Meltzer M I
National Center for Infectious Diseases, Centers for Disease Control and Prevention, US Dept. of Health and Human Services, Atlanta, GA 30333, USA.
Vet Parasitol. 1996 Dec 31;67(3-4):275-9. doi: 10.1016/s0304-4017(96)01018-7.
Adult male Amblyomma hebraeum tick infestations and the weights of 20 Brahman steers and 38 Mashona heifers were measured at different periods at the Veterinary Quarantine Area at Mbizi, Zimbabwe. The experiment for the Brahmans lasted 108 weeks and that for the Mashona for 113 weeks. The Brahman steers weighed a maximum average of 478.4 kg (SE 7.9 kg), which was significantly different to the Mashona heifers maximum average of 391.4 kg (SE 5.6 kg) (P < 0.001). The Brahmans had a maximum average of 112.1 (SE 18.5) adult males, while the Mashona heifers had a maximum average of 59.8 (SE 4.3). The difference was statistically significant (P < 0.05). There was no statistical difference between the two maximum average ticks per kilogram liveweight (P > 0.05). When differences in size are corrected for, then breed-related differences disappear. It is emphasized that the influence of confounding factors, especially time, cannot be corrected for in a satisfactory manner. Therefore, these statistical results should be regarded as illustrative rather than proof. To confirm these results, it is suggested that the authors of earlier studies should reanalyze their databases in a similar manner. It is important that such analyses be conducted, or new experiments carried out. Erroneous conclusions regarding the reason for different tick numbers between the breeds could result in farmers being incorrectly encouraged to utilize smaller breeds to obtain 'built-in' resistance to A. hebraeum ticks. One logical explanation for the size-related effect is that the males typically attach themselves around the belly and groin areas. Larger breeds of cattle, such as the Brahman, will naturally have larger surface areas of skin in the belly and groin regions than smaller breeds. Thus, it is suggested that there may be a simple physical explanation for the difference between breeds in the numbers of attached adult A. hebraeum males.
在津巴布韦姆比齐的兽医检疫区，于不同时期对20头婆罗门公牛和38头马绍纳小母牛身上成年雄性希伯来花蜱的寄生情况以及它们的体重进行了测量。婆罗门牛的实验持续了108周，马绍纳牛的实验持续了113周。婆罗门公牛的平均最大体重为478.4千克（标准误7.9千克），这与马绍纳小母牛的平均最大体重391.4千克（标准误5.6千克）有显著差异（P < 0.001）。婆罗门牛身上成年雄性蜱的平均最大数量为112.1只（标准误18.5只），而马绍纳小母牛身上成年雄性蜱的平均最大数量为59.8只（标准误4.3只）。差异具有统计学意义（P < 0.05）。每千克活体重的蜱平均最大数量在两者之间没有统计学差异（P > 0.05）。当对体型差异进行校正后，品种相关差异消失。需要强调的是，混杂因素的影响，尤其是时间因素，无法以令人满意的方式进行校正。因此，这些统计结果应被视为说明性的而非确凿证据。为了证实这些结果，建议早期研究的作者应以类似方式重新分析他们的数据库。进行此类分析或开展新的实验很重要。关于不同品种蜱数量差异原因的错误结论可能会导致农民被错误地鼓励使用较小品种的牛来获得对希伯来花蜱的“内在”抗性。与体型相关效应的一个合理解释是，雄性蜱通常附着在腹部和腹股沟区域周围。体型较大的牛品种，如婆罗门牛，其腹部和腹股沟区域的皮肤表面积自然会比体型较小的品种大。因此，对于附着的成年希伯来花蜱雄性数量在品种间的差异，可能存在一个简单的物理解释。
