这里是美国之音慢速英语农业报道。
East Coast fever kills hundreds of thousands of cattle in eastern and central Africa every year. The animals become infected when they get bitten by ticks carrying the parasite that causes the disease. A parasite is an organism that feeds on other organisms.
非洲东部和中部地区每年有数万头牛因“东海岸热”致死。当牛被携带了可以导致该疾病的寄生虫的蜱虫叮咬后就会感染。寄生虫是一种以其它生物为食的生物。
Donald Knowles directs the animal disease research unit in the Agricultural Research Service, part of the United States Department of Agriculture. The service is working with the International Livestock Research Institute in Kenya to find better ways to prevent parasitic diseases in cattle. Dr. Knowles is also a professor at Washington State University.
唐纳德·诺尔斯（Donald Knowles）负责美国农业部下属的农业研究服务中心的疾病研究部门。该部门与肯尼亚国际牲畜研究所合作，寻找防止牛类寄生虫病的更好办法。诺尔斯博士还是美国华盛顿州立大学的一名教授。
He points out that East Coast fever is not a contagious disease, so animals cannot give it to each other.
他指出，东海岸热不是一种传染性疾病，所以动物间不会互相传染。
DONALD KNOWLES: "You need a tick to transmit from one infected cow to the other. They won't transmit just by standing next to each other. You need a tick to move it between them."
诺尔斯：“被感染的牛传染给其它牛需要蜱虫来传播。这种疾病无法通过紧挨在一起的牛群直接传播，需要蜱虫将其传播至其它牛。”
Farmers in parts of Africa use a vaccination method against East Coast fever known as infect and treat. First they infect animals with live parasites. Then they treat them with drugs to help them recover.
非洲部分地区的农民使用一种被称为先感染再治疗的疫苗接种方法对抗东海岸热。他们首先用活体寄生虫感染动物，然后通过药物治疗帮助动物康复。
That way, explains Dr. Knowles, the animal becomes immunized or vaccinated against a full case of the deadly fever. But there are problems with this method of vaccination. Uninfected ticks that bite the vaccinated animal can still get infected and spread the parasite to other animals.
诺尔斯博士解释到，通过这种方式，动物对各类致命发热都具备免疫力。但这种疫苗接种方法也有问题。未受感染的蜱虫叮咬接种过的动物后仍然会被感染，继而传播寄生虫到其它动物。
DONALD KNOWLES: "Once a cow is infected with this parasite, all the data indicates that the cow stays infected for life. And the consequences of that, the big deal about that is, that means that cow, even a cow that has been vaccinated, now it's protected against the disease, but it can still transmit. See it's infected for life. And so that animal is still a source of transmission."
诺尔斯：“一旦牛被这种寄生虫感染，所有数据都表明，这头牛会终生保持被感染状态。这意味着的最大的问题是，这头牛，即使是接种过疫苗，能够预防这种疾病，但却仍然可以传播疾病，它终生被感染。所以这头牛仍然是一个传染源。”
And that is not the only problem with this method of vaccination.
这还不是这种疫苗接种方法的唯一问题。
DONALD KNOWLES: "One of the things in using live vaccines is that they usually require cold storage. And that adds to the cost of it, and also adds to the difficulty of using it in places like Africa."
诺尔斯：“使用活性疫苗的问题之一就是它们通常需要冷藏。这增加了疫苗的使用成本，也增加了它在非洲这种地方使用的难度。”
For more than four years, American and Kenyan scientists have studied diseases carried by ticks. The scientists in the United States centered their work on the parasite that causes Texas cattle fever. This fever is common to the Americas.
四年多来，美国和肯尼亚科学家对蜱虫携带的疾病进行研究。美国科学家将工作重点放到了引发德州牛类发热的寄生虫上。这类发热在美洲很是常见。
This year, the scientists began a new study in Africa. The study is aimed at developing a new vaccine for the East Coast fever parasite. Dr. Knowles says their goal is a vaccine that does not require infecting and treating animals or the need for cold storage.
今年，科学家在非洲开始了一项新研究，目的是开发一种针对东海岸热的新型疫苗。诺尔斯博士表示，他们的目标是开发一种不需要先感染再治疗的疫苗，或不需要冷藏的疫苗。
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