The Mekong Delta: a public health nightmare

The Mekong Delta is a vast and beautiful expanse of waterways in southern Vietnam. Having travelled over 4,000 kilometres from China, taking them through all the countries of South-East Asia, the waters of the Mekong spread out over much of the land south of Ho Chi Minh City. Arriving by night, each river crossed makes me think of the next tentacle which a dark octopus might be trying to block our route with.
By day, a vibrant, bustling hive of activity takes shape as the sun rises. Everybody here owns a boat. For some it is also their home. For all it is their way of making a living, taking them and their wares to the many floating markets of the Mekong. There are some laden with mangoes, bananas, watermelons or pumpkins; ice or rice; clay hearths or charcoal; and bread or pho, to cater for the morning munchies.
The river however is much more than an aquatic road to the nearest market. Most of the homes here have a back door which leads straight out onto the brown, murky Mekong waters. This is where clothes are washed, pots and pans are rinsed and litter is discarded. Children play in the lukewarm waters while teenage girls clean their bicycles nearby. A man lowers a bucket into the shallows to collect a little water to brush his teeth with. A young woman crouches down on a ledge, washing her long, dark hair in the river. The Mekong is everything to the people here: every activity involves its waters at some stage.
Drifting along in a small boat, I cannot help but think of all the other creatures which populate this river. Countless bacteria, viruses and parasites thrive in the warm, humid environment provided by the Mekong, repeatedly introduced there by humans and other animals. Hepatitis A, typhoid fever, cholera.... the list is long and frightening.
The waters of the Delta are a public health nightmare. The question is, how can one go about changing some of the behaviours of those whose lives depend on this river? Where should a benevolent Health Minister start? Try as I might, I cannot imagine that the situation here could change until there is a realistic alternative way of life for all the people who are born on the Mekong and only know how to survive thanks to its waters.

Avoid the snails, they're fresh.

One of the attractions of infectious diseases is that there is usually a high turnover of patients. As a general rule, treatment brings about a rapid improvement and patients can return home within a few days, even if they will be receiving on-going treatment for a longer period. My experience at the Hospital for Tropical Diseases has reflected that so far: most patients have been on the wards for only two or three days.
The Viet Anh (Vietnamese-British) ward specialises in neurological infections however, and as such defies the rules. Some patients arrived here before me and unfortunately it looks like they will stay here long after I've left. One of them hasn't moved since my first ward round. He lies on his back, eyes wide open, a ventilator and tracheostomy apparently keeping him alive. The only sign of life is the perpetual twitching of his left cheek, which causes a little foam to form at the corner of his mouth.
A few months ago, he and his twin brother were working in a field outside of Ho Chi Minh City. Pausing for lunch, they noticed the pond nearby was full of snails and didn't think twice: a few raw gastropods and back to work. Unfortunately, the snails were carrying the roundworm Angiostrongylus cantonensis. This parasite usually lives in the lungs of rats, but regularly makes excursions to their gut. Once excreted into the open world, it then relies on snails and slugs to ingest it so that it can develop into new, fully-infective larvae which can colonise new rats.
As is often the case with such worms, humans are only an "incidental host" (see Half a Brain). They become infected by eating raw or under-cooked snails and slugs, or vegetables contaminated by them. Having invaded a new host (be it a human or a rat), Angiostrongylus travels first to the brain and causes an inflammatory reaction which is characterised by the presence of a specific type of white blood cell: this is eosinophilic meningitis, and this is what brought our two brothers into hospital.
Though they both suffered from headaches, nausea and vomiting, neck stiffness and the occasional seizure, only one of them had read the textbook. He got better after a fortnight, and returned home. His brother, however, slipped into a coma and he is still there now. Most patients with eosinophilic meningitis make a full recovery; it is extremely rare for it to cause brain damage as it has in this case.
At this stage, after such a long coma, there is little cause for optimism. He may yet make a miraculous recovery, but it is unlikely. His family will eventually have to decide whether they wish to keep paying for him to receive supportive treatment in hospital, or whether they would rather he came home and were released from his bodily prison.
His brother, with whom he shares so much, reminds us that when two similar people are infected with the same parasite, the outcome can still vary enormously. We still have a lot to learn about the factors which dictate who will be the lucky ones. And we still have a mountain to climb in order to prevent poor, hungry people from eating a quick, easy and free lunch.

A Missed Opportunity

In the ICU today, a young girl lies unconscious. Oblivious to the crowd of doctors in the room, she is being kept alive by a ventilator and a feeding tube. She looks very peaceful, as sleeping children often do, but this belies the events going on in her head.
About 14 days ago, she was bitten by a mosquito of the Culex family. Young girls are not normally the target of Culex mosquitoes: they tend to go more for pigs and wading birds, which are the main reservoirs for Japanese Encephalitis Virus (JEV). However, every now and then, humans get bitten. This particular mosquito was carrying JEV and unwittingly transmitted it to our patient. She subsequently developed a fever, headaches and became nauseous. She fitted and then began to lapse into a coma. And now she is in our ICU, fighting for her life.
Only 1% of JEV infections cause encephalitis, accounting for some 50,000 cases annually. Unfortunately though, the outcome when it happens is terrible: 30% die; 30-50% survive, but with irreversible brain damage; and less than 30% make a complete recovery. The only antiviral treatments which exist have been shown to be useless in Japanese encephalitis - all we can do is wait and hope that she is in the minority which pull through.
It is terrible to see a young girl who may well die or be left brain-damaged by a childhood infection. What makes it worse is that Japanese encephalitis is a preventable disease. While the two vaccines offered to travellers are not ideally suited to mass immunisation programmes in the region, a Chinese vaccine has shown great promise. Several trials have shown it to be particularly effective in children, who are the main victims of JEV. Why it has not yet been incorporated into regional vaccination programmes is not clear to me, but it certainly appears to be a missed opportunity.
There are plenty of excellent vaccines out there which have the potential to prevent millions of childhood deaths every year. Most of them are not expensive to produce: the main challenge is making them available to the people who need them, and ensuring that as many people are immunised as possible. At the moment it seems we're investing far more in inventing new treatments than we are in using those that already exist.

Twitch, twitch, twitch.

It's International Women's Day today: all the women in the hospital are greeted with a rose and, if they're lucky, a lollipop. I don't recall anyone ever celebrating Women's Day in the UK, but then roses are far more expensive there.
Twitch. In the ICU, one woman is not spending Women's Day as she might have hoped. A few days ago, (twitch), she went to the dentist to have a cavity treated. Somewhere along the way, she became infected with Clostridium tetani, which, as its name suggests, is the bacterium responsible for causing tetanus. Twitch. Painful spasms in the muscles of her jaw brought her to the hospital. Now, after a hefty dose of sedation and muscle relaxants, she is beginning a long and dangerous hospital stay (twitch). She is at very high risk of developing a respiratory infection which, given the frightening rates of antibiotic resistance here, would surely be a death sentence. Despite the doctors' best efforts (twitch), uncontrollable spasms still shake her body every few minutes. You cannot help but look on, waiting for the next one. Twitch. If it wasn't for the sedatives, she would be in agony.

The Clostridium family is a nasty one, responsible as it is for tetanus, gas gangrene and botulism. C. tetani loves a dirty wound and, given the opportunity, will invade in a matter of days. It produces a toxin which specifically targets the central nervous system, impeding the normal mechanisms which regulate muscle contraction. The result is violent muscular spasms, typically starting with the masseters, leading to 'lock-jaw'. The expression risus sardonicus (sardonic smile) is still sometimes used to describe the snarl produced by the disease. (Interestingly, the word 'sardonic' apparently alludes to a Sardinian plant which, when eaten, would produce convulsive laughter and death - so much for herbal medicine). The other characteristic feature of tetanus, the arching of the back or opisthotonus, is more commonly seen in infants than in adults.

Fortunately, tetanus is very preventable. The vaccine probably confers ten years' protection, and it is thought that after three or four jabs there is life-long immunity. In Vietnam, 85% of the population is immunized; however that leaves nearly 13 million unprotected individuals. As the disease does not prevent subsequent re-infection, patients are always followed up with three jabs. Hopefully, with improving vaccine coverage, tetanus will become as rare in Vietnam as it is today in Europe, and patients such as this one will be able to celebrate Women's Day without all the twitching.