But it is true, sort of.

但這是真的，算是吧。

One thing that many people are aware of is that mosquitoes are the deadliest animals.

很多人都知道，蚊子是最致命的動物。

That is of course because they transmit the deadly single cell parasite which causes malaria.

這當然是因為它們傳播導致瘧疾的致命單細胞寄生蟲。

It is often said that malaria has killed half of all people who have ever lived.

人們常說，有一半的人死於瘧疾。

And while this is probably no longer true today, it was most likely true for most of mankind's history.

雖然這在今天可能已不再正確，但在人類歷史的大部分時間裡，這很可能是正確的。

Even today there are an estimated 200 million new malaria cases every year and between 300.000 and 1 million malaria related deaths.

時至今日，估計每年新增瘧疾病例 2 億例，與瘧疾相關的死亡人數在 30 萬到 100 萬之間。

This means malaria is still the most socio-economically devastating parasitic disease.

這意味著瘧疾仍然是對社會經濟破壞最大的寄生蟲病。

What has this to do with snails?

這和蝸牛有什麼關係？

Well, similar to mosquitoes, snails also transmit a deadly parasite, a parasitic flatworm which is the second most deadly parasitic disease in the world.

與蚊子類似，蝸牛也會傳播一種致命的寄生蟲--扁形寄生蟲，它是世界上第二大致命寄生蟲病。

This is however far less known which is probably why you are here.

然而，這一點卻鮮為人知，這也許就是你們來到這裡的原因。

So what exactly is schistosomiasis?

那麼，血吸蟲病究竟是什麼？

The disease is the result of an infection with what is commonly called blood flukes.

這種疾病是感染了俗稱的血吸蟲所致。

These are water-bound parasites that you can find in all kinds of freshwater habitats like lakes, swamps and rivers, rice fields, puddles or roadside ditches.

這些水生寄生蟲可以在湖泊、沼澤、河流、稻田、水坑或路邊溝渠等各種淡水棲息地找到。

Many parasites need to go through complex life cycles with morphological distinct generations and one or more intermediate hosts before they can infect their final host and these worms are no exception.

許多寄生蟲在感染最終宿主之前，需要經歷形態各異的複雜生命週期和一個或多箇中間宿主，這些蠕蟲也不例外。

They begin their life as tiny larvae floating in the water.

它們的一生是從漂浮在水面上的小幼蟲開始的。

Almost immediately after hatching they start actively looking for their intermediate host, freshwater snails which they need to develop further.

孵化後，它們幾乎立即開始積極尋找中間宿主--淡水蝸牛，因為它們需要淡水蝸牛來進一步發育。

Once they find one they penetrate the soft body of the snail and begin to reproduce asexually.

一旦它們找到蝸牛，就會鑽進蝸牛柔軟的身體，開始無性繁殖。

They do this multiple times during the 1-2 months inside the snails and as a result their larvae quickly grow exponentially.

在蝸牛體內的 1-2 個月裡，它們會多次這樣做，所以幼蟲很快就會成倍增長。

A process that started with a single larva has now produced thousands of offspring.

從一隻幼蟲開始的過程，現在已經產生了成千上萬的後代。

These so called Fog-tailed Sacarii then break out of the snail into the water and start looking for their final host for which they are now specifically adapted for.

然後，這些所謂的霧尾沙卡里翁就會從螺體內破殼而出，進入水中，開始尋找它們現在特別適應的最終宿主。

They have around 48 hours to do so before they die.

它們在死亡前大約有 48 小時的時間來完成這項工作。

There are dozens of different species of blood flukes each specialized on a specific set of vertebrate hosts.

血吸蟲有幾十種不同的種類，每種血吸蟲都專攻一組特定的脊椎動物宿主。

Birds, mammals and reptiles all fall victim to these parasites and of course humans.

鳥類、哺乳動物和爬行動物都是這些寄生蟲的受害者，當然還有人類。

There are 5 species that are responsible for the major forms of human schistosomiasis.

人類血吸蟲病的主要病原體有 5 種。

Once the Sacaria comes into contact with its host the larva penetrates the skin, sheds its tail and transforms into the juvenile form.

一旦沙卡利亞蟲接觸到宿主，幼蟲就會穿透皮膚，脫掉尾巴，變成幼蟲形態。

It then starts to bore through the flesh until it reaches the blood vessels.

然後，它開始在肉裡鑽來鑽去，直到抵達血管。

Here it will spend the next couple of weeks migrating through the circulatory system via the heart into the liver at which point it will have matured into an adult male or female worm around 1-2 cm in length.

在接下來的幾周裡，它將通過循環系統經由心臟進入肝臟，此時它將發育成熟，成為一條長約 1-2 釐米的成年雄蟲或雌蟲。

Next the worms begin to join together in pairs to reproduce, this time sexually.

接下來，蠕蟲開始成對地進行繁殖，這次是有性繁殖。

For that the more slender female is held permanently in a groove in front of the male's body.

為此，較為纖細的女性被固定在男性身體前方的凹槽中。

The two worms usually remain jointed together like this for life although it can happen that a female divorces a male to look for a more genetically distinct mate.

雖然雌蟲可能會與雄蟲離婚，以尋找基因更獨特的配偶，但兩隻蟲子通常會這樣終生結合在一起。

From the liver the pair eventually migrates to their final destination either in the veins of the warts of the intestine or the bladder depending on the species.

根據物種的不同，這對 "雌雄 "最終會從肝臟遷移到它們的最終目的地--腸道疣狀靜脈或膀胱。

They will remain here for the rest of their lives feeding on the red blood cells and the dissolved nutrients inside the blood, hence the name blood flukes, while the female continuously produces eggs.

它們將終生留在這裡，以紅細胞和血液中溶解的營養物質為食，所以被稱為血吸蟲，而雌蟲則不斷產卵。

Although all this sounds like something straight out of a horror movie the worms themselves are essentially harmless.

雖然這一切聽起來像是恐怖電影裡的情節，但蠕蟲本身基本上是無害的。

What causes the problems are the eggs they produce.

造成問題的是它們產生的卵。

A single female lays multiple hundred eggs per day for an average of 5 but sometimes as long as 20 years.

一隻雌鳥每天產卵數百枚，平均產卵 5 年，有時甚至長達 20 年。

Only about 50% of these eggs penetrate the warts of the veins, make their way into the bladder or intestines and are released with a feces or urine to start the cycle again.

這些蟲卵中只有約 50%能穿透靜脈疣，進入膀胱或腸道，並隨糞便或尿液排出，再次開始循環。

The rest remains embedded in the body, transported around by the bloodstream and will cause a host of long term chronic problems in many organs.

其餘的則會留在體內，通過血液四處傳播，並在許多器官中造成一系列長期慢性問題。

Which brings us to the disease itself.

這就涉及到疾病本身。

Schistosomiasis can have a wide range of symptoms depending on the species of worm or the individual.

血吸蟲病的症狀多種多樣，取決於血吸蟲的種類或個體。

Common symptoms are abdominal pain, diarrhea and blood in stool or urine, the accumulation of fluid in the peritoneal cavity and hypertension of abdominal blood vessels, long term kidney, liver and bladder damage as well as an increased risk of bladder cancer and HIV infection, the latter particularly in women.

常見症狀包括腹痛、腹瀉、便血或尿血、腹腔積液和腹腔血管高壓、長期的腎、肝和膀胱損傷以及膀胱癌和艾滋病毒感染風險增加，尤其是女性。

In children, which are most commonly affected by the disease, it can also cause anemia and the ability to learn.

兒童是該病的高發人群，它還會導致貧血和學習能力下降。

In most cases these symptoms impair and disable rather than kill but with over 78 countries affected and nearly 800 million people that live in areas where infection with blood flukes can occur, the raw number of deaths, even if they are comparably rare, is obviously still extraordinarily high.

在大多數情況下，這些症狀會造成損傷和殘疾，而不是死亡，但有超過 78 個國家受到影響，有近 8 億人生活在可能感染血吸蟲的地區，所以，即使死亡人數比較罕見，其原始數字顯然仍然非常高。

It is estimated that currently over 230 million people are infected and in need of medical treatment.

據估計，目前有超過 2.3 億人受到感染，需要接受治療。

The disease is only endemic to subtropical and tropical regions and is mainly a rural problem.

這種疾病只在亞熱帶和熱帶地區流行，主要是農村問題。

It affects mostly those who are unable to avoid contact with water, either because of their profession, agriculture or fishing, or because of a lack of a reliable source of safe water for drinking, washing or bathing.

這種疾病主要影響那些無法避免與水接觸的人，他們或是因為職業、農業或漁業，或是因為缺乏可靠的安全水源以供飲用、清洗或沐浴。

Children between age 10 and 15 are, due to their careless nature and their low level resistance, most heavily infected.

10 至 15 歲的兒童由於天性粗心，抵抗力低下，感染率最高。

Impacted regions are South America, South Asia, the Middle East, the Caribbean Islands and most notably Africa, which has around 90% of all known schistosomiasis cases.

受影響的地區包括南美洲、南亞、中東、加勒比群島，其中最突出的是非洲，非洲約佔所有已知血吸蟲病病例的 90%。

The impact this disease can have not just on the people but also on the economy of entire countries is serious.

這種疾病不僅會對人民造成影響，還會對整個國家的經濟造成嚴重影響。

In areas that are most severely affected, like northeastern Brazil and much of sub-Saharan Africa, the working ability of large portions of the population is severely reduced as a That's why, in the past few decades, health organizations have begun to work relentlessly on limiting the impact of schistosomiasis, but the process is difficult and complex and while successful in some regions, on a global scale it was relatively unsuccessful thus far.

在受影響最嚴重的地區，如巴西東北部和撒哈拉以南非洲的大部分地區，大部分人口的工作能力嚴重下降，這就是為什麼在過去幾十年裡，衛生組織開始不遺餘力地限制血吸蟲病的影響。

That's why the disease now ranks second on the list of 80 neglected tropical diseases issued by the World Health Organization.

所以，在世界衛生組織公佈的 80 種被忽視的熱帶疾病名單中，該疾病目前排名第二。

The biggest issue is the lack of an available vaccine or any other reliable form of immunization.

最大的問題是缺乏可用的疫苗或任何其他可靠的免疫方式。

Merely, the infection itself can be treated through the use of drugs.

只是，感染本身可以通過使用藥物來治療。

Normally, Praziquantel is used, which is effective against all forms of schistosomiasis, kills the parasites and even helps to reverse some of the damage done by the infection.

通常使用吡喹酮，它對所有形式的血吸蟲病都有效，可以殺死寄生蟲，甚至有助於逆轉感染造成的一些損害。

But while this treatment has helped to overcome many of the long-term problems of the disease and thereby reduced its mortality rate, it doesn't prevent reinfections.

但是，雖然這種治療方法幫助克服了該疾病的許多長期問題，從而降低了死亡率，但並不能防止再次感染。

That means that the ultimate goal, the elimination of schistosomiasis, is likely not reachable through medical means alone, at least not at the moment.

這意味著，僅靠醫學手段很可能無法實現消滅血吸蟲病的最終目標，至少目前還無法實現。

Instead, it needs an integrated approach, so a multi-component approach that targets the entire life cycle of the parasite, for instance preventive chemotherapy using Praziquantel, improved detection and treatment of sick people, improvement of sanitary facilities for safe and acceptable disposal of human excreta, provision of safe drinking water, reduction of contact with contaminated water, health education and snare control.

相反，它需要一種綜合方法，即針對寄生蟲整個生命週期的多成分方法，例如使用吡喹酮進行預防性化療、改進對病人的檢測和治療、改善衛生設施以安全和可接受地處理人類排洩物、提供安全飲用水、減少與受汙染水的接觸、開展健康教育和控制柵欄。

But such an approach is of course very difficult to realize and requires a long-term, well-structured control program.

但這種方法當然很難實現，需要一個長期的、結構合理的控制計劃。

What makes matters worse is that each region is unique.

更糟糕的是，每個地區都是獨一無二的。

The areas affected differ in part significantly, both socially, geographically and economically and in terms of flora and fauna.

受影響的地區在社會、地理、經濟和動植物方面都有很大的不同。

Each control measure must therefore be applied and adapted specifically for each area to be affected, which explains why the elimination of schistosomiasis is such a challenge.

所以，每項控制措施都必須根據每個受影響地區的具體情況加以應用和調整，這也解釋了為什麼消滅血吸蟲病是一項挑戰。

Even in China, where the disease has been actively battled for more than 60 years now, it still couldn't be eradicated completely.

即使在中國，積極防治這種疾病已有 60 多年，但仍無法徹底根除。

But China's example also demonstrates what is possible through a long-term, well-coordinated effort.

但中國的例子也表明，通過長期、協調良好的努力是可以做到的。

Since their program was initiated in 1956, the number of detected cases of schistosomiasis has dropped from more than 12 million to under 100,000.

自 1956 年啟動該計劃以來，發現的血吸蟲病病例已從 1200 多萬例下降到不足 10 萬例。

One country that could successfully eradicate the disease is Japan.

日本就是一個可以成功根除這種疾病的國家。

Here, schistosomiasis was endemic as far back as the 1600s.

早在 1600 年代，血吸蟲病就在這裡流行。

The southern, subtropical regions of the country were most affected.

該國南部亞熱帶地區受影響最大。

After the cause of the disease was finally identified in 1904, Japan, as one of the first countries to do so, began to implement a series of control measures to combat the disease.

在 1904 年最終確定病因後，日本作為最早確定病因的國家之一，開始實施一系列防治措施。

To kill the eggs, human fecal matter was stored for two weeks or more before using it as fertilizer.

為了殺死蟲卵，人類的糞便要存放兩週或更長時間才能用作肥料。

Handpicking, snare pesticides and other chemicals were used to reduce the snare population and to kill the cercariae, and susceptible cows were replaced with horses as the animal of burden for agriculture, which were more resilient to infection.

為了減少釘螺數量和殺滅蛔蟲，人們使用了人工採摘、釘螺殺蟲劑和其他化學品，並用抗感染能力更強的馬取代易感牛作為農業負擔動物。

To further control the snare population, wetlands were drained, river bottoms were dredged and ditches around rice fields were cemented, destroying much of the snare's habitats.

為了進一步控制蝸牛的數量，溼地被抽乾，河底被疏浚，稻田周圍的溝渠被水泥封堵，蝸牛的大部分棲息地都遭到了破壞。

All this was undertaken with government support and performed by the affected communities.

所有這些工作都是在政府的支持下由受災社區完成的。

And it worked.

它成功了。

In 1970, after 50 years of continuous effort, the number of infections had been reduced from around 10,000 to a few hundred, and no new cases have been reported since 1977.

1970 年，經過 50 年的不懈努力，感染人數已從約 10 000 人減少到幾百人，而且自 1977 年以來再無新病例報告。

In 1996, Schistosomiasis was then officially declared eradicated.

1996 年，血吸蟲病被正式宣佈根除。

As a consequence of the program, the freshwater snail responsible for the disease in Japan was largely eradicated with it, but a small population of them survived.

該計劃的結果是，在日本導致該疾病的淡水蝸牛也隨之被基本消滅，但仍有少量蝸牛存活下來。

They are now living a life free from the parasites as well.

他們現在也過上了沒有寄生蟲的生活。