apparent resistance of indigenous cattle to the tick and/or its effects and the potential for controlling the disease by immunoprophylaxis using tick derived immunogens. Current methods of controlling the disease depend on the control of ticks using chemical acaricides. Susceptibility to A. variegatum associated dermatophilosis varies between breeds of cattle therefore the level of tick control required is breed dependant. Rigorous tick control is necessary for the prevention of dermatophilosis on highly susceptible exotic breeds of cattle. The limited use of acaricides applied either at the predilection feeding sites of A. variegatum and/or at selected times when the level of challenge increases is sufficient to control the occurrence of the disease on indigenous cattle.
热带地区牛群皮肤真菌病的发生与杂色花蜱的侵袭密切相关。更易感染该病的动物往往携带的蜱虫负担也更高。在阿克拉平原进行的纵向研究表明，恩达马牛在初次接触后对这些蜱虫获得了更高程度的抵抗力。即使存在相对大量的蜱虫，瘤牛型加纳桑加牛的病变往往局限于成年杂色花蜱的偏好取食部位，这表明这些牛能够控制蜱虫的影响。需要进一步研究来调查本地牛对蜱虫及其影响的明显抵抗力的本质，以及使用蜱虫衍生免疫原通过免疫预防控制该病的潜力。目前控制该病的方法依赖于使用化学杀螨剂控制蜱虫。牛的品种对杂色花蜱相关皮肤真菌病的易感性各不相同，因此所需的蜱虫控制水平因品种而异。对高度易感的外来牛品种，严格控制蜱虫对于预防皮肤真菌病是必要的。在杂色花蜱的偏好取食部位和/或在挑战水平增加的特定时间有限使用杀螨剂，足以控制本地牛群中该病的发生。
