Rowlands G J, Leak S G, Mulatu W, Nagda S M, Wilson A, d'Ieteren G D
International Livestock Research Institute, Nairobi, Kenya.
Med Vet Entomol. 2001 Mar;15(1):87-96. doi: 10.1046/j.1365-2915.2001.00272.x.
A deltamethrin 'pour-on' insecticide was applied monthly to over 2000 cattle exposed to a high challenge of drug-resistant trypanosomes and high tsetse re-invasion pressure in the Ghibe valley, south-west Ethiopia. Blood samples were taken monthly from an average of 760 cattle for determination of PCV and presence of trypanosomes. The area of the valley is approximately 350 km2 and the cattle grazed in roughly four locations covering about a quarter to half of the area. Two years before the trial commenced, Glossina morsitans submorsitans Newstead (Diptera: Glossinidae) began to invade the valley. Despite the use of the pour-on the mean apparent density of G. m. submorsitans continued to rise, and, during the 4 years of tsetse control, was more than three-fold higher than that recorded during the previous 18 months. Over the same period there was little change in the apparent density of Glossina pallidipes Austen (Diptera: Glossinidae). By contrast, the mean monthly prevalence of trypanosome infections in cattle over 36 months of age decreased from 38.3 to 29.0%, the incidence of new infections decreased from 26.6 to 16.0% (a reduction of 40%), and packed cell volume in cattle increased from 21.7 to 24.1%. Evidence of a change in apparent parasite transmission rate was demonstrated by regression of infection incidence in cattle on the logarithm of apparent density of G. m. submorsitans. Before the trial started the regression coefficient was 45.8 +/- 6.3 and this reduced to 9.2 +/- 2.5% incidence per log(e) (flies/trap/day) during the period of tsetse control. It was concluded that this indicated reductions in tsetse numbers in the immediate vicinities of cattle in a way that was not reflected in overall tsetse catches. Nevertheless, the comparatively high levels of trypanosome prevalence that persisted in the cattle demonstrates that, where invasion prevalence is high, treatment of small pockets of cattle will not eradicate tsetse. To achieve more significant reduction in trypanosome prevalence in cattle, integrated methods of control utilizing target barriers in the major routes of invasion will be needed.
在埃塞俄比亚西南部的吉贝河谷，一种溴氰菊酯“浇泼式”杀虫剂每月施用于2000多头牛，这些牛面临着耐药性锥虫的高度挑战以及采采蝇的高再侵袭压力。每月从平均760头牛身上采集血样，以测定血细胞比容和锥虫的存在情况。该河谷面积约350平方公里，牛群在大约四个地点放牧，覆盖面积约为该地区的四分之一到一半。在试验开始前两年，莫氏采采蝇（双翅目：采采蝇科）开始侵入该河谷。尽管使用了浇泼式杀虫剂，但莫氏采采蝇的平均表观密度仍持续上升，并且在采采蝇控制的4年期间，比前18个月记录的密度高出三倍多。同期，淡足采采蝇（双翅目：采采蝇科）的表观密度几乎没有变化。相比之下，36月龄以上牛的锥虫感染平均月患病率从38.3%降至29.0%，新感染发病率从26.6%降至16.0%（降低了40%），牛的血细胞比容从21.7%升至24.1%。通过将牛的感染发病率与莫氏采采蝇的表观密度对数进行回归分析，证明了表观寄生虫传播率发生了变化。试验开始前，回归系数为45.8±6.3，在采采蝇控制期间，每自然对数（只/诱捕器/天）的发病率降至9.2±2.5%。得出的结论是，这表明牛附近的采采蝇数量减少，但这在总体采采蝇捕获量中并未体现。然而，牛群中持续存在的相对较高的锥虫患病率表明，在入侵患病率较高的地区，对小片牛群进行治疗并不能根除采采蝇。为了更显著地降低牛群中的锥虫患病率，将需要采用综合控制方法，在主要入侵路线上设置目标屏障。
