Scoles Glen A, Ueti Massaro W, Noh Susan M, Knowles Donald P, Palmer Guy H
USDA-ARS, Animal Disease Research Unit, Washington State University, Pullman, WA 99164, USA.
J Med Entomol. 2007 May;44(3):484-91. doi: 10.1603/0022-2585(2007)44[484:cotpoa]2.0.co;2.
Before the eradication of Boophilus ticks from the United States, Rhipicephalus (Boophilus) microplus (Canestrini) and Rhipicephalus (Boophilus) annulatus (Say) were important biological vectors of the cattle pathogen Anaplasma marginale Theiler. In the absence of Boophilus ticks, A. marginale continues to be transmitted by Dermacentor ticks. However, a few U.S. strains are not transmissible by Dermacentor andersoni Stiles, Dermacentor variabilis (Say), or both, raising the question of how these strains evolved and how they are maintained. We hypothesize that the U.S. non-Dermacentor-transmissible strains of A. marginale were formerly Boophilus-transmitted strains that have been maintained by a combination of persistent infection and mechanical transmission since the eradication of their biological vector from the United States. To test this hypothesis, we attempted to transmit a well-documented non-Dermacentor-transmissible A. marginale strain (Florida), by using D. andersoni and the two Boophilus species that formerly occurred in the United States. For comparison, we examined tick-borne transmission of a strain of A. marginale (Puerto Rico), which has previously been shown to be transmissible by both D. andersoni and B. microplus. All three species of tick transmitted the Puerto Rico strain, and immunohistochemical (IHC) analysis confirmed the presence ofA. marginale colonies in their salivary glands. All three tick species failed to transmit the Florida strain. Although both D. andersoni and B. microplus acquired transient midgut and salivary gland infections after acquisition feeding, we were unable to detect colonies of the Florida strain in the salivary glands with IHC. This demonstrates that the transmission phenotype ofA. marginale strains is conserved among tick species, and it suggests that the failure of the Florida strain to be transmitted by ticks is related to a general inability to efficiently invade or replicate in tick cells, rather than to a failure to invade or replicate in cells of a specific tick species.
在美国根除微小牛蜱（Boophilus ticks）之前，微小扇头蜱（Rhipicephalus (Boophilus) microplus (Canestrini)）和环形扇头蜱（Rhipicephalus (Boophilus) annulatus (Say)）是牛病原体边缘无形体（Anaplasma marginale Theiler）的重要生物传播媒介。在没有微小牛蜱的情况下，边缘无形体仍由革蜱传播。然而，一些美国菌株不能通过安德逊革蜱（Dermacentor andersoni Stiles）、变异革蜱（Dermacentor variabilis (Say)）或两者传播，这就引发了这些菌株如何进化以及如何维持的问题。我们推测，美国非革蜱传播的边缘无形体菌株以前是由微小牛蜱传播的菌株，自其生物传播媒介在美国被根除以来，通过持续感染和机械传播的组合得以维持。为了验证这一假设，我们试图利用安德逊革蜱以及美国以前存在的两种微小牛蜱来传播一种有充分记录的非革蜱传播的边缘无形体菌株（佛罗里达菌株）。为了进行比较，我们研究了一种边缘无形体菌株（波多黎各菌株）的蜱传播情况，该菌株先前已被证明可由安德逊革蜱和微小扇头蜱传播。所有三种蜱都传播了波多黎各菌株，免疫组织化学（IHC）分析证实其唾液腺中存在边缘无形体菌落。所有三种蜱都未能传播佛罗里达菌株。尽管安德逊革蜱和微小扇头蜱在吸食感染血后都获得了短暂的中肠和唾液腺感染，但我们无法通过免疫组织化学在唾液腺中检测到佛罗里达菌株的菌落。这表明边缘无形体菌株的传播表型在蜱种间是保守的，这表明佛罗里达菌株不能被蜱传播与一般无法有效侵入蜱细胞或在蜱细胞中复制有关，而不是无法侵入或在特定蜱种的细胞中复制。
